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  • Need to make sure value is within 0-255

    - by igor
    This is probably really easy, but I'm lost on how to "make sure" it is in this range.. So basically we have class Color and many functions to implement from it. this function I need is: Effects: corrects a color value to be within 0-255 inclusive. If value is outside this range, adjusts to either 0 or 255, whichever is closer. This is what I have so far: static int correctValue(int value) { if(value<0) value=0; if(value>255) value=255; } Sorry for such a simple question ;/

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  • structured vs. unstructured data in db

    - by Igor
    the question is one of design. i'm gathering a big chunk of performance data with lots of key-value pairs. pretty much everything in /proc/cpuinfo, /proc/meminfo/, /proc/loadavg, plus a bunch of other stuff, from several hundred hosts. right now, i just need to display the latest chunk of data in my UI. i will probably end up doing some analysis of the data gathered to figure out performance problems down the road, but this is a new application so i'm not sure what exactly i'm looking for performance-wise just yet. i could structure the data in the db -- have a column for each key i'm gathering. the table would end up being O(100) columns wide, it would be a pain to put into the db, i would have to add new columns if i start gathering a new stat. but it would be easy to sort/analyze the data just using SQL. or i could just dump my unstructured data blob into the table. maybe three columns -- host id, timestamp, and a serialized version of my array, probably using JSON in a TEXT field. which should I do? am i going to be sorry if i go with the unstructured approach? when doing analysis, should i just convert the fields i'm interested in and create a new, more structured table? what are the trade-offs i'm missing here?

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  • System.UnsupportedException using WCF on Windows Phone 7

    - by Igor Zevaka
    Has anyone been able to communicate using WCF on Windows Phone Series 7 emulator? I've been trying for the past two days and it's just happening for me. I can get a normal Silverlight control to work in both Silverlight 3 and Silverlight 4, but not the phone version. Here are two versions that I've tried: Version 1 - Using Async Pattern BasicHttpBinding basicHttpBinding = new BasicHttpBinding(); EndpointAddress endpointAddress = new EndpointAddress("http://localhost/wcf/Authentication.svc"); Wcf.IAuthentication auth1 = new ChannelFactory<Wcf.IAuthentication>(basicHttpBinding, endpointAddress).CreateChannel(endpointAddress); AsyncCallback callback = (result) => { Action<string> write = (str) => { this.Dispatcher.BeginInvoke(delegate { //Display something }); }; try { Wcf.IAuthentication auth = result.AsyncState as Wcf.IAuthentication; Wcf.AuthenticationResponse response = auth.EndLogin(result); write(response.Success.ToString()); } catch (Exception ex) { write(ex.Message); System.Diagnostics.Debug.WriteLine(ex.Message); } }; auth1.BeginLogin("user0", "test0", callback, auth1); This version breaks on this line: Wcf.IAuthentication auth1 = new ChannelFactory<Wcf.IAuthentication>(basicHttpBinding, endpointAddress).CreateChannel(endpointAddress); Throwing System.NotSupportedException. The exception is not very descriptive and the callstack is equally not very helpful: at System.ServiceModel.DiagnosticUtility.ExceptionUtility.BuildMessage(Exception x) at System.ServiceModel.DiagnosticUtility.ExceptionUtility.LogException(Exception x) at System.ServiceModel.DiagnosticUtility.ExceptionUtility.ThrowHelperError(Exception e) at System.ServiceModel.ChannelFactory`1.CreateChannel(EndpointAddress address) at WindowsPhoneApplication2.MainPage.DoLogin() .... Version 2 - Blocking WCF call Here is the version that doesn't use the async pattern. [System.ServiceModel.ServiceContract] public interface IAuthentication { [System.ServiceModel.OperationContract] AuthenticationResponse Login(string user, string password); } public class WcfClientBase<TChannel> : System.ServiceModel.ClientBase<TChannel> where TChannel : class { public WcfClientBase(string name, bool streaming) : base(GetBinding(streaming), GetEndpoint(name)) { ClientCredentials.UserName.UserName = WcfConfig.UserName; ClientCredentials.UserName.Password = WcfConfig.Password; } public WcfClientBase(string name) : this(name, false) {} private static System.ServiceModel.Channels.Binding GetBinding(bool streaming) { System.ServiceModel.BasicHttpBinding binding = new System.ServiceModel.BasicHttpBinding(); binding.MaxReceivedMessageSize = 1073741824; if(streaming) { //binding.TransferMode = System.ServiceModel.TransferMode.Streamed; } /*if(XXXURLXXX.StartsWith("https")) { binding.Security.Mode = BasicHttpSecurityMode.Transport; binding.Security.Transport.ClientCredentialType = HttpClientCredentialType.None; }*/ return binding; } private static System.ServiceModel.EndpointAddress GetEndpoint(string name) { return new System.ServiceModel.EndpointAddress(WcfConfig.Endpoint + name + ".svc"); } protected override TChannel CreateChannel() { throw new System.NotImplementedException(); } } auth.Login("test0", "password0"); This version crashes in System.ServiceModel.ClientBase<TChannel> constructor. The call stack is a bit different: at System.Reflection.MethodInfo.get_ReturnParameter() at System.ServiceModel.Description.ServiceReflector.HasNoDisposableParameters(MethodInfo methodInfo) at System.ServiceModel.Description.TypeLoader.CreateOperationDescription(ContractDescription contractDescription, MethodInfo methodInfo, MessageDirection direction, ContractReflectionInfo reflectionInfo, ContractDescription declaringContract) at System.ServiceModel.Description.TypeLoader.CreateOperationDescriptions(ContractDescription contractDescription, ContractReflectionInfo reflectionInfo, Type contractToGetMethodsFrom, ContractDescription declaringContract, MessageDirection direction) at System.ServiceModel.Description.TypeLoader.CreateContractDescription(ServiceContractAttribute contractAttr, Type contractType, Type serviceType, ContractReflectionInfo& reflectionInfo, Object serviceImplementation) at System.ServiceModel.Description.TypeLoader.LoadContractDescriptionHelper(Type contractType, Type serviceType, Object serviceImplementation) at System.ServiceModel.Description.TypeLoader.LoadContractDescription(Type contractType) at System.ServiceModel.ChannelFactory1.CreateDescription() at System.ServiceModel.ChannelFactory.InitializeEndpoint(Binding binding, EndpointAddress address) at System.ServiceModel.ChannelFactory1..ctor(Binding binding, EndpointAddress remoteAddress) at System.ServiceModel.ClientBase1..ctor(Binding binding, EndpointAddress remoteAddress) at Wcf.WcfClientBase1..ctor(String name, Boolean streaming) at Wcf.WcfClientBase`1..ctor(String name) at Wcf.AuthenticationClient..ctor() at WindowsPhoneApplication2.MainPage.DoLogin() ... Any ideas?

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  • Play and record streaming audio

    - by Igor
    I'm working on an iPhone app that should be able to play and record audio streaming data simultaneously. Is it actually possible? I'm trying to mix SpeakHere and AudioRecorder samples and getting an empty file with no audio data... Here is my .m code: import "AzRadioViewController.h" @implementation azRadioViewController static const CFOptionFlags kNetworkEvents = kCFStreamEventOpenCompleted | kCFStreamEventHasBytesAvailable | kCFStreamEventEndEncountered | kCFStreamEventErrorOccurred; void MyAudioQueueOutputCallback( void* inClientData, AudioQueueRef inAQ, AudioQueueBufferRef inBuffer, const AudioTimeStamp inStartTime, UInt32 inNumberPacketDescriptions, const AudioStreamPacketDescription inPacketDesc ) { NSLog(@"start MyAudioQueueOutputCallback"); MyData* myData = (MyData*)inClientData; NSLog(@"--- %i", inNumberPacketDescriptions); if(inNumberPacketDescriptions == 0 && myData-dataFormat.mBytesPerPacket != 0) { inNumberPacketDescriptions = inBuffer-mAudioDataByteSize / myData-dataFormat.mBytesPerPacket; } OSStatus status = AudioFileWritePackets(myData-audioFile, FALSE, inBuffer-mAudioDataByteSize, inPacketDesc, myData-currentPacket, &inNumberPacketDescriptions, inBuffer-mAudioData); if(status == 0) { myData-currentPacket += inNumberPacketDescriptions; } NSLog(@"status:%i curpac:%i pcdesct: %i", status, myData-currentPacket, inNumberPacketDescriptions); unsigned int bufIndex = MyFindQueueBuffer(myData, inBuffer); pthread_mutex_lock(&myData-mutex); myData-inuse[bufIndex] = false; pthread_cond_signal(&myData-cond); pthread_mutex_unlock(&myData-mutex); } OSStatus StartQueueIfNeeded(MyData* myData) { NSLog(@"start StartQueueIfNeeded"); OSStatus err = noErr; if (!myData-started) { err = AudioQueueStart(myData-queue, NULL); if (err) { PRINTERROR("AudioQueueStart"); myData-failed = true; return err; } myData-started = true; printf("started\n"); } return err; } OSStatus MyEnqueueBuffer(MyData* myData) { NSLog(@"start MyEnqueueBuffer"); OSStatus err = noErr; myData-inuse[myData-fillBufferIndex] = true; AudioQueueBufferRef fillBuf = myData-audioQueueBuffer[myData-fillBufferIndex]; fillBuf-mAudioDataByteSize = myData-bytesFilled; err = AudioQueueEnqueueBuffer(myData-queue, fillBuf, myData-packetsFilled, myData-packetDescs); if (err) { PRINTERROR("AudioQueueEnqueueBuffer"); myData-failed = true; return err; } StartQueueIfNeeded(myData); return err; } void WaitForFreeBuffer(MyData* myData) { NSLog(@"start WaitForFreeBuffer"); if (++myData-fillBufferIndex = kNumAQBufs) myData-fillBufferIndex = 0; myData-bytesFilled = 0; myData-packetsFilled = 0; printf("-lock\n"); pthread_mutex_lock(&myData-mutex); while (myData-inuse[myData-fillBufferIndex]) { printf("... WAITING ...\n"); pthread_cond_wait(&myData-cond, &myData-mutex); } pthread_mutex_unlock(&myData-mutex); printf("<-unlock\n"); } int MyFindQueueBuffer(MyData* myData, AudioQueueBufferRef inBuffer) { NSLog(@"start MyFindQueueBuffer"); for (unsigned int i = 0; i < kNumAQBufs; ++i) { if (inBuffer == myData-audioQueueBuffer[i]) return i; } return -1; } void MyAudioQueueIsRunningCallback( void* inClientData, AudioQueueRef inAQ, AudioQueuePropertyID inID) { NSLog(@"start MyAudioQueueIsRunningCallback"); MyData* myData = (MyData*)inClientData; UInt32 running; UInt32 size; OSStatus err = AudioQueueGetProperty(inAQ, kAudioQueueProperty_IsRunning, &running, &size); if (err) { PRINTERROR("get kAudioQueueProperty_IsRunning"); return; } if (!running) { pthread_mutex_lock(&myData-mutex); pthread_cond_signal(&myData-done); pthread_mutex_unlock(&myData-mutex); } } void MyPropertyListenerProc( void * inClientData, AudioFileStreamID inAudioFileStream, AudioFileStreamPropertyID inPropertyID, UInt32 * ioFlags) { NSLog(@"start MyPropertyListenerProc"); MyData* myData = (MyData*)inClientData; OSStatus err = noErr; printf("found property '%c%c%c%c'\n", (inPropertyID24)&255, (inPropertyID16)&255, (inPropertyID8)&255, inPropertyID&255); switch (inPropertyID) { case kAudioFileStreamProperty_ReadyToProducePackets : { AudioStreamBasicDescription asbd; UInt32 asbdSize = sizeof(asbd); err = AudioFileStreamGetProperty(inAudioFileStream, kAudioFileStreamProperty_DataFormat, &asbdSize, &asbd); if (err) { PRINTERROR("get kAudioFileStreamProperty_DataFormat"); myData-failed = true; break; } err = AudioQueueNewOutput(&asbd, MyAudioQueueOutputCallback, myData, NULL, NULL, 0, &myData-queue); if (err) { PRINTERROR("AudioQueueNewOutput"); myData-failed = true; break; } for (unsigned int i = 0; i < kNumAQBufs; ++i) { err = AudioQueueAllocateBuffer(myData-queue, kAQBufSize, &myData-audioQueueBuffer[i]); if (err) { PRINTERROR("AudioQueueAllocateBuffer"); myData-failed = true; break; } } UInt32 cookieSize; Boolean writable; err = AudioFileStreamGetPropertyInfo(inAudioFileStream, kAudioFileStreamProperty_MagicCookieData, &cookieSize, &writable); if (err) { PRINTERROR("info kAudioFileStreamProperty_MagicCookieData"); break; } printf("cookieSize %d\n", cookieSize); void* cookieData = calloc(1, cookieSize); err = AudioFileStreamGetProperty(inAudioFileStream, kAudioFileStreamProperty_MagicCookieData, &cookieSize, cookieData); if (err) { PRINTERROR("get kAudioFileStreamProperty_MagicCookieData"); free(cookieData); break; } err = AudioQueueSetProperty(myData-queue, kAudioQueueProperty_MagicCookie, cookieData, cookieSize); free(cookieData); if (err) { PRINTERROR("set kAudioQueueProperty_MagicCookie"); break; } err = AudioQueueAddPropertyListener(myData-queue, kAudioQueueProperty_IsRunning, MyAudioQueueIsRunningCallback, myData); if (err) { PRINTERROR("AudioQueueAddPropertyListener"); myData-failed = true; break; } break; } } } static void ReadStreamClientCallBack(CFReadStreamRef stream, CFStreamEventType type, void *clientCallBackInfo) { NSLog(@"start ReadStreamClientCallBack"); if(type == kCFStreamEventHasBytesAvailable) { UInt8 buffer[2048]; CFIndex bytesRead = CFReadStreamRead(stream, buffer, sizeof(buffer)); if (bytesRead < 0) { } else if (bytesRead) { OSStatus err = AudioFileStreamParseBytes(globalMyData-audioFileStream, bytesRead, buffer, 0); if (err) { PRINTERROR("AudioFileStreamParseBytes"); } } } } void MyPacketsProc(void * inClientData, UInt32 inNumberBytes, UInt32 inNumberPackets, const void * inInputData, AudioStreamPacketDescription inPacketDescriptions) { NSLog(@"start MyPacketsProc"); MyData myData = (MyData*)inClientData; printf("got data. bytes: %d packets: %d\n", inNumberBytes, inNumberPackets); for (int i = 0; i < inNumberPackets; ++i) { SInt64 packetOffset = inPacketDescriptions[i].mStartOffset; SInt64 packetSize = inPacketDescriptions[i].mDataByteSize; size_t bufSpaceRemaining = kAQBufSize - myData-bytesFilled; if (bufSpaceRemaining < packetSize) { MyEnqueueBuffer(myData); WaitForFreeBuffer(myData); } AudioQueueBufferRef fillBuf = myData-audioQueueBuffer[myData-fillBufferIndex]; memcpy((char*)fillBuf-mAudioData + myData-bytesFilled, (const char*)inInputData + packetOffset, packetSize); myData-packetDescs[myData-packetsFilled] = inPacketDescriptions[i]; myData-packetDescs[myData-packetsFilled].mStartOffset = myData-bytesFilled; myData-bytesFilled += packetSize; myData-packetsFilled += 1; size_t packetsDescsRemaining = kAQMaxPacketDescs - myData-packetsFilled; if (packetsDescsRemaining == 0) { MyEnqueueBuffer(myData); WaitForFreeBuffer(myData); } } } (IBAction)buttonPlayPressedid)sender { label.text = @"Buffering"; [self connectionStart]; } (IBAction)buttonSavePressedid)sender { NSLog(@"save"); AudioFileClose(myData.audioFile); AudioQueueDispose(myData.queue, TRUE); } bool getFilename(char* buffer,int maxBufferLength) { NSArray paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString docDir = [paths objectAtIndex:0]; NSString* file = [docDir stringByAppendingString:@"/rec.caf"]; return [file getCString:buffer maxLength:maxBufferLength encoding:NSUTF8StringEncoding]; } -(void)connectionStart { @try { MyData* myData = (MyData*)calloc(1, sizeof(MyData)); globalMyData = myData; pthread_mutex_init(&myData-mutex, NULL); pthread_cond_init(&myData-cond, NULL); pthread_cond_init(&myData-done, NULL); NSLog(@"Start"); myData-dataFormat.mSampleRate = 16000.0f; myData-dataFormat.mFormatID = kAudioFormatLinearPCM; myData-dataFormat.mFramesPerPacket = 1; myData-dataFormat.mChannelsPerFrame = 1; myData-dataFormat.mBytesPerFrame = 2; myData-dataFormat.mBytesPerPacket = 2; myData-dataFormat.mBitsPerChannel = 16; myData-dataFormat.mReserved = 0; myData-dataFormat.mFormatFlags = kLinearPCMFormatFlagIsSignedInteger | kLinearPCMFormatFlagIsPacked; int i, bufferByteSize; UInt32 size; AudioQueueNewInput( &myData-dataFormat, MyAudioQueueOutputCallback, &myData, NULL /* run loop /, kCFRunLoopCommonModes / run loop mode /, 0 / flags */, &myData-queue); size = sizeof(&myData-dataFormat); AudioQueueGetProperty(&myData-queue, kAudioQueueProperty_StreamDescription, &myData-dataFormat, &size); CFURLRef fileURL; char path[256]; memset(path,0,sizeof(path)); getFilename(path,256); fileURL = CFURLCreateFromFileSystemRepresentation(NULL, (UInt8*)path, strlen(path), FALSE); AudioFileCreateWithURL(fileURL, kAudioFileCAFType, &myData-dataFormat, kAudioFileFlags_EraseFile, &myData-audioFile); OSStatus err = AudioFileStreamOpen(myData, MyPropertyListenerProc, MyPacketsProc, kAudioFileMP3Type, &myData-audioFileStream); if (err) { PRINTERROR("AudioFileStreamOpen"); return 1; } CFStreamClientContext ctxt = {0, self, NULL, NULL, NULL}; CFStringRef bodyData = CFSTR(""); // Usually used for POST data CFStringRef headerFieldName = CFSTR("X-My-Favorite-Field"); CFStringRef headerFieldValue = CFSTR("Dreams"); CFStringRef url = CFSTR(RADIO_LOCATION); CFURLRef myURL = CFURLCreateWithString(kCFAllocatorDefault, url, NULL); CFStringRef requestMethod = CFSTR("GET"); CFHTTPMessageRef myRequest = CFHTTPMessageCreateRequest(kCFAllocatorDefault, requestMethod, myURL, kCFHTTPVersion1_1); CFHTTPMessageSetBody(myRequest, bodyData); CFHTTPMessageSetHeaderFieldValue(myRequest, headerFieldName, headerFieldValue); CFReadStreamRef stream = CFReadStreamCreateForHTTPRequest(kCFAllocatorDefault, myRequest); if (!stream) { NSLog(@"Creating the stream failed"); return; } if (!CFReadStreamSetClient(stream, kNetworkEvents, ReadStreamClientCallBack, &ctxt)) { CFRelease(stream); NSLog(@"Setting the stream's client failed."); return; } CFReadStreamScheduleWithRunLoop(stream, CFRunLoopGetCurrent(), kCFRunLoopCommonModes); if (!CFReadStreamOpen(stream)) { CFReadStreamSetClient(stream, 0, NULL, NULL); CFReadStreamUnscheduleFromRunLoop(stream, CFRunLoopGetCurrent(), kCFRunLoopCommonModes); CFRelease(stream); NSLog(@"Opening the stream failed."); return; } } @catch (NSException *exception) { NSLog(@"main: Caught %@: %@", [exception name], [exception reason]); } } (void)viewDidLoad { [[UIApplication sharedApplication] setIdleTimerDisabled:YES]; [super viewDidLoad]; } (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; } (void)viewDidUnload { } (void)dealloc { [super dealloc]; } @end

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  • POST data getting lost: Content Length = 0

    - by Igor K
    I've been trying to find a solution for ages with no success. On our app, customers submit a form and on the next page we process it. Sometimes though the data never arrives. This seems to happen for just a few of our customers. Seems to happen with IE7 and using a proxy. Here's some headers, note the HTTP_VIA: X-REWRITE-URL: /process.asp?r=699743 APPL_MD_PATH: /LM/W3SVC/31555/ROOT APPL_PHYSICAL_PATH: C:\inetpub\vhosts\mysite.com\httpdocs\ AUTH_PASSWORD: AUTH_TYPE: AUTH_USER: CERT_COOKIE: CERT_FLAGS: CERT_ISSUER: CERT_KEYSIZE: CERT_SECRETKEYSIZE: CERT_SERIALNUMBER: CERT_SERVER_ISSUER: CERT_SERVER_SUBJECT: CERT_SUBJECT: CONTENT_LENGTH: 0 CONTENT_TYPE: application/x-www-form-urlencoded GATEWAY_INTERFACE: CGI/1.1 HTTPS: off HTTPS_KEYSIZE: HTTPS_SECRETKEYSIZE: HTTPS_SERVER_ISSUER: HTTPS_SERVER_SUBJECT: INSTANCE_ID: 31555 INSTANCE_META_PATH: /LM/W3SVC/31555 LOCAL_ADDR: XXX.XXX.XXX.XXX LOGON_USER: PATH_INFO: /process.asp PATH_TRANSLATED: C:\inetpub\vhosts\mysite.com\httpdocs\process.asp QUERY_STRING: r=699743 REMOTE_ADDR: YYY.YYY.YYY.YYY REMOTE_HOST: YYY.YYY.YYY.YYY REMOTE_USER: REQUEST_METHOD: POST SCRIPT_NAME: /process.asp SERVER_NAME: www.mysite.com SERVER_PORT: 80 SERVER_PORT_SECURE: 0 SERVER_PROTOCOL: HTTP/1.1 SERVER_SOFTWARE: Microsoft-IIS/7.0 URL: /process.asp HTTP_CONNECTION: Keep-Alive HTTP_PRAGMA: no-cache HTTP_VIA: 1.1 WEBCACHE-2 HTTP_CONTENT_LENGTH: 0 HTTP_CONTENT_TYPE: application/x-www-form-urlencoded HTTP_ACCEPT: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/x-ms-application, application/x-ms-xbap, application/vnd.ms-xpsdocument, application/xaml+xml, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */* HTTP_ACCEPT_LANGUAGE: en-gb HTTP_COOKIE: ASPSESSIONIDQCKSDCTS=FENMPCMDCHEOENGOJPGDGPLN; HTTP_HOST: www.mysite.com HTTP_REFERER: http://www.mysite.com/theform.asp HTTP_USER_AGENT: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727; .NET CLR 1.1.4322; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022) HTTP_UA_CPU: x86 HTTP_X_REWRITE_URL: /process.asp?r=699743

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  • Is there a solution that lets Node.js act as an HTTP reverse proxy?

    - by Igor Zinov'yev
    Our company has a project that right now uses nginx as a reverse proxy for serving static content and supporting comet connections. We use long polling connections to get rid of constant refresh requests and let users get updates immediately. Now, I know there is a lot of code already written for Node.js, but is there a solution that lets Node.js act as a reverse proxy for serving static content as nginx does? Or maybe there is a framework that allows to quickly develop such a layer using Node.js?

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  • Cocoa multiple threads, locks don't work

    - by Igor
    I have a threadMethod which shows in console robotMotorsStatus every 0.5 sec. But when I try to change robotMotorsStatus in changeRobotStatus method I receive an exception. Where I need to put locks in that program. #import "AppController.h" @implementation AppController extern char *robotMotorsStatus; - (IBAction)runThread:(id)sender { [self performSelectorInBackground:@selector(threadMethod) withObject:nil]; } - (void)threadMethod { char string_to_send[]="QFF001100\r"; //String prepared to the port sending (first inintialization) string_to_send[7] = robotMotorsStatus[0]; string_to_send[8] = robotMotorsStatus[1]; while(1){ [theLock lock]; usleep(500000); NSLog (@"Robot status %s", robotMotorsStatus); [theLock unlock]; } } - (IBAction)changeRobotStatus:(id)sender { robotMotorsStatus[0]='1'; }

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  • how to atomically claim a row or resource using UPDATE in mysql

    - by Igor
    i have a table of resources (lets say cars) which i want to claim atomically. if there's a limit of one resource per one user, i can do the following trick: UPDATE cars SET user = 'bob' WHERE user IS NULL LIMIT 1 SELECT * FROM cars WHERE user IS bob that way, i claim the resource atomically and then i can see which row i just claimed. this doesn't work when 'bob' can claim multiple cars. i realize i can get a list of cars already claimed by bob, claim another one, and then SELECT again to see what's changed, but that feels hackish. What I'm wondering is, is there some way to see which rows i just updated with my last UPDATE? failing that, is there some other trick to atomically claiming a row? i really want to avoid using SERIALIZABLE isolation level. If I do something like this: 1 SELECT id FROM cars WHERE user IS NULL 2 <here, my PHP or whatever picks a car id> 3 UPDATE cars SET user = 'bob' WHERE id = <the one i picked> would REPEATABLE READ be sufficient here? in other words, could i be guaranteed that some other transactions won't claim the row my software has picked during step 2?

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  • Need to skip newline char (\n) from input file

    - by igor
    I am reading in a file into an array. It is reading each char, the problem arises in that it also reads a newline in the text file. This is a sudoku board, here is my code for reading in the char: bool loadBoard(Square board[BOARD_SIZE][BOARD_SIZE]) { ifstream ins; if(openFile(ins)){ char c; while(!ins.eof()){ for (int index1 = 0; index1 < BOARD_SIZE; index1++) for (int index2 = 0; index2 < BOARD_SIZE; index2++){ c=ins.get(); if(isdigit(c)){ board[index1][index2].number=(int)(c-'0'); board[index1][index2].permanent=true; } } } return true;} return false; } like i said, it reads the file, displays on screen, just not in correct order when it encounters the \n

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  • finding "distance" between two pixel's colors.

    - by igor
    Once more something relatively simple, but confused as to what they want. the method to find distance on cartesian coordinate system is distance=sqrt[(x2-x1)^2 + (y2-y1)^2] but how do i apply it here? //Requires: testColor to be a valid Color //Effects: returns the "distance" between the current Pixel's color and // the passed color // uses the standard method to calculate "distance" // uses the same formula as finding distance on a // Cartesian coordinate system double colorDistance(Color testColor) const;

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  • python iterators and thread-safety

    - by Igor
    I have a class which is being operated on by two functions. One function creates a list of widgets and writes it into the class: def updateWidgets(self): widgets = self.generateWidgetList() self.widgets = widgets the other function deals with the widgets in some way: def workOnWidgets(self): for widget in self.widgets: self.workOnWidget(widget) each of these functions runs in it's own thread. the question is, what happens if the updateWidgets() thread executes while the workOnWidgets() thread is running? I am assuming that the iterator created as part of the for...in loop will keep some kind of reference to the old self.widgets object? So I will finish iterating over the old list... but I'd love to know for sure.

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  • Incorrect logic flow? function that gets coordinates for a sudoku game

    - by igor
    This function of mine keeps on failing an autograder, I am trying to figure out if there is a problem with its logic flow? Any thoughts? Basically, if the row is wrong, "invalid row" should be printed, and clearInput(); called, and return false. When y is wrong, "invalid column" printed, and clearInput(); called and return false. When both are wrong, only "invalid row" is to be printed (and still clearInput and return false. Obviously when row and y are correct, print no error and return true. My function gets through most of the test cases, but fails towards the end, I'm a little lost as to why. bool getCoords(int & x, int & y) { char row; bool noError=true; cin>>row>>y; row=toupper(row); if(row>='A' && row<='I' && isalpha(row) && y>=1 && y<=9) { x=row-'A'; y=y-1; return true; } else if(!(row>='A' && row<='I')) { cout<<"Invalid row"<<endl; noError=false; clearInput(); return false; } else { if(noError) { cout<<"Invalid column"<<endl; } clearInput(); return false; } }

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  • How to check which files I fopen'ed on Windows?

    - by Igor Oks
    I received a "Too many open files" error when tried to do fopen (C++, Windows XP). Probably it happened because somewhere in my program I open files without closing them. Is there a way on Windows to see a list of all open file descriptors (or all files that my program fopened)?

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  • How to do UDP without port forwarding

    - by igor
    Hi all, I am creating an application in C#, It should send data with UDP. Everything works fine until, I try to communicate with a PC that is on the internet behind a router. How do I fix this so that I can use UDP without port forwarding?

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  • How to make iPhone application accept incorrect server certificate but only specific one?

    - by Igor Romanov
    I need to work with private HTTPS API and client has incorrect certificate on the host. Certificate is for www.clienthost.com and I'm working with api.clienthost.com. So I need to connect via HTTPS to api.clienthost.com ignoring incorrect certificate but still make sure it is the one for www.clienthost.com and not something else. I found this answer: http://stackoverflow.com/questions/933331/how-to-use-nsurlconnection-to-connect-with-ssl-for-an-untrusted-cert and it seems to solve half of my problem but I'm trying to figure out how to still check certificate for host is one I expect to see and not different.

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  • Good articles to read on SSL and HTTPS?

    - by Igor Romanov
    I had a problem with accepting invalid SSL certificate in my iPhone program. That problem is solved now, however I came to understanding that I have very abstract idea on how exactly the whole thing is working: how web browser is verifying that received certificate is really for host it communicates to and not faked by same party in the middle? if browser talks to some 3rd party (CA?) to do certificate check? and many other questions... Would someone please recommend good source of information with in-depth enough description of how all parts click together?

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  • RESTful services and update operations

    - by Igor Brejc
    I know REST is meant to be resource-oriented, which roughly translates to CRUD operations on these resources using standard HTTP methods. But what I just wanted to update a part of a resource? For example, let's say I have Payment resource and I wanted to mark its status as "paid". I don't want to POST the whole Payment object through HTTP (sometimes I don't even have all the data). What would be the RESTful way of doing this? I've seen that Twitter uses the following approach for updating Twitter statuses: http://api.twitter.com/1/statuses/update.xml?status=playing with cURL and the Twitter API Is this approach in "the spirit" of REST? UPDATE: PUT - POST Some links I found in the meantime: PUT or POST: The REST of the Story PUT is not UPDATE PATCH Method for HTTP

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  • Subdomain URL Rewriting and Web Apps

    - by Igor K
    So a lot of web apps have the customer choose their own subdomain, ie mycompany.webapp.com Presumably, every subdomain works off the same set of files and the unique subdomain is perhaps stored as a session object. So how does the URL rewriting work? If someone goes to mycompany.webapp.com, you have to rewrite their unique address to a dynamic page to set the session variable, ie webapp.com/mypage.php?cusomer=mycompany But then when you redirected, you'd be at webapp.com/theappdirectory/ and not mycompany.webapp.com/ So how do they do it?

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  • Fill figure with JSFL

    - by Igor
    I draw figure in Flsh ID with JSFL methods, for example // draw rectangle doc.addNewLine({x:0, y:0}, {x:2000, y:0}); doc.addNewLine({x:2000, y:0}, {x:2000, y:500}); doc.addNewLine({x:2000, y:500}, {x:0, y:500}); doc.addNewLine({x:0, y:500}, {x:0, y:0}); // how can I fill it, because this way doesn't work doc.setFillColor('#0000ff');

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  • Rails route, show all elements on the same page

    - by Igor Oliveira Antonio
    I need to show all my elements on the same page. In routes: namespace :nourishment do resources :diets do resources :nourishment_meals, :controller => 'meals' get 'nourishment_meals/show_all_meals' => 'meals#show_all_meals', as: "show_all_meals" end end which will generate: nourishment_diet_nourishment_meals_path GET /nourishment/diets/:diet_id/nourishment_meals(.:format) nourishment/meals#index POST /nourishment/diets/:diet_id/nourishment_meals(.:format) nourishment/meals#create new_nourishment_diet_nourishment_meal_path GET /nourishment/diets/:diet_id/nourishment_meals/new(.:format) nourishment/meals#new edit_nourishment_diet_nourishment_meal_path GET /nourishment/diets/:diet_id/nourishment_meals/:id/edit(.:format) nourishment/meals#edit nourishment_diet_nourishment_meal_path GET /nourishment/diets/:diet_id/nourishment_meals/:id(.:format) nourishment/meals#show PATCH /nourishment/diets/:diet_id/nourishment_meals/:id(.:format) nourishment/meals#update PUT /nourishment/diets/:diet_id/nourishment_meals/:id(.:format) nourishment/meals#update DELETE /nourishment/diets/:diet_id/nourishment_meals/:id(.:format) nourishment/meals#destroy [**THIS**] nourishment_diet_show_all_meals_path GET /nourishment/diets/:diet_id/nourishment_meals/show_all_meals(.:format) nourishment/meals#show_all_meals The problem, when I do this: <%= link_to "Show all meals", nourishment_diet_show_all_meals_path, :class=>"button green" %> This error raise: Problem: Document(s) not found for class NourishmentMeal with id(s) show_all. Summary: When calling NourishmentMeal.find with an id or array of ids, each parameter must match a document Can someone help me?

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  • ASP.NET MVC CookieTempDataProvider: any experience?

    - by Igor Brejc
    UPDATE: looks like I've misunderstood what TempData is for and what it isn't. It definitively shouldn't be used to "keep certain session-wide data" as I asked initially (see ASP.NET MVC TempData Is Really RedirectData why). I've modified the question accordingly. Has anyone used CookieTempDataProvider for TempData storage? Are there any caveats to watch out for (apart from keeping the session storage small)? Any issues with using it on Web farms?

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  • Other test cases for this openFile function?

    - by igor
    I am trying to figure out why my function to open a file is failing this autograder I submit my homework into. What type of input would fail here, I can't think of anything else? Code: bool openFile(ifstream& ins) { char fileName[256]; cout << "Enter board filename: "; cin.getline(fileName,256); cout << endl << fileName << endl; ins.open(fileName); if(!ins) { ins.clear(); cout<<"Error opening file"<<endl; return false; } return true; } Here is output from the 'Autograder' of what my program's output is, and what the correct output is supposed to be (and I do not know what is in the file they use for the input) Autograder output: ******************************************* ***** ***** ***** Your output is: ***** ***** ***** ******************************************* Testing function openFile Enter board filename: test.txt 1 Enter board filename: not a fileName Error opening file 0 ******************************************* ***** ***** ***** Correct Output ***** ***** ***** ******************************************* Testing function openFile Enter board filename: 1 Enter board filename: Error opening file 0

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