Programing Fun

What's wrong with this code - fun with assembly

2012-02-08T23:23:00.003-02:00

Since, I'm a bit busy to create new posts I decided to cheat, translating this post from my old (Portuguese) blog :)

Before we continue let me make this clear: finding the actual issue is not terrible hard (even though it toke me some time and of course I'll keep the answer to a future post :); the interesting part is to figure it out why it works (or at least, why it works when compiled with some compilers).

Ok, so lets go. Take a look in the following program:

This program accepts a number (command line) and calculates its factorial.

I came across it while I was corrigindo a programming assignment from one of my students (yep, 14 years ago I used to work as a professor teaching C, C++, assembly and the like).

At that time I used Borland C++ 3.0 to compile and to my astonishment it worked! Last time, when I tried to compile it with VC 6 I noticed a different behavior (the application produced a wrong result) but using Visual Studio 2010 I can reproduce the same behavior as when I first compiled it with Borland C++ 3.0; of course, the compiler generated some warnings which were promptly ignored!

Warning

To ignore compiler warnings is not such a smart idea and of course I'm not recommending you should do it!

Pelo contrário; check all compiler warnings in your code and understand the reasons leading the compiler to complain.Do not assume that the compiler has bugs (after all, Select is not broken). If the conclusion is that the code generating the warning is legitimate I suggest you to try to change it, or, in the worst case, disable the specific warning (via #pragma warning) just in the parts of the code that is producing the warning.

int fat(int n)
{
    if (n == 1)
        return 1;
    else
        n = n * fat(n - 1);
}

int main(int argc, char *argv[])
{
     int n = argc > 1 ? atoi(argv[1]) : 5;
     int i = fat(n);
   
     return printf("Fat(%d): %d", n, i);
 }

Have you figured it out already?

See you!

Interfaces in IL

2012-01-26T23:01:00.000-02:00

After a long period of silence, today I've something interesting (IMHO) (and the time to, of course :)) to post about.

Last night I was reading a book about MS IL (intermediate language) when suddenly I stumbled with an intriguing paragraph about interfaces. The "intriguing" part motivated me to write a sample application to test whenever that would be valid in C# or not.
Given the following NUnit test, how can you define a type "IAmAnInterface" so it can pass ?

 
using System;
using NUnit.Framework;

namespace Testing
{
 
 [TestFixture]
 public class BlobPost_Interface
 {
  [Test]
  public void Test()
  {
   var type = typeof(IAmAnInterface);
   Assert.That(type.IsInterface, Is.True);

   var field = type.GetField("fld");
   Console.WriteLine("    Field: {0}", field);
   Assert.That(field, Is.Not.Null);

   field.SetValue(null, 10);

   Assert.That(field.GetValue(null), Is.EqualTo(10));
  }
 }
}

Just in case you missed it, the crux here, is that the test expects IAmAnInterface to be an interface and (and here lies the issue) to define a (static) field!

How come? An interface with fields?

Well, it happens that the C# specification (and the compiler also!) disallows such constructs, but they are actually valid in IL (as described in Common Language Infrastructure ,session 8.9.4)!

So, in order to get this to work I simply created an assembly in IL (actually I disassembled an assembly written in C# and changed it) that looks like:

.assembly extern mscorlib
{
  .publickeytoken = (B7 7A 5C 56 19 34 E0 89 )                         
  .ver 4:0:0:0
}
.assembly TestString
{
  .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilationRelaxationsAttribute::.ctor(int32) = ( 01 00 08 00 00 00 00 00 ) 
  .custom instance void [mscorlib]System.Runtime.CompilerServices.RuntimeCompatibilityAttribute::.ctor() = ( 01 00 01 00 54 02 16 57 72 61 70 4E 6F 6E 45 78   // ....T..WrapNonEx
                                                                                                             63 65 70 74 69 6F 6E 54 68 72 6F 77 73 01 )       // ceptionThrows.
  .hash algorithm 0x00008004
  .ver 0:0:0:0
}
.module TestString.dll
// MVID: {64C46A76-194E-4608-A835-B41B179AF4FA}
.imagebase 0x00400000
.file alignment 0x00000200
.stackreserve 0x00100000
.subsystem 0x0003       // WINDOWS_CUI
.corflags 0x00000001    //  ILONLY
// Image base: 0x004D0000


// =============== CLASS MEMBERS DECLARATION ===================

.class interface public abstract auto ansi IAmAnInterface
{
  .method public hidebysig newslot specialname abstract virtual 
          instance int32  get_value() cil managed
  {
  } // end of method IAmAnInterface::get_value
  
  .field public static int32 fld

} // end of class IAmAnInterface


// =============================================================

and referenced it in my C# test application inside VS2010 which happily showed the field in IntelliSense but gave an error when I tried to compile the code (so I resorted to reflection, and it worked) (see picture below):

What do you think?

Best

Adriano

Do as I say, not as I do

2011-03-30T23:14:00.001-03:00

It has been a long time since my last post ...

As usual I have been busy taking care of my kids (if you have two kids you have an idea how much time they require :)), studying, playing with may pet projects and what not.

But something happened and motivated me to stay late and to write this post. To make a long history short, yesterday night I was working on one of my pet projects, binboo (basically a skype plugin that I and other team mates use to add/update issues on our bug tracker) and I spot some code that looked pretty useless to me.

Since I have unit tests (yeah, some of you would argue that strictly speeking they are not unit tests, but anyway, I have automated tests in place) I was not scared of changing the code, so in the next step I just removed the "dead" code running the tests after that. To my happiness, I saw only green in the unit test runner screen.

Perfect, I though, proud of myself.

After that I just committed my changes and went (happy) to bed only to be embarrassed in our meeting today with an ugly, idiot, ridiculous bug in the exact same code I have touched yesterday. It became clear to me that my unit test coverage can be improved.

After my normal work day I just loaded the project in VS to look at the specific test case that should have failed due to my change but, to my surprise, I had no test case for this particular scenario. Hum... stupid developer.

Lesson learned, I have written a test case before reverting the changes (and of course, I'll study the code to understand why it is required after all).

Ok, let me get back to my other pet projects.

Have fun!

Adriano

What's wrong with this code (Part XII)

2010-12-29T00:32:00.003-02:00

In the last post in this series ("what's wrong with this code") we discussed how db4o's reference system remembers which objects have been stored / retrieved.

In this post I'll show you another piece of code that doesn't always work as the developer expects:

class User
{
   public string Name;
   public User Manager;
   public IList Addresses;

   public User(string name, User manager)
   {
      Name = name;
      Manager = manager;
   }
}

class Address
{
   public string Street;

   public Address(string street)
   {
      Street = street;
   }
}  


using (var db = Db4oEmbedded.OpenFile(databaseFileName))
{
   List<Address> addrs = new List();
   addrs.Add(new Address("Street1"));
   addrs.Add(new Address("Street2"));
   User fooManager = new User("Foo") { Addresses = addrs };

   User fooBarManager = new User("FooBar", fooManager);
   User barManager = new User("John Doe",  fooBarManager);
   User user = new User("Adriano",  barManager);
    
   db.Store(user);
}

using (var db = Db4oEmbedded.OpenFile(databaseFileName))
{
   var query = db.Query();
   query.Constrain(typeof (User));
   query.Descend("Name").Constrain("Adriano");
   
   User user = (User) query.Execute()[0];
   Console.WriteLine(user.Manager.Manager.Manager.Addresses[0].Street);
}

Can you see the problem? No, I am not talking about Law of Demeter "violation" :) (By the way, if you are interested in this subject you can find a nice discussion here).

Again, if you have been working with db4o for some time I am sure you already spent some time debugging this kind of issue.

As always, the answer comes in a future post.

Have fun!

Adriano

Installing Nokia SDK on a Windows 7 box

2010-05-16T12:08:00.000-03:00

Hi

As you can figure out based on the post title, I want to start to play with Mobile development using Java (no, I haven't gave up on .Net :); it just happens that I own an N95 and I want to write a little application for it¹).

After downloading latest Nokia SDK I tried to follow the steps in the documentation (IDEs for Java Development) but I just get the infamous error:

Cannot start Series 60 SDK for MIDP

while importing the device.

Thanks God, it was just a matter of "googling" for the error message and I got the following page

http://wiki.urban.cens.ucla.edu/index.php?title=Nokia's_Java_Platform_(Carbide.j)

which fixed the issue (I just search in my hard disks and found 5 copies of the offending DLL).

Well, since my daughter has just born I guess this project will run really slowly but I hope it will not stall :)

Best

Adriano

1. I am planning to write an application that stores information about gym exercises in a db4o database.

Project deployed

2010-05-11T20:04:00.000-03:00

Hi

In the latest days I've been really busy with the deployment of the project formerly known as "baby 2.0" (by the way, the official project name is Gabriela).

Last Thursday (May, 6) my daughter was born with 4.1 Kg and 52 cm. Of course my whole family if very happy and I an my wife are very proud :)

Following you can see some pictures of her:

That's it for now (I'm gonna to sleep :))

Best

Adriano

I am not dead. Not yet

2010-03-18T20:34:00.000-03:00

Warning: Personal content ahead

I can hear someone screaming already: but it really looked like you have died! :)

Well, you know, I have been having to much ~~work~~ fun lately.

Also, more or less 7 months ago, I and my wife decided to start a new project, daughter 2.0, and since then we have been working hard to get the environment ready to the deployment (there are too many details in such projects deployment).

At this stage we can say that the project is growing as expected and that we are looking forward to the deployment date.

As always we expect the maintenance phase to consume much more time/resources than the development phase, but we are more than willing to do the required investment so the project will be able to meet its goals; after all, this is our baby :).

Last but not least, as you can see, I am actually alive :). So, bear with me! As soon as I get some spare time I'll do some more posts!

Good to get back to posting!

See you all.

Did you know ? (Part I) - Executing sub-queries

2009-08-10T17:35:00.002-03:00

With this post I want to start a series of "Did you know?" regarding programing related topics and db4o features / usage patterns that may not be well known.

As the first one, take a look in the following code:

class Address
{
  public Address(string streetName)
  {
     StreetName = streetName;
  }

  public string StreetName { get; set; }

  public override string ToString()
  {
     return "Address: " + StreetName;
  }
}

class Person
{
   public Person(string name, Address address)
   {
       Name = name;
      _address = address;
   }

   public Address Address
   {
      get { return _address; }
      set { _address = value; }
   }

   public string Name { get; set;}

   public override string ToString()
   {
      return "Person: " + Name;
   }
   private Address _address;
}

using (var db = Db4oEmbedded.OpenFile(databaseFileName))
{
   db.Store(new Person("Adriano", new Address("You know where I live")));
   db.Store(new Person("Sulivan", new Address("Monstropolis")));
   db.Store(new Person("Mike", new Address("Who cares?")));
   db.Store(new Address("Foo address"));

   IQuery q =  db.Query();
   q.Constrain(typeof(Person));
   IQuery descendantQuery = q.Descend("_address");
   
   foreach(var result in descendantQuery.Execute())
   {
      Console.WriteLine(result);
   }
}

What do you think will be the result?

Well, it will return all addresses objects that have a Person as a parent, i.e, "foo address" will not be retrieved/shown!

You can even specify constrains in both queries (getting the addresses for persons with a specific name!).

Note that this does not work for fields with value type semantics (basically any primitive value, enums [in .Net], string, etc.).

Do you have any db4o topic that, in your opinion, is commonly misunderstood and you would like to discuss? Please, let us know :)

Have fun!

Adriano

What's wrong with this code(Part XI) - Answer

2009-07-25T14:10:00.002-03:00

In this post I presented the following code.

using Db4objects.Db4o;
using Db4objects.Db4o.Linq;
using System.Linq;

class Item
{
public string Name { get; set; }
public Item Father { get; set ; }
}

public class Test
{
 private const string DatabaseFile = "wwwtc1.odb";
 private static void Main()
 {
     Item item1 = new Item { Name = "Adriano" };
     using (var db = Db4oEmbedded.OpenFile(DatabaseFile))
     {
         db.Store(item1);
     }

     using (var db = Db4oEmbedded.OpenFile(DatabaseFile))
     {
         Item item2 = new Item {Name = "Carol",  Father = item1 };
         db.Store(item2);
     }
 }
}

And asked what was wrong with it (and commenter "tehlike" got it :).

In line 20 we close the database (technically, the using statement will call IDisposable.Dispose() method on the object container which in turn will close it), reopen it at line 22 and finally add a new object (item2) at line 25.

Take a closer look in the program and you'll see that item2 references item1 which was stored in the database previously. As the documentation states (here and here), db4o uses a reference system to "memorize" which objects are known to be stored in the database (relying on object identity when checking if a given object is already present in this reference system).

When a database is opened its reference system is empty, so when storing item2 db4o will store item1 again (after all we re-opened the database, so there are no objects in the reference system and both objects are considered as "new", i.e, need to be inserted into the database), i.e, now we have 2 instances of class Item with the same contents in the database.

What can a developer do to avoid this behavior? Easy, just let the just opened object container know that item1 has already been persisted by retrieving it before referencing it from item2 :)

using Db4objects.Db4o;
using Db4objects.Db4o.Linq;
using System.Linq;

class Item
{
  public string Name { get; set; }
  public Item Father { get; set ; }
}

public class Test
{
 private const string DatabaseFile = "wwwtc1.odb";
 private static void Main()
 {
     Item item1 = new Item { Name = "Adriano" };
     using (var db = Db4oEmbedded.OpenFile(DatabaseFile))
     {
         db.Store(item1);
     }

     using (var db = Db4oEmbedded.OpenFile(DatabaseFile))
     {
         item1 = (from Person p in db where p.Name == "Adriano").Single();
         Item item2 = new Item {Name = "Carol",  Father = item1 };
         db.Store(item2);
     }
 }
}

Another possible solution (with less performance impact) would be to not close/reopen the database so item1 would be kept in the reference system and db4o would understand that it does not need to store this object again.

using Db4objects.Db4o;
using Db4objects.Db4o.Linq;
using System.Linq;

class Item
{
  public string Name { get; set; }
  public Item Father { get; set ; }
}

public class Test
{
  private const string DatabaseFile = "wwwtc1.odb";
  private static void Main()
  {
     Item item1 = new Item { Name = "Adriano" };
     using (var db = Db4oEmbedded.OpenFile(DatabaseFile))
     {
         db.Store(item1);
         Item item2 = new Item {Name = "Carol",  Father = item1 };
         db.Store(item2);
     }
  }
}

Have fun!

Adriano

What's wrong with this code(Part XI) ?

2009-07-16T15:34:00.003-03:00

Since I joined db4o I'm actively following our forums and trying to help developers to get their questions / issues answered.

Starting with this post I want to present the most recurring topics (don't know exactly how many) in the format of "What's wrong with this code".

But before we start you may be wondering where are the other parts (since this is titled as Part XI, where are parts from I to X). Well, they do exists in the portuguese posts (titled as "O que esta errado com este código (Parte ?)") so I decided to continue with the numbering schema ;)

Ok, for this first one, take a look in the following code:

using Db4objects.Db4o;
using Db4objects.Db4o.Linq;
using System.Linq;

class Item 
{
 public string Name { get; set; }
 public Item Father { get; set ; }
}

public class Test
{
    private const string DatabaseFile = "wwwtc1.odb";
    private static void Main()
    {
        Item item1 = new Item { Name = "Adriano" };
        using (var db = Db4oEmbedded.OpenFile(DatabaseFile))
        {
           db.Store(item1);
        }
  
        using (var db = Db4oEmbedded.OpenFile(DatabaseFile))
        {
          Item item2 = new Item {Name = "Carol",  Father = item1 };
          db.Store(item2);
        }  
    }
}

If you have done some work with db4o you probably will easily spot the problem.

I'll provide the answer in a future post.

Have fun!

Going to ICOODB

2009-06-20T10:27:00.002-03:00

Hi.

Next week I'll attend the second international conference on object databases in Zürich. Woow!

I am sure it will be really amazing moments; I'll have the chance to meet db4o fellows face to face again, to attend to interesting talks, to talk to db4o community members and db4o enthusiasts! Since most db4o team members will meet at Zurich we're taking the chance to discuss db4o directions also.

Of course, visiting another country (even though being a work trip) and getting in touch with a different culture will be really a great experience.

My friends knows how much I like chocolates, so I am sure I am going to get some extra weight :)

The not so nice part is that I'll have a 14 hours flight from Brazil to Switzerland and I must admit that I am a bit anxious with the latest flight news (the interesting thing is that I am almost sure I'll have some nice live pair programing session with my good friend Rodrigo while we wait for our flight).

The worst part is to be far from my wife / daughter (I'll miss my daughter's school presentation).

For those that I'll meet at Zurich, see you soon. For everyone else, see you in this blog :)

Best

Adriano

Hexadecimal Control Viewer DotNet

2009-06-19T12:03:00.001-03:00

Hi!

Some time ago I started developing a .Net application that requires a control to display hexadecimal values; considering that I could not find a suitable one (and also, that I do suffer for the NIH syndrome) I decided to write one myself.

After some time developing the application I lost interest (since I moved jobs and the main goal of the application was to make my previous job easier) and now it is kind of abandoned but I think that the hexadecimal control may be handy for some developers.

Here is a list of this control's main features:

Find
Print / Print Preview
Ranges: It's possible to specify that some byte ranges should be displayed with a specific color for instance

Selection
Cut/Past

Since the application is released under an open source license anyone can grab the sources, or, if you are interested I can add you as a developer on source forge!

Best

Adriano

Elementary my dear Watson

2009-06-18T23:29:00.065-03:00

In my last post I was talking about some issues I found while trying to automate the process of launching a web browser, navigating to a specific page and grabbing some results.

I do have a bunch of stickers with sayings: "Works on My Machine (tm)" but this time I could not even use one of them since even in my machine it refused to work :(. So, the goal of this post is to explain the reasons I got so much pain...

Since an image speak for 1000 words, here it is:

I am sure you already got it. As you can see I am running Vista x64 on my machine and, as explained here and here, when launching IE through Quick Launcher, the 32 bits version is the one that gets launched; by the other hand, when started through COM the bitness of the launcher defines which IE version gets started (32 or 64 bits).

In my case (remember, my first approach was to use a JScript script to automate IE) I was trying to start it from Windows console application (cmd.exe) that happens to be a 64 bit application. That's explain why IE insisted to offer me to install Silverlight; on IE 64 bit version I had not installed it (actually, unfortunately, as of today, Silverlight has support for this platform).

The next step was to figure out why my C# application (the one that hosts the WebBrowser control) was failing with the same symptoms. To be sincere, since I had already faced similar issues when using COM components on .Net applications in x64 machines, this one was a lot easier: Again, as explained here, by default VS sets your application to run on whichever processor architecture (regarding to bitness) you throw at it, i.e, it sets the "target platform" to "Any CPU":

That's mean that in a 64 bit machine (like mine) this application will run in 64 bit CLR, hence IE x64 being launched! Peace of cake :). All I had to do was to set this configuration to "x86". Finally my day would be a little less frustrating than I anticipated it to be.

Really fun, don't you agree?

For the next post I am planing to continue on this subject: 32 x 64 bits developer's pitfalls.

Have fun!

Adriano

Another day in a developer's life....

2009-06-15T18:12:00.014-03:00

Yesterday was a frustrating day. By the morning I started to work (pairing with a really smart friend) on an apparently simple task: to automate the process of starting an internet explorer (ie) instance, navigate to a specific page stored on the local machine, wait for some processing to finish (notified by the page) and grab the results. Having some years of experience with Microsoft technologies, mainly developing COM components, and aimed with (lack of) humbleness I started to write a jscript script to drive IE through automation, after all how hard could that that be? Indeed, the first part was really easy:

var browser = new ActiveXObject("InternetExplorer.Application");
browser.Visible = true;
browser.Navigate("http://programing-fun.blogspot.com");

I run the just finished prototype and the browser opened, navigating to the desired page. I was really happy (and thinking how I am smart). So far, so good. But things started to get weird really fast. Even having a good grasp on IE's object model (I don't know it by heart) I failed miserably to retrieve a reference to a page element:

var browser = new ActiveXObject("InternetExplorer.Application");
browser.Visible = true;
browser.Navigate("http://programing-fun.blogspot.com");
while (browser.Busy) {
WScript.Sleep(10);
}
var element = browser.Document.getElementById("some-id");

After some time we decided to give up on using jscript and switched to C#, so I created a Windows Form application to host WebBrower control (hum... someone said IE?) but we kept seeing strange behavior. For instance, the page we were trying to load hosts a Silverlight application but IE insisted that we should install Silverlight; WTF? I do have Silverlight installed !!! Well, at that time I was not felling so smart anymore; and since it was almost lunch time we decided to continue latter. When I got back to work I was determined to get it working so I did what any reasonable developer does in such situations: I decided to do something else :) and I ended up watching a screencast about how to improve the experience for users that don't have Silverlight installed; hum.. interesting. The presenter suggested to disable the Silverlight add-on (instead of uninstalling it). Great! Maybe the add-on was just disabled (due to some stricter security configuration when launching IE through automation). Why I haven't thought about this before? I started my application (C#) as fast as I could and a new browser appeared (in the same way as before), then I went to the add-on configuration dialog and voilà! There was no Silverlight add-on listed (how could I enable/disable it?) So the problem was that, for some reason, IE was not even considering Silverlight add-on to be installed (but that was what IE was trying to say me all the time no?). Then I launched IE manually (clicking on its icon on desktop) and opened the same add-on configuration dialog. This time I could see that Silverlight (and a lot of other add-ons) were installed and enabled.

Well, now I was starting to fell better :). But I still had to understand why I was getting different behaviors depending on how I launched IE. After some head screeching followed by some thinking and some extra searches I do figured out the issue, but that's the subject of the next post :) Have fun! Adriano

On test writing discipline and gains

2009-06-13T10:58:00.002-03:00

Hi.

Let's start this post with the usual disclaimers :). Actually, I have only one: Everything discussed here is related to my own experiences with unit testing and/or TDD in the last years.

In fact, I have been in contact with some sort of more formal testing procedures for some time now; in the early days it was more a desperate act trying to avoid SDD (sorry if I use potentially valid acronyms here), i.e, 'Shame Driven Development'. Since most of my code have no tests at all (other than the usual driver application that covered only the changes being applyied at the moment), it was not uncommon to have some developer, tester or even final users approaching me and complaining about some broken feature in a just released version of the module I've worked on (whence the shame). Of course the usual problems of lacking good tests were plain visible: resistance to refactor / change code, lack of confidence whether a piece of code was good enough or not, no sensible metric to declare completeness, regressions all over the place, etc.)

After understanding (thanks to my coach :) the importance of having a well developed ( one that values readability, maintainability, expressiveness, in the sense of making clear test intents, completeness, etc) test suite, finding the time and motivation to write such tests became easier. Even though understanding the benefits of having such tests, the urge to get something working, and so that it could be shown (to managers, clients, whoever), made me tempted to skip the test writing (remember, I haven't get into the TDD mind set yet, so tests were seen as a post development phase).

In these early days, most of my teammates had little or no idea of the concept of unit testing and it was hard to convice them that it worths the time dedicated to write such tests. Anyway, sometimes I took the burden upon myself and wrote unit tests (even though no time was allocated to that). Of course everybody noticed that my code was less buggy and that I was less concerned aboud changing it :)

Some years have passed and even though doing my best to start my coding sessions with a test I must admit that I am not a TDD practitioner yet, at least not in the strict sense of the definition. This becomes clear when it comes to my personal projects: most of them have no tests at all :(.

But thanks to some embarrassing episodes (related to one of these personal projects) (and to my coach :) I had finally decided to do "the right thing^(tm)" and I am writing the tests I should have writen long before :) (guess what, I've already found hidden bugs). I am even using a nice mock library for .Net called Moq.

Of course I am starting to see the pays off of pursuing this goal :)

Best regards (and have fun!)

Adriano

How to not ask for help on online forums

2009-06-10T21:46:00.000-03:00

Hi.

Well, you know, being a software developer automatically entitles you as your "family IT manager"; there's nothing we can do about it:). That's the way life is.

But if you are involved with an open source project chances are that you participate in that community either asking or answering questions (or both) in project's forums, mailing lists, etc. In the following lines I want to present some points I believe may make the difference between getting an effective answer or getting your question forgotten in some dirty corner in the internet.

Screaming for "help" like the good girls on movies is not effective.
Don't expect people to do our work. Don't get me wrong, but how many times, for whatever reason, we just cry for help without even trying to figure the problem out first?
A simple search in the internet before asking will at least allow us to be more precise or even eliminate the need to ask at all (chances are that someone else already faced the same problem/doubt we are facing). In the open source world there are lots of different places we can look for more information, for instance:

Project forums
Bug tracker / Issue system
Mailing lists
Source code (why not :)
etc.

Focus on what you are trying to achieve not in the problem: consider the possibility that you may be attacking the wrong problem.
Provide as much context as possible:

Calling your mechanic and saying: "You know what? may car isn't working" is a little bit vague and won't be that helpful. Probably saying: "I turn on the ignition but nothing happens" would be a little bit better (but not that much); providing more information, something like: "I checked it out and I can see that I am not out of gas; also I can see that the battery looks to be ok, but when I try to start the engine nothing happens other than the indication lights turning on" would be much better. I think that you got the idea :)
Environment (software version, etc)
If you have a stack trace, please, don't hide it from your buddy.

Be friendly (in general people is earn nothing, other than personal satisfaction, by helping you). Above anything, don't behave as if the person trying to help you had the obligation to provide you an answer/fix.
Reproducible behavior is a lot easier to debug / fix, so, if possible, prepare the smallest test case that triggers the problem. Even better, if you really want to rise the chances of people helping you, use the same test framework used in the project.

I do believe these "principles" apply equally well whenever you are about to submit a new bug/issue report to your favorite project bug/issue track system. I mean, I doubt that filling such systems with duplicated and/or misleading, inconsistent, etc. entries will help anyone in making a better project.

So, next time we fell compelled to ask for help let's refrain ourselves and first try a little bit harder; I am a fierce believer that this is the best way to learn (trying to fix it ourselves instead of just asking); as a side benefit we'll not disturb other developers letting them to use their time to improve the project instead of scanning / answering questions that was already answered before.

Last but not least, I don't want to give the false impression that I am against asking for help; I just think that we ought to leave this approach as our last resort, i.e, to situations where it's really not possible to figure out the problem alone (for instance, when a specific behavior/API/whatever is not documented and no information can be found, at least not easily found).

Of course this is not an exhaustive list, so, feel free to comment :)

Best regards (and lets have fun !)

Adriano

Db4o with Visual Studio 10 / .Net Framework 4

2009-03-23T17:51:00.000-03:00

Hi.

When Microsoft announced they would make available VS 2010 CTP I got curious about how easy (or hard) it would be to compile / run Db4o and also how OMN would behave in this early CTP (would it just work, without even require a recompilation? If not, how easy/hard it would be to make it work if possible at all, etc).

Well, yesterday I managed to download the CTP; after extracting the files (24 Gb!!) I just took OMN 2008 installation and give it a try. It was really amazing. The only change I've applied was to update the file %ALLUSERSPROFILE%\Application Data\Microsoft\MSEnvShared\Addins\OMAddin.addin in order to change the target VS (OMN 2008 will set it to 9.0 but VS 2010 is 10.0).

After this change I just fired up VS and OMN addin was there, working with no issues (as far as I tested :)) as you can see in the screen shot bellow. Cool.

Next step was to load Db4o 2008 solution file; VS 2010 asked whenever I'd like to convert the solution/project files to the newer version; I just consent to that and when it finished converting I just run Db4o Tests.

This time some tests failed due to missing jars (I didn't run a full build) required to run Java/.Net compatibility tests; besides that expected failure, only one test failed (I just disabled it for now).

My next steps will be:

Try to understand / fix the falling test.
Prepare the environment to at least run the target "build-before-checkin" defined in build.xml (and uncomment any test commented out to make the tests pass).
Reason whenever it makes sense to use some of C# 4.0 / .Net Framework 4.0 new features (for instance dynamic types) and how Db4o handle them.

Since these will require more time to investigate / test I'll leave them for a forthcoming post.

Adriano

Benefits of working from home - Epilogue

2009-03-21T16:46:00.000-03:00

After 9 posts in this subject (BTW, I have written this post long ago) I am going to finish it... and the big question is:

Did it worth?

Well, to answer this question I pondered on various aspects: It allowed me to move to a smaller city, closer to my wife's parents, a less violent, less expansive city, etc; it gave me the chance to spend more time with my family and a lot more benefits!

So, IMO it really worth the move! Even missing some "usual work style", I am pretty happy working with very smart people, in a really cool product, applying really nice development methodologies and last, but not least, being able to organize my own time :).

I don't know how long I'll be working with these stunning guys, but I do hope I could be there for a long time ;). There's just so many things to learn yet!

That's it ;)

See you all.

Adriano

Automating Skype through COM

2009-03-10T19:00:00.002-03:00

Wow.. finally a technical post again :)

Those of you who knows me knows that I am a firm believer of component technologies.

Personally I really appreciate Microsoft's COM technology; ok, it does has it drawbacks (as everything in life) but when used correctly it proved to be a very powerful way to support software automation and extensibility. Let me briefly explain what those funny words means for those who don't know yet.

Basically, software automation is the process of a software controlling another one. For instance, if you have Microsoft Office installed it's possible to write a program (even a JavaScript script) that creates a Word Document through automation, i.e, your program may "control" word (and Excel, Power Point, etc). This kind of flexibility can be very helpful in some scenarios.

By extensibility I mean ways of extending a given application. A good example is Windows Explorer; it's possible to add new items to a context menu (in the same way 7-Zip and many other applications do) simply by implementing an specific COM interface (and registering your component of course).

These are just 2 examples of what's possible; of course other softwares also support some level of automation (for instance Adobe Acrobat).

In this post I just want to talk (again, briefly) about Skype and how it's possible to extend it through COM (Skype also supports automation through Java, XXX, etc).

First let me just explain that the possibilities are infinite; what you may want to do with automation is not my business :); all I can say is that if you think a little bit you'll be able to find some nice use for skype automation.

For instance (as I said in my last posts) I use Skype heavily on my work to communicate with other team's members. At least once per week we do a Skype meeting in order to decide what we're going to do in that week; to manage these tasks we have a "queue" of tasks in our Jira installation.

One annoyance during this meeting is that once someone decide he wants to take a specific task the process involves at least 2 steps: to announce in the chat meeting and going to the browser to update Jira.

Since it's possible to automate Skype I wrote (to be more precise I am debugging it right now) a "plug-in" that simply keeps listening all chat messages and react accordingly for specific patterns; for instance if I want to take a task (let's say TSK-1) I may just type:

$jira assign TSK-1 myself

This way I announce to the team and update Jira at once :) (I don't need to go to the browser anymore)

The plugin is "smart" enough (through configuration) to figure out who I am ("myself") and to go to Jira (through a WebService) and update the specific issue (task).

And this is only a basic example about what can be done (the sky is the limit :).

For more information about Skype automation visit https://developer.skype.com/.

If you want to take a look into this plugin, just grab the code at: git@github.com:adrianoc/binboo.git or browse the code online at https://github.com/adrianoc/binboo (just keep in mind that there're lots of assumptions/dependencies to our Jira installation but I guess one can learn a lot about how to integrate to either Jira or Skype).

See you.

Adriano

WIX Tips

2009-01-21T23:38:00.000-02:00

Hi.

Since I have been playing a lot with MSI installers latelly and I'd like to share two tips with those authoring Windows Installers with WIX:

You can get a lot of information by running your installation package through msiexec:

msiexec /i CustomAction.msi /lvx log.txt

The command above just runs CustomAction.msi logging everything including the kitchen sink :)

You can use 7Zip to open msi files (and ofcourse, extract content from it)

Happing programming ;)

Adriano

First impressions of Windows 7

2009-01-07T21:01:00.008-02:00

Hi,

As a computer addicted I decided to download Windows 7 Beta 1 (32 bits) and give it a try (if you are interested, just search for "Windows 7 Beta1" in your favorite search engine and I am sure you'll find your way :)

In this post I want to present my first impressions about it. Please, note that I am not an expert in this subject and also that this is just my opinion based on my perception without any pretension regarding "data" accuracy.

I need to admit that I am impressed about it. My first impression is that it is way faster than Vista when running on the same machine; at least it is pretty responsive. Bellow you can find a list of items that caught my attention and won my respect (at least for now):

Fast Installation: ~ 20 min for a full install.
Few prompts during installation.
No problems with device drivers at all (Video, audio, keyboard, etc)

Some devices already have preliminary versions for Windows 7
I guess that this is more a result of not introducing deeper changes to the driver model (Vista introduced really deep changes there).

There are some compatible antivirus already.
Looks really fast on a relatively old hardware
I really liked the UI changes (even being minor changes).
Just a few UAC prompts

Using it for some time I have seem UAC prompts only for software installation.

IE 8 is not as fast as I'd like it to be. (But I've already installed firefox)

Bellow you can see a screen shot.

Well, that's it for now.

Adriano

Storing PowerShell objects into a Db4o database

2009-01-07T20:55:00.000-02:00

Hi,

First of all, Happy New Year :)

If you use both PowerShell and Db4o you maybe interested in this post.

Best

Adriano

Benefits of working from home - Part IX- Infrastructure

2008-11-21T19:50:00.000-02:00

In this post I described how using my computer in my home office was the first time that I'm getting a direct return on my investment.

In this post I'll take a look in the other side of the coin: the investment in infrastructure.

When my home computer used to be only that, i.e, my home computer, I had no hard requirements to keep it up to date. I could simply update it each 5 years or more if I wanted to; also, my internet connection need not to be very fast; the same applies for my desk; it could be very ordinary as I didn't spent a lot of time in my computer.

Of course, being a computer/programmer addicted as I am, shortened my computer's update cycle for something between 2 ~ 3 years, and

internet connection, you know: you never get enough bandwidth ;)

By the other hand, using my computer to work pushes it to its limits... and of course, each minute I spend looking at the hour glass represents a minute less with my family (or my Wii :) so I want to wait the lesser amount of time possible in front of it.

Just to put some numbers, the first time I run db4o build on my machine it took more or less 1 hour to run to completion (mostly running tests). I just couldn't believe that. My machine was not a top one but it was not so old/slow either. After a lot of tweaking I managed to get the build running in 15 minutes but that required some $$$ (nowadays, even with a new machine tests take 20 ~ 25 minutes to run due to lots of new tests).

Also, I never considered (or had the requirement to) run 2 VMs, 2 Visual Studio (one in one VM and another in the host OS), Eclipse and some other apps at the same time. So now, 2Gb of memory doesn't look that much anymore.

Another important aspect that will have great impact on your productivity/health is the overall quality of your office furniture: remember when you used to complain about your boss not willing to spend a few extra dollars on a good chair for you? I certainly remember myself complaining with mine :( Of course you don't need to go out and get the best chair in the world, but make sure you'll not get a "not so good" one only to save a few extra bucks either (If you are going to spend more than 4 hours seated I do recommend you to get a very good one - for instance, this one).

Well, that's not the end yet; telecommuting meant also that I became my own IT department ;). Not that I have any problem fixing my computer, installing software or whatsoever; the really big point is that all these maintenance work takes time (and time is money) and also that the burden to keep everything working is on me (to be fair, I'd rather be the one in charge for this task than to let someone else doing it anyway).

Last, but not least, consider having "hardware" backup; I mean, what are you going to do if next morning when you turn your computer on it don't actually turns on? Of course you do have backups of your important data (don't you?), but what about your hardware? How long it will take to be fixed? Are you willing to spend time on fixing it? Or do you have another computer that can be used so you can continue to work while someone else fixes it for you.

In the end of the day, you'll need to put some money on your office / infrastructure, so don't forget to take this into account.

That's it.

Bear with me ! We are approaching the end :)

See you

Adriano

Changes in Db4o configuration.....

2008-11-17T11:30:00.002-02:00

Hi,

If you take a look in our svn repository you'll see that lots of changes were applied to configuration code (starting with version 7.7). Take it easy, we kept the "old" configuration interface in place; we just deprecated it, so update your code to use the new interfaces if you have the chance ;)

In this post I'd like to discuss some of these changes.

New, specific, factory classes

Do you remember Db4oFactory OpenFile(), OpenServer() and OpenClient() methods? We decided to move them to more specific factory classes:

Db4oClientServer
Db4oEmbedded

This way the boilerplate code used to open an embedded database changed from:

IObjectContainer db = Db4oFactory.OpenFile("MyData.odb");

to:

IObjectContainer db = Db4oEmbedded.OpenFile(Db4oEmbedded.NewConfiguration(), "MyData.odb");

As an additional benefit now we use the same class in both platforms (Java/.Net) (Remember, we used to have Db4o.openXXXX() for Java and Db4oFactory.OpenXXX()for .Net).

Configuration interface split in File / Network / Common

We are applying Interface Segregation principle to configuration, so, now related configuration options are close together in specific interfaces.

For instance, all embedded related configuration lives in IEmbeddedConfiguration. But we didn't stopped there. We went a step further and broke common functionality in more coarse grained interfaces. For instance, there are configurations that do apply to both embedded and client server modes. So we introduced the concept of Configuration Providers which sole purpose is to help to aggregate configuration into specific interfaces, so it's easier (at least in our opinion :) to identify which configuration applies to each db4o mode and also make it more clear which aspect of db4o are being affected by that configuration.For instance:

IEmbeddedConfig config = Db4oEnbedded.NewConfiguration();
config.File.ReadOnly = true;

In this sample there's no space for doubts that ReadOnly configuration relates to a file system aspect of an embedded database.

That said, we basically partitioned configuration into four categories:

Embedded
Server
Client
Common

No more "default" configuration;

Suppose your application, at some point, requires a Db4o database with an activation depth configured to the highest possible value (in most scenarios this is not recommended) so you use some code like this:

IConfiguration globalConfig = Db4oFactory.Configure();
globalConfig.ActivationDepth(Int32.MaxValue);

using(IObjectContainer db = Db4oFactory.OpenFile("test.yap"))
{
/* Use the database */
}

So far, so good. Now, in a completely different point in your application you need to open another Db4o database and so you just type:

using(IObjectContainer anotherDb = Db4oFactory.OpenFile("test1.yap"))
{
/* Use the database */
}

This new database ends up configured to fully activate objects! Even knowing that you should avoid configuring activation depth this way (you did your homework, right?) it's possible to do it by accident.

The problem is that it is relatively easy to mess with configuration.

That's the reason that now, all OpenXXXX() methods (in the new factories) requires a configuration to be passed through!

We are considering reintroducing the original signature methods but with different semantics; instead of return a clone of the global configuration we can return a fresh configuration object populated with default values so developers can be sure about what configuration they get!

To wrap up the session on configuration I'd like to present a short "cheat sheet":

Emdedded	Old	Db4oFactory.OpenFile("dbfile");
Emdedded	New	Db4oEmbedded.OpenFile( Db4oEmbedded.NewConfiguration(), "dbfile");
S e r v e r	Old	Db4oFactory.OpenServer("dbfile", port);
S e r v e r	New	Db4oClientServer.OpenServer( Db4oClientServer.NewServerConfiguration(), "dbfile", port);
C l i e n t	Old	Db4oFactory.OpenClient( "dbfile", port, "user", "pwd");
C l i e n t	New	Db4oClientServer.OpenClient( Db4oClientServer.NewClientConfiguration(), "dbfile", port, "user", "pwd")

ExceptionsOnNotStorable is turned on by default

That's (IMHO) really nice. I don't like to just pretend that classes are storable on Db4o and let customers struggling trying to figure out why their applications doesn't work when we could follow fail fast principles and let they know that one or more classes may have problems as it is.

Use of properties in .Net

That's mean more natural code style for .Net developers :). Now, instead of saying:

config.OutStream(Console.Out);

you will write:

config.OutStream = Console.Out;

We are aware that there other places where using properties instead of methods (or even using a different approach) would make more sense (on .Net of course) but we just don't have the time to improve them now. But you may be sure we'll do our best to keep improving both .Net/Java developers experience.

That's it!

See you.

Are you a C# developer?

2008-11-05T10:52:00.000-02:00

If so, you should go and grab a copy (for free) of CodeRush Xpress for Visual Studio!

(I already own a copy of another addin, but I'll give it a try anyway :)

Adriano

PDC 2008 Videos - For free!! :)

2008-11-02T11:36:00.000-02:00

Hi.

Are you a Windows developer? Or simple a Windows enthusiast? So you probably is aware of Microsoft PDC 2008.

I'd love attend it but I couldn't :(

At least we can grab (all?) Microsoft PDC 2008 Videos.

Have fun!

Adriano

Benefits of working from home - Part VII - Alone in the office

2008-11-02T10:00:00.000-02:00

With this post I'll stop talking about the advantages of working from home and start to discuss some of the drawbacks related to this way of work.

(sorry for the subject, I just couldn't resist :)

Note that some points that I first took as an advantage may appear again, but this time, with a focus on possible disadvantages; this doesn't mean I've changed my mind (what I would say is perfectly normal); its just the other side of the same coin.

I'll start with the most problematic one (at least in my case), working from home meant to loose almost all contact with my friends and coworkers. I remember it perfectly when I was being interviewed (through skype) and I was asked how I felt about working alone, 8 hours per day; honestly, at that moment I did think it would not be an issue, but sometimes it is a little bit lonely.

Since I was not bound to an office anymore, after 4 months we (I and my wife) decided that the time to move to a quieter, safer, less violent place had come, so we moved from São Paulo to Londrina; you see, most of my friends still live in São Paulo and even having some (good) old friends (and my wife's parent) here in Londrina I somewhat miss personal contact.

Another important aspect of working from home is that all discussions (at least in my case) are done through some IM software (be it skype/msn/etc) and this is considerably harder to do than when you are engaged in a face-to-face talking.

It's enough for the first "not so good" series... let me play a little bit of "Star Wars" on my Wii ;)

See you.

Adriano

Benefits of working from home - VI - Mange my time

2008-10-30T23:20:00.000-02:00

Hi,

Have you ever needed to ask (embarrassed) your boss to let you leave early so you could go to the doctor or to address some personal issue?

Well, not have to do this is another benefit of working from home :) as (usually) you are in charge of managing your own time!

Of course this is not an "all or nothing situation". Even when I had a "traditional" job my bosses were kind (or intelligent) enough (I bet they were both :) to let me deal with my personal issues during my working time if that were necessary.

My point is that nowadays all I have to do is to get organized so I don't miss any meeting, pair session and/or a dead line and everything is fine :). It's even better as I can choose the best time (a time in which I'll get less traffic, that is not to hot, etc.) to do my personal stuff.

Thats it! Even though being far from a comprehensive list of the advantages of working from home, I finally reached the last (but not least) advantage I wanted to blog about. In the next posts I'll talk about some drawbacks.

Do you have any other advantages in mind? Please, share with us!

Best,

Adriano

PDC Talk: The future of C#

2008-10-30T08:34:00.000-02:00

Hi!

A very interesting PDC talk (by Anders Hejlsberg) about the future of C#.

As a teaser, just some subjects covered in the this talk:

More dynamic constructs
Optional / Named arguments
Concurrency

If you work with C#/.Net you can't miss this one!

Adriano

Never give up

2008-10-22T16:57:00.007-02:00

At least this seems to be the main approach of hackers.

In the last couple weeks I received at least 7 messages from the same sender, with the exact same contents:

It's in portuguese (at least) and says something like: "Hey dude, here are the photos!".

What photos? I don't remember asking any friend called "gabriel" to send me any photo ;) even more with supposedly annexed photos linked to files like "fotos_237.com" on a very suspicious server (at least the guy wrote my name correctly)! No thanks !!!

In this same time range I got other "phishing" emails like:

Another email in Portuguese, pretending to be from hotmail trying to foolish me to get in panic and click on a link.

This one (also in portuguese) is supposedly a "Virtual Card" from a girl named "Carla". It even includes a "copyright" notice in the end of the email.

Well, maybe may mommy would be tempted to clink on these links but not me. Anyway, this kind of threat is getting more sophisticated as time passes so pay attention where you put your mouse :).

Best.

Adriano

Hug a developer :)

2008-10-21T10:15:00.000-02:00

You need to see this!

Really amazing :)

See you.

Adriano

Benefits of working from home - Part V - Show me the money

2008-10-17T17:01:00.002-03:00

Wow.

I've always the feeling that my investment in computer hardware/software was somewhat a waste of money; you see, usually I get a pretty descent machine and stick with it for at least 3 years; so every 3 years I spend a lot of money to get a new one and I didn't get a direct return from my investment (not to mention that most of the day it keeps turned off), and to be fair, I should take internet connection fees into account.

Since I started working from home I may say that this is the first time I am getting a direct¹ (and measurable) return from this investment. It's even better, now it's easier to justify new hardware, software and other gadgets to the financial department, i.e, my wife :).

In other words, now my computer generates income and I feel compelled to invest more money to keep it up to date.

Adriano

¹ I mean, direct, because I always studied a lot in my home computers so, at least indirectly, they always gave me a financial return (even tough it is hard to measure how much return I got).

Running Sharpen tests faster...

2008-10-15T21:00:00.009-03:00

As you probably already know :), Sharpen is a tool (developed by db4o) that aims at easing development efforts by translating java source code into C#. This tools make it easier to provide native solutions in either Java/.Net platforms.

While talking about how to run Sharpen test suite in this post I told that I'd show how to improve these tests startup time.

After a long wait, here it is. So let's go.

If you tried to run Sharpen tests you probably noticed that whenever you launch them a new Eclipse instance starts also (with it's full GUI) and this is one of the culprits for these tests to take longer than necessary to run. The good news is that it's (relatively) easy to configure Eclipse to not display any GUI at all (since all feedback will be given through the main Eclipse window).

To do this, once you checkout all required projects from db4o SVN, just Right Click sharpen.ui.tests project and select Run As / Run Configurations menu.

Now, in "Run Configuration" dialog, right click on "JUnit Plug-in Test" and select New.

If you followed the previous steps, "Run all tests ...." should contain the right value (sharpen.ui.tests). Just make sure that you have the latest JUnit selected on "Test Runner" dropdown.

We are almost there... :)

The next step is to click on "Main" tab (1), then select "Run as Application" checkbox and select "[No Application] - Headless mode" in the dropdown (2) and finally, click "Run" button (3).

That's it :)

Notice that now sharpen test suite starts faster.

Many thanks to a great friend (Rodrigo) for sharing this information with me.

See you.

Benefits of working from home - Part IV - DIY

2008-10-13T20:30:00.001-03:00

Hi!

How many times a developer approached you to ask something he/she could have easily find by himself have he/she bothered to spend 10 minutes to do a google search?

And let's be fair, how many times you feel compelled to do the same? I have to confess that even being a firm believer of "search before asking" principle, sometimes I do find myself doing the opposite: asking before looking for information.

And this lead us to this post subject: Working from home gave me more incentive to do "the right thing™" :), i.e, to look for solutions prior to asking the guy next to me - after all there's no such thing as the "guy next to me" :)

At db4o we do exchange lots of information/knowledge but since we are not at the same room (and in most cases we are at different timezones also) it's more practical to do a quick search and try to fix/solve issues by myself. Only after spending some time in my own research I think about asking the gurus.

This attitude (searching before asking) leads to a better understanding of the subject and other developers will not be interrupted to explain. Of course (IMHO) there are times (and subjects) that requires someone with more knowledge to guide other developers.

Anyway, I do believe that the process of explaining some subject may help you to get more insight about it and I do appreciate helping other teammates to improve their knowledge (Nowadays I'm learning more than helping :).

What do you think?

Adriano

Benefits of working from home - Part VIII - Working Time

2008-10-11T10:06:00.000-03:00

One really great advantage (IMHO) of "traditional work style" is that usually you have very clear separation between work time/free time. Basically your working day finishes as soon as you get out of the office (ok, I known, in development, many times the solutions come to our heads at home :).

Working from home is a very different experience and you can find yourself working a lot more than you'd expect/are willing to :(. The problem (again, IMHO) is that it's hard to separate the matters; you see, the work is there, you are there, and the rest you can guess.

Of course other factors like your productivity, how your manager and you decide on what to do and how long it is expected to last, etc. also plays an important role and can turn your working experience more pleasant or more like a nightmare.

In my specific case, I participate in deciding which tasks I'll be working on every week so I am the only one to be blamed when my working days extends a little bit.

And theres an aggravating factor: I am kinda addicted to computers/programming and sometimes I get so excited to see the outcome of my code that I can't just stop :)

So if you are going to work from home, pay attention to these pretty common pitfalls to avoid getting trapped into them.

See you.

Adriano

Benefits of working from home - Part III - Time efficiency

2008-10-07T19:32:00.001-03:00

In my last post I was talking about not being required to commute to work and I pointed some related benefits.

Today, I'm going to talk about some more benefits (directly related to the previous one), so let's go.

As I explained in the previous post I used to spend 2 hours in traffic; well, since I started working from my home this was not an issue any more and not wasting my time on traffic jams made it possible to do other things (like sleep more, post more frequently, etc. :) and spend less money with gas, but (IMHO), more important than all, it made it possible to spend more time with my family.

Prior to joining db4o, I used to wake up at 7:00, take a short breakfast and drive to my work so I rarely joined my wife/daughter at breakfast. At lunch time I was not with them again (since it would take me 1 hour to go to home and another one to get back).

Now, even though I usually wake up at the same time, instead of having a (lonely) fast breakfast and going to my work I just go down to my office and start working (usually I put may email/web reading up to date) then 1 hour latter my daughter wakes up and we (I, my wife and my daughter) can have breakfast together. Them, at lunch time, we can have lunch together again :)

Pretty nice!

At the end of the day when my daughter returns from school I'm finishing my working day and we can spend a little more time together.

Well, as an interesting tv ad says:

Have a good breakfast: U$ 20,00; getting out to have a good meal: U$ 50,00; to be with your beloved ones at these moments: has no price! :)

See you!

Adriano

Back to Vista x64

2008-10-05T14:10:00.000-03:00

Hi,

Some time ago (sometime around 10/2006) I installed Windows Vista (a release candidate at that time) on my home machine in order to "try" it (to be sincere I've installed various Vista beta/release candidates).

Performance was not impressive but since I'm a software developer (and I didn't used the machine to work anyway) I decided that it worths to be able to experiment with new API / functionality so I kept it.

Some time after that it was released so I got a copy and installed in the same machine.

On 10/2007 I joined db4o and started to work from my home which means that my machine now plays an important role in my development productivity and I decided that I'd rather go with Windows XP (x86 or 32 bits) again (due to the performance impacts I got with Vista x64).

Well, one year passed and I got a new machine (a pretty fast one, lets say) and so I decided to give Vista x64 a try again.

In the first days I do got some BSODs (which made me feel frustrated) but after spending some time searching I found some suggestions regarding memory configurations; after applying such changes (I just set the times after memory manufacturer specifications and increased memory voltage by 0,1 volts) it became stable (no BSOD since them).

I can say that I'm satisfied up to now; no hardware or software conflicts, performance is pretty good (much faster than my previous machine running Windows XP - I know, XP would run even faster on this machine).

See you.

Adriano

Benefits of working from home - Part II : No need to commute

2008-10-03T18:00:00.004-03:00

In the previous post I just said I'd think aloud about advantages/drawbacks of working from home.

Let's take the half-full approach and present the advantages first starting with not needing to commute.

Well, before joining db4o I used to live in São Paulo - Brazil, so this point is pretty easy one ;)

Anyone that knows just a little bit about São Paulo knows that it has a very bad traffic! Usually, in the days that the traffic was not that bad, it used to took me no less than 1 hour from my house to my work place (and I was fortunate enough to not live that far from my job). So 2 hours of my life was spent in a car every day.

Also, not being required to commute (and so avoiding traffic jams) made my expenses with car maintenance drop a little bit and getting involved in a car crash less likely.

As a bonus of not commuting I don't have to find a place to park in a, usually, crowed place :)

So, IMHO this is a huge advantage.

The next post will be closely related to this one but I'll talk about my working time.

PS: Do you work from home? What are your opinion about the subject?

See you!

Adriano

Benefits of working from home - Part I - The dream job

2008-10-01T18:17:00.012-03:00

As I posted here, some time ago (to be more precise, exactly one year ago) I joined db4o and started to work from my home; that was not an easy decision/move but (thanks God and some really good friends also) I took it.

Since one year has passed, I think it is a good time to review this journey and rethink whenever its paying off or not.

In the next posts I'll discuss (shortly) some advantages and some shortcomings (from my point of view, of course :) regarding working from home. The order in which these topics are presented has no particular meaning.

Keep in mind that my opinion is largely influenced by the place I live in, the environment I am inserted into and the kind of work I am involved with, so, what I see as an disadvantage you may well see as an advantage :). Don't worry, we are not supposed to agree on everything.

Another important point is that some teleworkers (as people that work from home are called) usually do work "part time" in a real office; that's not my case; I am working 100% of the time from my home and the nearest fellow is at least 100 Km (and the others are 1000 Km) away.

To start with, here are a couple of interesting articles to read.

Hope you find this information useful/fun :)

See you.

Adriano

[edit: added link to following posts]

This post

DIY

Here we come again :) - Part III - The end

2008-09-10T17:25:00.004-03:00

Well, after some time researching and comparing prices I've ordered my new toy with the following configuration :

Component	Detail
Motherboard	GIGABYTE GA-EP45-DS3R
Processor	INTEL Core 2 Quad Q3300 2.66GHz 12MB 1.333MHz
Memoty	8 Gb - OCZ DDR2 800
Cooler	Cooler Master Vortex
Power	550W - Corsair
Keyboard	Microsoft Wireless Desktop 2000
Video Card	Geforce XFX 9600GSO 384MB
HD	750GB Samsung

I do hope that this machine can keep up with my needs ;) Also, I ordered a really big (at least for my standards) monitor .... Now I need to wait more or less one week to put my hands on this and starting installing (probably Windows Vista x64 and some Linux x64 distro also). OMG, I am to anxious! Adriano

Extracting files from a MSI file.

2008-08-11T12:09:00.005-03:00

Today I was looking for a way to extract files from a msi installation package when I found a blog just explaining how to do it:

msiexec /a filepath to MSI file /qb TARGETDIR=filepath to target folder

Despite the original blog title it does work with XP :) Adriano

Here we come again :) - Part II

2008-08-04T13:51:00.009-03:00

Just a little bit more information on my new toy (the one I am planning to get)

Component	Detail
Motherboard	GIGABYTE GA-EP45-DS3R
Processor	INTEL Core 2 Quad Q9450 2.66GHz 12MB 1.333MHz
Memoty	8 Gb - G.SKILL DDR2 800
Cooler	ARCTIC COOLING Freezer 7 Pro
Power	550W - Seventeam
Keyboard	Microsoft Wireless Desktop 2000 Optico
Video Card	Geforce XFX 8600GT 256MB
HD	750GB SEAGATE

Even not being the fastest possible configuration it is a pretty good one :) Why did I need such a beast: Well, working as a software developer sometimes I find myself running Eclipse, Visual Studio as well a guest OS within Virtualbox (running VS and some other programs there also ;). So I do believe (I'm not a expert in hardware) that a 4 core processor will be helpful; in the same way, 8 GB of memory doesn't seem that much :) I considered to get a WD Raptor but it's too expansive here; also, I'll install 2 other HDs (that are sitting in my current machine) so I'll get some performance gains due to a more distributed load. Do you have a raid 0 configuration? How does it perform? Is it reliable? Right now I am considering to build a Raid 0 array also but I'm not sure. My past experience wih Raid 0 was not so good. Adriano

Here we come again :)

2008-08-01T16:21:00.001-03:00

For some time now, my computer started to give me signs that its time is coming. It's a pity since it is only 2 years old and has a not so bad configuration. For me, it's always a dichotomy between a pain and a pleasure when I need to figure out a new configuration. Should I go for a brand computer or should I build it myself? Should I by the latest/fastest/expansive(est) :) processor/memory/whatever (in a useless try to protect my investment) or should I stick to more affordable parts? Please, keep in mind that I live in Brasil and here computers are not so cheap as in some other places. Anyway, just for fun, I am dumping all my previous computer's configuration along side my wishes for the new one:

Year	Processor	Freq.	# Core	RAM	Hard Disk	Graphics Card	Internet
1989	6502	0,75 Mhz	1	256 Kb	NA	OnBoard	NA
1992	Ciryx 486 DLC	40 Mhz	1	4 Mb	100 Mb	Trident	NA
1996	Pentium 100	100 Mhz	1	16 Mb	1.0 Gb	?	28 Kbps
1999	Athlon 400	400 Mhz	1	128 Mb	30 Gb	4 Mb	56 Kbps
2002	Athlon XP 2.1	1.8 Ghz	1	512 Mb	60 Gb	AGP 64Mb	350 Kbps
2006	Athlon 64 3.8 X2	2.0 Ghz	2	2.0 Gb	370 Gb	PCI-X 256Mb	2.0 Mbps
2008?	Core 2 Quad 9XXXX	> 2.50 Ghz	4	8.0 Gb	500 Gb	PCI-X 256Mb	6.0 Mbps

Well, what can I say? Current PC, RIP :) What do you think? Adriano

My mind is about to blow

2008-07-23T17:09:00.004-03:00

Hi. That computer technology evolves day by day and the amount of information in this area is gigantic many of you already know (so do I), but today I was talking to a friend of mine and I realized how many books I want to ready (only in the subject Windows + .Net). If you are curious you can see the list here but most of them were not published yet (and here you can find a list of some books I've already read / I'm reading). What do you think about them? Is there any other book related to .Net / Windows development you consider a must? PS: Feel free to give some of them as a gift when they get published :) Adriano

Implications of instrumenting assemblies for Transparent Activation / Persistence in db4o - Part I

2008-07-17T09:32:00.002-03:00

Hi, Just to let you know I've posted about Transparent Activation / Persistence to db4o blogs ;) Adriano

An interesting video on C# 4.0 design discussions

2008-07-16T23:45:00.002-03:00

C# 4.0: Meet the Design Team Have fun Adriano

Another one in the obscure codding practices ...

2008-07-15T18:06:00.005-03:00

As I said in this post, today I've found an interesting site about C++ programing practices. While reading this pages I learned another way to write a fragile application (as always, writing bad code is enough :) So, let's go for it! What will be the output of the following program?

void main(int argc, char* argv[])
{
  int n = 255;
  size_t size = sizeof(++n);
  printf("%d", n);
}

Maybe this be can pretty obvious to you, but it was not to me (maybe because I avoid to write obscure code as much as I can :) Adriano

CERT C++ Secure Coding Standard

2008-07-15T09:13:00.004-03:00

Hi. Today I reached this page (on cert.org) site talking about C++ secure standard practices. I haven't read it to the end yet but at a first glance it looks pretty interesting (and useful) to me. Wait, don't call yet!! There's a page regarding safe practices for C also! I'll be reading this as soon as I get some time to ;) Adriano

What is wrong with this code?

2008-07-02T23:38:00.004-03:00

I was reading some blogs this week and find an interesting story related to references in C++ (and as it has some time that I don't work/post about C++) so I decided to post about it. Take a look in the code and try to answer the following questions below:

#include "stdafx.h"
#include "stdio.h"

class SimpleClass
{
public:
SimpleClass(int n)
{
   value = n;
}

void FirstMethod(TCHAR* str)
{
  wprintf(str);
}

void SecondMethod()
{
  wprintf(L"Value: %d", value);
}

private:
int value;
};

void Test(SimpleClass &ref, int i)
{
switch(i)
{
  case 1:
     ref.FirstMethod(L"Hello world\r\n");
     break;

  case 2:
     ref.SecondMethod();
     break;
}
}

int _tmain(int argc, _TCHAR* argv[])
{
SimpleClass *p = 0;

Test(*p, 1);
Test(*p, 2);

return 0;
}

Will it compile? run?
What would be the outcome from Test being called in line 39?
What about line 40?
Is there any other issues?

(PS: VS 2008 compiled it with no warnings....) Adriano

Do it yourself

2008-06-29T08:06:00.001-03:00

Hi, I'm a strong believer that the DIY (Dot it yourself) philosophy helps to improve knowledge on the topic you are working on. So if you If you are a developer using (or planing to use) db4o (and have the time), I highly recommend to try do build it yourself as explained here. One point that can be further explored is the possibility to run the tests on a ramdisk in order to improve performance (in may machine I get an improvement of 20%). To be able to do this you need to create a ramdisk (personally I use this one) and them set 2 properties in our machine.properties file: java.vmargs=-Ddb4ounit.file.path=DIR -Djava.io.tmpdir=DIR dir.tests.temp=DIR Here, DIR is an path to your ramdisk (in may case I use r:/temp). Adriano

Type safe / refactor friendly configuration for Db4o - Part III

2008-06-25T15:15:00.019-03:00

Hi, In the first installment of this series I presented the idea of having a typesafe way to configure db4o. In the second one, I explored how we could use expression trees to figure out a property name being accessed. In this post I'll address the issue on how to dive into the property's IL (intermediate language) to come up with a field name which we want to configure (if you are not familiar to IL, please, read along some of the links here). The best tools I'm aware of (when it comes to read or even change a method's IL!) are the Mono Cecil library and Net Reflector, which is an invaluable tool when you want just to look at a method's IL without writing one line of code. I don't need to say that I used these tools a lot :) In order to come up with a field name to be indexed, the main approach is to find all return paths for the property getter in question and check the field being returned. Simple, right? Unfortunately no; what if the property getter returns only constants? what if there are more than one field involved? Before we dig into the details about IL handling, let's document the behavior for some possible use cases (the less obvious ones) regarding property getter return paths:

Only constants: Throw exception
More than one field involved: Throw exception
Chained method: returns the called method / property accessed field.

(we could come up with different requirements, for instance, every field referenced in one property return path must be indexed, but in order to keep it simple, let's stick to the rules presented above). From my previous posts, we already have a way to figure out the property get being accessed; the next step is to analyze the method body; I used Cecil.FlowAnalisys to accomplish this task (line 6) in the following function:

public FieldReference Resolve(MethodDefinition method)
{
if (CheckRecursion(FullName(method))) return null;
callStack.Push(FullName(method));

ControlFlowGraph graph = FlowGraphFactory.CreateControlFlowGraph(method);

graph.Dump(Console.Out);

Resolve(
graph.Blocks[0],
firstInstruction => Array.Find(
                   graph.Blocks,
                  candidate => candidate.FirstInstruction == firstInstruction));

callStack.Pop();

FieldReference reference = CheckReferencedFields(
                         referencedFields, method.Name);
referencedFields.Clear();

return reference;
}

Next, for each control block we inspect it's IL as shown in the following code:

void Resolve(
    InstructionBlock block,
    Func<Instruction, InstructionBlock> blockForStartingInstruction)
{
if (AnalyzeInstructions(block.FirstInstruction, block.LastInstruction))
{
 Resolve(
    blockForStartingInstruction(block.LastInstruction.Next),
    blockForStartingInstruction);
}

for (int i = 0; i < block.Successors.Length; i++)
{
  Resolve(block.Successors[i], blockForStartingInstruction);
}
}

In Line 5 we call a function that do the dirt work of analyzing the IL instructions. This function returns true if the block containing the next instruction (after the last instruction of the current block) should be handled as the "next block" (this is done to support finally blocks). Lines 12-15 just process the remaining blocks calling Resolve() recursively. The real fun is in AnalyzeInstructions() function which do the following:

Line 7/9: For Ldfld / Ret instruction sequences, add ldfld target to return field list (lines 11 and 12).
Line 16: Add an alias for the each Ldfld /Stloc sequence;
For Ldloc / Ret sequences, search the aliases to see if ldloc's operand is an alias for a field and add any alias found to the return field list (line 23).
If a method call is found, analyze the target's method body (lines 35 - 41).

bool AnalyzeInstructions(
Instruction current,
Instruction last)
{
while (current != last.Next)
{
if (IsLoadField(current))
{
 if (IsReturn(current.Next))
 {
     referencedFields.Add(
          (FieldReference)current.Operand);
 }
 else
 {
    EnsureLocalVariableAliasFor(current, () => (FieldReference)current.Operand);
 }
}
else if (IsLdloc(current.OpCode))
{
 if (IsReturn(InstructionOrBranchTarget(current.Next)))
 {
   FlushAliasesFor(current);
 }
 else if (IsStore(InstructionOrBranchTarget(current.Next)))
 {
    EnsureLocalVariableAliasFor(
        current,
        () => aliases.Find(
            candidate => candidate.OpCode == current.OpCode).Field);

    current = current.Next;
 }
}
else if (IsMethodCall(current))
{
 EnsureLocalVariableAliasFor(
   current,
   () => Resolve(
      ResolveMethod((MethodReference)current.Operand)));
}

current = current.Next;
}

return IsLeave(last);
}

That's it! You can download the full source code here. [Updated on 7/23/2008: Fixed the source code download link] Just in case you want to play with the code, one point can (need to) be improved is the handling of exception blocks. Thoughts? Adriano

Very interesting (and funny)

2008-06-23T11:55:00.003-03:00

Hi, This morning a friend of mine send me this link about colaborative development in eclipse. Very interesting Adriano

You are not paid to introduce bugs :)

2008-06-21T10:10:00.041-03:00

Hi, Today's post is in the series "what is wrong with this code" but before presenting the actual problematic code I want to give some background, so bear with me. At Db4o we run migration tests (regularly) in order to guarantee that we are able to load (and query) databases created by older versions of Db4o engine. The way it's accomplished is very simple:

for each configured version, create an database using it and perform a series of tests with the trunk version.

Some time ago, I was asked to fix an annoying bug in these migration tests. In order minimize the time required to run these tests, we do not run then against every existing Db4o version. To allow this selective running we introduced a way to specify the minimum version to be tested so, if one want to test versions 6.0 and above it is a simple matter of setting a constant in a C# source:

private const double MinimumVersionToTest = 6.0;

At some point in the code we called the following function (wrong version):

double VersionFromVersionName(string versionName)
{
Version version = new Version(versionName);
return version.Major + version.Minor / 10;
}

This function is supposed to return the double representation of an assembly version (string) but it fails miserably (this code works correctly only for versions with a decimal value 0 (zero); for instance, 6.0, 7.0, etc). Now the question is, what's is wrong with this function? To be fair I have to admit that it's not a hard to spot bug, but when you are in a hurry and have no test for your test code... The problem is that version.Minor is an integer field and so,

version.Minor / 10

will result in a integer number and the decimal part will be happily discarded. The developer who wrote this code (me) is aware of language type conversions but he didn't notice the error (shame on me) ; so whenever we passed a version number not finished in 0 (zero) we got the wrong double representation for it!

Actual Version	Function Return
6.0	6
6.1	6
7	7
7.2	7

The fix? Pretty easy: Just add a ".0" to the divisor :) (I could also add an F: 10F)

double VersionFromVersionName(string versionName)
{
 Version version = new Version(versionName);
 return version.Major + version.Minor / 10.0;
}

The bottom line? This episode just highlights (and reminds me about) the importance of double checking our test code! after all, as a friend of mine likes to ask:

who test that the tests test what they should test?

Have fun. Adriano

Running Sharpen Tests

2008-06-03T12:09:00.022-03:00

Hi.

If you start using sharpen, you'll probably find some limitation / bug and, maybe, want to take a look into the issue.

In this case the best approach (IMHO) would be to i) start a discussion in Sharpen Forum and, if appropriated (in the case there's no issue filed already), ii) file a new Jira issue into our issue tracking system.

Next, if you have the time, iii) try to replicate the behavior with a minimal test case. The last step iv) would be trying to fix the issue.

This post is all about iii, or to be more clear, on how to run / write unit tests for Sharpen.

Let's start by opening an empty eclipse workspace:

Next, open SVN perspective and add a new SVN repository pointing to

https://source.db4o.com/db4o/trunk/sharpen/

and checkout all projects.

No install the plugin (as explained here):

In package explorer (Java perspective), right click on sharpen.core and select "Export" from the context menu.
Expand the "Plug-in Development" folder and select "Deployable plug-ins and fragments".
Set "Destination" to the root folder of your eclipse installation and click "Finish";

Now you can run Sharpen Tests by right clicking on "sharpen.ui.tests" and selecting "Run as / JUnit Plug-in Test";

after some processing your screen should look something like:

When the tests finishes you should see 0 (zero) errors and failures (as of today, there's some issue with sharpen.builder and sometimes you will get 2 errors in its tests but these errors don't prevent sharpen to work properly and, as you can see, when I executed the tests the errors didn't showed up).

Now let's explore the general look 'n' feel of a Sharpen test. In package explorer expand the node sharpen.ui.tests then testscases.

For each sharpen functionality there will be at least one pair of files (collectively called Test Case Resource):

One .java.txt that stores the java source to be converted;
One .cs.txt storing the expected sharpened file;

In the above picture we are testing interface conversion. Take the time to poke around testcases folder checking some of the tests.

The next logical step is to add new tests. Basically to add a new tests we need to:

Create the original java source (.java.txt)
Create the expected cs file (.cs.txt)
Plug these two files into the test engine. In the common scenarios, all we have to do is to call runResourceTestCase() function.

To see an example, just expand sharpen.ui.tests/src/sharpen.ui.tests folder and double click on NativeInterfacesTestCase.java.

In a future post (soon I hope) I want to take a look in a few other points such as:

Getting a little better performance when starting sharpen using the approach presented in this post.
How to debug sharpen.
A trick to see the expected / actual values (useful when creating new tests).

Thoughts?

Adriano

Dumb security...

2008-06-02T23:53:00.001-03:00

Hi! Am I in a bad mood today? Well, maybe, but I really feel upset when something supposed to help me to be safer on the net starts to get into my way or, even worse, pushes me in the other direction. That is what happened today when I tried to use a well know credit card website (which I'll not name here :) to see my billing information. Of course, as I don't use this service very often, I didn't remember my user name / password! Ok, (I thought) I just need to call their support service and ask them to reset my user name / password to one that I do know. So, I picked up the phone and called them. My first issue was that they didn't allowed me to choose my user name! Ack! Ok, this is not a big issue anyway (I can always write it down somewhere). The real problem (in my opinion) is that they requires that you MUST set a password which is at least 6 but no more than 8 characters in lenght! And you MUST use numbers also! Ok, I understand that mixing numbers, digits, punctuation, etc. in a password helps to make it stronger, but these rules forces me to give up on my "password schema" (I use different passwords for each site; each password is an encoding of a lengthy phrase). The result? I'd never be able to remember the password I choose (no matter which one I pick); it's even worse as probably I'd choose a weaker one in a desperate (hopeless) try to not forget it again. After this episode I decided to take the time (ok, I'm a little bit lazy) and give some password manager a try (at least they succeeded in the purpose of forcing users - at least me - to use a stronger password :). I'll be experimenting with a firefox plugin called iMacros. Let's see how it works :) See you. Adriano.

New programing language!

2008-06-02T15:04:00.004-03:00

Hi! Today I got an "job opportunity" from one of jobs sites I'm registered (no, I'm not looking for a new job, I just didn't unregistered) with a really intriguing subject:

A skilled professional with 3 years of experience in C, Sharp and VB.NET.

I have to admit that I do know C and also a little of VB.NET, but I have never seen SHARP :) Ok, probably it was just a mistyping, but I bet the person who wrote this subject has no idea about programing languages whatsoever ;)

Where do you search for .Net tools?

2008-05-22T10:15:00.002-03:00

Hi. This will be a very short, but I hope useful, post! Of course I usually do a google search when I want to find some system/programing tools. Also I do keep an eye on some pretty helpful sites:

The Free Country (www.thefreecountry.net)
Source Forge (www.sourceforge.net)
Codeplex (www.codeplex.com)
Fresgmeat (freshmeat.net/)

One site that I really like when I want anything related to .Net is sharptoolbox (sharptoolbox.com). If you are a .Net developer you should take a serious look into this site. Which sites do you visit to get system/programing tools? Adriano

Usefull firefox trick

2008-05-15T00:01:00.008-03:00

There is one little trick in Firefox that few people I know are aware of: It's possible to create "shortcuts" in order to make it easy to browse for sites that accepts inputs.

As an example let's take the free dictionary, very nice (guess what ??) dictionary site :)

When you browse to www.tfd.com and enter a word to search it navigates to www.tdf.com/word.

In Firefox we can add a shortcut so we can speedy our browsing experience. See the example below

Instead going to the TheFreeDictionary site and then typing the word we want to look for (for instance, cake), just type tfd cake in firefox address bar! Simple like that! :)

In order to make this work we need to tell firefox that we want a shortcut named tfd (you can name it at your will) and that it must navigate to www.tfd.com/whatever-we-type-in-address-bar.

To do this, open bookmark manager (CTRL-B) add a new bookmark as follow:

(note the url: http://www.tfd.com/%s)

Press Add and you are done! Now just type tfd cake on firefox address bar!

Adriano

Type safe / refactor friendly configuration for Db4o - Part II

2008-05-14T20:05:00.004-03:00

In my last post I proposed to derive field names from a property accessor in order to gain type safety and compiler support when configuring some aspects of D4bo.

So, given the following class:

public class Test
{
   private int _age;
   public int Age
   {
      get { return _age; }
      set { _age = value; }
   }
}

we could use the following code:

IConfiguration cfg = Db4oFactory.NewConfiguration();
cfg.ObjectField((Test t) => t.Age).Indexed = true;

instead of:

IConfiguration cfg = Db4oFactory.NewConfiguration();
cfg.ObjectClass(typeof(Test)).ObjectField("_age").Indexed = true;

to configure a field to be indexed. The first step to use this syntax is to be able to figure out the property being accessed. To demonstrate how this can be done let's write a simple function that takes advantage of C# Expression Trees:

public string GetPropertyName<T,R>(
               Expression<Func<T,R> exp)
{
  // Get the property name here.
}

public static void Main()
{
   string s = GetPropertyName((Test t) => t.Age);
}

When compiling the above code, the C# compiler will create an expression tree representing our lambda expression ( (Test t) => t.Age) and pass it along to GetPropertyName() function.

Inside this function we can just use the Body property (which in this case represents t.Age part of our lambda expression) and cast it to MemberExpression. Now all we have to do is to consult MemberExpression.Meber.Name property:

public string GetPropertyName<T,R>(
               Expression<Func<T,R> exp)
{
    MemberExpression me = fieldExp.Body as
                             MemberExpression;
    if (me == null) return "na";

    MemberInfo m = me.Member;
    return m.DeclaringType.FullName + "." + m.Name;
}

At this point we are able to figure out the name of the property being accessed! If you take a deeper look into me.Member we will see that it is a PropertyInfo instance where you can get a lot more information about the property.

In the next post I'll dig a little bit deeper and investigate how we can select a field based on the property being accessed ;)

Thoughts?

Adriano

Linq Console Update

2008-05-10T14:57:00.003-03:00

Hi! I've just updated the Linq Console application! Now you don't need to copy your model assemblies to Linq Console folder anymore! You can use the load command as follow: :load "c:\my projects\test\Test.Model.dll" and the application will be able to load it :) The source code can be downloaded from our svn server: https://source.db4o.com/db4o/trunk/sandbox/rodrigo/NonOptimizedLinqSpikes/LinqConsole/ Adriano

Type safe / refactor friendly configuration for Db4o

2008-05-01T18:18:00.005-03:00

As of today, Db4o uses strings to reference fields in some scenarios such:

SODA queries
Configuration

See the sample bellow:

IConfiguration cfg = Db4oFactory.NewConfiguration();
cfg.ObjectClass(typeof(Test)).ObjectField("_age").Indexed = true;

IMHO, using strings in these situations is sub-optimal as:

Such solution relies in internal class details (field names)
Compiler can't check whenever the field actually exists.
We don't take advantage of modern IDE's refactorings so, chances are that these entities and references to them get out of sync breaking your code; it's even worst because you will figure it out only at runtime :(; it may even get unnoticed as Db4o is completely happy with some invalid field names.

With the introduction of C# 3.0 and its automatic properties we have another issue: we don't even know the field's name used to back the property! Sure, we can cheat by using some tool like reflector or ildasm to figure it out but this would be a fragile solution as C# compiler may choose whatever name it wants, so it may choose different names schemas in the future and we don't want to get our code breaking when new C# compilers come out, do we?

I do believe that this approach was chosen due to technical limitations at the time the code was written, but now, with the debut of C# 3.0 and its new features like extension methods, lambda expressions, expression trees, etc. I bet we can do better :).

To be fair, we've already been improving (removing) some string usages, for instance, Linq / Native Queries uses strong typing instead of strings to reference fields (under the hood they generate SODA queries that still use strings, but the crux here is that these "names" will always be in sync with its entities).

One area that, in my opinion, can be improved is configuration. For instance, in order to setup indexes, deletion behavior (when to cascade delete), etc. we still use strings to identify the field we want to apply the configuration. Suppose we have the following code to configure indexes:

IConfiguration cfg = Db4oFactory.NewConfiguration();
cfg.ObjectClass(typeof(Test)).ObjectField("_age").Indexed = true;

We could introduce new methods to IConfiguration interface so one would be able to do something like this:

IConfiguration cfg = Db4oFactory.NewConfiguration();
cfg.ObjectField((Test s) => s.Age).Indexed = true;

Wow! Using this syntax we no longer have issues with refactorings, abusive internal class knowledge and we get compiler time support for free :) (for instance, if we mistype "s.Afe" C# compiler will complain).

To be fair, we have some issues with refactorings. If we change field/class's name we need to inform Db4o about this changes as explained here (I do have some ideas on how to express these calls also but this is a little bit more complex topic that I won't cover here).

What do you think?

In a following post I'll discuss how we could implement this new configuration method. Go to part II of this post. Adriano

10 years ago....

2008-05-01T00:48:00.003-03:00

------------------------------ Warning: Personal post :) ------------------------------
Well, ten years ago (may, 1, 1998) I got married to Gislene, my wife :)

Since then, she has been helping me, providing me advice, being patient with me and loving me!
Gislene, thanks for all these years! I hope (and will do my best) to be at your side for the next 10 years, then for the next 10 and so on.

I couldn't finish this without saying.. Gislene, I love you!

Adriano

Redirecting standard error output in cmd.exe

2008-04-24T23:29:00.006-03:00

Hi. Suppose you have the following C++ program (in a Windows box):

#include "stdafx.h"
#include "string.h"


void write(char *str, FILE *target)
{
fwrite(str, strlen(str), 1, target);
}

void _tmain(int argc, _TCHAR* argv[])
{
write("Test:stderr\r\n", stderr);
write("Test:stdout\r\n", stdout);
}

and you want to redirect its output to a file. We could try something like in Windows console:

test.exe > myfile.txt

Unfortunately the naive approach don't work because there are data being outputted to stderr and we are redirecting only the standard output (stdout). In order to redirect stderr we can use the following syntax:

command handler# > target

let's try a sample:

test.exe 1>myfile.txt

This will redirect stdout (handle 1) to myfile.txt To redirect stderr (handle 2) we can use:

test.exe 2>myfile.txt

Ok. Now we can try:

test.exe > myfile.txt 2>myfile.txt

but, again, this doesn't work; instead we get an error message:

D:\temp\cpp\Test\Debug>Test > myfile.txt 2>myfile.txt
The process cannot access the file because it is being used by another process.

Ok, there's one last trick we can try (duplicate stderr to stdout):

test.exe > myfile.txt 2>&1

Great! Now it works as expected! Last, but not least, you can find more information here. Hope this can be useful :) Adriano

Db4o news!

2008-04-22T21:47:00.002-03:00

Hi, Db4o just announced a new release! Check it out here and let us know what you think about these new (IMO) cool features! Adriano

A Linq playground for you and your objects

2008-04-09T08:18:00.017-03:00

In this post we'll implement a very basic Linq Console application that supports "ad hoc" queries allowing users to enter Linq queries and run them against a db4o database. Our main goal is to show how such mechanism can be implemented on top of Linq/Db4o.

That said, let's play with the application for a while and them dig a little bit in its code.

How to use it ?

First, download the code here and compile it (any version of Visual Studio 2008 can be used).

Now populate a db4o database (with data) and copy the an assembly containing the types stored in that database to the LinqConsole.exe folder.


You will need to copy your model assembly to
LinqConsole executable directory, otherwise it
will not be able to find it.

Start the application and, once presented the prompt (>), enter commands (prefixed with ":") or a query (finished with ";"). The very first command you may want to try is :help to see a list of valid commands (type :help and press ):

Basically, we want to run a (Linq) query against a db4o database, so we need to specify:

the database file to query (through database command)
the assembly containing the types stored in the database; we call this assembly, model assembly because usually, it will hold your business objects (the model in MVC pattern). Unfortunately, this assembly must be in the same directory as the application, otherwise the application will not be it able to find it (technically one can configure the application using Linq.Console.exe.config file to allow assemblies to be stored in alternative directories).

With these parameters defined you can type Linq queries as you would do pragmatically, for instance:

from Type t in database select t;

and press to see the results:

As the application tries to run the query only when it finds a semicolon ";" it's also possible to enter a query in multiple lines. You can see a short demo of the application in bellow.

Before leaving this topic, I'd like to call your attention that in order to Linq for db4o to work you need to specify a type in the query (that's the entry point for our custom "Linq Provider"), otherwise, you will get an error like the one bellow:

Note that in this case I've omitted Person type in the query, i.e, I've typed:

from p in database select p;

instead of:

from Person p in database select p;

How it works ?

The basic idea behind this application is pretty simple: Given a model assembly (specified through load command), a db4o database (specified through database command) and a Linq query, find all types and namespaces defined in such assembly them emit code to run the query against the database.

In CompileQuery() method we emit a new type (TheQuery) using the specified values (database, namespace and query). This type implements IInteractiveQuery interface, so, after instantiating it we call its Run() method to execute the query.

In order to dynamically compile this type (TheQuery) we use classes defined in System.CodeDom.Compiler and Microsoft.CSharp namespaces; any compilation errors will be rendered in red on yellow background text.

Improvements

Well, I must admit: in its current state, this program has some limitations (but most of them are there to allow you to play with it ;)

From the top of my head, I can came up with a list (of coarse, not an exhaustive one) of possible improvements:

Support model assemblies in other directories
Currently in order to use a model assembly, users are required to copy it to the application folder.
Check if the types stored in the database can be found in the model assembly.
Better error handling in general
Warn users about invalid commands Currently nothing happens for invalid commands (no message).
List types inside an assembly A new command (for instance, types) could be added to allow users to list the types contained in an assembly.
Add support to query Db4o in server mode.
Auto-completion This probably would require major changes in the input handling, but it would be nice to add auto-completion to list types, assemblies, databases, etc. in the commands.
You name it! The sky is the limit :)

Final Words!

I really expect that you enjoyed this application; if you have questions/suggestions please, fell free to drop me a line :)

Thoughts?

Adriano

Activation in depth

2007-12-10T13:45:00.005-02:00

In this post I'll discuss a key concept of db4o and how it improved in our latest versions: object activation. I'll focus mainly on the .Net version but these concepts apply equally well to the Java version.

In order to access some resources listed in this post you will be required to register (for free) in http://developer.db4o.com.

Activation in depth

Activation in db4o parlance is the process of loading object data from the database to memory. You can see this concept in practice by asking db4o to not activate objects at all and having a look at them. Objects that are not activated will have only its object identity loaded from the database (In order to see the identifier for an object stored in db4o you can

IObjectContainer.Ext().GetId(obj);)

After building the graph of candidates (objects that satisfies a query's conditions), db4o needs to know how deep in this graph it must go activating (i.e, reading the object's data into memory). At this point it may seems that we have two contradictory objectives: i) we want to make db4o as transparent as possible to developers (making it easier to be used); ii) we do want to make sure that db4o will use computational resources (in this case memory) as efficiently as possible.

The simple approach to achieve i is to activate the whole graph but this clearly contrasts to ii because it may exhaust all free memory if the query returned a lot of objects. By the other hand, the easiest way to achieve ii (from the perspective of memory utilization) is to read only the identity of the objects in the graph and leave to the developer the responsibility to activate them when needed. Again, this strategy goes against the other one (i.e, simplicity of use). db4o latest versions includes a new functionality (conceptually called Transparent Activation, or simple TA for brevity) aimed to achieve both goals (i and ii) without sacrificing each other.

Consider the following classes:

public class Person : SupportObjectId
{
    private Address address;

    public Address Address
    {
        get { return address; }
        set { address = value; }
    }

    private string name;

    public string Name
   {
        get { return name; }
        set { name = value; }
   }

   private int age;

   public int Age
  {
      get { return age; }
     set { age = value; }
  }

   private Person parent;

   public Person Parent
   {
       get { return parent; }
       set { parent = value; }
   }

   public Person(string name, int age, Address address, Person parent)
   {
        this.name = name;
        this.address = address;
        this.age = age;
        this.parent = parent;
    }

   public override string ToString()
   {
       return PrintInfo(0);
   }

   private string PrintInfo(int i)
   {
       string tab = new string('\t', i);
      return string.Format("{0} {4} {1}{5}\r\n{4}{4}Address: {2}\r\n{4}{4}Parent: {3}",
                                        (name ?? "null"),
                                        age,
                                        (address != null ? address.ToString() : "null"),
                                        (parent != null ? parent.PrintInfo(i+1) : "null"),
                                       tab,
                                      base.ToString());
    }
}

public class Address : SupportObjectId
{
    private string street;
    public string Street
    {
         get { return street; }
         set { street = value; }
    }

    private int number;
    public int Number
    {
        get { return number; }
        set { number = value; }
    }

    private string city;
    public string City
   {
        get { return city; }
        set { city = value; }
   }

    public Address(string city, string street, int number)
   {
        this.city = city;
        this.street = street;
       this.number = number;
   }

   public override string ToString()
   {
        return "[" + (street ?? "**") + "(" + number + ") - " + (city ?? "**") + base.ToString() + "]" ;
   }
}

and the following objects in the database:

private static void InsertData()
{
     using (IObjectContainer db = Db4oFactory.OpenFile(DATABASE_FILE))
    {
         Person grandParent = new Person("Joseph", 65, new Address("Descalvado", "JV street", 160), null);
         Person father = new Person("Adrian", 36, new Address("São Paulo", "C. L. E. M. street", 250), grandParent);
         Person child = new Person("Caroline", 4, new Address("São Paulo", "C. L. E. M. street", 250), father);

         db.Set(child);
    }
}

The following image shows the result when querying for "Caroline" at different activation depths (with Transparent Activation disabled):

Note that at depth 0 (zero) only the object identifier for "Caroline" (1336) was loaded from the database; at depth 1 Caroline's value types were fully loaded and reference fields were initialized (to null) but not activated (see Caroline's address and parent fields). At depth 2 Caroline's parent object was also loaded (and activated) but its reference fields (for instance Caroline's grand father) were not activated yet.

Related Concepts

The same trade-of (simplicity/performance) applies when updating objects in a db4o database; I mean, usually you'll not want to update the whole set of objects reachable from the one you are currently updating because this would probably end up updating a lot of objects needlessly. To control this behavior you may configure the update depth through IConfiguration.UpdateDepth() method which takes an integer meaning how deep db4o will go when updating objects (keep in mind that when inserting, db4o will follow all references and insert all of then). This configuration may be globally (i.e, to all classes) or selectively applied (i.e, to specific classes). As of the current version db4o sets the default update depth to 0 that means that only value types and strings fields will be updated when an object is updated (i.e, reference fields will not be updated). Optionally it's possible to propagate updates to all objects reachable from the object being updated by configuring cascade on update for the specific classes you want to propagate updates.

IConfiguration.ObjectClass(typeof(your_type)).CascadeOnUpdate(true);

When configured this way, db4o will go down, updating all objects reachable from your_type until it reaches an object not configured for cascade updating (note that this may impact performance severely if this object references a lot of objects also configured for cascade updating).

Transparent Activation

Transparent Activation is a functionality that enables developers to handle objects returned by queries as if they were fully activated without incurring the cost of activating a whole graph of objects. In other words, when TA is enabled, developers may code as if activation depth was set to infinity without having to worry about the whole set of objects being loaded into memory. Basically, Transparent Activation transfers the responsibility of object activation from developers to db4o allowing them to focus on their business logic.

Configuring your db4o projects to use TA is 2 steps process:

Configure TA support (prior to opening the database):

IConfiguration.Add(new TransparentActivationSupport());

implement IActivatable interface in classes you want to be TA aware.

You can implement it by yourself or let us (ok, our tools) to do this work for you through Db4oTool (the old Db4oAdmin) application.

Keep in mind that when transparent activation support is enabled IConfiguration.ActivationDepth() is ignored; also, all objects that are note TA aware (i.e, that doesn't implement IActivatable interface) will be fully activated; so, we don't recommend to enable TA if you have lots of objects that doesn't implement this interface. While activating objects db4o will stop following references as soon as it reaches an TA aware object (after all it will be activated when needed).

More technical details about TA can be found here and a full sample along with details about it can be found here.

Putting it all together

Here you can checkout the sample application that shows the points discussed above. It inserts a simple graph of objects into a database and then queries for the root of the objects using different activation depth configurations. Also, you can ask the application to pretend that it's objects supports TA through the -ta command line option.

I recommend you to download it and do the following:

Poke around, looking into the code :)

Give it a try, i.e, run it without any parameter and see what you get;

Try to run it again, but this time passing -ta parameter, and, again, see what you get;

Make its classes TA aware (see here the easy way) and try to run it with and without -ta parameter.

If you have any question don't hesitate to ask them here!

Adriano

Old news from the front!

2007-11-20T15:03:00.000-02:00

Visual Studio 2008 has been released (Yep, I'm downloading it right now :) Niiice.

Do you fear ghosts?

2007-10-24T22:08:00.000-02:00

Well, me too, at least until one month ago :) Seriously, a long time ago (maybe not so long), Rodrigo, a great friend of mine, started talking about write a new language for the .Net platform. Of course, I promptly ignored him, after all, who needs another computer language? Some time passed and I started to hear about a new language called Boo. I was so deeply entrenched in my own world that it took me some time (and some books also :) to realize that that would be great to be exposed to a lot of new concepts (at least to me). Well, yesterday I've wrote my first Boo program! Sure, it's a humble one but it's a start. In order to learn (not only the syntax, but a lot of concepts such closures, ducking typing, etc.) I'll try to write more code using boo from now on :) And for those curious minds out there, here is my first piece of Boo code :)

def Sum(list):
 ret = 0
 for value as int in list:
    ret = ret + value
 return ret

list = (1, 2, 3, 4)
for v in list:
 print(v)
 
print Sum(list)

This is really very simple: Lines 1 ~ 5 defines a function called Sum. Line 7 declares a variable (list) that holds an integer list from 1 to 4 Lines 8 ~9 prints this list to console, item by item Line 11 prints the result of Sum when called with list as the argument. Thats it. Adriano

Enabling transparent activation in your db4o applications

2007-10-08T15:33:00.001-03:00

As a software developer, one common pattern I've found over and over again is the typical parent/child relationship.

In this post I'll present you a program (a WinForms based application) that lets you create, store and delete objects (representing tasks) that follows this common structure in a db4o database and take the opportunity to show how a new db4o feature (to be introduced in our next release) helps to solve some related problems.

Obs: I'll focus on the .Net side of db4o but these concepts apply equally to our Java interface. Also, in order to be able to access various links related in this post you'll be required to join (for free) the "db4o Developer Community"; it's a very simple process: just click on join when asked for your credentials (user name/password).

Ok, let's use the application for while ...

Open TaskSample.sln solution in Visual Studio 2005 (it should also work on the Express Edition) and compile it. Then, launch it and add some tasks by pressing "CTRL-A" or selecting "Tasks/Add.." menu.

Now add some tasks as the following structure ...

Work

Todo
Projects

Super hyper ultra mega project

Components

GoldenHammer.dll

GoldenNail.dll
GoldenHead.dll

... close the database selecting "File/Close" in the main menu ...

... and reload it (select "File/Open") .

Now expand the tasks in order to see "Super hyper ultra mega project" sub tasks.

What? What happened to Components, GodenHammer.dll, GodenNail.dll and GondelHead.dll? Where are they?

Take it easy; I assure you that db4o didn't ate your task objects :) What happened is that our old friend, the cost/benefit trade-off is showing its ugly head.

In order to keep memory consumption low and object throughput high, db4o sets a hard limit on "how deep the rabbit hole goes" (a concept called activation depth), or, in other words, how many levels it is willing to go down in the object graph reading (activating) them from the database.

It just happens that in its current version, db4o sets this limit to 5, i.e, starting from each object directly selected by a query, at most 5 levels bellow will be returned.

That explains why the sub tasks were not loaded from the database. (they are six levels down the root task so db4o stopped following references when it reached the "Super hyper ultra mega project" task.

How can we ensure smooth operation of our application?

setting the activation level to a higher value might be an option (but which value? small values will activate too little objects; higher values may lead to high memory consumption and possibly out of memory exceptions):
```
IConfiguration configuration = Db4oFactory.NewConfiguration();
configuration.ObjectClass(typeof(Task)).MinimumActivationDepth(10);

using(IObjectContainer db = Db4oFactory.OpenFile(configuration, Db4oFileName))
{
// perform some work here
}
```
To test this option, select a higher activation depth (let's say, 8) in the sample application; the database will be reopened; now you'll be able to see all the tasks :) For more details about activation depth, please, see here.
Manually activating objects as needed;

In this scenario we may track expansions in out task treeview and activate them as needed.
```
db.Activate(task, 1);
AddOutlines(task.FirsChild);
```
To test this option select the "Enables automatic activation" button on the toolbar (the little bulb lamp). The database will be reloaded and now you'll be able to see all tasks again.
Or, IMHO, the best one, letting db4o take care of this through Transparent Activation (herein referred only as TA), a new feature to be introduced in our next release (download the latest development build here) (for more details and samples about this feature look here and here);

Note that in order to benefit from TA (solution 3) objects must implement IActivable interface, either explicitly or through instrumentation as explained here.

I recommend following the instrumentation path (let the computer do the dirty work for us :). Db4o ships with an utility program (Db4oTool.exe) that you may use among other duties, to instrument assemblies to support TA.

All you need is to call Db4oAdmin.exe after building your assemblies and it'll add the required pieces to support TA.

Db4oTool -ta assembly_name.ext

If you prefer, add a post build step to TaskSample.snl project as follows:

\db4o-8.0\bin\net-3.0\Db4oTool.exe -ta "$(TargetPath)"

In order to instrument signed assemblies you'll need to delay sign them (because instrumentation process changes the assembly). For more information about delay signed assemblies, please, refer to this msdn article.

The application title bar shows you if the application was instrumented or not (if it supports TA or not).

Try to play with the sample and check the results. You may download the sample (source files) for this post here.

Thank you and see you soon ;)

Adriano

New challenges.

2007-10-06T17:26:00.000-03:00

This week I've joined db4objects team to contribute with the .Net development side (but I'm pretty sure I'll do a lot of Java development also). Indeed it has been a busy week; lots of new concepts and code to get to know, new management style, new tools, etc. I'll be working from my home (cool!!), collaborating with a distributed (talented) development team through skype. Some may call me crazy but db4objects have a cool product to work with and this opportunity will let me dedicate more time to my family, to study new topics (related to computers, of course), to watch movies, etc (I know, studies proved that working in home means to work more, but I'll get some spare time cause I'll not be required to go to jammed traffic :) Also, you can expect to see more posts on this blog covering db4o ;) Well, that's it. Adriano

Minor db4o tutorial problem

2007-09-18T18:34:00.000-03:00

Some time ago I started playing with db4objects, an object oriented database for Java and .Net.

After installing db4o it started this tutorial (C:\Program Files (x86)\Db4objects\db4o-6.3\doc\tutorial\Db4objects.Db4o.Tutorial.exe, on my 64 bits Windows Vista Box) and everything went as smooth as possible but, when I tried to restarted it in the next day, it failed and the following dialog was shown:

Looking at this dialog we can see that the program failed to delete a file called formula1.yap under C:\Program Files (x86)\Db4objects\db4o-6.3\doc\tutorial\ folder; so I launched Process Monitor and pushed Reset button in tutorial program again.

It just confirms that the tutorial is failing to delete the file but why? Worse, why have it worked when we started it for the first time?

The .Net tutorial that comes with db4o has some minor bugs related to the way Windows Vista x64 handles writes to some specific paths, more specifically to %ProgramFiles% and %ProgramFiles(x86)% folders.

It's a Windows Vista feature called UAC (for detailed information about this topic please refer to this technet article) that prevents standard users (non administrators) from writing to some folders/registry keys, basically to keep the system more stable and secure. Actually it worked in the first time because

Ok, so how to fix this problem?

Basically there are 3 different approaches that can be applied:

The "Quick and Dirty" way (probably the easiest and fastest one) is to run the tutorial as an administrator. To do this just right click on the tutorial program and select "run as administrator".
The second one consists in adding a manifest next to the tutorial program ( (warning: Windows Vista/.Net will cache the tutorial program and will not pick you fresh manifest :(. In this case you can just "touch" the tutorial program -- or move it to another folder -- and Windows will load the manifest in the next time you start it as explained here). This simply instructs Windows to start the program with administrator rights.

 <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestversion="1.0"> <assemblyidentity version="1.0.0.0" name="Db4objects.Db4o.Tutorial.exe" type="win32"> <trustinfo xmlns="urn:schemas-microsoft-com:asm.v3"> <security> <requestedprivileges> <requestedexecutionlevel level="requireAdministrator"> </requestedprivileges> </security> </trustinfo> </assembly>
The last one (and in my opinion the correct one) consists in fixing the tutorial in order to save this file under %LocalAppData% (or %AppData%) instead of its installation folder (thats the recommended action by Microsoft).

 private void UseDatabase() { string databaseFile = Path.Combine( Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), "Books.yap"); using (IObjectContainer db = InitializeDatabase(databaseFile)) { // use the database... }

That's all folks ;)

In a future post I'll discuss a bit more about a UAC feature called File System and Registry Virtualization and why it wasn't applied in this case.

Another post in the series RTFM :)

2007-09-10T21:06:00.000-03:00

As I've said in my last post, I'm reading C# 3.0 specification. Well, it's amazing what you can learn when you do take the time to learn more about the tools (in this case, the language) you use all day long :). This time I've find out that it's possible to use reserved words as identifiers! Amazing! (and of course, dangerous as it make it harder to read your code.) But this isn't a new feature of C# 3.0; it works with C# 2.0 (.Net Framework 2.0)! Just copy the following sample and compile it using CSharp compiler from .Net Framework 2.0!

public class @class
{
   private static void Main()
   {
      int @int = 10;
      int @delegate = @int + 30;;
      System.Console.WriteLine("Values {0} {1}", @int, @delegate);
   }
}

What do you think about using reserved words as identifiers? Let the world know your opinion! :) Adriano

?? Operator.. What is it good for?

2007-09-04T23:39:00.002-03:00

Hi, Other day I was poking around C# 2.0 documentation and noted a different operator I had never seen before, ?? so I thought with myself: what is it good for? Well, after reading the documentation (remember, RTFM :) I couldn't believe I didn't known this before! The ?? operator is a binary operator that checks the left operand against null. If it is null, the expression result is the right operand value otherwise (left operand is not null) it will be the left operand value. See a sample:

string name = null;
Console.WriteLine("Value: {0}", name ?? "(null)"); // Writes: Value: (null)

name = "Adriano";
Console.WriteLine("Value: {0}", name ?? "(null)"); // Writes: Value: Adriano

Also, it is useful when used in conjunction to nullable value types.

int? i = null;
Console.WriteLine("Value: {0}", i ?? -1); // Writes: Value: (null)

i = 20;
Console.WriteLine("Value: {0}", i ?? -1); // Writes: Value: 20

PS: I've just started to play with C# 3.0 (Visual Studio 2008 beta 2) and it seams to be a very strong language. PS2: Finally I managed to get SyntaxHighlighter to work with blogger (thanks to this post) As soon as I got more information I'll post my impressions here :) See you soon!

Mudanças

2007-09-04T08:31:00.000-03:00

Depois de ponderar algum tempo sobre o assunto estou considerando utilizar o inglês nos próximos posts. Porque esta decisão?

Basicamente entendo que a maioria das pessoas que possam vir a se interessar pelo conteúdo deste blog não teriam problemas para ler conteúdo (pelo menos técnico) em inglês.
Escrever em inglês me ajudaria a melhorar meus conhecimentos neste idioma.
Adotar o inglês tornaria este blog mais acessível a outras pessoas que não conhecem o português

Se você acompanha este blog e prefere que o conteúdo continue em português deixe um comentário. Dependendo do número de pessoas posso não mudar para o inglês ou então posso postar nos dois idiomas :) Adriano.

Silencio...

2007-08-28T00:48:00.000-03:00

Já faz algum tempo que não posto nada... o motivo, como todos já devem saber, é a absoluta falta de tempo, afinal de contas, tenho que me dedicar à obra de Deus, minha esposa, filha e aos jogos (need for speed rules!) ;) Como estou um pouco sem tempo para escrever um post mais interessante vou apenas listar algumas coisas com a qual tenho me envolvido atualmente:

Object Mocking em .Net (comecei a utilizar o Rhino.Mocks)
OODB, ou seja, Object Oriented Databases (estou estudando o DB4O)
Estou escrevendo um artigo sobre um dos novos recursos do Windows Vista (e também do Windows Server 2008), o KTM, ou, gerenciador de transações do Kernel, para uma revista sobre .Net.
Lendo alguns livros, principalmente um sobre WCF.
Etc.

É mais ou menos isso :) []'s Adriano

Stream de dados alternativas

2007-06-15T14:16:00.001-03:00

Para muitos usuários (e mesmo desenvolvedores) do Windows o conceito de arquivo esta tão sedimentado que muitas vezes melhorias significativas no sistema de arquivos deste sistema operacional (no caso o NTFS) são ignoradas.

Neste post apresento um dos recursos mais desconhecidos, stream alternativas de dados ou ADS (do inglês, Alternate Data Stream).

Para compreendermos este recurso é necessário primeiro definirmos (ou relembrarmos) alguns conceitos:

Uma stream de dados nada mais é que um conjunto de bytes arranjados de forma seqüencial.
Um arquivo é composto por uma ou mais streams de dados.
Streams de dados possuem um nome associado através do qual a mesma é referenciada. A regra básica para formação do nome de streams é: nome-arquivo.ext:nome-stream:tipo-stream
O nome da stream pode conter qualquer caracter válido para um nome de arquivo.

Como o Windows não possui meios (tanto no Explorer quanto no console) para detectar / mostrar arquivos que possuem ADS, abaixo listei algumas ferramentas úteis para tal finalidade:

Usando ADSs

A forma mais simples para demonstrarmos este conceito é através do console do Windows. Abra o console (cmd.exe) e digite:

echo teste de streams > teste.txt:dados

Simples assim! O comando acima cria uma stream chamada dados com o conteúdo teste de streams.

Agora você pode conferir que o arquivo teste.txt foi criado mas o comando dir reporta o mesmo com 0 (zero) bytes.

Finalmente, para visualisar o conteúdo da stream digite

more < teste.txt:dados

Abaixo apresento um pequeno programa de exemplo para criar ADSs (note que o mesmo não possui nenhum tratamento especial, ou seja, a forma de acessar data streams alternativas é idêntica à utilizada para acessar a data stream default).

#include "stdio.h"

#include "Windows.h"

void main(int argc, char *argv[])

    HANDLE handle;

    if (argc < 3)

        printf("Nome da stream (formato: arquivo.ext:stream) ou dados nao especificados.\r\nUso: ads.exe nome-stream dados");

        return;

    else

        printf("\r\nGravando dados em %s", argv[1]);

    handle = CreateFile(argv[1],

                        GENERIC_WRITE,

0,

                        NULL,

                        OPEN_ALWAYS,

                        0, 0);

    if (handle != INVALID_HANDLE_VALUE)

        DWORD numberOfBytesWritten;

        int n = WriteFile(  handle,

                            argv[2],

                            strlen(argv[2]),

                            &numberOfBytesWritten,

                            NULL);

        printf("\r\n%ld bytes gravados", numberOfBytesWritten);

        CloseHandle(handle);

    else

        printf("Não foi possivel criar a stream de dados.");

[Editado: Correção de um erros de português]

experimente executar o programa com alguns parâmetros como por exemplo:

ads teste.txt:dados "Teste de streams"

É isso ai.

Até a próxima.

Boa leitura

2007-05-15T11:31:00.001-03:00

Em se tratando de informática, ou mais especificamente de desenvolvimento de software, existem algumas ótimas publicações que podem ser lidas online (algumas delas podem ser baixadas), e o melhor, gratuitamente.

É claro, que leio pelo menos uma dúzia de blogs e outras publicações (sem contar livros :) além destas! Adriano

"COM" não esta morto (pelo menos eu espero)

2007-05-11T10:05:00.000-03:00

Assim como a morte de linguagens de programação como Cobol, Fortram, Basic, etc. e também a extinção dos programadores já foram anunciadas várias vezes, mas nunca se concretizaram ,graças a Deus, muitos já anunciaram a morte do COM (Component Object Model), uma tecnologia da MS para a componentização de soluções. Infelizmente (para estes "gurus" !) isso não aconteceu (preciso dizer: "eu já sabia que isso não aconteceria mesmo") ? Pelo contrário, se você observar o número de sub-sistemas do Windows Vista implementado usando esta tecnologia você irá notar um aumento razoável no número de componentes neste SO. Como grande parte da minha carreira foi dedicada a esta tecnologia é natural que eu tenha interesse nesta :). Assim, a alguns anos atrás (para ser mais preciso, entre 2002 e 2004), eu escrevi (e disponibilizei gratuitamente) um utilitário (ao qual chamei de Typelib Wizard) que, entre outras coisas, permite fazer Browse do conteúdo de TLBs (quer estas TLBs estejam isoladas ou incluídas como recurso de um executável) mais ou menos nos moldes dos browsers de classes encontrados nos ambientes de desenvolvimento atuais. Se você desenvolve componentes COM (ou se utiliza ambientes tais como ASP (não ASP.NET), VB 6, VBA, Power Builder, etc., em que a chance de estar utilizando componentes COM, mesmo sem saber, é grande) esta ferramenta é de grande utilidade. A algum tempo eu não realizo nenhuma manutenção no projeto mas tenho algumas idéias e seria um prazer adicionar outros desenvolvedores para que os mesmos possam atualizar o repositório de código (que aliás, vou passar para o subversion) e ajudar a manter o projeto "andando". Para saber mais sobre o projeto visite os sites abaixo:

Abraços. Adriano

Links sobre GC!

2007-04-10T14:06:00.000-03:00

Aqui estão alguns ótimos artigos (em ingles) sobre o Garbage Collector do .Net:

[Editado: Inclusão do link]

http://msdn.microsoft.com/msdnmag/issues/1100/gci/

Abraços, Adriano

SerialWizard: Uau! 1649 Downloads (1 Gb!)

2007-02-28T23:43:00.000-03:00

Quando comparado com outros aplicativos pode não parecer muito, mas para mim realmente é um número expressivo: o SerialWizard já foi baixado 1649 vezes totalizando 1 Gb ! Se tiver curiosidade para saber como o SerialWizard esta neste momento click aqui.

Descubra mais sobre você !

2007-02-28T08:40:00.000-03:00

Hoje (como de costume) estava lendo alguns blogs e me deparei com um site muito interessante; neste site você responde algumas perguntas e ele lhe diz qual "super heroi/vilão" você é! :). Veja os meus resultados:

You are Mr. Freeze
Mr. Freeze
 50%
The Joker
 48%
Dr. Doom
 44%
Apocalypse
 41%
Lex Luthor
 39%
Magneto
 38%
Riddler
 37%
Juggernaut
 36%
Venom
 33%
Mystique
 32%
Dark Phoenix
 26%
Kingpin
 26%
Green Goblin
 24%
Catwoman
 23%
Two-Face
 12%
Poison Ivy
 12%

You are cold and you think everyone else should be also, literally.



Click here to take the "Which Super Villain are you?" quiz...


You are Green Lantern
Green Lantern
 50%
Iron Man
 45%
Robin
 37%
Spider-Man
 35%
Superman
 35%
Catwoman
 35%
The Flash
 35%
Batman
 25%
Wonder Woman
 20%
Hulk
 20%
Supergirl
 15%

Hot-headed.  You have strong 
will power and a good imagination.



Click here to take the "Which Superhero am I?" quiz...

Neste site você pode descobrir qual SO você é :)



Which OS are You?
Neste site você pode descobrir qual linguagem de programação você é :)


Which Programming Language are You?


Finalmente qual extensão de arquivo você é!


Which File Extension are You?

COM/COM+ ? Alguém ta afim?

2007-02-22T08:48:00.000-02:00

Você desenvolve, ou conhece alguém que desenvolva, componentes COM/COM+? Integrando com o SNA/HIS server? A algum tempo atras eu já não encontrava muitas pessoas que conhecessem e/ou desenvolvessem usando COM/COM+; agora parece mais difícil ainda! Bom, pelo menos a MS ainda utiliza estas tecnologias de forma extensiva, visto que no Windows Vista o número de componentes COM aumentou :). No meu último emprego (em uma instituição financeira) utilizávamos muito componentes COM+ integrados com o HIS Server. Motivado pela instabilidade do nosso ambiente de testes (e outras coisas mais) iniciei o desenvolvimento de um mecanismo que nos permitisse "simular" a interação com o mainframe (ou seja, passar pelo SNA/HIS server) que acabou por tomar formas mais genéricas e permitir que uma grande gama de componentes COM/COM+ fossem passíveis de ser simulados. Abaixo apresento algumas das vantagens que este mecanismo apresenta:

Independência do mainframe (poderíamos continuar nossos testes mesmo que nosso ambiente de testes do mainframe estivesse parado)
Flexibilidade para realizar unit tests uma vez que, dado um conjunto de dados de entrada, poderíamos retornar qualquer valor desejado.
Simplicidade de configuração

Infelizmente não tive tempo hábil para terminar este projeto (que basicamente é dividido em dois módulos: i) um componente COM/COM+ cuja responsabilidade é simular outros componente; ii) um aplicativo GUI responsável por configurar/monitorar a utilização do componente) antes de me desligar desta instituição financeira e, no momento, não estou utilizando tanto componentes COM/COM+ para justificar o investimento necessário para finalizar o projeto junto a empresa que trabalho atualmente. O objetivo deste post é definir se há pessoas interessadas em continuar o projeto; eu poderia colocar o fonte no sourceforge (qualquer um poderia baixar os fontes) e incluir os interessados como desenvolvedores do projeto (estas pessoas poderiam fazer "commit", ou seja, atualizar os fontes no sourceforge. É claro que eu daria suporte :) Se alguém tiver interesse comente neste post e podemos discutir melhor como seria o processo. Até mais. Adriano

User Interface Design

2007-01-24T08:14:00.000-02:00

Se você participa do design, desenvolvimento, teste, documentação, etc. de programas não deixe de ver esta série de artigos (na realidade os capítulos do livro do autor do blog) sobre design de user interfaces. Mesmo que estando incompleto (o autor disponibilizou alguns capítulos apenas) eu recomendo a leitura do texto. Adriano

Não custa nada tentar...

2006-12-15T09:49:00.000-02:00

Ao chegar hoje no trabalho carreguei o firefox e abri minha conta de email do gmail (como faço usualmente) e qual não foi minha surpresa ao ver o seguinte email:

Uhm.... mais um hacker tentando instalar um cavalo de tróia (ou qualquer coisa parecida) em minha máquina.

Certo. Nice try Mr. hacker! Mas não vai ser desta vez :)

Fico imaginando o número de usuários que ao receber um email como este (ou outro qualquer, por exemplo convidando o usuário a ver as últimas fotos nuas de uma atriz bonitona qualquer) se desesperam, ou ingenuamente, e acabam por clicar no link (observe bem, é um executável). Certamente não deve ser um número pequeno :(.

Não sou especialista em segurança, mas de qualquer forma aqui vão algumas dicas de segurança:

Não acredite em propostas fantásticas (que normalmente o induzem a fazer algo impensado pois a tal proposta é "válida apenas para hoje"; como minha esposa diz: "Negócio da China? deixa para o chines!"
Via de regra as instituições financeiras (bancos) não enviam emails com links. Se você receber algum email em nome de um banco e este possuir links e você tiver dúvida se o mesmo foi realmente enviado pelo banco ou não, entre em contato com o Banco, ou entre no site do banco.
NUNCA click em links dentro de emails supostamente enviados por instituições financeiras, órgãos públicos, etc. Procure sempre verificar o destino do link (no email que eu recebi o destino era um executável!!! NUNCA MESMO CLICK EM LINKS CUJO DESTINO SÃO PROGRAMAS EXECUTÁVEIS. Nem mesmo se você conheçe a pessoa que enviou o email pois é possível enviar emails se passando por uma pessoa qualquer)
Procure utilizar o computador com um usuário com poucos privilégios.
Mantenha um bom antivirus sempre atualizado em seu computador.
Apesar de algumas pessoas não verem como essencial, eu prefiro manter um bom firewall instalado também
Instale também um bom programa para verificação de rootkits, spyware e comania.
Utilize senhas fortes (nada de utilizar a data de nascimento, nome do cachorro ou informações facilmente deduzíveis e/ou suscetíveis a ataques de dicionário).
Mantenha seu SO (Windows, Linux, Mac OS X, etc.) sempre atualizado.
Esta dica é derivada da anterior mas considero a mesma tão importante que vou ser explícito: Mantenha seu Web Browser (Firefox, IE, Opera, etc) sempre atualizado.
Acho desnecessário dizer que não é seguro anotar senhas em agendas, papéis (principalmente debaixo do teclado), etc. Se for necessário armazenar várias senhas (para evitar esquecê-las) utilize um programa que guarde as mesmas de forma segura.
Não acesse sites duvidosos.
Se realmente for necessário acessar algum site duvidoso procure fazê-lo a partir de uma virtual machine (VM) (a Microsof distribui gratuitamente o Virtual PC; a VMWare distribui o VMWare Player de graça, mas neste caso você terá que criar a Virtual Machine de alguma forma [existem vários programas gratuítos que podem criar VMs para o VMWare]). Ok, reconheço que apenas usuários mais avançados possuem condições técnicas para fazer isto)
Cuidado com programas baixados de redes P2P (Kazza, Bit Torrent, etc.). Hackers estão utilizando estas redes para espalhar vírus, cavalos de tróia, etc.

Bom, espero que isso o ajude a tornar mais seguro seu computador ;)

Adriano.

Problema de gases?

2006-12-13T08:59:00.000-02:00

Outro dia minha esposa me enviou um email com este vídeo; não costumo promover este tipo de email mas como achei muito engraçado aqui esta....

Lista de livros atualizada....

2006-12-11T15:24:00.000-02:00

Este posto é apenas para informar que atualizei a lista de livros comentada neste post. Adriano

Sinais dos tempos....

2006-12-08T14:10:00.000-02:00

Eu não pretendia postar hoje mas um fato inusitado me fez mudar de idéia... Bom, hoje é sexta feira, e como sempre, eu e o pessoal da empresa, almoçamos mais rápido para jogar Counter Strike (CS). Chegando à lan-house que sempre jogamos o atendente nos informou que um vírus havia infectado as máquinas e que justamente o CS poderia não funcionar. Para evitar prejuízos financeiros aos clientes o atendente estava liberando 10 minutos para testarmos se o CS iria funcionar na máquina que cada um escolheu para jogar. Até aqui tudo bem. Então lá fui eu; escolhi uma máquina e liguei a mesma; alguns instantes depois dou um click no menu do windows, seleciono o CS e.... Bum! Este programa executou uma instrução ilegal e será finalizado! Droga! Tudo bem, pensei comigo; desliguei a máquina, me dirigi a outro computador, liguei o mesmo e.... Bum! Mesma coisa. Quando já estava quase desistindo um adolescente de uns 13 anos (compadecido com meu desespero :) virou e disse:

"Eu sei como fazer para funcionar! Quer que eu te ensine?"

Ótimo, pensei comigo mesmo! Posso ser orgulhoso e dizer que não (afinal de contas, sou mais capacitado para resolver problemas com computadores que um adolescente de 13 anos) e tentar resolver o problema (ou tentar outro computador) ou responder sim e ver no que dava. Bom, depois de infindáveis 3 segundos, respondi que sim; então o adolescente abriu um sorriso, pediu licença, pegou o teclado da minha mão e saiu pressionando o mesmo como louco (na realidade de forma ordenada :). É claro que eu entendi o que ele estava fazendo (abrindo o Windows Explorer e copiando o executável do jogo de uma pasta compartilhada na rede, que supostamente estava livre do vírus). Algumas teclas pressionadas depois e pronto! Ele vira novamente para mim e diz:

"Pronto, pode jogar!"

Eu conversei um pouco mais com ele, agradeci e tentei executar o jogo novamente... Bum! O mesmo problema! Comentei que não havia funcionado e o adolescente disse que ele havia se deparado com o mesmo problema e que este procedimento havia funcionado para ele. Pensei por alguns instantes e comentei que o vírus poderia ter infectado o programa novamente (enquanto conversávamos). Então copiei o executável do jogo novamente (é claro que ele me ajudou a encontrar a pasta da rede onde eu poderia encontrar o executável) e tentei novamente... Agora sim o jogo carregou e pude me divertir :) O que mais me chamou a atenção neste acontecimento? Um adolescente me auxiliando a solucionar problemas em um computador :) é... sinais dos tempos!!!!! Adriano

Aplicativo (útil) da Semana - Parte 2

2006-12-01T13:28:00.000-02:00

Como sempre a falta de tempo tem me impedido de postar mais frequentemente :( De qualquer forma, hoje pretendo apresentar um aplicativo bastante útil que usuários do Unix/Linux já estam bastante acostumados mas, por motivos que não importam, a marioria dos usuários do Windows desconhecem. Quando comecei a trabalhar na empresa que me encontro atualmente me deparei com a seguinte situação: todos os desenvolvedores criavam uma estrutura de diretórios fixa (por exemplo: c:\Projetos\NomeProjeto, ou algo parecido) e algumas ferramentas dependiam destes caminhos (pois usavam caminhos absolutos). Como sempre tive o habito de particionar meus HDs em pelo menos duas partições (uma para dados e a outra para programas) o drive C ficou para o SO (sistema operacional) e a partição de dados acabou ficando como E (ok, eu sei que posso mudar este mapeamento, mas eu não queria fazer isto por outros motivos). Para resolver este impasse (eu desejava colocar o diretório de projetos no drive E, mas algumas ferramentas esperavam que o mesmo se encontrasse no drive C) eu criei um Junction Point (ou ponto de junção) no drive C apontando para o drive E. Junction Points permitem que sejam criados links para diretórios em qualquer volume (por exemplo o diretório c:\projetos pode ser um Junction Point, ou seja, pode apontar, para o diretório c:\meus documentos\projetos). Assim, para solucionar o impasse fiz o seguinte:

Criei a estrutura de diretórios no drive E (E:\Projetos\Nome Projeto)
No drive C eu criei um Junction Point chamado Projetos apontando para E:\Projetos
desta forma ao acessar o diretório c:\Projetos na realidade estou acessando E:\Projetos.

O resultado pode ser visto na seguinte imagem: Observe que o c:\Projetos aparece no console como JUNCTION (e não como DIR como os demais diretórios) enquando e:\Projetos é apresentado (como era de se esperar) como DIR, indicando que o mesmo é um diretório comum. Agora, todas as operações que forem realizadas em c:\projetos na realidade estarão sendo realizadas em e:\projetos. E como criamos (manipulamos) Junction Points? A resposta rápida é que apesar do Windows suportar Junction Points desde o Windows 2000, por algum motivo que desconheço, a MS não possui uma forma simples para manipular Junction Points (aqui você pode encontrar explicações [em inglês] de como criar Junction Points com ferramentas da própria MS). Porém nem tudo esta perdido :). Você pode encontrar utilitários (gratuítos) que manipulam Junction Points aqui, aqui e aqui. Eu, particularmente, uso a primeira delas pois a mesma permite criar também Hard Links e Symbolik Links (no Windows Vista) além de possuir versões para x86 e x64.

Aplicativo (útil) da Semana - Parte 1

2006-10-24T22:45:00.000-03:00

O primeiro aplicativo que eu gostaria de sugerir é o Notepad++, um ótimo editor de textos (e o que é melhor, gratuito!) com vários recursos úteis, entre os quais gostaria de citar: tabbed editing, syntax highlighting, folding/undolding (para tipos de arquivos que suportam este conceito), seleçao de blocos, entre outros. Já faz algum tempo que uso este aplicativo; o mesmo é bastante estável e não possui muitos bugs. Não deixe de testar o Notepad++! Abraços. Adriano

Windows Vista RC2

2006-10-09T08:41:00.000-03:00

A Microsoft liberou o Release Candidate 2 (RC2) (build 5744) do Windows Vista para o público. Tanto a versão 32 bits (x86) quanto a 64 (x64) podem ser baixadas em: http://download.windowsvista.com/preview/rc2/en/download.htm Se você tem interesse baixe logo pois o download público será por tempo limitado (eu já baixei :). Adriano

O que esta errado com esta código (Parte X)

2006-09-30T11:13:00.000-03:00

Infelizmente, por motivo de tempo, já faz algum tempo que não posto neste blog :(. Infelizmente ao postar a última entrada desta série (Oque esta errado com este código?) não inclui um número. Assim sendo, vou atribuir o valor X para o mesmo. Com relação ao post referido, o problema esta relacionado ao acesso de propriedades de controles da UI em uma thread diferente daquela que o componente.

Observe novamente o código abaixo:

Created with colorer-take5 library. Type 'csharp'

0: using System;
1: using System.Windows.Forms;
2: using System.Threading;
3:
4: namespace TestWinForm
5: {
6:     public partial class TestCallBackFromDiferentThread : Form
7:     {
8:         private System.Threading.Thread workerThread;
9:
10:         public TestCallBackFromDiferentThread()
11:         {
12:             InitializeComponent();
13:         }
14:
15:         private void button1_Click(object sender, EventArgs e)
16:         {
17:             ThreadStart ts = new ThreadStart(AddNewLine);
18:             workerThread = new Thread(ts);
19:             workerThread.Start();
20:         }
21:
22:         private void AddNewLine()
23:         {
24:             listBox1.Items.Add(textBox1.Text);
25:         }
26:     }
27: }

Nas linhas # 17 ~ 19 criamos uma thread e iniciamos a execução da mesma; esta thread chama a função AddNewLine() que por sua vez tenta incluir um item em uma listbox. O problema (como explicado aqui) é que o acesso a controles em WinForms não são thread safe automaticamente, ou seja, se duas threads modificarem o estado de um controle simultaneamente o mesmo pode ficar em um estado inconsistente ou mesmo gerar exceções (oque seria melhor que a primeira possibilidade). Crie uma aplicação WinForm, adicionar os controles listbox, textbox e um botão e copie o código acima para o formulário da aplicação. Se você executar esta aplicação a partir do explorer pode lhe parecer que a mesma não possui problema nenhum; ou seja, aparentemente a mesma funcionou. Contudo execute a mesma a partir do Visual Studio; se a opção "enable exception assistence" estiver habilitada uma exceção será gerada quando a thread tentar acessar o listbox na linha 24. Ok, e como solucionar o problema? Simples, usando a propriedade InvokeRequerid do controle... No método AddNewLine(), antes de incluir o item no listbox consulte a propriedade InvokeRequired; se a mesma for true então execute o método Invoke() passando um delegate que irá executar o mesmo método (AddNewLine()).

Veja no exemplo abaixo:

Created with colorer-take5 library. Type 'csharp'

using System;
using System.Windows.Forms;
using System.Threading;

namespace TestWinForm
{
    public partial class TestCallBackFromDiferentThread : Form
    {
        private System.Threading.Thread workerThread;

         public TestCallBackFromDiferentThread()
         {
             InitializeComponent();
         }

         private void button1_Click(object sender, EventArgs e)
         {
             ThreadStart ts = new ThreadStart(AddNewLine);
             workerThread = new Thread(ts);
             workerThread.Start();
         }

         private void AddNewLine()
         {
             if (listBox1.InvokeRequired)
             {
                listbox1.Invoke(new MethodInvoker(AddNewLine));
             }
             else
             {
                listBox1.Items.Add(textBox1.Text);
             }
         }
     }
 }

Você pode encontrar mais informações (em inglês) sobre o assunto aqui.

A partir do próximo post irei iniciar uma série onde em cada post falarei sobre um aplicativo/site que uso com frequência e que acho interessante. Fique atento.

Adriano

Eficiência dos antivirus gratuitos...

2006-09-20T00:01:00.000-03:00

Estou escrevendo este post a partir do Windows Vista RC1; não porque eu pretendia fazer desta forma mas sim porque meu Windows XP foi contaminado com o bagle_ge; e a pobre da minha esposa foi quem sofreu as primeiras consequências :(. Então, enquanto baixo as novas versões da bios, drivers do chipset etc eu aproveitei para escrever este post. Em parte o fato ocorrido foi bom pois não tenho mais dúvida que a qualidade das versões personal de alguns antivirus deixa bastante a desejar; por outro lado este problema também me fez considerar ainda mais passar a utilizar o Windows Vista (RC1) como meu SO primário. Mas para isto antes necessito fazer alguns testes (principalmente com a impressora já que a mesma já completou 7 anos de vida e o fabricante não me parece muito empolgado com a idéia de escrever um driver de 64 bits para a mesma [ps: o Windows reconheceu a impressora mas não sei se a mesma esta funcionando corretamente pois ainda não imprimi nada nela]) Adriano

Apresentação (novamente)

2006-09-06T20:24:00.000-03:00

Este é meu primeiro post neste novo blog :) Antes de mais nada gostaria de dizer que não vou abandonar meu blog antigo (AccessViolation); só mudei para este novo blog para poder usar alguns recursos que ainda estão na versão beta (a que mais me interessou foi a possibilidade de incluir "labels" mas tem muito mais :) Assim que estes recursos estiverem disponíveis para meu blog antigo devo voltar para o mesmo.