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  • Emulating Dynamic Dispatch in C++ based on Template Parameters

    - by Jon Purdy
    This is heavily simplified for the sake of the question. Say I have a hierarchy: struct Base { virtual int precision() const = 0; }; template<int Precision> struct Derived : public Base { typedef Traits<Precision>::Type Type; Derived(Type data) : value(data) {} virtual int precision() const { return Precision; } Type value; }; I want a function like: Base* function(const Base& a, const Base& b); Where the specific type of the result of the function is the same type as whichever of first and second has the greater Precision; something like the following pseudocode: template<class T> T* operation(const T& a, const T& b) { return new T(a.value + b.value); } Base* function(const Base& a, const Base& b) { if (a.precision() > b.precision()) return operation((A&)a, A(b.value)); else if (a.precision() < b.precision()) return operation(B(a.value), (B&)b); else return operation((A&)a, (A&)b); } Where A and B are the specific types of a and b, respectively. I want f to operate independently of how many instantiations of Derived there are. I'd like to avoid a massive table of typeid() comparisons, though RTTI is fine in answers. Any ideas?

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  • Views jump during ViewDidLoad

    - by Jon-Paul
    Hi, I have a custom button, subclassed from UIButton that is initialised as below (obviously all the button does is use a custom font). @implementation HWButton - (id)initWithCoder:(NSCoder *)decoder { if (self = [super initWithCoder: decoder]) { [self.titleLabel setFont:[UIFont fontWithName: @"eraserdust" size: self.titleLabel.font.pointSize]]; } return self; } So far so good. But when I use the custom class in my nib and launch the app, the button initially displays for a split second as tiny with small text, then grows. So the outcome is what I want, but I don't want to see the transition. Can anyone put me right? Thanks. JP

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  • Are there any generic shipping calculators out there for DJango?

    - by Jon Cage
    I'm in the process of settings up a website (I'm using DJango) to begin selling some toys I build and need a way of calculating shipping costs for my customers. Are there any (preferably free) shipping calculators which accept a customers address and return the cost for different delivery companies / delivery options? It would be nice if the API could indicate cost vs delivery time. We'll be shipping world-wide if that makes a difference?

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  • JUnit Custom Rules

    - by Jon
    JUnit 4.7 introduced the concept of custom rules: http://www.infoq.com/news/2009/07/junit-4.7-rules There are a number of built in JUnit rules including TemporaryFolder which helps by clearing up folders after a test has been run: @Rule public TemporaryFolder tempFolder = new TemporaryFolder(); There's a full list of built in rules here: http://kentbeck.github.com/junit/javadoc/latest/org/junit/rules/package-summary.html I'm interested in finding out what custom rules are in place where you work or what useful custom rules you currently use?

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  • Issue using Visual Studio 2010 compiled C++ DLL in Windows 2000

    - by Jon Tackabury
    I have a very simple DLL written in unmanaged C++ that I access from my application. I recently switch to Visual Studio 2010, and the DLL went from 55k down to 35k with no code changes, and now it will no longer load in Windows 2000. I didn't change any code or compiler settings. I have my defines setup for 0x0500, which should include Windows 2000 support. Has anyone else run into this, or have any ideas of what I can do?

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  • Poor DB4O performance - What am I doing wrong?

    - by Jon
    I read Rob Conery's post about Object databases and thought I'd give it a go. I have a class lets say Book with 15 properties mostly string, some int, one Datetime and 2 decimals. I used Rob's code to open the database file etc to test on a Winforms project not a Web project. So I did the following: for(int i = 0; i < 1000000; i++) { var Book = new Book(); //Assign variables s.Save(Book); } s.CommitChanges(); This took at least a couple of minutes. I then tried to retrieve all data to test speed: var spp = s.All<Passports>(); This one line was quick, however, then doing: sppp.Count() as well as a seperate test doing a foreach loop and incrementing a counter took a couple of minutes. This seems quite slow to me. Am I doing something wrong or am I expecting too much?

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  • When doing a Schema Export with hbm2ddl, is there a way to specify that you DO NOT want Nullable For

    - by Jon Erickson
    The DDL that is being created is putting all of my many to many associations into 1 table, but I actually want each many to many association in its' own table (for other reasons) Right now hbm2ddl is creating this table (only Table1Key OR Table2Key OR Table3Key should be filled out for any given record, causing this table to have nullable foreign keys): +-----------+ | xRef | +-----------+ | Table1Key | | Table2Key | | Table3Key | | RiskKey | +-----------+ I want hbm2ddl to create the following 3 tables so that there are no nullable foreign keys. +-----------+ +-----------+ +-----------+ | xRef1 | | xRef2 | | xRef3 | +-----------+ +-----------+ +-----------+ | Table1Key | | Table2Key | | Table3Key | | RiskKey | | RiskKey | | RiskKey | +-----------+ +-----------+ +-----------+

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  • Get the ID of user that like my page.

    - by jon
    Hello I would like to know if there is any API feature that can tell me which users liked my application page. I know that it is possible to check if a user is a fan of any given Page using page.isFan verification or to get the number of fans. But is it possible to get the fans' User ID? If so, is it possible to get that data ordered by the date they became fans of the page? For exemple usign FQL i can get the user ID of someone o like an facebook object like post or photo. http://developers.facebook.com/docs/reference/fql/like Can i do this for the people who liked my page? Thanks for any help or guideline .

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  • Java paint speed relative to color model

    - by Jon
    I have a BufferedImage with an IndexColorModel. I need to paint that image onto the screen, but I've noticed that this is slow when using an IndexColorModel. However, if I run the BufferedImage through an identity affine transform it creates an image with a DirectColorModel and the painting is significantly faster. Here's the code I'm using AffineTransformOp identityOp = new AffineTransformOp(new AffineTransform(), AffineTransformOp.TYPE_BILINEAR); displayImage = identityOp.filter(displayImage, null); I have three questions 1. Why is painting the slower on an IndexColorModel? 2. Is there any way to speed up the painting of an IndexColorModel? 3. If the answer to 2. is no, is this the most efficient way to convert from an IndexColorModel to a DirectColorModel? I've noticed that this conversion is dependent on the size of the image, and I'd like to remove that dependency. Thanks for the help

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  • Automatic e-mail processing

    - by Jon Harrop
    I'd like to write a .NET application in F# to automate some of the processing of my e-mails. For example, when an order comes in my program might compute a new htpasswd from the e-mail's contents, upload it to our web server and reply to the customer with login details. How do people do this? I've tried Outlook 2007 automation but it just prompts the user for security and my attempts to get it to stop doing this have failed so I cannot automate anything with it. Is there a .NET-friendly e-mail client I can use more easily? This has been so tedious that I'm seriously considering writing my own .NET-friendly e-mail client...

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  • Exiting from the Middle of an Expression Without Using Exceptions

    - by Jon Purdy
    Is there a way to emulate the use of flow-control constructs in the middle of an expression? Is it possible, in a comma-delimited expression x, y, for y to cause a return? Edit: I'm working on a compiler for something rather similar to a functional language, and the target language is C++. Everything is an expression in the source language, and the sanest, simplest translation to the destination language leaves as many things expressions as possible. Basically, semicolons in the target language become C++ commas. In-language flow-control constructs have presented no problems thus far; it's only return. I just need a way to prematurely exit a comma-delimited expression, and I'd prefer not to use exceptions unless someone can show me that they don't have excessive overhead in this situation. The problem of course is that most flow-control constructs are not legal expressions in C++. The only solution I've found so far is something like this: try { return x(), // x(); (1 ? throw Return(0) : 0); // return 0; } catch (Return& ret) { return ref.value; } The return statement is always there (in the event that a Return construct is not reached), and as such the throw has to be wrapped in ?: to get the compiler to shut up about its void result being used in an expression. I would really like to avoid using exceptions for flow control, unless in this case it can be shown that no particular overhead is incurred; does throwing an exception cause unwinding or anything here? This code needs to run with reasonable efficiency. I just need a function-level equivalent of exit().

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  • Setting a Forms Authentication cookie from a .NET client application

    - by Jon DellOro
    We currently have a .NET 2.0 web app that uses forms authentication via cookies. Associated with this web app is an old VB6 client application that has its own login system. Currently, the users have to login to the VB6 app, and then when they click on a link, need to authenticate themselves again with the .NET forms authentication system. I'm wondering if it's possible to create a client side .NET application, give it the username and password, and set the forms authentication cookie (without the browser being opened). Is that possible??

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  • Escaping Code for Different Shells

    - by Jon Purdy
    Question: What characters do I need to escape in a user-entered string to securely pass it into shells on Windows and Unix? What shell differences and version differences should be taken into account? Can I use printf "%q" somehow, and is that reliable across shells? Backstory (a.k.a. Shameless Self-Promotion): I made a little DSL, the Vision Web Template Language, which allows the user to create templates for X(HT)ML documents and fragments, then automatically fill them in with content. It's designed to separate template logic from dynamic content generation, in the same way that CSS is used to separate markup from presentation. In order to generate dynamic content, a Vision script must defer to a program written in a language that can handle the generation logic, such as Perl or Python. (Aside: using PHP is also possible, but Vision is intended to solve some of the very problems that PHP perpetuates.) In order to do this, the script makes use of the @system directive, which executes a shell command and expands to its output. (Platform-specific generation can be handled using @unix or @windows, which only expand on the proper platform.) The problem is obvious, I should think: test.htm: <!-- ... --> <form action="login.vis" method="POST"> <input type="text" name="USERNAME"/> <input type="password" name="PASSWORD"/> </form> <!-- ... --> login.vis: #!/usr/bin/vision # Think USERNAME = ";rm -f;" @system './login.pl' { USERNAME; PASSWORD } One way to safeguard against this kind of attack is to set proper permissions on scripts and directories, but Web developers may not always set things up correctly, and the naive developer should get just as much security as the experienced one. The solution, logically, is to include a @quote directive that produces a properly escaped string for the current platform. @system './login.pl' { @quote : USERNAME; @quote : PASSWORD } But what should @quote actually do? It needs to be both cross-platform and secure, and I don't want to create terrible problems with a naive implementation. Any thoughts?

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  • PHP DOMDocument Error Handling Problem

    - by Jon
    I'm having trouble trying to write an if statement for DOM that will check if $html is blank. However whenever the html page does end up blank, it just removes everything that would be below DOM (including what I had to check if it was blank). $html = file_get_contents("http://example.com/"); $dom = new DOMDocument; @$dom->loadHTML($html); $links = $dom->getElementById('dividhere')->getElementsByTagName('img'); foreach ($links as $link) { echo $link->getAttribute('src'); } All this does is grab an image url in the specified div, which works perfectly until the page is a blank html page. I've tried using SimpleHTMLDOM, which didn't work either (it didn't even fetch the image on working pages). Did I happen to miss something with this one or am I just missing something in both? include_once('simple_html_dom.php') $html = file_get_html("http://example.com/"); foreach($html->find('div[id="dividhere"]') as $div) { if(empty($div->src)) { continue; } echo $div->src; }

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  • Switch statements: do you need the last break? (Javascript mainly)

    - by Jon Raasch
    When using a switch() statement, you add break; in between separate case: declarations. But what about the last one? Normally I just leave it off, but I'm wondering if this has some performance implication I'm not thinking about? I've been wondering about this for a while and don't see it asked elsewhere on Stack-O, but sorry if I missed it. I'm mainly asking this question regarding Javascript, although I'm guessing the answer will apply to all switch() statements.

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  • Java getInputStreat SocketTimeoutException instead of NoRouteToHostException

    - by Jon
    I have an odd issue happening when trying to open multiple Input Streams (in separate threads) on Linux (RHEL). The behaviour works as expected on windows. I am kicking off 3 threads to open https connections to 3 different servers. All three are invalid IP addresses (in this test case), so I expect an NoRouteToHostException for each of them. The first two return these as expected, and quite quickly. (see stack trace below) However the third (and 4th when I tested it that way) do NOT give a no route exception. They wait for ages, and then give a SocketTimeoutException (see other stack trace below). This takes ages to come back, and does not accurately express the connection issue. The offending line of code is: reader = new BufferedReader(new InputStreamReader(conn.getInputStream())); Has anyone seen something like this before? Are there multi-threading issues with sockets on REHL or some limit somewhere to how many can connect at once...or...something? Expected stack trace, as received for first two: java.net.NoRouteToHostException: No route to host at java.net.PlainSocketImpl.socketConnect(Native Method) at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333) at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195) at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366) at java.net.Socket.connect(Socket.java:529) at com.sun.net.ssl.internal.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:559) at sun.net.NetworkClient.doConnect(NetworkClient.java:158) at sun.net.www.http.HttpClient.openServer(HttpClient.java:394) at sun.net.www.http.HttpClient.openServer(HttpClient.java:529) at sun.net.www.protocol.https.HttpsClient.(HttpsClient.java:272) at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:329) at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:172) at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:916) at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:158) at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1177) at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:234) Unexpected stack trace, as received on 3rd: java.net.SocketTimeoutException: connect timed out at java.net.PlainSocketImpl.socketConnect(Native Method) at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333) at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195) at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182) at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366) at java.net.Socket.connect(Socket.java:529) at com.sun.net.ssl.internal.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:559) at sun.net.NetworkClient.doConnect(NetworkClient.java:158) at sun.net.www.http.HttpClient.openServer(HttpClient.java:394) at sun.net.www.http.HttpClient.openServer(HttpClient.java:529) at sun.net.www.protocol.https.HttpsClient.(HttpsClient.java:272) at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:329) at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:172) at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:916) at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:158) at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1177) at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:234)

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  • Bug: files uploaded via desktop or web client have hidden tag when listed via API

    - by Jon Webb
    Files uploaded to Google Drive sometimes incorrectly have a hidden tag when listed via the Document List v3 REST API: <category scheme='http://schemas.google.com/g/2005/labels' term='http://schemas.google.com/g/2005/labels#hidden' label='hidden'/> This happens if: a subfolder is created via the Google Drive desktop client and files are copied in, or a folder is uploaded via the Google Drive web client. The folder does not have the hidden tag, but the files that were uploaded do. The files do not have this tag if: they are individually uploaded via the Google Drive web client to the subfolder, or they are uploaded via the REST API to the subfolder, or they are uploaded via the desktop client to the My Drive root. The files and folders show up in Google Drive whether they have the hidden tag or not. We're using the API with the following scope: https://docs.google.com/feeds/ https://spreadsheets.google.com/feeds/ https://docs.googleusercontent.com/ I have verified and can recreate this with the OAuth 2.0 playground. Google Drive desktop client version 1.3.3209.2600 on Win7 32-bit I guess these must be bugs in the API...

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  • Client Web Browser Behavior When Handling 301 Redirect

    - by Jon Swanson
    The RFC seems to suggest that the client should permanently cache the response: http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html 10.3.2 301 Moved Permanently The requested resource has been assigned a new permanent URI and any future references to this resource SHOULD use one of the returned URIs. Clients with link editing capabilities ought to automatically re-link references to the Request-URI to one or more of the new references returned by the server, where possible. This response is cacheable unless indicated otherwise. The new permanent URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s). If the 301 status code is received in response to a request other than GET or HEAD, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which the request was issued. Note: When automatically redirecting a POST request after receiving a 301 status code, some existing HTTP/1.0 user agents will erroneously change it into a GET request. I'm having a hard time finding concrete browser documentation for any major browser that states how they handle these. I've started digging through the source code of firefox, but quickly got lost. Is the following scenario true for which (if any) browsers, and is there definitive documentation for either Firefox or IE that states as much?: First Time Around: 1.1: User enters link to site A, or clicks on a link directed at Site A 1.2: Browser interprets link at Site A, first time, no cache. Sends GET to Site A. 1.2: Site A responds with 301 Redirect to Site B 1.3: Browser sends GET to Site B. Any Subsequent Times Around: 2.2: User clicks on a link directed at Site A 2.2: Browser sees that, due to a past 301 redirect, Site A should now be Site B. 2.3: Without initiating any request whatsoever at Site A, browser initiates GET at Site B.

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  • What is the best URL strategy to handle multiple search parameters and operators?

    - by Jon Winstanley
    Searching with mutltiple Parameters In my app I would like to allow the user to do complex searches based on several parameters, using a simple syntax similar to the GMail functionality when a user can search for "in:inbox is:unread" etc. However, GMail does a POST with this information and I would like the form to be a GET so that the information is in the URL of the search results page. Therefore I need the parameters to be formatted in the URL. Requirements: Keep the URL as clean as possible Avoid the use of invalid URL chars such as square brackets Allow lots of search functionality Have the ability to add more functions later. I know StackOverflow allows the user to search by multiple tags in this way: http://stackoverflow.com/questions/tagged/c+sql However, I'd like to also allow users to search with multiple additional parameters. Initial Design My design is currently to do use URLs such as these: http://example.com/search/tagged/c+sql/searchterm/transactions http://example.com/search/searchterm/transactions http://example.com/search/tagged/c+sql http://example.com/search/tagged/c+sql/not-tagged/java http://example.com/search/tagged/c+sql/created/yesterday http://example.com/search/created_by/user1234 I intend to parse the URL after the search parameter, then decide how to construct my search query. Has anyone seen URL parameters like this implemented well on a website? If so, which do it best?

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  • passing custom object as parameter to a webmethod of asp.net web service

    - by Jon
    Hi, I have a custom class declared as follows (in vb.net) <Serializable()> _ Public Class NumInfo Public n As String Public f As Integer Public fc As char() Public t As Integer Public tc As char() Private validFlag As Boolean = True Public Sub New() End Sub 'I also have public properties(read/write) for all the public variablesEnd Class In my service.asmx codebehind class I have a webmethod as follows: <WebMethod()> _ <XmlInclude(GetType(NumInfo))> _ Public Function ConvertTo(ByVal info As NumInfo) As String Return mbc(info)'mbc is another function defined in my service.asmx "service" class End Function The problem is that when I start debugging it to test it, the page that I get does not contain any fields where I could input the values for the public fields of numInfo. How do I initialise the class? There is no "Invoke" button either. All I see are soap details as below: ConvertToTestThe test form is only available for methods with primitive types as parameters.SOAP 1.1The following is a sample SOAP 1.1 request and response. The placeholders shown need to be replaced with actual values.POST /Converter/BC.asmx HTTP/1.1Host: localhostContent-Type: text/xml; charset=utf-8Content-Length: lengthSOAPAction: "http://Services/ConvertTo"<?xml version="1.0" encoding="utf-8"?> <soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"> <soap:Body> <ConvertTo xmlns="http://Services/"> <info> <n>string</n> <f>int&lt/f> <fc> <char>char</char> <char>char>/char> </fc>..etc.. What am I doing wrong? For the record I tried replacing char() with string to see if it was the array causing problems but that didn't help either. I'm fairly new to web services. I tried replacing the custom object parameter with a primitive parameter just to check how things worked and it rendered a page with an input field and invoke button. I just can't seem to get it working with custom object. Help!

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  • Implementing a robust async stream reader for a console

    - by Jon
    I recently provided an answer to this question: C# - Realtime console output redirection. As often happens, explaining stuff (here "stuff" was how I tackled a similar problem) leads you to greater understanding and/or, as is the case here, "oops" moments. I realized that my solution, as implemented, has a bug. The bug has little practical importance, but it has an extremely large importance to me as a developer: I can't rest easy knowing that my code has the potential to blow up. Squashing the bug is the purpose of this question. I apologize for the long intro, so let's get dirty. I wanted to build a class that allows me to receive input from a Stream in an event-based manner. The stream, in my scenario, is guaranteed to be a FileStream and there is also an associated StreamReader already present to leverage. The public interface of the class is this: public class MyStreamManager { public event EventHandler<ConsoleOutputReadEventArgs> StandardOutputRead; public void StartSendingEvents(); public void StopSendingEvents(); } Obviously this specific scenario has to do with a console's standard output. StartSendingEvents and StopSendingEvents do what they advertise; for the purposes of this discussion, we can assume that events are always being sent without loss of generality. The class uses these two fields internally: protected readonly StringBuilder inputAccumulator = new StringBuilder(); protected readonly byte[] buffer = new byte[256]; The functionality of the class is implemented in the methods below. To get the ball rolling: public void StartSendingEvents(); { this.stopAutomation = false; this.BeginReadAsync(); } To read data out of the Stream without blocking, and also without requiring a carriage return char, BeginRead is called: protected void BeginReadAsync() { if (!this.stopAutomation) { this.StandardOutput.BaseStream.BeginRead( this.buffer, 0, this.buffer.Length, this.ReadHappened, null); } } The challenging part: BeginRead requires using a buffer. This means that when reading from the stream, it is possible that the bytes available to read ("incoming chunk") are larger than the buffer. Since we are only handing off data from the stream to a consumer, and that consumer may well have inside knowledge about the size and/or format of these chunks, I want to call event subscribers exactly once for each chunk. Otherwise the abstraction breaks down and the subscribers have to buffer the incoming data and reconstruct the chunks themselves using said knowledge. This is much less convenient to the calling code, and detracts from the usefulness of my class. Edit: There are comments below correctly stating that since the data is coming from a stream, there is absolutely nothing that the receiver can infer about the structure of the data unless it is fully prepared to parse it. What I am trying to do here is leverage the "flush the output" "structure" that the owner of the console imparts while writing on it. I am prepared to assume (better: allow my caller to have the option to assume) that the OS will pass me the data written between two flushes of the stream in exactly one piece. To this end, if the buffer is full after EndRead, we don't send its contents to subscribers immediately but instead append them to a StringBuilder. The contents of the StringBuilder are only sent back whenever there is no more to read from the stream (thus preserving the chunks). private void ReadHappened(IAsyncResult asyncResult) { var bytesRead = this.StandardOutput.BaseStream.EndRead(asyncResult); if (bytesRead == 0) { this.OnAutomationStopped(); return; } var input = this.StandardOutput.CurrentEncoding.GetString( this.buffer, 0, bytesRead); this.inputAccumulator.Append(input); if (bytesRead < this.buffer.Length) { this.OnInputRead(); // only send back if we 're sure we got it all } this.BeginReadAsync(); // continue "looping" with BeginRead } After any read which is not enough to fill the buffer, all accumulated data is sent to the subscribers: private void OnInputRead() { var handler = this.StandardOutputRead; if (handler == null) { return; } handler(this, new ConsoleOutputReadEventArgs(this.inputAccumulator.ToString())); this.inputAccumulator.Clear(); } (I know that as long as there are no subscribers the data gets accumulated forever. This is a deliberate decision). The good This scheme works almost perfectly: Async functionality without spawning any threads Very convenient to the calling code (just subscribe to an event) Maintains the "chunkiness" of the data; this allows the calling code to use inside knowledge of the data without doing any extra work Is almost agnostic to the buffer size (it will work correctly with any size buffer irrespective of the data being read) The bad That last almost is a very big one. Consider what happens when there is an incoming chunk with length exactly equal to the size of the buffer. The chunk will be read and buffered, but the event will not be triggered. This will be followed up by a BeginRead that expects to find more data belonging to the current chunk in order to send it back all in one piece, but... there will be no more data in the stream. In fact, as long as data is put into the stream in chunks with length exactly equal to the buffer size, the data will be buffered and the event will never be triggered. This scenario may be highly unlikely to occur in practice, especially since we can pick any number for the buffer size, but the problem is there. Solution? Unfortunately, after checking the available methods on FileStream and StreamReader, I can't find anything which lets me peek into the stream while also allowing async methods to be used on it. One "solution" would be to have a thread wait on a ManualResetEvent after the "buffer filled" condition is detected. If the event is not signaled (by the async callback) in a small amount of time, then more data from the stream will not be forthcoming and the data accumulated so far should be sent to subscribers. However, this introduces the need for another thread, requires thread synchronization, and is plain inelegant. Specifying a timeout for BeginRead would also suffice (call back into my code every now and then so I can check if there's data to be sent back; most of the time there will not be anything to do, so I expect the performance hit to be negligible). But it looks like timeouts are not supported in FileStream. Since I imagine that async calls with timeouts are an option in bare Win32, another approach might be to PInvoke the hell out of the problem. But this is also undesirable as it will introduce complexity and simply be a pain to code. Is there an elegant way to get around the problem? Thanks for being patient enough to read all of this.

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  • Why doesn't my QsciLexerCustom subclass work in PyQt4 using QsciScintilla?

    - by Jon Watte
    My end goal is to get Erlang syntax highlighting in QsciScintilla using PyQt4 and Python 2.6. I'm running on Windows 7, but will also need Ubuntu support. PyQt4 is missing the necessary wrapper code for the Erlang lexer/highlighter that "base" scintilla has, so I figured I'd write a lightweight one on top of QsciLexerCustom. It's a little bit problematic, because the Qsci wrapper seems to really want to talk about line+index rather than offset-from-start when getting/setting subranges of text. Meanwhile, the lexer gets arguments as offset-from-start. For now, I get a copy of the entire text, and split that up as appropriate. I have the following lexer, and I apply it with setLexer(). It gets all the appropriate calls when I open a new file and sets this as the lexer, and prints a bunch of appropriate lines based on what it's doing... but there is no styling in the document. I tried making all the defined styles red, and the document is still stubbornly black-on-white, so apparently the styles don't really "take effect" What am I doing wrong? If nobody here knows, what's the appropriate discussion forum where people might actually know these things? (It's an interesting intersection between Python, Qt and Scintilla, so I imagine the set of people who would know is small) Let's assume prefs.declare() just sets up a dict that returns the value for the given key (I've verified this -- it's not the problem). Let's assume scintilla is reasonably properly constructed into its host window QWidget. Specifically, if I apply a bundled lexer (such as QsciLexerPython), it takes effect and does show styled text. prefs.declare('font.name.margin', "MS Dlg") prefs.declare('font.size.margin', 8) prefs.declare('font.name.code', "Courier New") prefs.declare('font.size.code', 10) prefs.declare('color.editline', "#d0e0ff") class LexerErlang(Qsci.QsciLexerCustom): def __init__(self, obj = None): Qsci.QsciLexerCustom.__init__(self, obj) self.sci = None self.plainFont = QtGui.QFont() self.plainFont.setPointSize(int(prefs.get('font.size.code'))) self.plainFont.setFamily(prefs.get('font.name.code')) self.marginFont = QtGui.QFont() self.marginFont.setPointSize(int(prefs.get('font.size.code'))) self.marginFont.setFamily(prefs.get('font.name.margin')) self.boldFont = QtGui.QFont() self.boldFont.setPointSize(int(prefs.get('font.size.code'))) self.boldFont.setFamily(prefs.get('font.name.code')) self.boldFont.setBold(True) self.styles = [ Qsci.QsciStyle(0, QtCore.QString("base"), QtGui.QColor("#000000"), QtGui.QColor("#ffffff"), self.plainFont, True), Qsci.QsciStyle(1, QtCore.QString("comment"), QtGui.QColor("#008000"), QtGui.QColor("#eeffee"), self.marginFont, True), Qsci.QsciStyle(2, QtCore.QString("keyword"), QtGui.QColor("#000080"), QtGui.QColor("#ffffff"), self.boldFont, True), Qsci.QsciStyle(3, QtCore.QString("string"), QtGui.QColor("#800000"), QtGui.QColor("#ffffff"), self.marginFont, True), Qsci.QsciStyle(4, QtCore.QString("atom"), QtGui.QColor("#008080"), QtGui.QColor("#ffffff"), self.plainFont, True), Qsci.QsciStyle(5, QtCore.QString("macro"), QtGui.QColor("#808000"), QtGui.QColor("#ffffff"), self.boldFont, True), Qsci.QsciStyle(6, QtCore.QString("error"), QtGui.QColor("#000000"), QtGui.QColor("#ffd0d0"), self.plainFont, True), ] print("LexerErlang created") def description(self, ix): for i in self.styles: if i.style() == ix: return QtCore.QString(i.description()) return QtCore.QString("") def setEditor(self, sci): self.sci = sci Qsci.QsciLexerCustom.setEditor(self, sci) print("LexerErlang.setEditor()") def styleText(self, start, end): print("LexerErlang.styleText(%d,%d)" % (start, end)) lines = self.getText(start, end) offset = start self.startStyling(offset, 0) print("startStyling()") for i in lines: if i == "": self.setStyling(1, self.styles[0]) print("setStyling(1)") offset += 1 continue if i[0] == '%': self.setStyling(len(i)+1, self.styles[1]) print("setStyling(%)") offset += len(i)+1 continue self.setStyling(len(i)+1, self.styles[0]) print("setStyling(n)") offset += len(i)+1 def getText(self, start, end): data = self.sci.text() print("LexerErlang.getText(): " + str(len(data)) + " chars") return data[start:end].split('\n') Applied to the QsciScintilla widget as follows: _lexers = { 'erl': (Q.SCLEX_ERLANG, LexerErlang), 'hrl': (Q.SCLEX_ERLANG, LexerErlang), 'html': (Q.SCLEX_HTML, Qsci.QsciLexerHTML), 'css': (Q.SCLEX_CSS, Qsci.QsciLexerCSS), 'py': (Q.SCLEX_PYTHON, Qsci.QsciLexerPython), 'php': (Q.SCLEX_PHP, Qsci.QsciLexerHTML), 'inc': (Q.SCLEX_PHP, Qsci.QsciLexerHTML), 'js': (Q.SCLEX_CPP, Qsci.QsciLexerJavaScript), 'cpp': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'h': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'cxx': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'hpp': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'c': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'hxx': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'tpl': (Q.SCLEX_CPP, Qsci.QsciLexerCPP), 'xml': (Q.SCLEX_XML, Qsci.QsciLexerXML), } ... inside my document window class ... def addContentsDocument(self, contents, title): handler = self.makeScintilla() handler.title = title sci = handler.sci sci.append(contents) self.tabWidget.addTab(sci, title) self.tabWidget.setCurrentWidget(sci) self.applyLexer(sci, title) EventBus.bus.broadcast('command.done', {'text': 'Opened ' + title}) return handler def applyLexer(self, sci, title): (language, lexer) = language_and_lexer_from_title(title) if lexer: l = lexer() print("making lexer: " + str(l)) sci.setLexer(l) else: print("setting lexer by id: " + str(language)) sci.SendScintilla(Qsci.QsciScintillaBase.SCI_SETLEXER, language) linst = sci.lexer() print("lexer: " + str(linst)) def makeScintilla(self): sci = Qsci.QsciScintilla() sci.setUtf8(True) sci.setTabIndents(True) sci.setIndentationsUseTabs(False) sci.setIndentationWidth(4) sci.setMarginsFont(self.smallFont) sci.setMarginWidth(0, self.smallFontMetrics.width('00000')) sci.setFont(self.monoFont) sci.setAutoIndent(True) sci.setBraceMatching(Qsci.QsciScintilla.StrictBraceMatch) handler = SciHandler(sci) self.handlers[sci] = handler sci.setMarginLineNumbers(0, True) sci.setCaretLineVisible(True) sci.setCaretLineBackgroundColor(QtGui.QColor(prefs.get('color.editline'))) return handler Let's assume the rest of the application works, too (because it does :-)

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