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• Returning null vs Throwing exceptions

  - by Svish

  Is in a bit of disagreement with a more experienced developer on this issue, and was wondering what you guys here think about this. Environment is Java, EJB 3, services, etc. The code I wrote calls a service to get things and to create things. Problem was that I got null pointer exceptions in places that didn't make sense. For example when I asked the service to create an object, I got null back. And when I tried to look up an object with an id I knew existed, I still got null back. Was like it was ignoring me. Spent some time trying to figure out what was wrong in my code (since I'm less experienced I usually assume I have messed up). Turns out the reason was security. If the user principal using my service didn't have the right permissions to use the service I called from my service, then that service simply returned null. The services that are here already are usually not documented either, so this is just something you have to know... somehow... So here is the thing: I mean that this is rather confusing as a developer interacting with this service. To me it would make much more sense if that service thew an exception which would tell me that hey, you don't have the proper permissions to get info about this thing or to create this new thing. I would then immediately know why my service wasn't working as expected. However, he argued that asking is not wrong. Exceptions should only be thrown when there is an error and asking for a thing is not an error. Even if you don't have permission to "see" that the thing you asked for. The things are often looked up in a GUI by users and for those users not having the right permissions, these things simply "do not exist". So, in short: Asking is not wrong, hence no exception. Get methods return null because to those users those things "doesn't exist". Create methods return null because nothing was created, since the user wasn't allowed to create anything. So, what do you guys think? Is this normal and/or good practice? I prefer exceptions as I prefer throwing and catching exceptions because I find it much easier to know what's going on. So I would for example also prefer to throw a NotFoundException if you asked for an id which didn't exist, rather than returning null. Anyways, just curious to what others think about this as I'm not the most experienced developer yet.

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• Tracing Silex from PHP to the OS with DTrace

  - by cj

  In this blog post I show the full stack tracing of Brendan Gregg's php_syscolors.d script in the DTrace Toolkit. The Toolkit contains a dozen very useful PHP DTrace scripts and many more scripts for other languages and the OS. For this example, I'll trace the PHP micro framework Silex, which was the topic of the second of two talks by Dustin Whittle at a recent SF PHP Meetup. His slides are at Silex: From Micro to Full Stack. Installing DTrace and PHP The php_syscolors.d script uses some static PHP probes and some kernel probes. For Oracle Linux I discussed installing DTrace and PHP in DTrace PHP Using Oracle Linux 'playground' Pre-Built Packages. On other platforms with DTrace support, follow your standard procedures to enable DTrace and load the correct providers. The sdt and systrace providers are required in addition to fasttrap. On Oracle Linux, I loaded the DTrace modules like: # modprobe fasttrap # modprobe sdt # modprobe systrace # chmod 666 /dev/dtrace/helper Installing the DTrace Toolkit I download DTraceToolkit-0.99.tar.gz and extracted it: $ tar -zxf DTraceToolkit-0.99.tar.gz The PHP scripts are in the Php directory and examples in the Examples directory. Installing Silex I downloaded the "fat" Silex .tgz file from the download page and extracted it: $ tar -zxf silex_fat.tgz I changed the demonstration silex/web/index.php so I could use the PHP development web server: <?php // web/index.php $filename = __DIR__.preg_replace('#(\?.*)$#', '', $_SERVER['REQUEST_URI']); if (php_sapi_name() === 'cli-server' && is_file($filename)) { return false; } require_once __DIR__.'/../vendor/autoload.php'; $app = new Silex\Application(); //$app['debug'] = true; $app->get('/hello', function() { return 'Hello!'; }); $app->run(); ?> Running DTrace The php_syscolors.d script uses the -Z option to dtrace, so it can be started before PHP, i.e. when there are zero of the requested probes available to be traced. I ran DTrace like: # cd DTraceToolkit-0.99/Php # ./php_syscolors.d Next, I started the PHP developer web server in a second terminal: $ cd silex $ php -S localhost:8080 -t web web/index.php At this point, the web server is idle, waiting for requests. DTrace is idle, waiting for the probes in php_syscolors.d to be fired, at which time the action associated with each probe will run. I then loaded the demonstration page in a browser: http://localhost:8080/hello When the request was fulfilled and the simple output of "Hello" was displayed, I ^C'd php and dtrace in their terminals to stop them. DTrace output over a thousand lines long had been generated. Here is one snippet from when run() was invoked: C PID/TID DELTA(us) FILE:LINE TYPE -- NAME ... 1 4765/4765 21 Application.php:487 func -> run 1 4765/4765 29 ClassLoader.php:182 func -> loadClass 1 4765/4765 17 ClassLoader.php:198 func -> findFile 1 4765/4765 31 ":- syscall -> access 1 4765/4765 26 ":- syscall <- access 1 4765/4765 16 ClassLoader.php:198 func <- findFile 1 4765/4765 25 ":- syscall -> newlstat 1 4765/4765 15 ":- syscall <- newlstat 1 4765/4765 13 ":- syscall -> newlstat 1 4765/4765 13 ":- syscall <- newlstat 1 4765/4765 22 ":- syscall -> newlstat 1 4765/4765 14 ":- syscall <- newlstat 1 4765/4765 15 ":- syscall -> newlstat 1 4765/4765 60 ":- syscall <- newlstat 1 4765/4765 13 ":- syscall -> newlstat 1 4765/4765 13 ":- syscall <- newlstat 1 4765/4765 20 ":- syscall -> open 1 4765/4765 16 ":- syscall <- open 1 4765/4765 26 ":- syscall -> newfstat 1 4765/4765 12 ":- syscall <- newfstat 1 4765/4765 17 ":- syscall -> newfstat 1 4765/4765 12 ":- syscall <- newfstat 1 4765/4765 12 ":- syscall -> newfstat 1 4765/4765 12 ":- syscall <- newfstat 1 4765/4765 20 ":- syscall -> mmap 1 4765/4765 14 ":- syscall <- mmap 1 4765/4765 3201 ":- syscall -> mmap 1 4765/4765 27 ":- syscall <- mmap 1 4765/4765 1233 ":- syscall -> munmap 1 4765/4765 53 ":- syscall <- munmap 1 4765/4765 15 ":- syscall -> close 1 4765/4765 13 ":- syscall <- close 1 4765/4765 34 Request.php:32 func -> main 1 4765/4765 22 Request.php:32 func <- main 1 4765/4765 31 ClassLoader.php:182 func <- loadClass 1 4765/4765 33 Request.php:249 func -> createFromGlobals 1 4765/4765 29 Request.php:198 func -> __construct 1 4765/4765 24 Request.php:218 func -> initialize 1 4765/4765 26 ClassLoader.php:182 func -> loadClass 1 4765/4765 89 ClassLoader.php:198 func -> findFile 1 4765/4765 43 ":- syscall -> access ... The output shows PHP functions being called and returning (and where they are located) and which system calls the PHP functions in turn invoked. The time each line took from the previous one is displayed in the third column. The first column is the CPU number. In this example, the process was always on CPU 1 so the output is naturally ordered without requiring post-processing, or the D script requiring to be modified to display a time stamp. On a terminal, the output of php_syscolors.d is color-coded according to whether each function is a PHP or system one, hence the file name. Summary With one tool, I was able to trace the interaction of a user application with the operating system. I was able to do this to an application running "live" in a web context. The DTrace Toolkit provides a very handy repository of DTrace information. Even though the PHP scripts were created in the time frame of the original PHP DTrace PECL extension, which only had PHP function entry and return probes, the scripts provide core examples for custom investigation and resolution scripts. You can easily adapt the ideas and and create scripts using the other PHP static probes, which are listed in the PHP Manual. Because DTrace is "always on", you can take advantage of it to resolve development questions or fix production situations.

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• Consuming the Amazon S3 service from a Win8 Metro Application

  - by cibrax

  As many of the existing Http APIs for Cloud Services, AWS also provides a set of different platform SDKs for hiding many of complexities present in the APIs. While there is a platform SDK for .NET, which is open source and available in C#, that SDK does not work in Win8 Metro Applications for the changes introduced in WinRT. WinRT offers a complete different set of APIs for doing I/O operations such as doing http calls or using cryptography for signing or encrypting data, two aspects that are absolutely necessary for consuming AWS. All the I/O APIs available as part of WinRT are asynchronous, and uses the TPL model for .NET applications (HTML and JavaScript Metro applications use a model based in promises, which is similar concept).  In the case of S3, the http Authorization header is used for two purposes, authenticating clients and make sure the messages were not altered while they were in transit. For doing that, it uses a signature or hash of the message content and some of the headers using a symmetric key (That's just one of the available mechanisms). Windows Azure for example also uses the same mechanism in many of its APIs. There are three challenges that any developer working for first time in Metro will have to face to consume S3, the new WinRT APIs, the asynchronous nature of them and the complexity introduced for generating the Authorization header. Having said that, I decided to write this post with some of the gotchas I found myself trying to consume this Amazon service. 1. Generating the signature for the Authorization header All the cryptography APIs in WinRT are available under Windows.Security.Cryptography namespace. Many of operations available in these APIs uses the concept of buffers (IBuffer) for representing a chunk of binary data. As you will see in the example below, these buffers are mainly generated with the use of static methods in a WinRT class CryptographicBuffer available as part of the namespace previously mentioned. private string DeriveAuthToken(string resource, string httpMethod, string timestamp) { var stringToSign = string.Format("{0}\n" + "\n" + "\n" + "\n" + "x-amz-date:{1}\n" + "/{2}/", httpMethod, timestamp, resource); var algorithm = MacAlgorithmProvider.OpenAlgorithm("HMAC_SHA1"); var keyMaterial = CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(this.secret)); var hmacKey = algorithm.CreateKey(keyMaterial); var signature = CryptographicEngine.Sign( hmacKey, CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(stringToSign)) ); return CryptographicBuffer.EncodeToBase64String(signature); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The algorithm that determines the information or content you need to use for generating the signature is very well described as part of the AWS documentation. In this case, this method is generating a signature required for creating a new bucket. A HmacSha1 hash is computed using a secret or symetric key provided by AWS in the management console. 2. Sending an Http Request to the S3 service WinRT also ships with the System.Net.Http.HttpClient that was first introduced some months ago with ASP.NET Web API. This client provides a rich interface on top the traditional WebHttpRequest class, and also solves some of limitations found in this last one. There are a few things that don't work with a raw WebHttpRequest such as setting the Host header, which is something absolutely required for consuming S3. Also, HttpClient is more friendly for doing unit tests, as it receives a HttpMessageHandler as part of the constructor that can fake to emulate a real http call. This is how the code for consuming the service with HttpClient looks like, public async Task<S3Response> CreateBucket(string name, string region = null, params string[] acl) { var timestamp = string.Format("{0:r}", DateTime.UtcNow); var auth = DeriveAuthToken(name, "PUT", timestamp); var request = new HttpRequestMessage(HttpMethod.Put, "http://s3.amazonaws.com/"); request.Headers.Host = string.Format("{0}.s3.amazonaws.com", name); request.Headers.TryAddWithoutValidation("Authorization", "AWS " + this.key + ":" + auth); request.Headers.Add("x-amz-date", timestamp); var client = new HttpClient(); var response = await client.SendAsync(request); return new S3Response { Succeed = response.StatusCode == HttpStatusCode.OK, Message = (response.Content != null) ? await response.Content.ReadAsStringAsync() : null }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You will notice a few additional things in this code. By default, HttpClient validates the values for some well-know headers, and Authorization is one of them. It won't allow you to set a value with ":" on it, which is something that S3 expects. However, that's not a problem at all, as you can skip the validation by using the TryAddWithoutValidation method. Also, the code is heavily relying on the new async and await keywords to transform all the asynchronous calls into synchronous ones. In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, public class FakeHttpMessageHandler : HttpMessageHandler { HttpResponseMessage response; public FakeHttpMessageHandler(HttpResponseMessage response) { this.response = response; } protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) { var tcs = new TaskCompletionSource<HttpResponseMessage>(); tcs.SetResult(response); return tcs.Task; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You can use this handler for injecting any response while you are unit testing the code.

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• Consuming the Amazon S3 service from a Win8 Metro Application

  - by cibrax

  As many of the existing Http APIs for Cloud Services, AWS also provides a set of different platform SDKs for hiding many of complexities present in the APIs. While there is a platform SDK for .NET, which is open source and available in C#, that SDK does not work in Win8 Metro Applications for the changes introduced in WinRT. WinRT offers a complete different set of APIs for doing I/O operations such as doing http calls or using cryptography for signing or encrypting data, two aspects that are absolutely necessary for consuming AWS. All the I/O APIs available as part of WinRT are asynchronous, and uses the TPL model for .NET applications (HTML and JavaScript Metro applications use a model based in promises, which is similar concept).  In the case of S3, the http Authorization header is used for two purposes, authenticating clients and make sure the messages were not altered while they were in transit. For doing that, it uses a signature or hash of the message content and some of the headers using a symmetric key (That's just one of the available mechanisms). Windows Azure for example also uses the same mechanism in many of its APIs. There are three challenges that any developer working for first time in Metro will have to face to consume S3, the new WinRT APIs, the asynchronous nature of them and the complexity introduced for generating the Authorization header. Having said that, I decided to write this post with some of the gotchas I found myself trying to consume this Amazon service. 1. Generating the signature for the Authorization header All the cryptography APIs in WinRT are available under Windows.Security.Cryptography namespace. Many of operations available in these APIs uses the concept of buffers (IBuffer) for representing a chunk of binary data. As you will see in the example below, these buffers are mainly generated with the use of static methods in a WinRT class CryptographicBuffer available as part of the namespace previously mentioned. private string DeriveAuthToken(string resource, string httpMethod, string timestamp) { var stringToSign = string.Format("{0}\n" + "\n" + "\n" + "\n" + "x-amz-date:{1}\n" + "/{2}/", httpMethod, timestamp, resource); var algorithm = MacAlgorithmProvider.OpenAlgorithm("HMAC_SHA1"); var keyMaterial = CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(this.secret)); var hmacKey = algorithm.CreateKey(keyMaterial); var signature = CryptographicEngine.Sign( hmacKey, CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(stringToSign)) ); return CryptographicBuffer.EncodeToBase64String(signature); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The algorithm that determines the information or content you need to use for generating the signature is very well described as part of the AWS documentation. In this case, this method is generating a signature required for creating a new bucket. A HmacSha1 hash is computed using a secret or symetric key provided by AWS in the management console. 2. Sending an Http Request to the S3 service WinRT also ships with the System.Net.Http.HttpClient that was first introduced some months ago with ASP.NET Web API. This client provides a rich interface on top the traditional WebHttpRequest class, and also solves some of limitations found in this last one. There are a few things that don't work with a raw WebHttpRequest such as setting the Host header, which is something absolutely required for consuming S3. Also, HttpClient is more friendly for doing unit tests, as it receives a HttpMessageHandler as part of the constructor that can fake to emulate a real http call. This is how the code for consuming the service with HttpClient looks like, public async Task<S3Response> CreateBucket(string name, string region = null, params string[] acl) { var timestamp = string.Format("{0:r}", DateTime.UtcNow); var auth = DeriveAuthToken(name, "PUT", timestamp); var request = new HttpRequestMessage(HttpMethod.Put, "http://s3.amazonaws.com/"); request.Headers.Host = string.Format("{0}.s3.amazonaws.com", name); request.Headers.TryAddWithoutValidation("Authorization", "AWS " + this.key + ":" + auth); request.Headers.Add("x-amz-date", timestamp); var client = new HttpClient(); var response = await client.SendAsync(request); return new S3Response { Succeed = response.StatusCode == HttpStatusCode.OK, Message = (response.Content != null) ? await response.Content.ReadAsStringAsync() : null }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You will notice a few additional things in this code. By default, HttpClient validates the values for some well-know headers, and Authorization is one of them. It won't allow you to set a value with ":" on it, which is something that S3 expects. However, that's not a problem at all, as you can skip the validation by using the TryAddWithoutValidation method. Also, the code is heavily relying on the new async and await keywords to transform all the asynchronous calls into synchronous ones. In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, public class FakeHttpMessageHandler : HttpMessageHandler { HttpResponseMessage response; public FakeHttpMessageHandler(HttpResponseMessage response) { this.response = response; } protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) { var tcs = new TaskCompletionSource<HttpResponseMessage>(); tcs.SetResult(response); return tcs.Task; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You can use this handler for injecting any response while you are unit testing the code.

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• SQL Search- The Search and the Sequel

  It started out as an experiment to try to explore different ways of creating a software tool that people would want. It ended up as a tool that Red Gate is giving away to the SQL Server community in return for the contribution to the project of so many of Red Gate's friends within the community. But was it easy to do? Bob Cramblitt and Richard Collins went to find out by talking to Tanya Joseph, who managed the project that turned the concept into a product.

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• OpenGL font rendering

  - by DEElekgolo

  I am trying to make an openGL text rendering class using FreeType. I was originally following this code but it doesn't seem to work out for me. I get nothing reguardless of what parameters I put for Draw(). class Font { public: Font() { if (FT_Init_FreeType(&ftLibrary)) { printf("Could not initialize FreeType library\n"); return; } glGenBuffers(1,&iVerts); } bool Load(std::string sFont, unsigned int Size = 12.0f) { if (FT_New_Face(ftLibrary,sFont.c_str(),0,&ftFace)) { printf("Could not open font: %s\n",sFont.c_str()); return true; } iSize = Size; FT_Set_Pixel_Sizes(ftFace,0,(int)iSize); FT_GlyphSlot gGlyph = ftFace->glyph; //Generating the texture atlas. //Rather than some amazing rectangular packing method, I'm just going //to have one long strip of letters with the height being that of the font size. int width = 0; int height = 0; for (int i = 32; i < 128; i++) { if (FT_Load_Char(ftFace,i,FT_LOAD_RENDER)) { printf("Error rendering letter %c for font %s.\n",i,sFont.c_str()); } width += gGlyph->bitmap.width; height += std::max(height,gGlyph->bitmap.rows); } //Generate the openGL texture glActiveTexture(GL_TEXTURE0); //if I texture exists then delete it. iTexture ? glDeleteBuffers(1,&iTexture):0; glGenTextures(1,&iTexture); glBindTexture(GL_TEXTURE_2D,iTexture); glPixelStorei(GL_UNPACK_ALIGNMENT,1); glTexImage2D(GL_TEXTURE_2D,0,GL_ALPHA,width,height,0,GL_ALPHA,GL_UNSIGNED_BYTE,0); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); //load the glyphs and set the glyph data int x = 0; for (int i = 32; i < 128; i++) { if (FT_Load_Char(ftFace,i,FT_LOAD_RENDER)) { //if it cant load the character continue; } //load the glyph map into the texture glTexSubImage2D(GL_TEXTURE_2D,0,x,0, gGlyph->bitmap.width, gGlyph->bitmap.rows, GL_ALPHA, GL_UNSIGNED_BYTE, gGlyph->bitmap.buffer); //move the "pen" down the strip x += gGlyph->bitmap.width; chars[i].ax = (float)(gGlyph->advance.x >> 6); chars[i].ay = (float)(gGlyph->advance.y >> 6); chars[i].bw = (float)gGlyph->bitmap.width; chars[i].bh = (float)gGlyph->bitmap.rows; chars[i].bl = (float)gGlyph->bitmap_left; chars[i].bt = (float)gGlyph->bitmap_top; chars[i].tx = (float)x/width; } printf("Loaded font: %s\n",sFont.c_str()); return true; } void Draw(std::string sString,Vector2f vPos = Vector2f(0,0),Vector2f vScale = Vector2f(1,1)) { struct pPoint { pPoint() { x = y = s = t = 0; } pPoint(float a,float b,float c,float d) { x = a; y = b; s = c; t = d; } float x,y; float s,t; }; pPoint* cCoordinates = new pPoint[6*sString.length()]; int n = 0; for (const char *p = sString.c_str(); *p; p++) { float x2 = vPos.x() + chars[*p].bl * vScale.x(); float y2 = -vPos.y() - chars[*p].bt * vScale.y(); float w = chars[*p].bw * vScale.x(); float h = chars[*p].bh * vScale.y(); float x = vPos.x() + chars[*p].ax * vScale.x(); float y = vPos.y() + chars[*p].ay * vScale.y(); //skip characters with no pixels //still advances though if (!w || !h) { continue; } //triangle one cCoordinates[n++] = pPoint( x2 , -y2 , chars[*p].tx , 0); cCoordinates[n++] = pPoint( x2+w , -y2 , chars[*p].tx + chars[*p].bw / w , 0); cCoordinates[n++] = pPoint( x2 , -y2-h , chars[*p].tx , chars[*p].bh / h); cCoordinates[n++] = pPoint( x2+w , -y2 , chars[*p].tx + chars[*p].bw / w , 0); cCoordinates[n++] = pPoint( x2 , -y2-h , chars[*p].tx , chars[*p].bh / h); cCoordinates[n++] = pPoint( x2+w , -y2-h , chars[*p].tx + chars[*p].bw / w , chars[*p].bh / h); } glBindBuffer(GL_ARRAY_BUFFER,iVerts); glBindBuffer(GL_TEXTURE_2D,iTexture); //Vertices glEnableClientState(GL_VERTEX_ARRAY); glVertexPointer(2,GL_FLOAT,sizeof(pPoint),&cCoordinates[0].x); //TexCoord 0 glClientActiveTexture(GL_TEXTURE0); glEnableClientState(GL_TEXTURE_COORD_ARRAY); glTexCoordPointer(2,GL_FLOAT,sizeof(pPoint),&cCoordinates[0].s); glCullFace(GL_NONE); glBufferData(GL_ARRAY_BUFFER,6*sString.length(),cCoordinates,GL_DYNAMIC_DRAW); glDrawArrays(GL_TRIANGLES,0,n); glCullFace(GL_BACK); glBindBuffer(GL_ARRAY_BUFFER,0); glBindBuffer(GL_TEXTURE_2D,0); glDisableClientState(GL_VERTEX_ARRAY); glDisableClientState(GL_TEXTURE_COORD_ARRAY); } ~Font() { glDeleteBuffers(1,&iVerts); glDeleteBuffers(1,&iTexture); } private: unsigned int iSize; //openGL texture atlas unsigned int iTexture; //openGL geometry buffer; unsigned int iVerts; FT_Library ftLibrary; FT_Face ftFace; struct Character { float ax,ay;//Advance float bw,bh;//bitmap size float bl,bt;//bitmap left and top float tx; } chars[128]; };

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• Calling methods on Objects

  - by Mashael

  Let's say we have a class called 'Automobile' and we have an instance of that class called 'myCar'. I would like to ask why do we need to put the values that our methods return in a variable for the object? Why just don't we call the method? For example: Why should we write: string message = myCar.SpeedMessage(); Console.WriteLine(message); instead of: Console.WriteLine(myCar.SpeedMessage());

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• Customer Experience Management : A conversation with world experts RTD

  - by David lefranc

  A conversation with world experts in Customer Experience Management in Rome, Italy - Wed, June 20, 2012 It is our pleasure to share the registration link below for your chance to meet active members of the Oracle Real-Time Decisions Customer Advisory Board. Join us to hear how leading brands across the world have achieved tremendous return on investment through their Oracle Real-Time Decisions deployments and do not miss this unique opportunity to ask them specific questions directly during our customer roundtable. Please share this information with anyone interested in real-time decision management and cross-channel predictive process optimization.http://www.oracle.com/goto/RealTimeDecisions

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• Customer Experience Management : A conversation with world experts RTD

  - by David lefranc

  A conversation with world experts in Customer Experience Management in Rome, Italy - Wed, June 20, 2012 It is our pleasure to share the registration link below for your chance to meet active members of the Oracle Real-Time Decisions Customer Advisory Board. Join us to hear how leading brands across the world have achieved tremendous return on investment through their Oracle Real-Time Decisions deployments and do not miss this unique opportunity to ask them specific questions directly during our customer roundtable. Please share this information with anyone interested in real-time decision management and cross-channel predictive process optimization.http://www.oracle.com/goto/RealTimeDecisions

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• Secret of SQL Trace Duration Column

  - by Dan Guzman

  Why would a trace of long-running queries not show all queries that exceeded the specified duration filter?  We have a server-side SQL Trace that includes RPC:Completed and SQL:BatchCompleted events with a filter on Duration >= 100000.  Nearly all of the queries on this busy OLTP server run in under this 100 millisecond threshold so any that appear in the trace are candidates for root cause analysis and/or performance tuning opportunities. After an application experienced query timeouts, the DBA looked at the trace data to corroborate the problem.  Surprisingly, he found no long-running queries in the trace from the application that experienced the timeouts even though the application’s error log clearly showed detail of the problem (query text, duration, start time, etc.).  The trace did show, however, that there were hundreds of other long-running queries from different applications during the problem timeframe.  We later determined those queries were blocked by a large UPDATE query against a critical table that was inadvertently run during this busy period. So why didn’t the trace include all of the long-running queries?  The reason is because the SQL Trace event duration doesn’t include the time a request was queued while awaiting a worker thread.  Remember that the server was under considerable stress at the time due to the severe blocking episode.  Most of the worker threads were in use by blocked queries and new requests were queued awaiting a worker to free up (a DMV query on the DAC connection will show this queuing: “SELECT scheduler_id, work_queue_count FROM sys.dm_os_schedulers;”).  Technically, those queued requests had not started.  As worker threads became available, queries were dequeued and completed quickly.  These weren’t included in the trace because the duration was under the 100ms duration filter.  The duration reflected the time it took to actually run the query but didn’t include the time queued waiting for a worker thread. The important point here is that duration is not end-to-end response time.  Duration of RPC:Completed and SQL:BatchCompleted events doesn’t include time before a worker thread is assigned nor does it include the time required to return the last result buffer to the client.  In other words, duration only includes time after the worker thread is assigned until the last buffer is filled.  But be aware that duration does include the time need to return intermediate result set buffers back to the client, which is a factor when large query results are returned.  Clients that are slow in consuming results sets can increase the duration value reported by the trace “completed” events.

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• Is it important for reflection-based serialization maintain consistent field ordering?

  - by Matchlighter

  I just finished writing a packet builder that dynamically loads data into a data stream for eventual network transmission. Each builder operates by finding fields in a given class (and its superclasses) that are marked with a @data annotation. When I finishing my implementation, I remembered that getFields() does not return results in any specific order. Should reflection-based methods for serializing arbitrary data (like my packets) attempt to preserve a specific field ordering (such as alphabetical), and if so, how?

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• Composite-like pattern and SRP violation

  - by jimmy_keen

  Recently I've noticed myself implementing pattern similar to the one described below. Starting with interface: public interface IUserProvider { User GetUser(UserData data); } GetUser method's pure job is to somehow return user (that would be an operation speaking in composite terms). There might be many implementations of IUserProvider, which all do the same thing - return user basing on input data. It doesn't really matter, as they are only leaves in composite terms and that's fairly simple. Now, my leaves are used by one own them all composite class, which at the moment follows this implementation: public interface IUserProviderComposite : IUserProvider { void RegisterProvider(Predicate<UserData> predicate, IUserProvider provider); } public class UserProviderComposite : IUserProviderComposite { public User GetUser(SomeUserData data) ... public void RegisterProvider(Predicate<UserData> predicate, IUserProvider provider) ... } Idea behind UserProviderComposite is simple. You register providers, and this class acts as a reusable entry-point. When calling GetUser, it will use whatever registered provider matches predicate for requested user data (if that helps, it stores key-value map of predicates and providers internally). Now, what confuses me is whether RegisterProvider method (brings to mind composite's add operation) should be a part of that class. It kind of expands its responsibilities from providing user to also managing providers collection. As far as my understanding goes, this violates Single Responsibility Principle... or am I wrong here? I thought about extracting register part into separate entity and inject it to the composite. As long as it looks decent on paper (in terms of SRP), it feels bit awkward because: I would be essentially injecting Dictionary (or other key-value map) ...or silly wrapper around it, doing nothing more than adding entires This won't be following composite anymore (as add won't be part of composite) What exactly is the presented pattern called? Composite felt natural to compare it with, but I realize it's not exactly the one however nothing else rings any bells. Which approach would you take - stick with SRP or stick with "composite"/pattern? Or is the design here flawed and given the problem this can be done in a better way?

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• How do I calculate the boundary of the game window after transforming the view?

  - by Cypher

  My Camera class handles zoom, rotation, and of course panning. It's invoked through SpriteBatch.Begin, like so many other XNA 2D camera classes. It calculates the view Matrix like so: public Matrix GetViewMatrix() { return Matrix.Identity * Matrix.CreateTranslation(new Vector3(-this.Spatial.Position, 0.0f)) * Matrix.CreateTranslation(-( this.viewport.Width / 2 ), -( this.viewport.Height / 2 ), 0.0f) * Matrix.CreateRotationZ(this.Rotation) * Matrix.CreateScale(this.Scale, this.Scale, 1.0f) * Matrix.CreateTranslation(this.viewport.Width * 0.5f, this.viewport.Height * 0.5f, 0.0f); } I was having a minor issue with performance, which after doing some profiling, led me to apply a culling feature to my rendering system. It used to, before I implemented the camera's zoom feature, simply grab the camera's boundaries and cull any game objects that did not intersect with the camera. However, after giving the camera the ability to zoom, that no longer works. The reason why is visible in the screenshot below. The navy blue rectangle represents the camera's boundaries when zoomed out all the way (Camera.Scale = 0.5f). So, when zoomed out, game objects are culled before they reach the boundaries of the window. The camera's width and height are determined by the Viewport properties of the same name (maybe this is my mistake? I wasn't expecting the camera to "resize" like this). What I'm trying to calculate is a Rectangle that defines the boundaries of the screen, as indicated by my awesome blue arrows, even after the camera is rotated, scaled, or panned. Here is how I've more recently found out how not to do it: public Rectangle CullingRegion { get { Rectangle region = Rectangle.Empty; Vector2 size = this.Spatial.Size; size *= 1 / this.Scale; Vector2 position = this.Spatial.Position; position = Vector2.Transform(position, this.Inverse); region.X = (int)position.X; region.Y = (int)position.Y; region.Width = (int)size.X; region.Height = (int)size.Y; return region; } } It seems to calculate the right size, but when I render this region, it moves around which will obviously cause problems. It needs to be "static", so to speak. It's also obscenely slow, which causes more of a problem than it solves. What am I missing?

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• Planning for Disaster

  There is a certain paradox in being advised to expect the unexpected, but the DBA must plan and prepare in advance to protect their organisation's data assets in the event of an unexpected crisis, and return them to normal operating conditions. To minimise downtime in such circumstances should be the aim of every effective DBA. To plan for recovery, It pays to have the mindset of a pessimist.

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• Help with "Cannot find ContentTypeReader BB.HeightMapInfoReader, BB, Version=1.0.0.0, Culture=neutral." needed

  - by rFactor

  Hi, I have this irritating problem in XNA that I have spent my Saturday with: Cannot find ContentTypeReader BB.HeightMapInfoReader, BB, Version=1.0.0.0, Culture=neutral. It throws me that when I do (within the game assembly's Renderer.cs class): this.terrain = this.game.Content.Load<Model>("heightmap"); There is a heightmap.bmp and I don't think there's anything wrong with it, because I used it in a previous version which I switched to this new better system. So, I have a GeneratedGeometryPipeline assembly that has these classes: HeightMapInfoContent, HeightMapInfoWriter, TerrainProcessor. The GeneratedGeometryPipeline assembly does not reference any other assemblies under the solution. Then I have the game assembly that neither references any other solution assemblies and has these classes: HeightMapInfo, HeightMapInfoReader. All game assembly classes are under namespace BB and the GeneratedGeometryPipeline classes are under the namespace GeneratedGeometryPipeline. I do not understand why it does not find it. Here's some code from the GeneratedGeometryPipeline.HeightMapInfoWriter: /// <summary> /// A TypeWriter for HeightMapInfo, which tells the content pipeline how to save the /// data in HeightMapInfo. This class should match HeightMapInfoReader: whatever the /// writer writes, the reader should read. /// </summary> [ContentTypeWriter] public class HeightMapInfoWriter : ContentTypeWriter<HeightMapInfoContent> { protected override void Write(ContentWriter output, HeightMapInfoContent value) { output.Write(value.TerrainScale); output.Write(value.Height.GetLength(0)); output.Write(value.Height.GetLength(1)); foreach (float height in value.Height) { output.Write(height); } foreach (Vector3 normal in value.Normals) { output.Write(normal); } } /// <summary> /// Tells the content pipeline what CLR type the /// data will be loaded into at runtime. /// </summary> public override string GetRuntimeType(TargetPlatform targetPlatform) { return "BB.HeightMapInfo, BB, Version=1.0.0.0, Culture=neutral"; } /// <summary> /// Tells the content pipeline what worker type /// will be used to load the data. /// </summary> public override string GetRuntimeReader(TargetPlatform targetPlatform) { return "BB.HeightMapInfoReader, BB, Version=1.0.0.0, Culture=neutral"; } } Can someone help me out?

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• How to TDD test that objects are being added to a collection if the collection is private?

  - by Joshua Harris

  Assume that I planned to write a class that worked something like this: public class GameCharacter { private Collection<CharacterEffect> _collection; public void Add(CharacterEffect e) { ... } public void Remove(CharacterEffect e) { ... } public void Contains(CharacterEffect e) { ... } } When added an effect does something to the character and is then added to the _collection. When it is removed the effect reverts the change to the character and is removed from the _collection. It's easy to test if the effect was applied to the character, but how do I test that the effect was added to _collection? What test could I write to start constructing this class. I could write a test where Contains would return true for a certain effect being in _collection, but I can't arrange a case where that function would return true because I haven't implemented the Add method that is needed to place things in _collection. Ok, so since Contains is dependent on having Add working, then why don't I try to create Add first. Well for my first test I need to try and figure out if the effect was added to the _collection. How would I do that? The only way to see if an effect is in _collection is with the Contains function. The only way that I could think to test this would be to use a FakeCollection that Mocks the Add, Remove, and Contains of a real collection, but I don't want _collection being affected by outside sources. I don't want to add a setEffects(Collection effects) function, because I do not want the class to have that functionality. The one thing that I am thinking could work is this: public class GameCharacter<C extends Collection> { private Collection<CharacterEffect> _collection; public GameCharacter() { _collection = new C<CharacterEffect>(); } } But, that is just silly making me declare what some private data structures type is on every declaration of the character. Is there a way for me to test this without breaking TDD principles while still allowing me to keep my collection private?

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• Superclass Sensitive Actions

  - by Geertjan

  I've created a small piece of functionality that enables you to create actions for Java classes in the IDE. When the user right-clicks on a Java class, they will see one or more actions depending on the superclass of the selected class. To explain this visually, here I have "BlaTopComponent.java". I right-click on its node in the Projects window and I see "This is a TopComponent": Indeed, when you look at the source code of "BlaTopComponent.java", you'll see that it implements the TopComponent class. Next, in the screenshot below, you see that I have right-click a different class. In this case, there's an action available because the selected class implements the ActionListener class. Then, take a look at this one. Here both TopComponent and ActionListener are superclasses of the current class, hence both the actions are available to be invoked: Finally, here's a class that subclasses neither TopComponent nor ActionListener, hence neither of the actions that I created for doing something that relates to TopComponents or ActionListeners is available, since those actions are irrelevant in this context: How does this work? Well, it's a combination of my blog entries "Generic Node Popup Registration Solution" and "Showing an Action on a TopComponent Node". The cool part is that the definition of the two actions that you see above is remarkably trivial: import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JOptionPane; import org.openide.loaders.DataObject; import org.openide.util.Utilities; public class TopComponentSensitiveAction implements ActionListener { private final DataObject context; public TopComponentSensitiveAction() { context = Utilities.actionsGlobalContext().lookup(DataObject.class); } @Override public void actionPerformed(ActionEvent ev) { //Do something with the context: JOptionPane.showMessageDialog(null, "TopComponent: " + context.getNodeDelegate().getDisplayName()); } } The above is the action that will be available if you right-click a Java class that extends TopComponent. This, in turn, is the action that will be available if you right-click a Java class that implements ActionListener: import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JOptionPane; import org.openide.loaders.DataObject; import org.openide.util.Utilities; public class ActionListenerSensitiveAction implements ActionListener { private final DataObject context; public ActionListenerSensitiveAction() { context = Utilities.actionsGlobalContext().lookup(DataObject.class); } @Override public void actionPerformed(ActionEvent ev) { //Do something with the context: JOptionPane.showMessageDialog(null, "ActionListener: " + context.getNodeDelegate().getDisplayName()); } } Indeed, the classes, at this stage are the same. But, depending on what I want to do with TopComponents or ActionListeners, I now have a starting point, which includes access to the DataObject, from where I can get down into the source code, as shown here. This is how the two ActionListeners that you see defined above are registered in the layer, which could ultimately be done via annotations on the ActionListeners, of course: <folder name="Actions"> <folder name="Tools"> <file name="org-netbeans-sbas-impl-TopComponentSensitiveAction.instance"> <attr stringvalue="This is a TopComponent" name="displayName"/> <attr name="instanceCreate" methodvalue="org.netbeans.sbas.SuperclassSensitiveAction.create"/> <attr name="type" stringvalue="org.openide.windows.TopComponent"/> <attr name="delegate" newvalue="org.netbeans.sbas.impl.TopComponentSensitiveAction"/> </file> <file name="org-netbeans-sbas-impl-ActionListenerSensitiveAction.instance"> <attr stringvalue="This is an ActionListener" name="displayName"/> <attr name="instanceCreate" methodvalue="org.netbeans.sbas.SuperclassSensitiveAction.create"/> <attr name="type" stringvalue="java.awt.event.ActionListener"/> <attr name="delegate" newvalue="org.netbeans.sbas.impl.ActionListenerSensitiveAction"/> </file> </folder> </folder> <folder name="Loaders"> <folder name="text"> <folder name="x-java"> <folder name="Actions"> <file name="org-netbeans-sbas-impl-TopComponentSensitiveAction.shadow"> <attr name="originalFile" stringvalue="Actions/Tools/org-netbeans-sbas-impl-TopComponentSensitiveAction.instance"/> <attr intvalue="150" name="position"/> </file> <file name="org-netbeans-sbas-impl-ActionListenerSensitiveAction.shadow"> <attr name="originalFile" stringvalue="Actions/Tools/org-netbeans-sbas-impl-ActionListenerSensitiveAction.instance"/> <attr intvalue="160" name="position"/> </file> </folder> </folder> </folder> </folder> The most important parts of the layer registration are the lines that are highlighted above. Those lines connect the layer to the generic action that delegates back to the action listeners defined above, as follows: public final class SuperclassSensitiveAction extends AbstractAction implements ContextAwareAction { private final Map map; //This method is called from the layer, via "instanceCreate", //magically receiving a map, which contains all the attributes //that are defined in the layer for the file: static SuperclassSensitiveAction create(Map map) { return new SuperclassSensitiveAction(Utilities.actionsGlobalContext(), map); } public SuperclassSensitiveAction(Lookup context, Map m) { super(m.get("displayName").toString()); this.map = m; String superclass = m.get("type").toString(); //Enable the menu item only if //we're dealing with a class of type superclass: JavaSource javaSource = JavaSource.forFileObject( context.lookup(DataObject.class).getPrimaryFile()); try { javaSource.runUserActionTask(new ScanTask(this, superclass), true); } catch (IOException ex) { Exceptions.printStackTrace(ex); } //Hide the menu item if it isn't enabled: putValue(DynamicMenuContent.HIDE_WHEN_DISABLED, true); } @Override public void actionPerformed(ActionEvent ev) { ActionListener delegatedAction = (ActionListener)map.get("delegate"); delegatedAction.actionPerformed(ev); } @Override public Action createContextAwareInstance(Lookup actionContext) { return new SuperclassSensitiveAction(actionContext, map); } private class ScanTask implements Task<CompilationController> { private SuperclassSensitiveAction action = null; private String superclass; private ScanTask(SuperclassSensitiveAction action, String superclass) { this.action = action; this.superclass = superclass; } @Override public void run(final CompilationController info) throws Exception { info.toPhase(Phase.ELEMENTS_RESOLVED); new EnableIfGivenSuperclassMatches(info, action, superclass).scan( info.getCompilationUnit(), null); } } private static class EnableIfGivenSuperclassMatches extends TreePathScanner<Void, Void> { private CompilationInfo info; private final AbstractAction action; private final String superclassName; public EnableIfGivenSuperclassMatches(CompilationInfo info, AbstractAction action, String superclassName) { this.info = info; this.action = action; this.superclassName = superclassName; } @Override public Void visitClass(ClassTree t, Void v) { Element el = info.getTrees().getElement(getCurrentPath()); if (el != null) { TypeElement te = (TypeElement) el; List<? extends TypeMirror> interfaces = te.getInterfaces(); if (te.getSuperclass().toString().equals(superclassName)) { action.setEnabled(true); } else { action.setEnabled(false); } for (TypeMirror typeMirror : interfaces) { if (typeMirror.toString().equals(superclassName)){ action.setEnabled(true); } } } return null; } } } This is a pretty cool solution and, as you can see, very generic. Create a new ActionListener, register it in the layer so that it maps to the generic class above, and make sure to set the type attribute, which defines the superclass to which the action should be sensitive.

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• Is throwing an error in unpredictable subclass-specific circumstances a violation of LSP?

  - by Motti Strom

  Say, I wanted to create a Java List<String> (see spec) implementation that uses a complex subsystem, such as a database or file system, for its store so that it becomes a simple persistent collection rather than an basic in-memory one. (We're limiting it specifically to a List of Strings for the purposes of discussion, but it could extended to automatically de-/serialise any object, with some help. We can also provide persistent Sets, Maps and so on in this way too.) So here's a skeleton implementation: class DbBackedList implements List<String> { private DbBackedList() {} /** Returns a list, possibly non-empty */ public static getList() { return new DbBackedList(); } public String get(int index) { return Db.getTable().getRow(i).asString(); // may throw DbExceptions! } // add(String), add(int, String), etc. ... } My problem lies with the fact that the underlying DB API may encounter connection errors that are not specified in the List interface that it should throw. My problem is whether this violates Liskov's Substitution Principle (LSP). Bob Martin actually gives an example of a PersistentSet in his paper on LSP that violates LSP. The difference is that his newly-specified Exception there is determined by the inserted value and so is strengthening the precondition. In my case the connection/read error is unpredictable and due to external factors and so is not technically a new precondition, merely an error of circumstance, perhaps like OutOfMemoryError which can occur even when unspecified. In normal circumstances, the new Error/Exception might never be thrown. (The caller could catch if it is aware of the possibility, just as a memory-restricted Java program might specifically catch OOME.) Is this therefore a valid argument for throwing an extra error and can I still claim to be a valid java.util.List (or pick your SDK/language/collection in general) and not in violation of LSP? If this does indeed violate LSP and thus not practically usable, I have provided two less-palatable alternative solutions as answers that you can comment on, see below. Footnote: Use Cases In the simplest case, the goal is to provide a familiar interface for cases when (say) a database is just being used as a persistent list, and allow regular List operations such as search, subList and iteration. Another, more adventurous, use-case is as a slot-in replacement for libraries that work with basic Lists, e.g if we have a third-party task queue that usually works with a plain List: new TaskWorkQueue(new ArrayList<String>()).start() which is susceptible to losing all it's queue in event of a crash, if we just replace this with: new TaskWorkQueue(new DbBackedList()).start() we get a instant persistence and the ability to share the tasks amongst more than one machine. In either case, we could either handle connection/read exceptions that are thrown, perhaps retrying the connection/read first, or allow them to throw and crash the program (e.g. if we can't change the TaskWorkQueue code).

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• Action delegate in C#

  - by Jalpesh P. Vadgama

  In last few posts about I have written lots of things about delegates and this post is also part of that series. In this post we are going to learn about Action delegates in C#.  Following is a list of post related to delegates. Delegates in C#. Multicast Delegates in C#. Func Delegates in C#. Action Delegates in c#: As per MSDN action delegates used to pass a method as parameter without explicitly declaring custom delegates. Action Delegates are used to encapsulate method that does not have return value. C# 4.0 Action delegates have following different variants like following. It can take up to 16 parameters. Action – It will be no parameter and does not return any value. Action(T) Action(T1,T2) Action(T1,T2,T3) Action(T1,T2,T3,T4) Action(T1,T2,T3,T4,T5) Action(T1,T2,T3,T4,T5,T6) Action(T1,T2,T3,T4,T5,T6,T7) Action(T1,T2,T3,T4,T5,T6,T7,T8) Action(T1,T2,T3,T4,T5,T6,T7,T8,T9) Action(T1,T2,T3,T4,T5,T6,T7,T8,T9,T10) Action(T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11) Action(T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12) Action(T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13) Action(T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14) Action(T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,T15) Action(T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,T15,T16) So for this Action delegate you can have up to 16 parameters for Action.  Sound interesting!!… Enough theory now. It’s time to implement real code. Following is a code for that. using System; using System.Collections.Generic; namespace DelegateExample { class Program { static void Main(string[] args) { Action<String> Print = p => Console.WriteLine(p); Action<String,String> PrintAnother = (p1,p2)=> Console.WriteLine(string.Format("{0} {1}",p1,p2)); Print("Hello"); PrintAnother("Hello","World"); } } } In the above code you can see that I have created two Action delegate Print and PrintAnother. Print have one string parameter and its printing that. While PrintAnother have two string parameter and printing both the strings via Console.Writeline. Now it’s time to run example and following is the output as expected. That’s it. Hope you liked it. Stay tuned for more updates!!

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• Paypal PDT and IPN , how does it work?

  - by slow diver

  PDT Payment Data Transfer is getting the transaction data of the purchase that was made on paypal site and you want to fetch that on your own site and display to the user. Also you may want to store it in your database for archive and tracking purposes. But I cannot exactly follow the documentation here What I am not getting is Once you have activated PDT, every time a buyer makes a website payment and is redirected to your return URL, a transaction token will be passed along as a "GET" variable to this return URL. In order to properly use PDT and display transaction details to your customer, you should fetch the transaction token, variable name "tx", and retreive transaction details from PayPal by constructing an HTTP POST to PayPal. Your POST should be sent to https://www.paypal.com/cgi-bin/webscr. You must post the transaction token using the variable "tx" and the value of the transaction token previously received (e.g. "tx=transaction_token"), and the special identity token using the variable at and the value of your PDT identity token (e.g. "at=identity_token"). You will also need to append a variable named "cmd" with the value "_notify-synch", for example "cmd=_notify-synch", to the POST string. IPN I have setup Instant Payment Notification through setting according to this documentation. This is basically logging into your paypal account and enable IPN while specifying a url where the notification will be sent. This is used to complete an order so that the product can be shipped. What I did is setup a PHP page. I have created a table and whenever that page is called (or hit), it registers an entry in the table so I know a notification came from Paypal. But it does not work either. What am I really doing wrong? The first thing I want to trouble shoot though is when the buyer pays the amount, he is automatically redirected to my site. I have enabled this but automatic redirection just does not work. Instead he is shown the url as an option after payment confirmation is shown. Can someone guide my how the PDT process goes? Where do I make the request for PDT, is it along the very first request (Buy Now button) or it is sent later? Addition I found some good sampling code of how everything should work but it still does not work. I use this code http://officetrio.com/modules/free-php-paypal-ipn-script.php for IPN. I am using this for PDT. This one uses SSL, I changed SSL to regular HTTP (copied paypal version), still does not work. http://ykyuen.wordpress.com/2010/02/17/paypal-payment-data-transfer-sample-code/

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• Use CSS Selectors with HtmlUnit

  - by kerry

  HtmlUnit is a great library for performing web integration tests in Java.  But sometimes node traversal can be somewhat cumbersome. Fear not fellow automated tester (good for you!).  I found a great little project on Github that will allow you to query your document for elements via css selectors similar to jQuery. The project is located at https://github.com/chrsan/css-selectors.  You can use Maven to build it, or download 1.0.2 here.  Beware.  I will not be updating this link so I suggest you download the latest code. In any case, you can use it like so: // from HtmlUnit getting started final WebClient webClient = new WebClient(); final HtmlPage page = webClient.getPage("http://htmlunit.sourceforge.net"); final DOMNodeSelector cssSelector = new DOMNodeSelector(page.getDocumentElement()); final Set elements = cssSelector.querySelectorAll("div.section h2"); final Node first = elements.iterator().next(); assertThat(first.getTextContent(), equalTo("HtmlUnit")); The only problem here is that the querySelectAll returns a Set<Node>.  Not HtmlElement like we may want in some cases.   However, if you were to reflect on the Set, you would find that it is indeed a Set of HtmlElement objects. Typically, I like to create a base class for my web tests.  Just for fun, I am using the $ method similar to jQuery. public class WebTestBase { protected WebClient webClient; protected HtmlPage htmlPage; protected void goTo(final String url){ return (HtmlPage)webClient.getPage(url); } protected List $(final String cssSelector) { final DOMNodeSelector cssSelector = new DOMNodeSelector(htmlPage.getDocumentElement()); final Set nodes = cssSelector.querySelectorAll("div.section h2"); // for some reason Set cannot be cast to Set? final List elements = new ArrayList(nodes.size()); for (final Node node : nodes) { elements.add((HtmlElement)node); } return elements; } } Now we can write tests like this: public class LoginWebTest extends WebTestBase { @Test public void login_page_has_instructions() throws Exception { goTo(baseUrl + "/login") assertThat( $("p.instructions").size(), equalTo(1) ); } }

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• Ord function implementation in Delphi

  - by Federico Zancan

  Purely as an exercise at home, aimed to better understand some language basics, I tried to reimplement the Ord function, but I came across a problem. In fact, the existing Ord function can accept arguments of a variety of different types (AnsiChar, Char, WideChar, Enumeration, Integer, Int64) and can return Integer or Int64. I can't figure out how to declare multiple versions of the same function. How should this be coded in Delphi?

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• add collision detection to sprite?

  - by xBroak

  bassically im trying to add collision detection to the sprite below, using the following: self.rect = bounds_rect collide = pygame.sprite.spritecollide(self, wall_list, False) if collide: # yes print("collide") However it seems that when the collide is triggered it continuously prints 'collide' over and over when instead i want them to simply not be able to walk through the object, any help? def update(self, time_passed): """ Update the creep. time_passed: The time passed (in ms) since the previous update. """ if self.state == Creep.ALIVE: # Maybe it's time to change the direction ? # self._change_direction(time_passed) # Make the creep point in the correct direction. # Since our direction vector is in screen coordinates # (i.e. right bottom is 1, 1), and rotate() rotates # counter-clockwise, the angle must be inverted to # work correctly. # self.image = pygame.transform.rotate( self.base_image, -self.direction.angle) # Compute and apply the displacement to the position # vector. The displacement is a vector, having the angle # of self.direction (which is normalized to not affect # the magnitude of the displacement) # displacement = vec2d( self.direction.x * self.speed * time_passed, self.direction.y * self.speed * time_passed) self.pos += displacement # When the image is rotated, its size is changed. # We must take the size into account for detecting # collisions with the walls. # self.image_w, self.image_h = self.image.get_size() global bounds_rect bounds_rect = self.field.inflate( -self.image_w, -self.image_h) if self.pos.x < bounds_rect.left: self.pos.x = bounds_rect.left self.direction.x *= -1 elif self.pos.x > bounds_rect.right: self.pos.x = bounds_rect.right self.direction.x *= -1 elif self.pos.y < bounds_rect.top: self.pos.y = bounds_rect.top self.direction.y *= -1 elif self.pos.y > bounds_rect.bottom: self.pos.y = bounds_rect.bottom self.direction.y *= -1 self.rect = bounds_rect collide = pygame.sprite.spritecollide(self, wall_list, False) if collide: # yes print("collide") elif self.state == Creep.EXPLODING: if self.explode_animation.active: self.explode_animation.update(time_passed) else: self.state = Creep.DEAD self.kill() elif self.state == Creep.DEAD: pass #------------------ PRIVATE PARTS ------------------# # States the creep can be in. # # ALIVE: The creep is roaming around the screen # EXPLODING: # The creep is now exploding, just a moment before dying. # DEAD: The creep is dead and inactive # (ALIVE, EXPLODING, DEAD) = range(3) _counter = 0 def _change_direction(self, time_passed): """ Turn by 45 degrees in a random direction once per 0.4 to 0.5 seconds. """ self._counter += time_passed if self._counter > randint(400, 500): self.direction.rotate(45 * randint(-1, 1)) self._counter = 0 def _point_is_inside(self, point): """ Is the point (given as a vec2d) inside our creep's body? """ img_point = point - vec2d( int(self.pos.x - self.image_w / 2), int(self.pos.y - self.image_h / 2)) try: pix = self.image.get_at(img_point) return pix[3] > 0 except IndexError: return False def _decrease_health(self, n): """ Decrease my health by n (or to 0, if it's currently less than n) """ self.health = max(0, self.health - n) if self.health == 0: self._explode() def _explode(self): """ Starts the explosion animation that ends the Creep's life. """ self.state = Creep.EXPLODING pos = ( self.pos.x - self.explosion_images[0].get_width() / 2, self.pos.y - self.explosion_images[0].get_height() / 2) self.explode_animation = SimpleAnimation( self.screen, pos, self.explosion_images, 100, 300) global remainingCreeps remainingCreeps-=1 if remainingCreeps == 0: print("all dead")

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• iPad2 - Yet Another Fundamental Defect in an Apple product

  - by Kit Ong

  First it was antenna defect in iPhone4 now it has been reported that some iPad 2 have display issues, Apple really needs to look at their manufacturing process. It doesn't help that workers are working like robots in their main supplier's factory Foxconn. More info on reported display light bleeding http://www.cultofmac.com/if-your-ipad-2-has-display-problems-do-not-return-it-heres-why/87197   How to check your iPad for dead pixel / light leak / bleed http://www.theipadguide.com/content/ipad-dead-pixel-test-how/7171269

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• RemoveAll Dictionary Extension Method

  - by João Angelo

  Removing from a dictionary all the elements where the keys satisfy a set of conditions is something I needed to do more than once so I implemented it as an extension method to the IDictionary<TKey, TValue> interface. Here’s the code: public static class DictionaryExtensions { /// <summary> /// Removes all the elements where the key match the conditions defined by the specified predicate. /// </summary> /// <typeparam name="TKey"> /// The type of the dictionary key. /// </typeparam> /// <typeparam name="TValue"> /// The type of the dictionary value. /// </typeparam> /// <param name="dictionary"> /// A dictionary from which to remove the matched keys. /// </param> /// <param name="match"> /// The <see cref="Predicate{T}"/> delegate that defines the conditions of the keys to remove. /// </param> /// <exception cref="ArgumentNullException"> /// dictionary is null /// <br />-or-<br /> /// match is null. /// </exception> /// <returns> /// The number of elements removed from the <see cref="IDictionary{TKey, TValue}"/>. /// </returns> public static int RemoveAll<TKey, TValue>( this IDictionary<TKey, TValue> dictionary, Predicate<TKey> match) { if (dictionary == null) throw new ArgumentNullException("dictionary"); if (match == null) throw new ArgumentNullException("match"); var keysToRemove = dictionary.Keys.Where(k => match(k)).ToList(); if (keysToRemove.Count == 0) return 0; foreach (var key in keysToRemove) { dictionary.Remove(key); } return keysToRemove.Count; } }

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