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• C++: get const or non-const reference type from trait

  - by maciekp

  I am writing a functor F which takes function of type void (*func)(T) and func's argument arg. Then functor F calls func with arg. I would like F not to copy arg, just to pass it as reference. But then I cannot simply write "void F(void (*func)(T), T&)" because T could be a reference. So I am trying to write a trait, which allows to get proper reference type of T: T -> T& T& -> T& const T -> const T& const T& -> const T& I come up with something like this: template<typename T> struct type_op { typedef T& valid_ref_type; }; template<typename T> struct type_op<T&> { typedef typename type_op<T>::valid_ref_type valid_ref_type; }; template<typename T> struct type_op<const T> { typedef const T& valid_ref_type; }; template<typename T> struct type_op<const T&> { typedef const T& valid_ref_type; }; Which doesn't work for example for void a(int x) { std::cout << x << std::endl; } F(&a, 7); Giving error: invalid initialization of non-const reference of type ‘int&’ from a temporary of type ‘int’ in passing argument 2 of ‘void f(void (*)(T), typename type_op::valid_ref_type) [with T = int]’ How to get this trait to work?

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• Declaration for object for which creation is wrapped in macro

  - by learner

  The following macro is defined in our code: #define MSGMacro(obj, arg) MyPaymentClass obj(arg) Where MSGMacro is used to creates the object of type MyPaymentClass using code like MSGMacro(Card, 1); MSGMacro(Cash, 2); ---- ---- //removed unwanted things to keep question cleaner. All the above code is in one cpp file, Now the problem is how we can expose these two objects of MyPaymentClass to other units in my project? i.e. I want to use Card and Cash in other CPP files. Please suggest how I can give the declaration for the same in some header file?

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• Executing functions parallelly in PHP

  - by binaryLV

  Hi! Can PHP call a function and don't wait for it to return? So something like this: function callback($pause, $arg) { sleep($pause); echo $arg, "\n"; } header('Content-Type: text/plain'); fast_call_user_func_array('callback', array(3, 'three')); fast_call_user_func_array('callback', array(2, 'two')); fast_call_user_func_array('callback', array(1, 'one')); would output one (after 1 second) two (after 2 seconds) three (after 3 seconds) rather than three (after 3 seconds) two (after 3 + 2 = 5 seconds) one (after 3 + 2 + 1 = 6 seconds) Main script is intended to be run as a permanent process (TCP server). callback() function would receive data from client, execute external PHP script and then do something based on other arguments that are passed to callback(). The problem is that main script must not wait for external PHP script to finish. Result of external script is important, so exec('php -f file.php &') is not an option.

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• why Observable snapshot observer vector

  - by han14466

  In Observable's notifyObservers method, why does the coder use arrLocal = obs.toArray();? Why does not coder iterate vector directly? Thanks public void notifyObservers(Object arg) { Object[] arrLocal; synchronized (this) { /* We don't want the Observer doing callbacks into * arbitrary code while holding its own Monitor. * The code where we extract each Observable from * the Vector and store the state of the Observer * needs synchronization, but notifying observers * does not (should not). The worst result of any * potential race-condition here is that: * 1) a newly-added Observer will miss a * notification in progress * 2) a recently unregistered Observer will be * wrongly notified when it doesn't care */ if (!changed) return; arrLocal = obs.toArray(); clearChanged(); } for (int i = arrLocal.length-1; i>=0; i--) ((Observer)arrLocal[i]).update(this, arg); }

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• problem with threads

  - by Nadeem

  i want to be done for 10 times!!, to scan teh number and print it again!!, how i can do that #include <stdio.h> #include <pthread.h> #include <semaphore.h> sem_t m; int n; void *readnumber(void *arg) { scanf("%d",&n); sem_post(&m); } void *writenumber(void *arg) { //int x =3; //while(x>0) //{ //x = x-1; sem_wait(&m); printf("%d",n); //} } int main(){ pthread_t t1, t2; sem_init(&m, 0, 0); pthread_create(&t2, NULL, writenumber, NULL); pthread_create(&t1, NULL, readnumber, NULL); pthread_join(t2, NULL); pthread_join(t1, NULL); sem_destroy(&m); return 0; }

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• abt oracle procedure agv and deleting the csv file from procedures of oracle

  - by kishroe

  Hi can u give me the info abt how can we pass the arg to the oracle procedures how can i delete the csv file from oracle procedures

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• Best way to have common class shared by both C++ and Ruby?

  - by shuttle87

  I am currently working on a project where a team of us are designing a game, all of us are proficient in ruby and some (but not all) of us are proficient in c++. Initially we made the backend in ruby but we ported it to c++ for more speed. The c++ port of the backend has exactly the same features and algorithms as the original ruby code. However we still have a bunch of code in ruby that does useful things but we want it to now get the data from the c++ classes. Our first thought was that we could save some of the data structures in something like XML or redis and call that, but some of the developers don't like that idea. We don't need anything particularly complex data structures to be passed between the different parts of the code, just tuples, strings and ints. Is there any way of integrating the ruby code so that it can call the c++ stuff natively? Will we need to embed code? Will we have to make a ruby extension? If so are there any good resources/tutorials you could suggest? For example say we have this code in the c++ backend: class The_game{ private: bool printinfo; //print the player diagnostic info at the beginning if true int numplayers; std::vector<Player*> players; string current_action; int action_is_on; // the index of the player in the players array that the action is now on //more code here public: Table(std::vector<Player *> in_players, std::vector<Statistics *> player_stats ,const int in_numplayers); ~Table(); void play_game(); History actions_history; }; class History{ private: int action_sequence_number; std::vector<Action*> hand_actions; public: void print_history(); void add_action(Action* the_action_to_be_added); int get_action_sequence_number(){ return action_sequence_number;} bool history_actions_are_equal(); int last_action_size(int street,int number_of_actions_ago); History(); ~History(); }; Is there any way to natively call something in the actions_history via The_game object in ruby? (The objects in the original ruby code all had the same names and functionality) By this I mean: class MyRubyClass def method1(arg1) puts arg1 self.f() # ... but still available puts cpp_method.the_current_game.actions_history.get_action_sequence_number() end # Constructor: def initialize(arg) puts "In constructor with arg #{arg}" #get the c++ object here and call it cpp_method end end Is this possible? Any advice or suggestions are appreciated.

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• Regex to match a Java method signature

  - by nitesh

  I am having this particular requirement where a method has to be identified by different regular expressions for different components. For example, there need to be a regex for return parameter, one for method name, one for argument type and one for argument name. I was able to come up with an expression till this step as follows - ([^,]+) ([^,]+)\((([^,]+) ([^,]+))\) It works well for a method signature like - ReturnType foo(Arg parameter) The regular expression identifies ReturnType, foo, Arg and parameter separately. Now the problem is that a method can have no/one/multiple arguments separated by commas. I am not able to get a repeating expression for this. Help will be appreciated.

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• Explicitly persist states in Workflow 4.0 rather than everything.

  - by jlafay

  I have ran into an issue with my SQL instance store attached to a WorkflowApplication that is running. When I exit my application I'm calling an Unload() on the WF app to persist it. I didn't think about it during design time, but it does makes sense, it's persisting an arg that was passed in to the WorkflowApplication constructor when instanced. When the application runs, everything in the workflow works as expected. When I call Unload() I get an unhandled exception that states that the arg is not serializable and needs [DataContractAttribute]. What's passed into the workflow is my applications custom logger object that I wrote so that the WF can log to disk in a uniform way that I prefer. How do I prevent the workflow app from persisting this one argument and persist everything else? I'm sure something can be done with extensions but I'm having a hard time finding info on them or finding persistence examples for my scenario.

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• pthreads recursively calling system command and segfault appears

  - by jess

  I have a code base where i am creating 8 threads and each thread just calls system command to display date in a continuous cycle, as shown below: void * system_thread(void *arg) { int cpu = (int)arg; printf("thread : start %d\n", cpu); for (;;) { // date ã³ãã³ãã®å®è¡ if (mode == 0) { system("date"); } else { f_hfp_nlc_Fsystem("date"); } } sleep(timerval); return NULL; } This application segfaults after running for 2-3 seconds, due to following 2 reasons: 1. read access, where the address is out of VM area 2. write acces, where it does not of write permission and its trying to modify some structure.

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• HTML5 Video Javascript

  - by user373721

  Hi, I am not experienced in Javascript, I have the following script to play video files on Andriod phone, and it works fine. <script type="text/javascript"> function PlayMyVideo(arg) { var myVideo = document.getElementById([arg]); myVideo.play(); } </script> <video id="what" src="what.mp4" poster="" /> <input type="button" onclick="PlayMyVideo('what')" value="Play" /> I am trying to write the tag on the fly: <script type="text/javascript"> function PlayVideo() { new_video = document.createElement('video'); new_video.setAttribute('scr', 'what.mp4'); new_video.play(); } </script> <input type="button" onclick="PlayVideo()" value="Play2" /> Nothing happen, would appreciate your suggestions. Thanks in advance

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• C++ and virtual methods overriding

  - by silent

  Sorry for this stupid question, but I can't find an answer by myself, I'm too new in C++ :( class DBObject : public QObject { ... protected: virtual QString tableName() { return ""; }; }; class DBUserObject : public DBObject { ... protected: virtual QString tableName() { return "profiles"; }; }; And I have this code in parent: bool DBObject::load(quint32 id) { QString query = QString("select %1 from %2 where id = :id") .arg(fieldList().join(",")) .arg(tableName()); <--- here is trouble ... } So I'm trying to execute: DBUserObject user; user.load(3); But in result I have a query with empty table name cause tableName() method returns empty string. Why not "profiles"?

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• How do I restrict accepting only one type in my generic method?

  - by kunjaan

  I have a generic function foo, which accepts any type and prints them out. public static <T> T foo(T... arg) { List<T> foo = Arrays.asList(arg); for (T t : foo) { System.out.println(t); } return null; } How do I make sure that the arguments received are of only 1 type. For example, {1,'a',3} should be invalid. It should either be all numbers or all characters.

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• Changing a Widget's name based on a string read in from an XML form in Qt.

  - by Nick

  I'm writing a code for a voting machine that will allow user to read in custom XML ballots and then vote on them, however in the current build I have in QtCreator, I don't see an easy way to edit buttons in my GUI directly. In the code snippet below, I assign an element to pull out the names and type of ballot being read in, but I need to append a label on the GUI as well as change buttons to the names of candidates read in. Any ideas on how to do this? while(!n.isNull()){ QDomNode x = n.firstChildElement(); QDomElement e = n.toElement(); QMessageBox::information(0, tr( "Loading Element" ), tr( "Our element is %1" ).arg(e.tagName()) ); QDomElement p = x.firstChildElement();//p finds Races QMessageBox::information(0,tr("Foo"),tr("p = %1").arg(p.text()));//finds Race and Ballot types n = n.nextSibling(); } }

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• how to force drupal function to not use DB cache?

  - by Alaa

  Hi All, i have a module and i am using node_load(array('nid' = arg(1))); now the problem is that this function keep getting its data for node_load from DB cache. how can i force this function to not use DB cache? Example my link is http://mydomain.com/node/344983 now: $node=node_load(array('nid'=arg(1)),null,true); echo $node-nid; output 435632 which is a randomly node id (available on the system) and everytime i ctrl+F5 my browser i get new nid!! Thanks for your help

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• Ant command line arguments

  - by js7354

  Program works fine when run with eclipse run configurations, but when run with ant, it is unable to parse int from args[0], which I do not understand. Full code is available here https://gist.github.com/4108950/e984a581d5e9de889eaf0c8faf0e57752e825a97 I believe it has something to do with ant, target name="run" description="run the project"> java dir="${build.dir}" classname="BinarySearchTree" fork="yes"> <arg value="6 in.txt"/> /java> /target> the arg value will be changed via the -D flag, as in ant -Dargs="6 testData1.txt" run. Any help would be much appreciated, it is very frustrating.

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• Wrapping ASP.NET Client Callbacks

  - by Ricardo Peres

  Client Callbacks are probably the less known (and I dare say, less loved) of all the AJAX options in ASP.NET, which also include the UpdatePanel, Page Methods and Web Services. The reason for that, I believe, is it’s relative complexity: Get a reference to a JavaScript function; Dynamically register function that calls the above reference; Have a JavaScript handler call the registered function. However, it has some the nice advantage of being self-contained, that is, doesn’t need additional files, such as web services, JavaScript libraries, etc, or static methods declared on a page, or any kind of attributes. So, here’s what I want to do: Have a DOM element which exposes a method that is executed server side, passing it a string and returning a string; Have a server-side event that handles the client-side call; Have two client-side user-supplied callback functions for handling the success and error results. I’m going to develop a custom control without user interface that does the registration of the client JavaScript method as well as a server-side event that can be hooked by some handler on a page. My markup will look like this: 1: <script type="text/javascript"> 1:  2:  3: function onCallbackSuccess(result, context) 4: { 5: } 6:  7: function onCallbackError(error, context) 8: { 9: } 10:  </script> 2: <my:CallbackControl runat="server" ID="callback" SendAllData="true" OnCallback="OnCallback"/> The control itself looks like this: 1: public class CallbackControl : Control, ICallbackEventHandler 2: { 3: #region Public constructor 4: public CallbackControl() 5: { 6: this.SendAllData = false; 7: this.Async = true; 8: } 9: #endregion 10:  11: #region Public properties and events 12: public event EventHandler<CallbackEventArgs> Callback; 13:  14: [DefaultValue(true)] 15: public Boolean Async 16: { 17: get; 18: set; 19: } 20:  21: [DefaultValue(false)] 22: public Boolean SendAllData 23: { 24: get; 25: set; 26: } 27:  28: #endregion 29:  30: #region Protected override methods 31:  32: protected override void Render(HtmlTextWriter writer) 33: { 34: writer.AddAttribute(HtmlTextWriterAttribute.Id, this.ClientID); 35: writer.RenderBeginTag(HtmlTextWriterTag.Span); 36:  37: base.Render(writer); 38:  39: writer.RenderEndTag(); 40: } 41:  42: protected override void OnInit(EventArgs e) 43: { 44: String reference = this.Page.ClientScript.GetCallbackEventReference(this, "arg", "onCallbackSuccess", "context", "onCallbackError", this.Async); 45: String script = String.Concat("\ndocument.getElementById('", this.ClientID, "').callback = function(arg, context, onCallbackSuccess, onCallbackError){", ((this.SendAllData == true) ? "__theFormPostCollection.length = 0; __theFormPostData = ''; WebForm_InitCallback(); " : String.Empty), reference, ";};\n"); 46:  47: this.Page.ClientScript.RegisterStartupScript(this.GetType(), String.Concat("callback", this.ClientID), script, true); 48:  49: base.OnInit(e); 50: } 51:  52: #endregion 53:  54: #region Protected virtual methods 55: protected virtual void OnCallback(CallbackEventArgs args) 56: { 57: EventHandler<CallbackEventArgs> handler = this.Callback; 58:  59: if (handler != null) 60: { 61: handler(this, args); 62: } 63: } 64:  65: #endregion 66:  67: #region ICallbackEventHandler Members 68:  69: String ICallbackEventHandler.GetCallbackResult() 70: { 71: CallbackEventArgs args = new CallbackEventArgs(this.Context.Items["Data"] as String); 72:  73: this.OnCallback(args); 74:  75: return (args.Result); 76: } 77:  78: void ICallbackEventHandler.RaiseCallbackEvent(String eventArgument) 79: { 80: this.Context.Items["Data"] = eventArgument; 81: } 82:  83: #endregion 84: } And the event argument class: 1: [Serializable] 2: public class CallbackEventArgs : EventArgs 3: { 4: public CallbackEventArgs(String argument) 5: { 6: this.Argument = argument; 7: this.Result = String.Empty; 8: } 9:  10: public String Argument 11: { 12: get; 13: private set; 14: } 15:  16: public String Result 17: { 18: get; 19: set; 20: } 21: } You will notice two properties on the CallbackControl: Async: indicates if the call should be made asynchronously or synchronously (the default); SendAllData: indicates if the callback call will include the view and control state of all of the controls on the page, so that, on the server side, they will have their properties set when the Callback event is fired. The CallbackEventArgs class exposes two properties: Argument: the read-only argument passed to the client-side function; Result: the result to return to the client-side callback function, set from the Callback event handler. An example of an handler for the Callback event would be: 1: protected void OnCallback(Object sender, CallbackEventArgs e) 2: { 3: e.Result = String.Join(String.Empty, e.Argument.Reverse()); 4: } Finally, in order to fire the Callback event from the client, you only need this: 1: <input type="text" id="input"/> 2: <input type="button" value="Get Result" onclick="document.getElementById('callback').callback(callback(document.getElementById('input').value, 'context', onCallbackSuccess, onCallbackError))"/> The syntax of the callback function is: arg: some string argument; context: some context that will be passed to the callback functions (success or failure); callbackSuccessFunction: some function that will be called when the callback succeeds; callbackFailureFunction: some function that will be called if the callback fails for some reason. Give it a try and see if it helps!

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• Is it okay to define a [] method in ruby's NilClass?

  - by Silasj

  Ruby by default does not include the method [] for NilClass For example, to check if foo["bar"] exists when foo may be nil, I have to do: foo = something_that_may_or_may_not_return_nil if foo && foo["bar"] # do something with foo["bar"] here end If I define this method: class NilClass def [](arg) nil end end Something like that would make this possible, even if foo is nil: if foo["bar"] # do something with foo["bar"] end Or even: if foo["bar"]["baz"] # do something with foo["bar"]["baz"] here end Question: Is this a good idea or is there some reason ruby doesn't include this functionality by default?

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• Jetty - 401 Unauthorized when using basic authentication

  - by JP.

  I am running SOLR on jetty in Ubuntu (a bitnami VM, if that helps) and am trying to lock down access to both the admin pages and the update/delete/etc. pages using basic authentication. When I attempt to connect to the admin console via a web browser I am prompted for a user name and password, but the username and password I use simply does not work. For test purposes I am using foo:bar as the credentials, but I receive a '401 Unauthorized' response. I see the following in my request log. 127.0.0.1 - - [10/Nov/2013:05:35:46 +0000] "GET /solr/ HTTP/1.1" 401 1376 Am I doing something wrong and/or is there anything obviously incorrect with the below configuration? Any help is greatly appreciated. Jetty.xml <Call name="addBean"> <Arg> <New class="org.eclipse.jetty.security.HashLoginService"> <Set name="name">solr</Set> <Set name="config"><SystemProperty name="jetty.home" default="."/>/etc/realm.properties</Set> <Set name="refreshInterval">5</Set> </New> </Arg> </Call> /etc/realm.properties foo: bar, solr_admin webdefault.xml <security-constraint> <web-resource-collection> <url-pattern>/</url-pattern> </web-resource-collection> <auth-constraint> <role-name>solr_admin</role-name> </auth-constraint> </security-constraint> <login-config> <auth-method>BASIC</auth-method> <realm-name>solr</realm-name> </login-config>

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• How can I get Solr listening on 0.0.0.0 instead of just localhost?

  - by Neil

  I'm trying to get Solr to listen on 0.0.0.0 instead of just localhost, and it doesn't seem to be picking up the configuration options. I downloaded apache-solr-1.4.1 from the Solr website, and I'm running: user@:apache-solr-1.4.1/example $ java -jar start.jar With these configuration options: <Call name="addConnector"> <Arg> <New class="org.mortbay.jetty.bio.SocketConnector"> <Set name="host"><SystemProperty name="jetty.host" default="0.0.0.0" /></Set> <Set name="port"><SystemProperty name="jetty.port" default="8983" /></Set> <Set name="maxIdleTime">50000</Set> <Set name="lowResourceMaxIdleTime">1500</Set> </New> </Arg> </Call> Where the only line changed from the default is this one: <Set name="host"><SystemProperty name="jetty.host" default="0.0.0.0" /></Set> And when I check netstat, I see this: $ netstat -an | egrep 'Proto|\b8983\b' Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 127.0.0.1:8983 0.0.0.0:* LISTEN tcp6 0 0 ::1:8983 :::* LISTEN Where Local Address should be 0.0.0.0:8983 instead of 127.0.0.1:8983. Does anyone know why this might not be working?

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• Scala parser combinator runs out of memory

  - by user3217013

  I wrote the following parser in Scala using the parser combinators: import scala.util.parsing.combinator._ import scala.collection.Map import scala.io.StdIn object Keywords { val Define = "define" val True = "true" val False = "false" val If = "if" val Then = "then" val Else = "else" val Return = "return" val Pass = "pass" val Conj = ";" val OpenParen = "(" val CloseParen = ")" val OpenBrack = "{" val CloseBrack = "}" val Comma = "," val Plus = "+" val Minus = "-" val Times = "*" val Divide = "/" val Pow = "**" val And = "&&" val Or = "||" val Xor = "^^" val Not = "!" val Equals = "==" val NotEquals = "!=" val Assignment = "=" } //--------------------------------------------------------------------------------- sealed abstract class Op case object Plus extends Op case object Minus extends Op case object Times extends Op case object Divide extends Op case object Pow extends Op case object And extends Op case object Or extends Op case object Xor extends Op case object Not extends Op case object Equals extends Op case object NotEquals extends Op case object Assignment extends Op //--------------------------------------------------------------------------------- sealed abstract class Term case object TrueTerm extends Term case object FalseTerm extends Term case class FloatTerm(value : Float) extends Term case class StringTerm(value : String) extends Term case class Identifier(name : String) extends Term //--------------------------------------------------------------------------------- sealed abstract class Expression case class TermExp(term : Term) extends Expression case class UnaryOp(op : Op, exp : Expression) extends Expression case class BinaryOp(op : Op, left : Expression, right : Expression) extends Expression case class FuncApp(funcName : Term, args : List[Expression]) extends Expression //--------------------------------------------------------------------------------- sealed abstract class Statement case class ExpressionStatement(exp : Expression) extends Statement case class Pass() extends Statement case class Return(value : Expression) extends Statement case class AssignmentVar(variable : Term, exp : Expression) extends Statement case class IfThenElse(testBody : Expression, thenBody : Statement, elseBody : Statement) extends Statement case class Conjunction(left : Statement, right : Statement) extends Statement case class AssignmentFunc(functionName : Term, args : List[Term], body : Statement) extends Statement //--------------------------------------------------------------------------------- class myParser extends JavaTokenParsers { val keywordMap : Map[String, Op] = Map( Keywords.Plus -> Plus, Keywords.Minus -> Minus, Keywords.Times -> Times, Keywords.Divide -> Divide, Keywords.Pow -> Pow, Keywords.And -> And, Keywords.Or -> Or, Keywords.Xor -> Xor, Keywords.Not -> Not, Keywords.Equals -> Equals, Keywords.NotEquals -> NotEquals, Keywords.Assignment -> Assignment ) def floatTerm : Parser[Term] = decimalNumber ^^ { case x => FloatTerm( x.toFloat ) } def stringTerm : Parser[Term] = stringLiteral ^^ { case str => StringTerm(str) } def identifier : Parser[Term] = ident ^^ { case value => Identifier(value) } def boolTerm : Parser[Term] = (Keywords.True | Keywords.False) ^^ { case Keywords.True => TrueTerm case Keywords.False => FalseTerm } def simpleTerm : Parser[Expression] = (boolTerm | floatTerm | stringTerm) ^^ { case term => TermExp(term) } def argument = expression def arguments_aux : Parser[List[Expression]] = (argument <~ Keywords.Comma) ~ arguments ^^ { case arg ~ argList => arg :: argList } def arguments = arguments_aux | { argument ^^ { case arg => List(arg) } } def funcAppArgs : Parser[List[Expression]] = funcEmptyArgs | ( Keywords.OpenParen ~> arguments <~ Keywords.CloseParen ^^ { case args => args.foldRight(List[Expression]()) ( (a,b) => a :: b ) } ) def funcApp = identifier ~ funcAppArgs ^^ { case funcName ~ argList => FuncApp(funcName, argList) } def variableTerm : Parser[Expression] = identifier ^^ { case name => TermExp(name) } def atomic_expression = simpleTerm | funcApp | variableTerm def paren_expression : Parser[Expression] = Keywords.OpenParen ~> expression <~ Keywords.CloseParen def unary_operation : Parser[String] = Keywords.Not def unary_expression : Parser[Expression] = operation(0) ~ expression(0) ^^ { case op ~ exp => UnaryOp(keywordMap(op), exp) } def operation(precedence : Int) : Parser[String] = precedence match { case 0 => Keywords.Not case 1 => Keywords.Pow case 2 => Keywords.Times | Keywords.Divide | Keywords.And case 3 => Keywords.Plus | Keywords.Minus | Keywords.Or | Keywords.Xor case 4 => Keywords.Equals | Keywords.NotEquals case _ => throw new Exception("No operations with this precedence.") } def binary_expression(precedence : Int) : Parser[Expression] = precedence match { case 0 => throw new Exception("No operation with zero precedence.") case n => (expression (n-1)) ~ operation(n) ~ (expression (n)) ^^ { case left ~ op ~ right => BinaryOp(keywordMap(op), left, right) } } def expression(precedence : Int) : Parser[Expression] = precedence match { case 0 => unary_expression | paren_expression | atomic_expression case n => binary_expression(n) | expression(n-1) } def expression : Parser[Expression] = expression(4) def expressionStmt : Parser[Statement] = expression ^^ { case exp => ExpressionStatement(exp) } def assignment : Parser[Statement] = (identifier <~ Keywords.Assignment) ~ expression ^^ { case varName ~ exp => AssignmentVar(varName, exp) } def ifthen : Parser[Statement] = ((Keywords.If ~ Keywords.OpenParen) ~> expression <~ Keywords.CloseParen) ~ ((Keywords.Then ~ Keywords.OpenBrack) ~> statements <~ Keywords.CloseBrack) ^^ { case ifBody ~ thenBody => IfThenElse(ifBody, thenBody, Pass()) } def ifthenelse : Parser[Statement] = ((Keywords.If ~ Keywords.OpenParen) ~> expression <~ Keywords.CloseParen) ~ ((Keywords.Then ~ Keywords.OpenBrack) ~> statements <~ Keywords.CloseBrack) ~ ((Keywords.Else ~ Keywords.OpenBrack) ~> statements <~ Keywords.CloseBrack) ^^ { case ifBody ~ thenBody ~ elseBody => IfThenElse(ifBody, thenBody, elseBody) } def pass : Parser[Statement] = Keywords.Pass ^^^ { Pass() } def returnStmt : Parser[Statement] = Keywords.Return ~> expression ^^ { case exp => Return(exp) } def statement : Parser[Statement] = ((pass | returnStmt | assignment | expressionStmt) <~ Keywords.Conj) | ifthenelse | ifthen def statements_aux : Parser[Statement] = statement ~ statements ^^ { case st ~ sts => Conjunction(st, sts) } def statements : Parser[Statement] = statements_aux | statement def funcDefBody : Parser[Statement] = Keywords.OpenBrack ~> statements <~ Keywords.CloseBrack def funcEmptyArgs = Keywords.OpenParen ~ Keywords.CloseParen ^^^ { List() } def funcDefArgs : Parser[List[Term]] = funcEmptyArgs | Keywords.OpenParen ~> repsep(identifier, Keywords.Comma) <~ Keywords.CloseParen ^^ { case args => args.foldRight(List[Term]()) ( (a,b) => a :: b ) } def funcDef : Parser[Statement] = (Keywords.Define ~> identifier) ~ funcDefArgs ~ funcDefBody ^^ { case funcName ~ funcArgs ~ body => AssignmentFunc(funcName, funcArgs, body) } def funcDefAndStatement : Parser[Statement] = funcDef | statement def funcDefAndStatements_aux : Parser[Statement] = funcDefAndStatement ~ funcDefAndStatements ^^ { case stmt ~ stmts => Conjunction(stmt, stmts) } def funcDefAndStatements : Parser[Statement] = funcDefAndStatements_aux | funcDefAndStatement def parseProgram : Parser[Statement] = funcDefAndStatements def eval(input : String) = { parseAll(parseProgram, input) match { case Success(result, _) => result case Failure(m, _) => println(m) case _ => println("") } } } object Parser { def main(args : Array[String]) { val x : myParser = new myParser() println(args(0)) val lines = scala.io.Source.fromFile(args(0)).mkString println(x.eval(lines)) } } The problem is, when I run the parser on the following example it works fine: define foo(a) { if (!h(IM) && a) then { return 0; } if (a() && !h()) then { return 0; } } But when I add threes characters in the first if statement, it runs out of memory. This is absolutely blowing my mind. Can anyone help? (I suspect it has to do with repsep, but I am not sure.) define foo(a) { if (!h(IM) && a(1)) then { return 0; } if (a() && !h()) then { return 0; } } EDIT: Any constructive comments about my Scala style is also appreciated.

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• ASP.NET exception gives irrelevant stack trace on YSOD, very challenging!

  - by pootow

  Here is the YSOD: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Data.SqlClient.SqlException: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [SqlException (0x80131904): Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.] System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) +428 System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) +65 System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) +117 System.Data.SqlClient.SqlConnection.Open() +122 ECommerce.PMethod.Sql.SqlConns.Open() +78 ECommerce.PMethod.Sql.SqlConns..ctor() +120 ECommerce.login.DatasInfo.Proc.UserCenter.IsLogin(String UserGUID, Int32 UserID) +49 ECommerce.login.Rules.Users.UserLogin.isLogin() +44 Config.isUserLogined() +5 Shopping_Shopping.Page_Load(Object sender, EventArgs e) +10 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35 System.Web.UI.Control.OnLoad(EventArgs e) +99 System.Web.UI.Control.LoadRecursive() +50 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627 [TypeInitializationException: The type initializer for 'ECommerce.ERP.DAL.DBConn' threw an exception.] ECommerce.ERP.DAL.DBConn.get_ConnString() +0 [ObjectDefinitionStoreException: Factory method 'System.String get_ConnString()' threw an Exception.] Spring.Objects.Factory.Support.SimpleInstantiationStrategy.Instantiate(RootObjectDefinition definition, String name, IObjectFactory factory, MethodInfo factoryMethod, Object[] arguments) +257 Spring.Objects.Factory.Support.ConstructorResolver.InstantiateUsingFactoryMethod(String name, RootObjectDefinition definition, Object[] arguments) +624 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.InstantiateUsingFactoryMethod(String name, RootObjectDefinition definition, Object[] arguments) +60 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.CreateObjectInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +56 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.InstantiateObject(String name, RootObjectDefinition definition, Object[] arguments, Boolean allowEagerCaching, Boolean suppressConfigure) +436 [ObjectCreationException: Error thrown by a dependency of object 'styleService' defined in 'assembly [ECommerce.Services.Impl, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Services.Impl.AppContext.xml] line 56' : Initialization of object failed : Factory method 'System.String get_ConnString()' threw an Exception. while resolving 'constructor argument with name promotionservice' to 'promotionService' defined in 'assembly [ECommerce.Services.Impl, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Services.Impl.AppContext.xml] line 31' while resolving 'constructor argument with name domainservice' to 'promotionDomainService' defined in 'assembly [ECommerce.Domain, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Domain.AppContext.xml] line 20' while resolving 'constructor argument with name promotionrepos' to 'promotionRepos' defined in 'assembly [ECommerce.Data.AdoNet, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Data.AdoNet.AppContext.xml] line 34' while resolving 'constructor argument with name connstr' to 'ECommerce.ERP.DAL.DBConn#389F399' defined in 'assembly [ECommerce.Data.AdoNet, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null], resource [ECommerce.Data.AdoNet.AppContext.xml] line 34'] Spring.Objects.Factory.Support.ObjectDefinitionValueResolver.ResolveReference(IObjectDefinition definition, String name, String argumentName, RuntimeObjectReference reference) +394 Spring.Objects.Factory.Support.ObjectDefinitionValueResolver.ResolvePropertyValue(String name, IObjectDefinition definition, String argumentName, Object argumentValue) +312 Spring.Objects.Factory.Support.ObjectDefinitionValueResolver.ResolveValueIfNecessary(String name, IObjectDefinition definition, String argumentName, Object argumentValue) +17 Spring.Objects.Factory.Support.ConstructorResolver.ResolveConstructorArguments(String objectName, RootObjectDefinition definition, ObjectWrapper wrapper, ConstructorArgumentValues cargs, ConstructorArgumentValues resolvedValues) +993 Spring.Objects.Factory.Support.ConstructorResolver.AutowireConstructor(String objectName, RootObjectDefinition rod, ConstructorInfo[] chosenCtors, Object[] explicitArgs) +171 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.AutowireConstructor(String name, RootObjectDefinition definition, ConstructorInfo[] ctors, Object[] explicitArgs) +65 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.CreateObjectInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +161 Spring.Objects.Factory.Support.AbstractAutowireCapableObjectFactory.InstantiateObject(String name, RootObjectDefinition definition, Object[] arguments, Boolean allowEagerCaching, Boolean suppressConfigure) +636 Spring.Objects.Factory.Support.AbstractObjectFactory.CreateAndCacheSingletonInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +174 Spring.Objects.Factory.Support.WebObjectFactory.CreateAndCacheSingletonInstance(String objectName, RootObjectDefinition objectDefinition, Object[] arguments) +150 Spring.Objects.Factory.Support.AbstractObjectFactory.GetObjectInternal(String name, Type requiredType, Object[] arguments, Boolean suppressConfigure) +990 Spring.Objects.Factory.Support.AbstractObjectFactory.GetObject(String name) +10 Spring.Context.Support.AbstractApplicationContext.GetObject(String name) +20 ECommerce.Common.ServiceLocator.GetService() +334 ECommerce.Mvc.Controllers.StylesController..ctor() +72 [TargetInvocationException: Exception has been thrown by the target of an invocation.] System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandle& ctor, Boolean& bNeedSecurityCheck) +0 System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean fillCache) +86 System.RuntimeType.CreateInstanceImpl(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean fillCache) +230 System.Activator.CreateInstance(Type type, Boolean nonPublic) +67 System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +80 [InvalidOperationException: An error occurred when trying to create a controller of type 'ECommerce.Mvc.Controllers.StylesController'. Make sure that the controller has a parameterless public constructor.] System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +190 System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName) +68 System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& controller, IControllerFactory& factory) +118 System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +46 System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state) +63 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData) +13 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8677954 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155 Version Information: Microsoft .NET Framework Version:2.0.50727.3082; ASP.NET Version:2.0.50727.3082 Question is: the first stack trace is irrelevant to others, what happened? Any ideas? Let me make this more clear: a MVC page uses the spring part trying to load a lazy-init service which constructor wants a connection string through a static property like this: <object id="promotionRepos" type="ECommerce.Data.AdoNet.Promotions.PromotionRepos, ECommerce.Data.AdoNet" lazy-init="true"> <constructor-arg name="provider"> <null /> </constructor-arg> <constructor-arg name="connStr"> <object type="ECommerce.ERP.DAL.DBConn, ECommerce.ERP.DAL" factory-method="get_ConnString" /> </constructor-arg> <property name="RefreshInterval" value="00:00:10" /> </object> the timeout part is some what irrelevent to all others. see this in the first exception: Shopping_Shopping.Page_Load(Object sender, EventArgs e) +10 it's another page at all. And also, ECommerce.PMethod.Sql.SqlConns.Open() uses its own connection string, not the one loaded by spring, it's different module from diffrent team. And I am sure the connection string is correct. And, this ysod cames up randomly. Sometimes nothing is wrong, and sometimes, it appears. I thought there could be something wrong with my database or the network/firewall, I will check it later, but now I want understand this tricky stack trace.

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• Ajax, Callback, postback and Sys.WebForms.PageRequestManager.getInstance().add_beginRequest

  - by user338262

  Hi, I have a user control which encapsulates a NumericUpDownExtender. This UserControl implements the interface ICallbackEventHandler, because I want that when a user changes the value of the textbox associated a custom event to be raised in the server. By the other hand each time an async postback is done I shoe a message of loading and disable the whole screen. This works perfect when something is changed in for example an UpdatePanel through this lines of code: Sys.WebForms.PageRequestManager.getInstance().add_beginRequest( function (sender, args) { var modalPopupBehavior = $find('programmaticSavingLoadingModalPopupBehavior'); modalPopupBehavior.show(); } ); The UserControl is placed inside a detailsview which is inside an UpdatePanel in an aspx. When the custom event is raised I want another textbox in the aspx to change its value. So far, When I click on the UpDownExtender, it goes correctly to the server and raises the custom event, and the new value of the textbox is assigned in the server. but it is not changed in the browser. I suspect that the problem is the callback, since I have the same architecture for a UserControl with an AutoCompleteExtender which implement IPostbackEventHandler and it works. Any clues how can I solve this here to make the UpDownNumericExtender user control to work like the AutComplete one? This is the code of the user control and the parent: using System; using System.Web.UI; using System.ComponentModel; using System.Text; namespace Corp.UserControls { [Themeable(true)] public partial class CustomNumericUpDown : CorpNumericUpDown, ICallbackEventHandler { protected void Page_PreRender(object sender, EventArgs e) { if (!Page.IsPostBack) { currentInstanceNumber = CorpAjaxControlToolkitUserControl.getNextInstanceNumber(); } registerControl(this.HFNumericUpDown.ClientID, currentInstanceNumber); string strCallServer = "NumericUpDownCallServer" + currentInstanceNumber.ToString(); // If this function is not written the callback to get the disponibilidadCliente doesn't work if (!Page.ClientScript.IsClientScriptBlockRegistered("ReceiveServerDataNumericUpDown")) { StringBuilder str = new StringBuilder(); str.Append("function ReceiveServerDataNumericUpDown(arg, context) {}").AppendLine(); Page.ClientScript.RegisterClientScriptBlock(typeof(CorpNumericUpDown), "ReceiveServerDataNumericUpDown", str.ToString(), true); } nudeNumericUpDownExtender.BehaviorID = "NumericUpDownEx" + currentInstanceNumber.ToString(); ClientScriptManager cm = Page.ClientScript; String cbReference = cm.GetCallbackEventReference(this, "arg", "ReceiveServerDataNumericUpDown", ""); String callbackScript = "function " + strCallServer + "(arg, context)" + Environment.NewLine + "{" + Environment.NewLine + cbReference + ";" + Environment.NewLine + "}" + Environment.NewLine; cm.RegisterClientScriptBlock(typeof(CustomNumericUpDown), strCallServer, callbackScript, true); base.Page_PreRender(sender,e); } [System.ComponentModel.Browsable(true)] [System.ComponentModel.Bindable(true)] public Int64 Value { get { return (string.IsNullOrEmpty(HFNumericUpDown.Value) ? Int64.Parse("1") : Int64.Parse(HFNumericUpDown.Value)); } set { HFNumericUpDown.Value = value.ToString(); //txtAutoCompleteCliente_AutoCompleteExtender.ContextKey = value.ToString(); // TODO: Change the text of the textbox } } [System.ComponentModel.Browsable(true)] [System.ComponentModel.Bindable(true)] [Description("The text of the numeric up down")] public string Text { get { return txtNumericUpDown.Text; } set { txtNumericUpDown.Text = value; } } public delegate void NumericUpDownChangedHandler(object sender, NumericUpDownChangedArgs e); public event NumericUpDownChangedHandler numericUpDownEvent; [System.ComponentModel.Browsable(true)] [System.ComponentModel.Bindable(true)] [System.ComponentModel.Description("Raised after the number has been increased or decreased")] protected virtual void OnNumericUpDownEvent(object sender, NumericUpDownChangedArgs e) { if (numericUpDownEvent != null) //check to see if anyone has attached to the event numericUpDownEvent(this, e); } #region ICallbackEventHandler Members public string GetCallbackResult() { return "";//throw new NotImplementedException(); } public void RaiseCallbackEvent(string eventArgument) { NumericUpDownChangedArgs nudca = new NumericUpDownChangedArgs(long.Parse(eventArgument)); OnNumericUpDownEvent(this, nudca); } #endregion } /// <summary> /// Class that adds the prestamoList to the event /// </summary> public class NumericUpDownChangedArgs : System.EventArgs { /// <summary> /// The current selected value. /// </summary> public long Value { get; private set; } public NumericUpDownChangedArgs(long value) { Value = value; } } } using System; using System.Collections.Generic; using System.Text; namespace Corp { /// <summary> /// Summary description for CorpAjaxControlToolkitUserControl /// </summary> public class CorpNumericUpDown : CorpAjaxControlToolkitUserControl { private Int16 _currentInstanceNumber; // This variable hold the instanceNumber assignated at first place. public short currentInstanceNumber { get { return _currentInstanceNumber; } set { _currentInstanceNumber = value; } } protected void Page_PreRender(object sender, EventArgs e) { const string strOnChange = "OnChange"; const string strCallServer = "NumericUpDownCallServer"; StringBuilder str = new StringBuilder(); foreach (KeyValuePair<String, Int16> control in controlsToRegister) { str.Append("function ").Append(strOnChange + control.Value).Append("(sender, eventArgs) ").AppendLine(); str.Append("{").AppendLine(); str.Append(" if (sender) {").AppendLine(); str.Append(" var hfield = document.getElementById('").Append(control.Key).Append("');").AppendLine(); str.Append(" if (hfield.value != eventArgs) {").AppendLine(); str.Append(" hfield.value = eventArgs;").AppendLine(); str.Append(" ").Append(strCallServer + control.Value).Append("(eventArgs, eventArgs);").AppendLine(); str.Append(" }").AppendLine(); str.Append(" }").AppendLine(); str.Append("}").AppendLine(); Page.ClientScript.RegisterClientScriptBlock(typeof(CorpNumericUpDown), Guid.NewGuid().ToString(), str.ToString(), true); } str = new StringBuilder(); foreach (KeyValuePair<String, Int16> control in controlsToRegister) { str.Append(" funcsPageLoad[funcsPageLoad.length] = function() { $find('NumericUpDownEx" + control.Value + "').add_currentChanged(").Append(strOnChange + control.Value).Append(");};").AppendLine(); str.Append(" funcsPageUnLoad[funcsPageUnLoad.length] = function() { $find('NumericUpDownEx" + control.Value + "').remove_currentChanged(").Append(strOnChange + control.Value).Append(");};").AppendLine(); } Page.ClientScript.RegisterClientScriptBlock(typeof(CorpNumericUpDown), Guid.NewGuid().ToString(), str.ToString(), true); } } } and to create the loading view I use this: //The beginRequest event is raised before the processing of an asynchronous postback starts and the postback is sent to the server. You can use this event to call custom script to set a request header or to start an animation that notifies the user that the postback is being processed. Sys.WebForms.PageRequestManager.getInstance().add_beginRequest( function (sender, args) { var modalPopupBehavior = $find('programmaticSavingLoadingModalPopupBehavior'); modalPopupBehavior.show(); } ); //The endRequest event is raised after an asynchronous postback is finished and control has been returned to the browser. You can use this event to provide a notification to users or to log errors. Sys.WebForms.PageRequestManager.getInstance().add_endRequest( function (sender, arg) { var modalPopupBehavior = $find('programmaticSavingLoadingModalPopupBehavior'); modalPopupBehavior.hide(); } ); Thanks in advance! Daniel.

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• The fastest way to resize images from ASP.NET. And it’s (more) supported-ish.

  - by Bertrand Le Roy

  I’ve shown before how to resize images using GDI, which is fairly common but is explicitly unsupported because we know of very real problems that this can cause. Still, many sites still use that method because those problems are fairly rare, and because most people assume it’s the only way to get the job done. Plus, it works in medium trust. More recently, I’ve shown how you can use WPF APIs to do the same thing and get JPEG thumbnails, only 2.5 times faster than GDI (even now that GDI really ultimately uses WIC to read and write images). The boost in performance is great, but it comes at a cost, that you may or may not care about: it won’t work in medium trust. It’s also just as unsupported as the GDI option. What I want to show today is how to use the Windows Imaging Components from ASP.NET APIs directly, without going through WPF. The approach has the great advantage that it’s been tested and proven to scale very well. The WIC team tells me you should be able to call support and get answers if you hit problems. Caveats exist though. First, this is using interop, so until a signed wrapper sits in the GAC, it will require full trust. Second, the APIs have a very strong smell of native code and are definitely not .NET-friendly. And finally, the most serious problem is that older versions of Windows don’t offer MTA support for image decoding. MTA support is only available on Windows 7, Vista and Windows Server 2008. But on 2003 and XP, you’ll only get STA support. that means that the thread safety that we so badly need for server applications is not guaranteed on those operating systems. To make it work, you’d have to spin specialized threads yourself and manage the lifetime of your objects, which is outside the scope of this article. We’ll assume that we’re fine with al this and that we’re running on 7 or 2008 under full trust. Be warned that the code that follows is not simple or very readable. This is definitely not the easiest way to resize an image in .NET. Wrapping native APIs such as WIC in a managed wrapper is never easy, but fortunately we won’t have to: the WIC team already did it for us and released the results under MS-PL. The InteropServices folder, which contains the wrappers we need, is in the WicCop project but I’ve also included it in the sample that you can download from the link at the end of the article. In order to produce a thumbnail, we first have to obtain a decoding frame object that WIC can use. Like with WPF, that object will contain the command to decode a frame from the source image but won’t do the actual decoding until necessary. Getting the frame is done by reading the image bytes through a special WIC stream that you can obtain from a factory object that we’re going to reuse for lots of other tasks: var photo = File.ReadAllBytes(photoPath); var factory = (IWICComponentFactory)new WICImagingFactory(); var inputStream = factory.CreateStream(); inputStream.InitializeFromMemory(photo, (uint)photo.Length); var decoder = factory.CreateDecoderFromStream( inputStream, null, WICDecodeOptions.WICDecodeMetadataCacheOnLoad); var frame = decoder.GetFrame(0); We can read the dimensions of the frame using the following (somewhat ugly) code: uint width, height; frame.GetSize(out width, out height); This enables us to compute the dimensions of the thumbnail, as I’ve shown in previous articles. We now need to prepare the output stream for the thumbnail. WIC requires a special kind of stream, IStream (not implemented by System.IO.Stream) and doesn’t directlyunderstand .NET streams. It does provide a number of implementations but not exactly what we need here. We need to output to memory because we’ll want to persist the same bytes to the response stream and to a local file for caching. The memory-bound version of IStream requires a fixed-length buffer but we won’t know the length of the buffer before we resize. To solve that problem, I’ve built a derived class from MemoryStream that also implements IStream. The implementation is not very complicated, it just delegates the IStream methods to the base class, but it involves some native pointer manipulation. Once we have a stream, we need to build the encoder for the output format, which could be anything that WIC supports. For web thumbnails, our only reasonable options are PNG and JPEG. I explored PNG because it’s a lossless format, and because WIC does support PNG compression. That compression is not very efficient though and JPEG offers good quality with much smaller file sizes. On the web, it matters. I found the best PNG compression option (adaptive) to give files that are about twice as big as 100%-quality JPEG (an absurd setting), 4.5 times bigger than 95%-quality JPEG and 7 times larger than 85%-quality JPEG, which is more than acceptable quality. As a consequence, we’ll use JPEG. The JPEG encoder can be prepared as follows: var encoder = factory.CreateEncoder( Consts.GUID_ContainerFormatJpeg, null); encoder.Initialize(outputStream, WICBitmapEncoderCacheOption.WICBitmapEncoderNoCache); The next operation is to create the output frame: IWICBitmapFrameEncode outputFrame; var arg = new IPropertyBag2[1]; encoder.CreateNewFrame(out outputFrame, arg); Notice that we are passing in a property bag. This is where we’re going to specify our only parameter for encoding, the JPEG quality setting: var propBag = arg[0]; var propertyBagOption = new PROPBAG2[1]; propertyBagOption[0].pstrName = "ImageQuality"; propBag.Write(1, propertyBagOption, new object[] { 0.85F }); outputFrame.Initialize(propBag); We can then set the resolution for the thumbnail to be 96, something we weren’t able to do with WPF and had to hack around: outputFrame.SetResolution(96, 96); Next, we set the size of the output frame and create a scaler from the input frame and the computed dimensions of the target thumbnail: outputFrame.SetSize(thumbWidth, thumbHeight); var scaler = factory.CreateBitmapScaler(); scaler.Initialize(frame, thumbWidth, thumbHeight, WICBitmapInterpolationMode.WICBitmapInterpolationModeFant); The scaler is using the Fant method, which I think is the best looking one even if it seems a little softer than cubic (zoomed here to better show the defects): Cubic Fant Linear Nearest neighbor We can write the source image to the output frame through the scaler: outputFrame.WriteSource(scaler, new WICRect { X = 0, Y = 0, Width = (int)thumbWidth, Height = (int)thumbHeight }); And finally we commit the pipeline that we built and get the byte array for the thumbnail out of our memory stream: outputFrame.Commit(); encoder.Commit(); var outputArray = outputStream.ToArray(); outputStream.Close(); That byte array can then be sent to the output stream and to the cache file. Once we’ve gone through this exercise, it’s only natural to wonder whether it was worth the trouble. I ran this method, as well as GDI and WPF resizing over thirty twelve megapixel images for JPEG qualities between 70% and 100% and measured the file size and time to resize. Here are the results: Size of resized images   Time to resize thirty 12 megapixel images Not much to see on the size graph: sizes from WPF and WIC are equivalent, which is hardly surprising as WPF calls into WIC. There is just an anomaly for 75% for WPF that I noted in my previous article and that disappears when using WIC directly. But overall, using WPF or WIC over GDI represents a slight win in file size. The time to resize is more interesting. WPF and WIC get similar times although WIC seems to always be a little faster. Not surprising considering WPF is using WIC. The margin of error on this results is probably fairly close to the time difference. As we already knew, the time to resize does not depend on the quality level, only the size does. This means that the only decision you have to make here is size versus visual quality. This third approach to server-side image resizing on ASP.NET seems to converge on the fastest possible one. We have marginally better performance than WPF, but with some additional peace of mind that this approach is sanctioned for server-side usage by the Windows Imaging team. It still doesn’t work in medium trust. That is a problem and shows the way for future server-friendly managed wrappers around WIC. The sample code for this article can be downloaded from: http://weblogs.asp.net/blogs/bleroy/Samples/WicResize.zip The benchmark code can be found here (you’ll need to add your own images to the Images directory and then add those to the project, with content and copy if newer in the properties of the files in the solution explorer): http://weblogs.asp.net/blogs/bleroy/Samples/WicWpfGdiImageResizeBenchmark.zip WIC tools can be downloaded from: http://code.msdn.microsoft.com/wictools To conclude, here are some of the resized thumbnails at 85% fant:

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• boost::function & boost::lambda again

  - by John Dibling

  Follow-up to post: http://stackoverflow.com/questions/2978096/using-width-precision-specifiers-with-boostformat I'm trying to use boost::function to create a function that uses lambdas to format a string with boost::format. Ultimately what I'm trying to achieve is using width & precision specifiers for strings with format. boost::format does not support the use of the * width & precision specifiers, as indicated in the docs: Width or precision set to asterisk (*) are used by printf to read this field from an argument. e.g. printf("%1$d:%2$.*3$d:%4$.*3$d\n", hour, min, precision, sec); This class does not support this mechanism for now. so such precision or width fields are quietly ignored by the parsing. so I'm trying to find other ways to accomplish the same goal. Here is what I have so far, which isn't working: #include <string> #include <boost\function.hpp> #include <boost\lambda\lambda.hpp> #include <iostream> #include <boost\format.hpp> #include <iomanip> #include <boost\bind.hpp> int main() { using namespace boost::lambda; using namespace std; boost::function<std::string(int, std::string)> f = (boost::format("%s") % boost::io::group(setw(_1*2), setprecision(_2*2), _3)).str(); std::string s = (boost::format("%s") % f(15, "Hello")).str(); return 0; } This generates many compiler errors: 1>------ Build started: Project: hacks, Configuration: Debug x64 ------ 1>Compiling... 1>main.cpp 1>.\main.cpp(15) : error C2872: '_1' : ambiguous symbol 1> could be 'D:\Program Files (x86)\boost\boost_1_42\boost/lambda/core.hpp(69) : boost::lambda::placeholder1_type &boost::lambda::`anonymous-namespace'::_1' 1> or 'D:\Program Files (x86)\boost\boost_1_42\boost/bind/placeholders.hpp(43) : boost::arg<I> `anonymous-namespace'::_1' 1> with 1> [ 1> I=1 1> ] 1>.\main.cpp(15) : error C2664: 'std::setw' : cannot convert parameter 1 from 'boost::lambda::placeholder1_type' to 'std::streamsize' 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called 1>.\main.cpp(15) : error C2872: '_2' : ambiguous symbol 1> could be 'D:\Program Files (x86)\boost\boost_1_42\boost/lambda/core.hpp(70) : boost::lambda::placeholder2_type &boost::lambda::`anonymous-namespace'::_2' 1> or 'D:\Program Files (x86)\boost\boost_1_42\boost/bind/placeholders.hpp(44) : boost::arg<I> `anonymous-namespace'::_2' 1> with 1> [ 1> I=2 1> ] 1>.\main.cpp(15) : error C2664: 'std::setprecision' : cannot convert parameter 1 from 'boost::lambda::placeholder2_type' to 'std::streamsize' 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called 1>.\main.cpp(15) : error C2872: '_3' : ambiguous symbol 1> could be 'D:\Program Files (x86)\boost\boost_1_42\boost/lambda/core.hpp(71) : boost::lambda::placeholder3_type &boost::lambda::`anonymous-namespace'::_3' 1> or 'D:\Program Files (x86)\boost\boost_1_42\boost/bind/placeholders.hpp(45) : boost::arg<I> `anonymous-namespace'::_3' 1> with 1> [ 1> I=3 1> ] 1>.\main.cpp(15) : error C2660: 'boost::io::group' : function does not take 3 arguments 1>.\main.cpp(15) : error C2228: left of '.str' must have class/struct/union 1>Build log was saved at "file://c:\Users\john\Documents\Visual Studio 2005\Projects\hacks\x64\Debug\BuildLog.htm" 1>hacks - 7 error(s), 0 warning(s) ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== My fundamental understanding of boost's lambdas and functions is probably lacking. How can I get this to work?

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