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• linux raw socket programming question

  - by user194420

  Hi all, I am trying to create a raw socket which send and receive message with ip/tcp header under linux. I can successfully binds to a port and receive tcp message(ie:syn) However, the message seems to be handled by the os, but not mine. I am just a reader of it(like wireshark). My raw socket binds to port 8888, and then i try to telnet to that port . In wireshark, it shows that the port 8888 reply a "rst ack" when it receive the "syn" request. In my program, it shows that it receive a new message and it doesnot reply with any message. Any way to actually binds to that port?(prevent os handle it) Here is part of my code, i try to cut those error checking for easy reading sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_TCP); int tmp = 1; const int *val = &tmp; setsockopt (sockfd, IPPROTO_IP, IP_HDRINCL, val, sizeof (tmp)); servaddr.sin_family = AF_INET; servaddr.sin_addr.s_addr = htonl(INADDR_ANY); servaddr.sin_port = htons(8888); bind(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)); //call recv in loop

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• Problem with close socket

  - by zp26

  Hi, I have a problem with my socket program. I create the client program (my code is below) I have a problem when i close the socket with the disconnect method. Can i help me? Thanks and sorry for my English XP CFSocketRef s; -(void)CreaConnessione { CFSocketError errore; struct sockaddr_in sin; CFDataRef address; CFRunLoopSourceRef source; CFSocketContext context = { 0, self, NULL, NULL, NULL }; s = CFSocketCreate( NULL, PF_INET, SOCK_STREAM, IPPROTO_TCP, kCFSocketDataCallBack, AcceptDataCallback, &context); memset(&sin, 0, sizeof(sin)); int port = [fieldPorta.text intValue]; NSString *tempIp = fieldIndirizzo.text; const char *ip = [tempIp UTF8String]; sin.sin_family = AF_INET; sin.sin_port = htons(port); sin.sin_addr.s_addr = (long)inet_addr(ip); address = CFDataCreate(NULL, (UInt8 *)&sin, sizeof(sin)); errore = CFSocketConnectToAddress(s, address, 0); if(errore == 0){ buttonInvioMess.enabled = TRUE; fieldMessaggioInvio.enabled = TRUE; labelTemp.text = [NSString stringWithFormat:@"Connesso al Server"]; CFRelease(address); source = CFSocketCreateRunLoopSource(NULL, s, 0); CFRunLoopAddSource(CFRunLoopGetCurrent(), source, kCFRunLoopDefaultMode); CFRelease(source); CFRunLoopRun(); } else{ labelTemp.text = [NSString stringWithFormat:@"Errore di connessione. Verificare Ip e Porta"]; switchConnection.on = FALSE; } } //the socket doesn't disconnect -(void)Disconnetti{ CFSocketInvalidate(s); CFRelease(s); } -(IBAction)Connetti { if(switchConnection.on) [self CreaConnessione]; else [self Disconnetti]; }

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• Android XmlSerializer limitation?

  - by Rexb

  Hi all, My task is just to get an xml string using XmlSerializer. Problem is that it seems like the serializer stops adding any new element and/or attribute to the xml document when it reaches certain length (perhaps 10,000 char?). My questions: have you experience this kind of problem? What could be possible solutions? Here is my sample test code: public void doSerialize() throws XmlPullParserException, IllegalArgumentException, IllegalStateException, IOException { StringWriter writer = new StringWriter(); XmlSerializer serializer = XmlPullParserFactory.newInstance().newSerializer(); serializer.setOutput(writer); serializer.startDocument(null, null); serializer.startTag(null, "START"); for (int i = 0; i < 20; i++) { serializer.attribute(null, "ATTR" + i, "VAL " + i); } serializer.startTag(null, "DATA"); for (int i = 0; i < 500; i++) { serializer.attribute(null, "attr" + i, "value " + i); } serializer.endTag(null, "DATA"); serializer.endTag(null, "START"); serializer.endDocument(); String xml = writer.toString(); // value: until 493rd attribute int n = xml.length(); // value: 10125 } Any help will be greatly appreciated.

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• Program repeats each time a character is scanned .. How to stop it ?

  - by ZaZu

  Hello there, I have a program that has this code : #include<stdio.h> main(){ int input; char g; do{ printf("Choose a numeric value"); printf(">"); scanf("\n%c",&input); g=input-'0'; }while((g>=-16 && g<=-1)||(g>=10 && g<=42)||(g>=43 && g<=79)); } It basically uses ASCII manipulation to allow the program to accept numbers only .. '0' is given the value 48 by default...the ASCII value - 48 gives a ranges of numbers above (in the while statement) Anyway, whenever a user inputs numbers AND alphabets, such as : abr39293afakvmienb23 The program ignores : a,b,r .. But takes '3' as the first input. For a b and r, the code under the do loop repeats. So for the above example, I get : Choose a numeric value >Choose a numeric value> Choose a numeric value >3 Is there a way I can stop this ??? I tried using \n%c to scan the character and account for whitespace, but that didnt work :( Please help thank you very much !

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• Dealing with array of IntPtr

  - by Padu Merloti

  I think I'm close and I bet the solution is something stupid. I have a C++ native DLL where I define the following function: DllExport bool __stdcall Open(const char* filePath, int *numFrames, void** data); { //creates the list of arrays here... don't worry, lifetime is managed somewhere else //foreach item of the list: { BYTE* pByte = GetArray(i); //here's where my problem lives *(data + i * sizeofarray) = pByte; } *numFrames = total number of items in the list return true; } Basically, given a file path, this function creates a list of byte arrays (BYTE*) and should return a list of pointers via the data param. Each pointing to a different byte array. I want to pass an array of IntPtr from C# and be able to marshal each individual array in order. Here's the code I'm using: [DllImport("mydll.dll",EntryPoint = "Open")] private static extern bool MyOpen( string filePath, out int numFrames, out IntPtr[] ptr); internal static bool Open( string filePath, out int numFrames, out Bitmap[] images) { var ptrList = new IntPtr[512]; MyOpen(filePath, out numFrames, out ptrList); images = new Bitmap[numFrames]; var len = 100; //for sake of simplicity for (int i=0; i<numFrames;i++) { var buffer = new byte[len]; Marshal.Copy(ptrList[i], buffer, 0, len); images[i] = CreateBitmapFromBuffer(buffer, height, width); } return true; } Problem is in my C++ code. When I assign *(data + i * sizeofarray) = pByte; it corrupts the array of pointers... what am I doing wrong?

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• Exercise for exam about comparing string on file

  - by Telmo Vaz

  I'm trying to do this exercise for my exam tomorrow. I need to compare a string of my own input and see if that string is appearing on the file. This needs to be done directly on the file, so I cannot extract the string to my program and compare them "indirectly". I found this way but I'm not getting it right, and I don't know why. The algorithm sounds good to me. Any help, please? I really need to focus on this one. Thanks in advance, guys. #include<stdio.h> void comp(); int main(void) { comp(); return 0; } void comp() { FILE *file = fopen("e1.txt", "r+"); if(!file) { printf("Not possible to open the file"); return; } char src[50], ch; short i, len; fprintf(stdout, "What are you looking for? \nwrite: "); fgets(src, 200, stdin); len = strlen(src); while((ch = fgetc(file)) != EOF) { i = 0; while(ch == src[i]) { if(i <= len) { printf("%c - %c", ch, src[i]); fseek(file, 0, SEEK_CUR + 1); i++; } else break; } } }

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• C socket programming: client send() but server select() doesn't see it

  - by Fantastic Fourier

  Hey all, I have a server and a client running on two different machines where the client send()s but the server doesn't seem to receive the message. The server employs select() to monitor sockets for any incoming connections/messages. I can see that when the server accepts a new connection, it updates the fd_set array but always returns 0 despite the client send() messages. The connection is TCP and the machines are separated by like one router so dropping packets are highly unlikely. I have a feeling that it's not select() but perhaps send()/sendto() from client that may be the problem but I'm not sure how to go about localizing the problem area. while(1) { readset = info->read_set; ready = select(info->max_fd+1, &readset, NULL, NULL, &timeout); } above is the server side code where the server has a thread that runs select() indefinitely. rv = connect(sockfd, (struct sockaddr *) &server_address, sizeof(server_address)); printf("rv = %i\n", rv); if (rv < 0) { printf("MAIN: ERROR connect() %i: %s\n", errno, strerror(errno)); exit(1); } else printf("connected\n"); sleep(3); char * somemsg = "is this working yet?\0"; rv = send(sockfd, somemsg, sizeof(somemsg), NULL); if (rv < 0) printf("MAIN: ERROR send() %i: %s\n", errno, strerror(errno)); printf("MAIN: rv is %i\n", rv); rv = sendto(sockfd, somemsg, sizeof(somemsg), NULL, &server_address, sizeof(server_address)); if (rv < 0) printf("MAIN: ERROR sendto() %i: %s\n", errno, strerror(errno)); printf("MAIN: rv is %i\n", rv); and this is the client side where it connects and sends messages and returns connected MAIN: rv is 4 MAIN: rv is 4 any comments or insightful insights are appreciated.

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• C system calls open / read / write / close problem.

  - by Andrei Ciobanu

  Hello, given the following code (it's supposed to write "hellowolrd" in a "helloworld" file, and then read the text): #include <fcntl.h> #include <sys/types.h> #include <sys/stat.h> #define FNAME "helloworld" int main(){ int filedes, nbytes; char buf[128]; /* Creates a file */ if((filedes=open(FNAME, O_CREAT | O_EXCL | O_WRONLY | O_APPEND, S_IRUSR | S_IWUSR)) == -1){ write(2, "Error1\n", 7); } /* Writes hellow world to file */ if(write(filedes, FNAME, 10) != 10) write(2, "Error2\n", 7); /* Close file */ close(filedes); if((filedes = open(FNAME, O_RDONLY))==-1) write(2, "Error3\n", 7); /* Prints file contents on screen */ if((nbytes=read(filedes, buf, 128)) == -1) write(2, "Error4\n", 7); if(write(1, buf, nbytes) != nbytes) write(2, "Error5\n", 7); /* Close rile afte read */ close(filedes); return (0); } The first time i run the program, the output is: helloworld After that every time I to run the program, the output is: Error1 Error2 helloworld I don't understand why the text isn't appended, as I've specified the O_APPEND file. Is it because I've included O_CREAT ? It the file is already created, shouldn't O_CREAT be ignored ?

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• Clone existing structs with different alignment in Visual C++

  - by Crend King

  Is there a way to clone an existing struct with different member alignment in Visual C++? Here is the background: I use an 3rd-party library, which uses several structs. To fill up the structs, I pass the address of the struct instances to some functions. Unfortunately, the functions only returns unaligned buffer, so that data of some members are always wrong. /Zp is out of choice, since it breaks the other parts of the program. I know #pragma pack modifies the alignment of the following struct, but I would like to avoid copying the structs into my code, for the definitions in the library might change in the future. Sample code: test.h: struct am_aligned { BYTE data1[10]; ULONG data2; }; test.cpp: #include "test.h" // typedef alignment(1) struct am_aligned am_unaligned; int APIENTRY wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow) { char buffer[20] = {}; for (int i = 0; i < sizeof(unaligned_struct); i++) { buffer[i] = i; } am_aligned instance = *(am_aligned*) buffer; return 0; } Consider am_aligned is defined in the library header file. am_unaligned is my custom declaration, and only effective in test.cpp. The commented line does not work of course. instance.data2 is 0x0f0e0d0c, while 0x0d0c0b0a is desired. Thanks for help!

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• Multiple dispatching issue

  - by user1440263

  I try to be synthetic: I'm dispatching an event from a MovieClip (customized symbol in library) this way: public function _onMouseDown(e:MouseEvent){ var obj = {targetClips:["tondo"],functionString:"testFF"}; dispatchEvent(new BridgeEvent(BridgeEvent.BRIDGE_DATA,obj)); } The BridgeEvent class is the following: package events { import flash.events.EventDispatcher; import flash.events.Event; public class BridgeEvent extends Event { public static const BRIDGE_DATA:String = "BridgeData"; public var data:*; public function BridgeEvent(type:String, data:*) { this.data = data; super(type, true); } } } The document class listens to the event this way: addEventListener(BridgeEvent.BRIDGE_DATA,eventSwitcher); In eventSwitcher method I have a simple trace("received"). What happens: when I click the MovieClip the trace action gets duplicated and the output window writes many "received" (even if the click is only one). What happens? How do I prevent this behaviour? What is causing this? Any help is appreciated. [SOLVED] I'm sorry, you will not believe this. A colleague, to make me a joke, converted the MOUSE_DOWN handler to MOUSE_OVER.

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• escape sequence in c

  - by prp

  int main() { char *arr="\\0\1\8234\0"; int i=0; while(arr[i]) { switch(arr[i]) { case '0': printf("is no"); break; case '00': printf("is debugging\n"); break; case 0: printf("It is Avishkar\n"); break; case '\\': printf("This "); break; case '\1': printf("t s"); break; case '8': printf("o s"); break; case '2': printf("imp"); break; case '3': printf("le as"); break; case 2: case 3: case 4: case 8: printf("This "); break; default: printf(" it seems\n"); break;} i++; } } please explain the o/p ? i am not able to get it..

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• Pass Memory in GB Using Import-CSV Powershell to New-VM in Hyper-V Version 3

  - by PowerShell

  I created the below function to pass memory from a csv file to create a VM in Hyper-V Version 3 Function Install-VM { param ( [Parameter(Mandatory=$true)] [int64]$Memory=512MB ) $VMName = "dv.VMWIN2K8R2-3.Hng" $vmpath = "c:\2012vms" New-VM -MemoryStartupBytes ([int64]$memory*1024) -Name $VMName -Path $VMPath -Verbose } Import-Csv "C:\2012vms\Vminfo1.csv" | ForEach-Object { Install-VM -Memory ([int64]$_.Memory) } But when i try to create the VM it says mismatch between the memory parameter passed from import-csv, i receive an error as below VERBOSE: New-VM will create a new virtual machine "dv.VMWIN2K8R2-3.Hng". New-VM : 'dv.VMWIN2K8R2-3.Hng' failed to modify device 'Memory'. (Virtual machine ID CE8D36CA-C8C6-42E6-B5C6-2AA8FA15B4AF) Invalid startup memory amount assigned for 'dv.VMWIN2K8R2-3.Hng'. The minimum amount of memory you can assign to a virtual machine is '8' MB. (Virtual machine ID CE8D36CA-C8C6-42E6-B5C6-2AA8FA15B4AF) A parameter that is not valid was passed to the operation. At line:48 char:9 + New-VM -ComputerName $HyperVHost -MemoryStartupBytes ([int64]$memory*10 ... + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : InvalidArgument: (Microsoft.HyperV.PowerShell.VMTask:VMTask) [New-VM], VirtualizationOpe rationFailedException + FullyQualifiedErrorId : InvalidParameter,Microsoft.HyperV.PowerShell.Commands.NewVMCommand Also please not in the csv file im passing memory as 1,2,4.. etc as shown below, and converting them to MB by multiplying them with 1024 later Memory 1 Can Anyone help me out on how to format and pass the memory details to the function

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• How do I display java.lang.* object allocations in Eclipse profiler?

  - by Martin Wickman

  I am profiling an application using the Eclipse profiler. I am particularly interested in number of allocated object instances of classes from java.lang (for instance java.lang.String or java.util.HashMap). I also want to know stuff like number of calls to String.equals() etc. I use the "Object Allocations" tab and I shows all classes in my application and a count. It also shows all int[], byte[], long[] etc, but there is no mention of any standard java classes. For instance, this silly code: public static void main(String[] args) { Object obj[] = new Object[1000]; for (int i = 0; i < 1000; i++) { obj[i] = new StringBuffer("foo" + i); } System.out.println (obj[30]); } Shows up in the Object Allocations tab as 7 byte[]s, 4 char[]s and 2 int[]s. It doesn't matter if I use 1000 or 1 iterations. It seems the profiler simply ignores everything that is in any of the java.* packages. The same applies to Execution Statistics as well. Any idea how to display instances of java.* in the Eclipse Profiler?

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• scanf segfaults and various other anomalies inside while loop

  - by Shadow

  while(1){ //Command prompt char *command; printf("%s>",current_working_directory); scanf("%s",command);<--seg faults after input has been received. printf("\ncommand:%s\n",command); } I am getting a few different errors and they don't really seem reproducible(except for the segfault at this point .<). This code worked fine about 10 minutes ago, then it infinite looped the printf command and now it seg faults on the line mentioned above. The only thing I changed was scanf("%s",command); to what it currently is. If I change the command variable to be an array it works, obviously this is because the storage is set aside for it. 1) I got prosecuted about telling someone that they needed to malloc a pointer* (But that usually seems to solve the problem such as making it an array) 2) the command I am entering is "magic" 5 characters so there shouldn't be any crazy stack overflow. 3) I am running on mac OSX 10.6 with newest version of xCode(non-OS4) and standard gcc 4) this is how I compile the program: gcc --std=c99 -W sfs.c Just trying to figure out what is going on. Being this is for a school project I am never going to have to see again, I will just code some noob work around that would make my boss cry :) But for afterwards I would love to figure out why this is happening and not just make some fix for it, and if there is some fix for it why that fix works.

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• C++ syntax issue

  - by Doug

  It's late and I can't figure out what is wrong with my syntax. I have asked other people and they can't find the syntax error either so I came here on a friend's advice. template <typename TT> bool PuzzleSolver<TT>::solve ( const Clock &pz ) { possibConfigs_.push( pz.getInitial() ); vector< Configuration<TT> > next_; //error is on next line map< Configuration<TT> ,Configuration<TT> >::iterator found; while ( !possibConfigs_.empty() && possibConfigs_.front() != pz.getGoal() ) { Configuration<TT> cfg = possibConfigs_.front(); possibConfigs_.pop(); next_ = pz.getNext( cfg ); for ( int i = 0; i < next_.size(); i++ ) { found = seenConfigs_.find( next_[i] ); if ( found != seenConfigs_.end() ) { possibConfigs_.push( next_[i] ); seenConfigs_.insert( make_pair( next_[i], cfg ) ); } } } } What is wrong? Thanks for any help.

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• "Access is denied" by executing .hta file with JScript on Windows XP x64

  - by mem64k

  I have a simple HTML (as HTA) application that shows strange behavior on Windows XP x64 machine. I getting periodically (not every time) error message "Access is denied." when i start the application. The same application on Windows XP 32bit runs just fine... Does somebody has any idea or explanation? Error message: Line: 18 Char: 6 Error: Access is denied. Code: 0 URL: file:///D:/test_j.hta Here is the code of my "test_j.hta": <html> <head> <title>Test J</title> <HTA:APPLICATION ID="objTestJ" APPLICATIONNAME="TestJ" SCROLL="no" SINGLEINSTANCE="yes" WINDOWSTATE="normal" > <script language="JScript"> function main() { //window.alert("test"); window.resizeTo(500, 300); } function OnExit() { window.close(); } </script> </head> <body onload="main()"> <input type="button" value="Exit" name="Exit" onClick="OnExit()" title="Exit"> </body> </html>

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• segmentation fault in file operations in c

  - by mekasperasky

  #include<stdio.h> /* this is a lexer which recognizes constants , variables ,symbols, identifiers , functions , comments and also header files . It stores the lexemes in 3 different files . One file contains all the headers and the comments . Another file will contain all the variables , another will contain all the symbols. */ int main() { int i; char a,b[20],c; FILE *fp1; fp1=fopen("source.txt","r"); //the source file is opened in read only mode which will passed through the lexer //now lets remove all the white spaces and store the rest of the words in a file if(fp1==NULL) { perror("failed to open source.txt"); //return EXIT_FAILURE; } i=0; while(1) { a=fgetc(fp1); if(a !="") { b[i]=a; } else { fprintf(fp1, "%.20s\n", b); i=0; continue; } i=i+1; /*Switch(a) { case EOF :return eof; case '+':sym=sym+1; case '-':sym=sym+1; case '*':sym=sym+1; case '/':sym=sym+1; case '%':sym=sym+1; case ' */ } return 0; } how does this code end up in segmentation fault?

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• Why does this program take up so much memory?

  - by Adrian

  I am learning Objective-C. I am trying to release all of the memory that I use. So, I wrote a program to test if I am doing it right: #import <Foundation/Foundation.h> #define DEFAULT_NAME @"Unknown" @interface Person : NSObject { NSString *name; } @property (copy) NSString * name; @end @implementation Person @synthesize name; - (void) dealloc { [name release]; [super dealloc]; } - (id) init { if (self = [super init]) { name = DEFAULT_NAME; } return self; } @end int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; Person *person = [[Person alloc] init]; NSString *str; int i; for (i = 0; i < 1e9; i++) { str = [NSString stringWithCString: "Name" encoding: NSUTF8StringEncoding]; person.name = str; [str release]; } [person release]; [pool drain]; return 0; } I am using a mac with snow leopard. To test how much memory this is using, I open Activity Monitor at the same time that it is running. After a couple of seconds, it is using gigabytes of memory. What can I do to make it not use so much?

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• Qt 101: Why can't I use this class?

  - by Airjoe

  I have experience with C++ but I've never really used Qt before. I'm trying to connect to a SQLite database, so I found a tutorial here and am going with that. In the QtCreator IDE, I went to Add New -- C++ Class and in the header file pasted in the header the header from that link and in the .cpp file I pasted the source. My main.cpp looks like this: #include <QtGui/QApplication> #include "mainwindow.h" #include "databasemanager.h" #include <qlabel.h> int main(int argc, char *argv[]) { QApplication a(argc, argv); MainWindow w; w.show(); DatabaseManager db(); QLabel hello("nothing..."); if(db.openDB()){ hello.setText("Win!"); } else{ hello.setText("Lame!"); } hello.resize(100, 30); hello.show(); return a.exec(); } And I'm getting this error: main.cpp:13: error: request for member 'openDB' in 'db', which is of non-class type 'DatabaseManager()' Can anyone point me in the right direction? I know "copypaste" code isn't good, I just wanted to see if I could get DB connectivity working and I figured something like this would be simple... thanks for the help.

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• How to specify MQ channel table location for .net web application using web.config

  - by Matt

  I've been going around in circles for a while on this one now. I'm trying to connect to a distributed queue manager using a supplied channel table file. I can get this to work if I specify the environmental variable MQCHLLIB and MQCHLTAB on my server. However the IBM documentation states that the .net config file can override these variables. Here is what I have placed in my web.config file: ... <configSections> <section name="CHANNELS" type="System.Configuration.NameValueSectionHandler" /> </configSections> <CHANNELS> <add key="ChannelDefinitionDirectory" value="C:\temp"></add> <add key="ChannelDefinitionFile" value="DSM_MOM_TEST.tab"></add> </CHANNELS> ... And here is the code that is executing: Hashtable properties = new Hashtable(); //Add managed connection type to parameters. const String connectionType = MQC.TRANSPORT_MQSERIES_CLIENT; properties.Add(MQC.TRANSPORT_PROPERTY, connectionType); return new MQQueueManager(queueManagerName, properties); queueManagerName is set to the generic queue manager "*Q101T". However this isn't working and I get an error returned: 2058 MQRC_Q_MGR_NAME_ERROR I've been unable to find any more documentation on how to get this to work other than the environmental variables and the standard mqclient.ini should be overriden by the channels stanza in the web.config. Is there something that I've missed in the code? Any tips would be greatly appreciated.

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• std::string.resize() and std::string.length()

  - by dreamlax

  I'm relatively new to C++ and I'm still getting to grips with the C++ Standard Library. To help transition from C, I want to format a std::string using printf-style formatters. I realise stringstream is a more type-safe approach, but I find myself finding printf-style much easier to read and deal with (at least, for the time being). This is my function: using namespace std; string formatStdString(const string &format, ...) { va_list va; string output; size_t needed; size_t used; va_start(va, format); needed = vsnprintf(&output[0], 0, format.c_str(), va); output.resize(needed + 1); // for null terminator?? used = vsnprintf(&output[0], output.capacity(), format.c_str(), va); // assert(used == needed); va_end(va); return output; } This works, kinda. A few things that I am not sure about are: Do I need to make room for a null terminator, or is this unnecessary? Is capacity() the right function to call here? I keep thinking length() would return 0 since the first character in the string is a '\0'. Occasionally while writing this string's contents to a socket (using its c_str() and length()), I have null bytes popping up on the receiving end, which is causing a bit of grief, but they seem to appear inconsistently. If I don't use this function at all, no null bytes appear.

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• How do I keep my DataService up to date with ObservableCollection?

  - by joebeazelman

  I have a class called CustomerService which simply reads a collection of customers from a file or creates one and passes it back to the Main Model View where it is turned into an ObservableCollection. What the best practice for making sure the items in the CustomerService and ObservableCollection are in sync. I'm guessing I could hookup the CustomerService object to respond to RaisePropertyChanged, but isn't this only for use with WPF controls? Is there a better way? using System; public class MainModelView { public MainModelView() { _customers = new ObservableCollection<CustomerViewModel>(new CustomerService().GetCustomers()); } public const string CustomersPropertyName = "Customers" private ObservableCollection<CustomerViewModel> _customers; public ObservableCollection<CustomerViewModel> Customers { get { return _customers; } set { if (_customers == value) { return; } var oldValue = _customers; _customers = value; // Update bindings and broadcast change using GalaSoft.MvvmLight.Messenging RaisePropertyChanged(CustomersPropertyName, oldValue, value, true); } } } public class CustomerService { /// <summary> /// Load all persons from file on disk. /// </summary> _customers = new List<CustomerViewModel> { new CustomerViewModel(new Customer("Bob", "" )), new CustomerViewModel(new Customer("Bob 2", "" )), new CustomerViewModel(new Customer("Bob 3", "" )), }; public IEnumerable<LinkViewModel> GetCustomers() { return _customers; } }

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• What are some methods to prevent double posting in a form? (PHP)

  - by jpjp

  I want to prevent users from accidentally posting a comment twice. I use the PRG (post redirect get) method, so that I insert the data on another page then redirect the user back to the page which shows the comment. This allows users to refresh as many times as they want. However this doesn't work when the user goes back and clicks submit again or when they click submit 100 times really fast. I don't want 100 of the same comments. I looked at related questions on SO and found that a token is best. But I am having trouble using it. //makerandomtoken(20) returns a random 20 length char. <form method="post" ... > <input type="text" id="comments" name="comments" class="commentbox" /><br/> <input type="hidden" name="_token" value="<?php echo $token=makerandomtoken(20); ?>" /> <input type="submit" value="submit" name="submit" /> </form> if (isset($_POST['submit']) && !empty($comments)) { $comments= mysqli_real_escape_string($dbc,trim($_POST['comments'])); //how do I make the if-statment to check if the token has been already set once? if ( ____________){ //don't insert comment because already clicked submit } else{ //insert the comment into the database } } So I have the token as a hidden value, but how do I use that to prevent multiple clicking of submit. METHODS: someone suggested using sessions. I would set the random token to $_SESSION['_token'] and check if that session token is equal to the $_POST['_token'], but how do I do that? When I tried, it still doesn't check

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• How might I wrap the FindXFile-style APIs to the STL-style Iterator Pattern in C++?

  - by BillyONeal

  Hello everyone :) I'm working on wrapping up the ugly innards of the FindFirstFile/FindNextFile loop (though my question applies to other similar APIs, such as RegEnumKeyEx or RegEnumValue, etc.) inside iterators that work in a manner similar to the Standard Template Library's istream_iterators. I have two problems here. The first is with the termination condition of most "foreach" style loops. STL style iterators typically use operator!= inside the exit condition of the for, i.e. std::vector<int> test; for(std::vector<int>::iterator it = test.begin(); it != test.end(); it++) { //Do stuff } My problem is I'm unsure how to implement operator!= with such a directory enumeration, because I do not know when the enumeration is complete until I've actually finished with it. I have sort of a hack together solution in place now that enumerates the entire directory at once, where each iterator simply tracks a reference counted vector, but this seems like a kludge which can be done a better way. The second problem I have is that there are multiple pieces of data returned by the FindXFile APIs. For that reason, there's no obvious way to overload operator* as required for iterator semantics. When I overload that item, do I return the file name? The size? The modified date? How might I convey the multiple pieces of data to which such an iterator must refer to later in an ideomatic way? I've tried ripping off the C# style MoveNext design but I'm concerned about not following the standard idioms here. class SomeIterator { public: bool next(); //Advances the iterator and returns true if successful, false if the iterator is at the end. std::wstring fileName() const; //other kinds of data.... }; EDIT: And the caller would look like: SomeIterator x = ??; //Construct somehow while(x.next()) { //Do stuff } Thanks! Billy3

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• Visual C++ doesn't operator<< overload

  - by PierreBdR

  I have a vector class that I want to be able to input/output from a QTextStream object. The forward declaration of my vector class is: namespace util { template <size_t dim, typename T> class Vector; } I define the operator<< as: namespace util { template <size_t dim, typename T> QTextStream& operator<<(QTextStream& out, const util::Vector<dim,T>& vec) { ... } template <size_t dim, typename T> QTextStream& operator>>(QTextStream& in,util::Vector<dim,T>& vec) { .. } } However, if I ty to use these operators, Visual C++ returns this error: error C2678: binary '<<' : no operator found which takes a left-hand operand of type 'QTextStream' (or there is no acceptable conversion) A few things I tried: Originaly, the methods were defined as friends of the template, and it is working fine this way with g++. The methods have been moved outside the namespace util I changed the definition of the templates to fit what I found on various Visual C++ websites. The original friend declaration is: friend QTextStream& operator>>(QTextStream& ss, Vector& in) { ... } The "Visual C++ adapted" version is: friend QTextStream& operator>> <dim,T>(QTextStream& ss, Vector<dim,T>& in); with the function pre-declared before the class and implemented after. I checked the file is correctly included using: #pragma message ("Including vector header") And everything seems fine. Doesn anyone has any idea what might be wrong?

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