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• KeepAlive packets over a Soap request

  - by Nycto

  I've been debugging some Soap requests we are making between two servers on the same VLAN. The app on one server is written in PHP, the app on the other is written in Java. I can control and make changes to the PHP code, but I can't affect the Java server. The PHP app forms the XML using the DOMDocument objects, then sends the request using the cURL extension. When the soap request took longer than 5 minutes to complete, it would always wait until the max timeout limit and exit with a message like this: Operation timed out after 900000 milliseconds with 0 bytes received After sniffing the packets that were being sent, it turns out that the problem was caused by a 5 minute timeout in the network that was closing what it thought was a stale connection. There were two ways to fix it: bump up the timeout in iptables, or start sending KeepAlive packets over the request. To be thorough, I would like to implement both solutions. Bumping up the timeout was easy for ops to do, but sending KeepAlive packets is turning out to be difficult. The cURL library itself supports this (see the --keepalive-time flag for the CLI app), but it doesn't appear that this has been implemented in the PHP cURL library. I even checked the source to make sure it wasn't an undocumented feature. So my question is this: How the heck can I get these packets sent? I see a few clear options, but I don't like any of them: Write a wrapper that will kick off the request by shell_execing the CLI app. This is a hack that I just don't like Update the cURL extension to support this. This is a non-option according to Ops. Open the socket myself. I know just enough to be dangerous. I also haven't seen a way to do this with fsockopen, but I could be missing something. Switch to another library. What exists that supports this? Thanks for any help you can offer.

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• AS3 Working With Arbitrarily Large Files

  - by Kekoa

  I am trying to read a very large file in AS3 and am having problems with the runtime just crashing on me. I'm currently using a FileStream to open the file asynchronously. This does not work(crashes without an Exception) for files bigger than about 300MB. _fileStream = new FileStream(); _fileStream.addEventListener(IOErrorEvent.IO_ERROR, loadError); _fileStream.addEventListener(Event.COMPLETE, loadComplete); _fileStream.openAsync(myFile, FileMode.READ); In looking at the documentation, it sounds like the FileStream class still tries to read in the entire file to memory(which is bad for large files). Is there a more suitable class to use for reading large files? I really would like something like a buffered FileStream class that only loads the bytes from the files that are going to be read next. I'm expecting that I may need to write a class that does this for me, but then I would need to read only a piece of a file at a time. I'm assuming that I can do this by setting the position and readAhead properties of the FileStream to read a chunk out of a file at a time. I would love to save some time if there is a class like this that already exists. Is there a good way to process large files in AS3, without loading entire contents into memory?

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• Getting started with character and text processing (encoding, regular expressions)

  - by TK

  I'd like to learn foundations of encodings, characters and text. Understanding these is important for dealing with a large set of text whether that are log files or text source for building algorithms for collective intelligence. My current knowledge is pretty basic: something like "As long as I use UTF-8, I'm okay." I don't say I need to learn about advanced topics right away. But I need to know: Bit and bytes level knowledge of encodings. Characters and alphabets not used in English. Multi-byte encodings. (I understand some Chinese and Japanese. And parsing them is important.) Regular expressions. Algorithm for text processing. Parsing natural languages. I also need an understanding of mathematics and corpus linguistics. The current and future web (semantic, intelligent, real-time web) needs processing, parsing and analyzing large text. I'm looking for some resources (maybe books?) that get me started with some of the bullets. (I find many helpful discussion on regular expressions here on Stack Overflow. So, you don't need to suggest resources on that topic.)

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• Memory leak with NSData

  - by Kamchatka

  I'm having a leak with this code without being able to find where it's coming from. This function get called within an autorelease pool. I release the IplImage* image argument. When I run the ObjAlloc tool, it tells me that "NSData* data" is leaking. If I try to manually release the UIImage returned by this function, I get an EXC_BAD_ACCESS error, probably because this UIImage is autoreleased. I'm a bit confused, any hint would be appreciated. Thanks! UIImage *UIImageFromIplImage(IplImage *image) { NSLog(@"IplImage (%d, %d) %d bits by %d channels, %d bytes/row %s", image->width, image->height, image->depth, image->nChannels, image->widthStep, image->channelSeq); CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); NSData *data = [NSData dataWithBytes:image->imageData length:image->imageSize]; CGDataProviderRef provider = CGDataProviderCreateWithCFData((CFDataRef)data); CGImageRef imageRef = CGImageCreate(image->width, image->height, image->depth, image->depth * image->nChannels, image->widthStep, colorSpace, kCGImageAlphaNone|kCGBitmapByteOrderDefault, provider, NULL, false, kCGRenderingIntentDefault); UIImage *ret = [UIImage imageWithCGImage:imageRef]; CGImageRelease(imageRef); CGDataProviderRelease(provider); CGColorSpaceRelease(colorSpace); return ret; }

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• Obj-msg-send error in numberOfSectionsInTableView

  - by mukeshpawar

  import "AddBillerCategoryViewController.h" import "Globals.h" import "AddBillerViewController.h" import "AddBillerListViewController.h" import"KlinnkAppDelegate.h" @implementation AddBillerCategoryViewController @synthesize REASON, RESPVAR, currentAttribute,tbldata,strOptions; // This recipe adds a title for each section //Initialize the table view controller with the grouped style (AddBillerCategoryViewController *) init { if (self = [super initWithStyle:UITableViewStyleGrouped]);// self.title = @"Crayon Colors"; return self; } -(void)showBack { [[self navigationController] pushViewController:[[AddBillerViewController alloc] init] animated:YES]; } (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated { if ([viewController isKindOfClass:[AddBillerCategoryViewController class]]) { AddBillerCategoryViewController *controller = (AddBillerCategoryViewController *)viewController; [controller.tbldata reloadData]; } } (void)viewDidLoad { appDelegate = (KlinnkAppDelegate *)[[UIApplication sharedApplication] delegate]; appDelegate.catListArray.count; // Uncomment the following line to display an Edit button in the navigation bar for this view controller. // self.navigationItem.rightBarButtonItem = self.editButtonItem; //self.navigationItem.leftBarButtonItem = [[[UIBarButtonItem alloc] // initWithTitle:@"Back" // style:UIBarButtonItemStylePlain // target:self // action:@selector(showBack)] autorelease]; if(gotOK == 0) { //self.navigationItem.leftBarButtonItem.enabled = FALSE; dt = [[DateTime alloc] init]; strChannelID = @"IGLOO|MOBILE"; strDateTime = [dt findDateTime]; strTemp = [dt findSessionTime]; strSessionID = [appDelegate.KMobile stringByAppendingString:strTemp]; strResponseURL = @"http://115.113.110.139/Test/CbbpServerRequestHandler"; strResponseVar = @"serverResponseXML"; strRequestType = @"GETCATEGORY"; NSLog(@"Current Session id - %@", strSessionID); //conn = [[NSURLConnection alloc] init]; receivedData = [[NSMutableData data] retain]; //.................... currentAttribute = [[NSMutableString alloc] init]; // create XMl xmlData = [[NSData alloc] init]; xmlData = [self createXML]; // XMl has been created now convert it in to string xmlString = [[NSString alloc] initWithData:xmlData encoding:NSASCIIStringEncoding]; // Ataching other infromatin to he xml parameterString = [[NSString alloc] initWithString:@"mobileRequestXML="]; requestString = [[NSString alloc] init]; requestString = [parameterString stringByAppendingString:xmlString]; // give space betn two element. requestString = [requestString stringByReplacingOccurrencesOfString:@"<" withString:@" <"]; // Initalizing other parameters postData = [requestString dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES]; postLength = [NSString stringWithFormat:@"%d",[postData length]]; firstRequest = [[[NSMutableURLRequest alloc] init] autorelease]; REASON = [[NSMutableString alloc] init]; RESPVAR = [[NSMutableString alloc] init]; NSLog(@"\n \n Sending for 1st time........\n"); [self sendRequest]; NSLog(@"\n \n Sending for 2nd time........\n"); [self sendRequest]; NSLog(@"\n \n both request send........\n \n "); } //[tbldata reloadData]; [self retain]; [super viewDidLoad]; } -(void)sendRequest { finished = FALSE; NSLog(@"\n Sending Request \n\n %@", requestString); conn = [[NSURLConnection alloc] init]; if(gotOK == 0) [firstRequest setURL:[NSURL URLWithString:@"http://115.113.110.139/Test/CbbpMobileRequestHandler"]]; if(gotOK == 1) { [firstRequest setURL:[NSURL URLWithString:@"http://115.113.110.139//secure"]]; gotOK = 2; } [firstRequest setHTTPMethod:@"POST"]; [firstRequest setValue:postLength forHTTPHeaderField:@"Content-Length"]; [firstRequest setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"]; [firstRequest setHTTPBody:postData]; conn = [conn initWithRequest:firstRequest delegate:self startImmediately:YES]; [conn start]; while(!finished) { [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]]; } if (conn) { //receivedData = [[NSMutableData data] retain]; NSLog(@"\n\n Received %d bytes of data",[receivedData length]); } else { NSLog(@"\n Not responding"); } } (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { NSLog(@" \n Send didReciveResponse"); [receivedData setLength:0]; } (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { NSLog(@" \n Send didReciveData"); [receivedData appendData:data]; } (void)connectionDidFinishLoading:(NSURLConnection *)connection { finished = TRUE; NSLog(@" \n Send didFinishLaunching"); // do something with the data // receivedData is declared as a method instance elsewhere NSLog(@"\n\n Succeeded! DIDFINISH Received %d bytes of data\n\n ",[receivedData length]); NSString *aStr = [[NSString alloc] initWithData:receivedData encoding:NSASCIIStringEncoding]; NSLog(aStr); //[conn release]; if([aStr isEqualToString:@"OK"]) gotOK = 1; NSLog(@" Value of gotOK - %d", gotOK); if(gotOK == 2) { responseData = [aStr dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES]; parser = [[NSXMLParser alloc] initWithData:responseData]; [parser setDelegate:self]; NSLog(@"\n start parsing"); [parser parse]; NSLog(@"\n PArsing over"); NSLog(@"\n check U / S and the RESVAR is - %@",RESPVAR); NSRange textRange; textRange =[aStr rangeOfString:@"<"]; if(textRange.location != NSNotFound) { if([RESPVAR isEqualToString:@"U"]) { self.navigationItem.rightBarButtonItem.enabled = TRUE; self.navigationItem.leftBarButtonItem.enabled = TRUE; NSLog(@" \n U......."); UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:REASON delegate:self cancelButtonTitle:nil otherButtonTitles:@"OK", nil]; [alert show]; [alert release]; } if([RESPVAR isEqualToString:@"S"]) { NSLog(@"\n S........"); [[self navigationController] pushViewController:[[AddBillerCategoryViewController alloc] init] animated:YES]; //[self viewDidLoad]; //[tbldata reloadData]; } } else { UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Connection Problem" message:@"Enable to process your request at this time. Please try again." delegate:self cancelButtonTitle:nil otherButtonTitles:@"OK", nil]; [alert show]; [alert release]; //self.navigationItem.leftBarButtonItem.enabled = TRUE; } } NSLog(@"\n Last line of connectionDidFinish "); //[tableView reloadData]; } -(NSData *)createXML { NSString *strXmlNode = @" channel alliaceid session reqtype responseurl responsevar "; NSString *tempchannel = [strXmlNode stringByReplacingOccurrencesOfString:@"channel" withString:strChannelID options:NSBackwardsSearch range:NSMakeRange(0, [strXmlNode length])]; NSString *tempalliance = [tempchannel stringByReplacingOccurrencesOfString:@"alliaceid" withString:@"WALLET365" options:NSBackwardsSearch range:NSMakeRange(0, [tempchannel length])]; NSString *tempsession = [tempalliance stringByReplacingOccurrencesOfString:@"session" withString:strSessionID options:NSBackwardsSearch range:NSMakeRange(0, [tempalliance length])]; NSString *tempreqtype = [tempsession stringByReplacingOccurrencesOfString:@"reqtype" withString:strRequestType options:NSBackwardsSearch range:NSMakeRange(0,[tempsession length])]; NSString *tempresponseurl = [tempreqtype stringByReplacingOccurrencesOfString:@"responseurl" withString:strResponseURL options:NSBackwardsSearch range:NSMakeRange(0, [tempreqtype length])]; NSString *tempresponsevar = [tempresponseurl stringByReplacingOccurrencesOfString:@"responsevar" withString:strResponseVar options:NSBackwardsSearch range:NSMakeRange(0,[tempresponseurl length])]; NSData *data= [[NSString stringWithString:tempresponsevar] dataUsingEncoding:NSUTF8StringEncoding]; return data; } (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict { if([elementName isEqualToString:@"RESPVAL"]) currentAttribute = [NSMutableString string]; if([elementName isEqualToString:@"REASON"]) currentAttribute = [NSMutableString string]; if([elementName isEqualToString:@"COUNT"]) currentAttribute = [NSMutableString string]; if([elementName isEqualToString:@"CATNAME"]) currentAttribute = [NSMutableString string]; } (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName { if([elementName isEqualToString:@"RESPVAL"]) { [RESPVAR setString:currentAttribute]; //NSLog(@"\n Response VAR - %@", RESPVAR); } if([elementName isEqualToString:@"REASON"]) { [REASON setString:currentAttribute]; //NSLog(@"\n Reason - %@", REASON); } if([elementName isEqualToString:@"COUNT"]) { NSString *temp1 = [[NSString alloc] init]; temp1 = [temp1 stringByAppendingString:currentAttribute]; catCount = [temp1 intValue]; [temp1 release]; //NSLog(@"\n Cat Count - %d", catCount); } if([elementName isEqualToString:@"CATNAME"]) { [appDelegate.catListArray addObject:[NSString stringWithFormat:currentAttribute]]; //NSLog(@"%@", appDelegate.catListArray); } } (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string { if(self.currentAttribute) [self.currentAttribute setString:string]; } /* (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; } */ /* (void)viewDidAppear:(BOOL)animated { [super viewDidAppear:animated]; } */ /* (void)viewWillDisappear:(BOOL)animated { [super viewWillDisappear:animated]; } */ /* (void)viewDidDisappear:(BOOL)animated { [super viewDidDisappear:animated]; } */ /* // Override to allow orientations other than the default portrait orientation. (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { // Return YES for supported orientations return (interfaceOrientation == UIInterfaceOrientationPortrait); } */ (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Releases the view if it doesn't have a superview // Release anything that's not essential, such as cached data } pragma mark Table view methods -(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return 1; } // Customize the number of rows in the table view. -(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { KlinnkAppDelegate *appDelegated = (KlinnkAppDelegate *)[[UIApplication sharedApplication] delegate]; return appDelegated.catListArray.count; } // Customize the appearance of table view cells. (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier] autorelease]; } // Set up the cell... AddBillerCategoryViewController *mbvc = (AddBillerCategoryViewController *)[appDelegate.catListArray objectAtIndex:indexPath.row]; [cell setText:mbvc.strOptions]; return cell; } (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { // Navigation logic may go here. Create and push another view controller. // AnotherViewController *anotherViewController = [[AnotherViewController alloc] initWithNibName:@"AnotherView" bundle:nil]; // [self.navigationController pushViewController:anotherViewController]; // [anotherViewController release]; gotOK = 0; int j = indexPath.row; appDelegate.catName = [[NSString alloc] init]; appDelegate.catName = [appDelegate.catName stringByAppendingString:[appDelegate.catListArray objectAtIndex:j]]; [[self navigationController] pushViewController:[[AddBillerListViewController alloc] init] animated:YES]; } /* // Override to support conditional editing of the table view. (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath { // Return NO if you do not want the specified item to be editable. return YES; } */ /* // Override to support editing the table view. (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath { if (editingStyle == UITableViewCellEditingStyleDelete) { // Delete the row from the data source [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:YES]; } else if (editingStyle == UITableViewCellEditingStyleInsert) { // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view } } */ /* // Override to support rearranging the table view. (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath { } */ /* // Override to support conditional rearranging of the table view. (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath { // Return NO if you do not want the item to be re-orderable. return YES; } */ (void)dealloc { [REASON release]; [RESPVAR release]; [currentAttribute release]; [tbldata release]; [super dealloc]; } @end In the Above code .. numberOfSectionsInTableView ,i get error of obj-msg-send i have intialize the array catlist and even not released it anywhere still why i am getting this error please help me i am badly stuck' thanks in advacnce

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• C# FileStream position is off after calling ReadLine()

  - by Cristi Diaconescu

  I'm trying to read a (small-ish) file in chunks of a few lines at a time, and I need to return to the beginning of particular chunks. The problem is, after the very first call to streamReader.ReadLine(); the streamReader.BaseStream.Position property is set to the end of the file! Now I assume some caching is done in the backstage, but I was expecting this property to reflect the number of bytes that I used from that file. For instance, calling ReadLine() again will (naturally) return the next line in the file, which does not start at the position previously reported by streamReader.BaseStream.Position. My question is, how can I find the actual position where the 1st line ends, so I can return there later? I can only think of manually doing the bookkeeping, by adding the lengths of the strings returned by ReadLine(), but even here there are a couple of caveats: ReadLine() strips the new-line character(s) which may have a variable length (is is '\n' ? is it "\r\n" ? etc) I'm not sure if this would work ok with variable-length characters ...so right now it seems like my only option is to rethink how I parse the file, so I don't have to rewind. If it helps, I open my file like this: using (var reader = new StreamReader( new FileStream(m_path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))) {...} Any suggestions?

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• Silverlight 4, Out of browser, Printing, Automatic updates

  - by minal

  I have a very critial business application presently running using Winforms. The application is a very core UI shell. It accepts input data, calls a webservice on my server to do the computation, displays the results on the winforms app and finally send a print stream to the printer. Presently the application is deployed using Click-once. Moving forward, I am trying to contemplate wheather I should move the application into a Silverlight application. Couple of reasons I am thinking silverlight. Gives clients the feel that it is a cloud based solution. Can be accessed from any PC. While the clickonce app is able to do this as well, they have to install an app, and when updates are available they have to click "Yes" to update. The application presently has a drop down list of customers, this list has expanded to over 3000 records. Scrolling through the list is very painful. With Silverlight I am thinking of the auto complete ability. Out of the browser - this will be handy for those users who use the app daily. I haven't used Silverlight previous hence looking for some expert advice on a few things: Printing - does silverlight allow sending raw print data to the printer. The application prints to a Zebra Thermal label printer. I have to send raw bytes to the printer with the commands. Can this be done with SL, or will it always prompt the "Print" dialog? Out of browser - when SL apps are installed as out of browser, how to updates come through, does the app update automatically or is the user prompted to opt for update?

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• How do I play back a WAV in ActionScript?

  - by Jeremy White

  Please see the class I have created at http://textsnip.com/51013f for parsing a WAVE file in ActionScript 3.0. This class is correctly pulling apart info from the file header & fmt chunks, isolating the data chunk, and creating a new ByteArray to store the data chunk. It takes in an uncompressed WAVE file with a format tag of 1. The WAVE file is embedded into my SWF with the following Flex embed tag: [Embed(source="some_sound.wav", mimeType="application/octet-stream")] public var sound_class:Class; public var wave:WaveFile = new WaveFile(new sound_class()); After the data chunk is separated, the class attempts to make a Sound object that can stream the samples from the data chunk. I'm having issues with the streaming process, probably because I'm not good at math and don't really know what's happening with the bits/bytes, etc. Here are the two documents I'm using as a reference for the WAVE file format: http://www.lightlink.com/tjweber/StripWav/Canon.html https://ccrma.stanford.edu/courses/422/projects/WaveFormat/ Right now, the file IS playing back! In real time, even! But...the sound is really distorted. What's going on?

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• x86 instruction encoding tables

  - by Cheery

  I'm in middle of rewriting my assembler. While at it I'm curious about implementing disassembly as well. I want to make it simple and compact, and there's concepts I can exploit while doing so. It is possible to determine rest of the x86 instruction encoding from opcode (maybe prefix bytes are required too, a bit). I know many people have written tables for doing it. I'm not interested about mnemonics but instruction encoding, because it is an actual hard problem there. For each opcode number I need to know: does this instruction contain modrm? how many immediate fields does this instruction have? what encoding does an immediate use? is the immediate in field an instruction pointer -relative address? what kind of registers does the modrm use for operand and register fields? sandpile.org has somewhat quite much what I'd need, but it's in format that isn't easy to parse. Before I start writing and validating those tables myself, I decided to write this question. Do you know about this kind of tables existing somewhere? In a form that doesn't require too much effort to parse.

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• Speed up bitstring/bit operations in Python?

  - by Xavier Ho

  I wrote a prime number generator using Sieve of Eratosthenes and Python 3.1. The code runs correctly and gracefully at 0.32 seconds on ideone.com to generate prime numbers up to 1,000,000. # from bitstring import BitString def prime_numbers(limit=1000000): '''Prime number generator. Yields the series 2, 3, 5, 7, 11, 13, 17, 19, 23, 29 ... using Sieve of Eratosthenes. ''' yield 2 sub_limit = int(limit**0.5) flags = [False, False] + [True] * (limit - 2) # flags = BitString(limit) # Step through all the odd numbers for i in range(3, limit, 2): if flags[i] is False: # if flags[i] is True: continue yield i # Exclude further multiples of the current prime number if i <= sub_limit: for j in range(i*3, limit, i<<1): flags[j] = False # flags[j] = True The problem is, I run out of memory when I try to generate numbers up to 1,000,000,000. flags = [False, False] + [True] * (limit - 2) MemoryError As you can imagine, allocating 1 billion boolean values (1 byte 4 or 8 bytes (see comment) each in Python) is really not feasible, so I looked into bitstring. I figured, using 1 bit for each flag would be much more memory-efficient. However, the program's performance dropped drastically - 24 seconds runtime, for prime number up to 1,000,000. This is probably due to the internal implementation of bitstring. You can comment/uncomment the three lines to see what I changed to use BitString, as the code snippet above. My question is, is there a way to speed up my program, with or without bitstring?

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• Extracting images from a PDF

  - by sagar

  My Query I want to extract only images from a PDF document, using Objective-C in an iPhone Application. My Efforts I have gone through the info on this link, which has details regarding different operators on PDF documents. I also studied this document from Apple about PDF parsing with Quartz. I also went through the entire PDF reference document from the Adobe site. According to that document, for each image there are the following operators: q Q BI EI I have created a table to get the image: myTable = CGPDFOperatorTableCreate(); CGPDFOperatorTableSetCallback(myTable, "q", arrayCallback2); CGPDFOperatorTableSetCallback(myTable, "TJ", arrayCallback); CGPDFOperatorTableSetCallback(myTable, "Tj", stringCallback); I use this method to get the image: void arrayCallback2(CGPDFScannerRef inScanner, void *userInfo) { // THIS DOESN'T WORK // CGPDFStreamRef stream; // represents a sequence of bytes // if (CGPDFDictionaryGetStream (d, "BI", &stream)){ // CGPDFDataFormat t=CGPDFDataFormatJPEG2000; // CFDataRef data = CGPDFStreamCopyData (stream, &t); // } } This method is called for the operator "q", but I don't know how to extract an image from it. What should be the solution for extracting the images from the PDF documents? Thanks in advance for your kind help.

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• How to keep unreachable code?

  - by Gabriel

  I'd like to write a function that would have some optional code to execute or not depending on user settings. The function is cpu-intensive and having ifs in it would be slow since the branch predictor is not that good. My idea is making a copy in memory of the function and replace NOPs with jumps when I don't want to execute some code. My working example goes like this: int Test() { int x = 2; for (int i=0 ; i<10 ; i++) { x *= 2; __asm {NOP}; // to skip it replace this __asm {NOP}; // by JMP 2 (after the goto) x *= 2; // Op to skip or not x *= 2; } return x; } In my test's main, I copy this function into a newly allocated executable memory and replace the NOPs by a JMP 2 so that the following x *= 2 is not executed. The problem is that I would have to change the JMP operand every time I change the code to be skipped. An alternative that would fix this problem would be: __asm {NOP}; // to skip it replace this __asm {NOP}; // by JMP 2 (after the goto) goto dont_do_it; x *= 2; // Op to skip or not dont_do_it: x *= 2; This way, as a goto uses 2 bytes of binary, I would be able to replace the NOPs by a fixed JMP of alway 2 in order to skip the goto. Unfortunately, in full optimization mode, the goto and the x*=2 are removed because they are unreachable at compilation time. Hence the need to keep that dead code.

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• Multiple sendto() using UDP socket

  - by ereOn

  Hi, I have a network software which uses UDP to communicate with other instances of the same program. For different reasons, I must use UDP here. I recently had problems sending huge ammounts of data over UDP and had to implement a fragmentation system to split my messages into small data chunks. So far, it worked well but I now encounter an issue when I have to send a lot of data chunks. I have the following algorithm: Split message into small data chunks (around 1500 bytes) Iterate over the data chunks list and for each, send it using sendto() However, when I send a lot of data chunks, the receiver only gets the first 6 messages. Sometimes it misses the sixth and receives the seventh. It depends. Anyway, sendto() always indicates success. This always happen when I test my software over a loopback interface (127.0.0.1) but never over my LAN network. If I add something like std::cout << "test" << std::endl; between the sendto() then every frame is received. I am aware that UDP allows packet loss and that my frames might be loss for a lot of reasons and I suppose it has to do with the rate I am sending the data chunks at. What would be the right approach here ? Implementing some acknowledgement mechanism (just like TCP) seems overkill. Adding some arbitrary waiting time between the sendto() is ugly and will probably decrease performance. Increasing (if possible) the receiver UDP internal buffer ? I don't even know if this is possible. Something else ? I really need your advices here. Thank very much.

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• HTTP requests and Apache modules: Creative attack vectors

  - by pinkgothic

  Slightly unorthodox question here: I'm currently trying to break an Apache with a handful of custom modules. What spawned the testing is that Apache internally forwards requests that it considers too large (e.g. 1 MB trash) to modules hooked in appropriately, forcing them to deal with the garbage data - and lack of handling in the custom modules caused Apache in its entirety to go up in flames. Ouch, ouch, ouch. That particular issue was fortunately fixed, but the question's arisen whether or not there may be other similar vulnerabilities. Right now I have a tool at my disposal that lets me send a raw HTTP request to the server (or rather, raw data through an established TCP connection that could be interpreted as an HTTP request if it followed the form of one, e.g. "GET ...") and I'm trying to come up with other ideas. (TCP-level attacks like Slowloris and Nkiller2 are not my focus at the moment.) Does anyone have a few nice ideas how to confuse the server and/or its modules to the point of self-immolation? Broken UTF-8? (Though I doubt Apache cares about encoding - I imagine it just juggles raw bytes.) Stuff that is only barely too long, followed by a 0-byte, followed by junk? et cetera I don't consider myself a very good tester (I'm doing this by necessity and lack of manpower; I unfortunately don't even have a more than basic grasp of Apache internals that would help me along), which is why I'm hoping for an insightful response or two or three. Maybe some of you have done some similar testing for your own projects? (If stackoverflow is not the right place for this question, I apologise. Not sure where else to put it.)

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• How important is managing memory in Objective-C?

  - by Alex Mcp

  Background: I'm (jumping on the bandwagon and) starting learning about iPhone/iPad development and Objective-C. I have a great background in web development and most of my programming is done in javascript (no libraries), Ruby, and PHP. Question: I'm learning about allocating and releasing memory in Objective-C, and I see it as quite a tricky task to layer on top of actually getting the farking thing to run. I'm trying to get a sense of applications that are out there and what will happen with a poorly memory-managed program. A) Are apps usually released with no memory leaks? Is this a feasible goal, or do people more realistically just excise the worst offenders and that's ok? B) If I make an NSString for a title of a view, let's say, and forget to deallocate it it, does this really only become a problem if I recreate that string repeatedly? I imagine what I'm doing is creating an overhead of the memory needed to store that string, so it's probably quite piddling (a few bytes?) However if I have a rapidly looping cycle in a game that 'leaks' an int every cycle or something, that would overflow the app quite quickly. Are these assumptions correct? Sorry if this isn't up the community-wiki alley, I'm just trying to get a handle on how to think about memory and how careful I'll need to be. Any anecdotes or App Store-submitted app experiences would be awesome to hear as well.

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• C file read leaves garbage characters

  - by KJ

  Hi. I'm trying to read the contents of a file into my program but I keep occasionally getting garbage characters at the end of the buffers. I haven't been using C a lot (rather I've been using C++) but I assume it has something to do with streams. I don't really know what to do though. I'm using MinGW. Here is the code (this gives me garbage at the end of the second read): include include char* filetobuf(char *file) { FILE *fptr; long length; char *buf; fptr = fopen(file, "r"); /* Open file for reading */ if (!fptr) /* Return NULL on failure */ return NULL; fseek(fptr, 0, SEEK_END); /* Seek to the end of the file */ length = ftell(fptr); /* Find out how many bytes into the file we are */ buf = (char*)malloc(length+1); /* Allocate a buffer for the entire length of the file and a null terminator */ fseek(fptr, 0, SEEK_SET); /* Go back to the beginning of the file */ fread(buf, length, 1, fptr); /* Read the contents of the file in to the buffer */ fclose(fptr); /* Close the file */ buf[length] = 0; /* Null terminator */ return buf; /* Return the buffer */ } int main() { char* vs; char* fs; vs = filetobuf("testshader.vs"); fs = filetobuf("testshader.fs"); printf("%s\n\n\n%s", vs, fs); free(vs); free(fs); return 0; } The filetobuf function is from this example http://www.opengl.org/wiki/Tutorial2:_VAOs,_VBOs,_Vertex_and_Fragment_Shaders_%28C_/_SDL%29. It seems right to me though. So anyway, what's up with that?

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• Editing 8bpp indexed Bitmaps

  - by Pedro Sá

  hi, i'm trying to edit the pixels of a 8bpp. Since this PixelFormat is indexed i'm aware that it uses a Color Table to map the pixel values. Even though I can edit the bitmap by converting it to 24bpp, 8bpp editing is much faster (13ms vs 3ms). But, changing each value when accessing the 8bpp bitmap results in some random rgb colors even though the PixelFormat remains 8bpp. I'm currently developing in c# and the algorithm is as follows: (C#) 1- Load original Bitmap at 8bpp 2- Create Empty temp Bitmap with 8bpp with the same size as the original 3-LockBits of both bitmaps and, using P/Invoke, calling c++ method where I pass the Scan0 of each BitmapData object. (I used a c++ method as it offers better performance when iterating through the Bitmap's pixels) (C++) 4- Create a int[256] palette according to some parameters and edit the temp bitmap bytes by passing the original's pixel values through the palette. (C#) 5- UnlockBits. My question is how can I edit the pixel values without having the strange rgb colors, or even better, edit the 8bpp bitmap's Color Table? Regards, Pedro

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• Accessing a com object's vtable in c#

  - by Martin Booth

  I'm attempting to access a com object's vtable in memory and getting nowhere. From what I have read, the first 4 bytes in memory of a com object should be a pointer to the vtableptr, which in turn is a pointer to the vtable. Although I'm not sure I expect to find my test method at slot 7 in this com object I have tried them all and nothing looks like the address of my function. If anyone can make the necessary changes to this sample to get it to work (the aim is just to try and invoke the Test method on the Tester class by accessing the com object's vtable and locating the method in whichever row it turns up) I would be very grateful. I know it is rare that anyone would need to do this, but please accept I do need to do something quite similar and have considered the alternatives Thanks in advance [ComVisible(true)] public class Tester { public void Test() { MessageBox.Show("Here"); } } public delegate void TestDelegate(); private void main() { Tester t = new Tester(); GCHandle objectHandle = GCHandle.Alloc(t); IntPtr objectPtr = GCHandle.ToIntPtr(objectHandle); IntPtr vTable = (IntPtr)Marshal.ReadInt32(objectPtr); IntPtr vTablePtr = (IntPtr)Marshal.ReadInt32(vTable); IntPtr functionPtr = (IntPtr)Marshal.ReadInt32(vTablePtr, 7 * 4); // 7 may be incorrect but i have tried many different values TestDelegate func = (TestDelegate)Marshal.GetDelegateForFunctionPointer(functionPtr, typeof(TestDelegate)); func(); objectHandle.Free(); }

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• Character Encoding: â??

  - by akaphenom

  I am trying to piece together the mysterious string of characters â?? I am seeing quite a bit of in our database - I am fairly sure this is a result of conversion between character encodings, but I am not completely positive. The users are able to enter text (or cut and paste) into a Ext-Js rich text editor. The data is posted to a severlet which persists it to the database, and when I view it in the database i see those strange characters... is there any way to decode these back to their original meaning, if I was able to discover the correct encoding - or is there a loss of bits or bytes that has occured through the conversion process? Users are cutting and pasting from multiple versions of MS Word and PDF. Does the encoding follow where the user copied from? Thank you website is UTF-8 We are using ms sql server 2005; SELECT serverproperty('Collation') -- Server default collation. Latin1_General_CI_AS SELECT databasepropertyex('xxxx', 'Collation') -- Database default SQL_Latin1_General_CP1_CI_AS and the column: Column_name Type Computed Length Prec Scale Nullable TrimTrailingBlanks FixedLenNullInSource Collation text varchar no -1 yes no yes SQL_Latin1_General_CP1_CI_AS The non-Unicode equivalents of the nchar, nvarchar, and ntext data types in SQL Server 2000 are listed below. When Unicode data is inserted into one of these non-Unicode data type columns through a command string (otherwise known as a "language event"), SQL Server converts the data to the data type using the code page associated with the collation of the column. When a character cannot be represented on a code page, it is replaced by a question mark (?), indicating the data has been lost. Appearance of unexpected characters or question marks in your data indicates your data has been converted from Unicode to non-Unicode at some layer, and this conversion resulted in lost characters. So this may be the root cause of the problem... and not an easy one to solve on our end.

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• Cocoa Read NSInputStream from FTP connection

  - by Chuck

  Hi, I (apparently) manage to make a ftp connection, but fail to read anything from it, and with good cause: I don't reach the reading until the connection has timed out. Here's my code: NSHost *host = [NSHost hostWithAddress:@"127.0.0.1"]; [NSStream getStreamsToHost:host port:3333 inputStream:&iStream outputStream:&oStream]; NSMutableDictionary *settings = [NSMutableDictionary dictionaryWithCapacity:1]; [settings setObject:(NSString *)NSStreamSocketSecurityLevelTLSv1 forKey:(NSString *)kCFStreamSSLLevel]; [settings setObject:[NSNumber numberWithBool:YES] forKey:(NSString *)kCFStreamSSLAllowsAnyRoot]; [iStream retain]; [iStream setDelegate:self]; [iStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; CFReadStreamSetProperty((CFReadStreamRef)iStream, kCFStreamPropertySSLSettings, (CFTypeRef)settings);forKey:NSStreamSocketSecurityLevelKey]; [iStream open]; [oStream retain]; [oStream setDelegate:self]; [oStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode]; CFWriteStreamSetProperty((CFWriteStreamRef)oStream, kCFStreamPropertySSLSettings, (CFTypeRef)settings); forKey:NSStreamSocketSecurityLevelKey]; [oStream open]; NSMutableData *returnMessage = [NSMutableData dataWithLength: 300]; [iStream read: [returnMessage mutableBytes] maxLength: 300]; NSString *readData = [[NSString alloc] initWithBytes: [returnMessage bytes] length: 300 encoding: NSUTF8StringEncoding]; NSRunAlertPanel(@"response", readData, nil, nil, nil); I have not sent a request to the FTP to switch to ssl yet. Any help is greatly appreciated as I find Xcode quite horrible for debugging (no exception or error msg on failed steps what so ever). Chuck

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• Loading a RSA private key from memory using libxmlsec

  - by ereOn

  Hello, I'm currently using libxmlsec into my C++ software and I try to load a RSA private key from memory. To do this, I searched trough the API and found this function. It takes binary data, a size, a format string and several PEM-callback related parameters. When I call the function, it just stucks, uses 100% of the CPU time and never returns. Quite annoying, because I have no way of finding out what is wrong. Here is my code: d_xmlsec_dsig_context->signKey = xmlSecCryptoAppKeyLoadMemory( reinterpret_cast<const xmlSecByte*>(data), static_cast<xmlSecSize>(datalen), xmlSecKeyDataFormatBinary, NULL, NULL, NULL ); data is a const char* pointing to the raw bytes of my RSA key (using i2d_RSAPrivateKey(), from OpenSSL) and datalen the size of data. My test private key doesn't have a passphrase so I decided not to use the callbacks for the time being. Has someone already done something similar ? Do you guys see anything that I could change/test to get forward on this problem ? I just discovered the library on yesterday, so I might miss something obvious here; I just can't see it. Thank you very much for your help.

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• Receiving broadcast messages

  - by Prasad

  Hi, I'm trying to receive broadcast messages using C# code in an ISDN network with BRI interface at my end. I see the packets sent to the broadcast ip address (239.255.255.255) on some ports using Comm View tool. But when I try to listen to this IP address, it says the address is not in a valid context. But when I send broadcast messages to 255.255.255.255 on a port, I can receive those messages with the below code.. What could be the problem with this ip address - 239.255.255.255 ? The code I use to listen to broadcast messages is.. UdpClient udp = new UdpClient(); IPEndPoint receiveEndPoint = new IPEndPoint(IPAddress.Any, 8013); // If I use IPAddress.Parse("239.255.255.255") to listen to, // it says "the address is not in a valid // context." udp.Client.Bind(receiveEndPoint); udp.BeginReceive(_Callback, udp); static private void _Callback(IAsyncResult iar) { try { UdpClient client = (UdpClient)iar.AsyncState; client.BeginReceive(_Callback, client); IPEndPoint ipRemote = new IPEndPoint(IPAddress.Any, 8013); byte[] rgb = client.EndReceive(iar, ref ipRemote); Console.WriteLine("Received {0} bytes: \"{1}\"", rgb.Length.ToString(), Encoding.UTF8.GetString(rgb)); } catch (ObjectDisposedException) { Console.WriteLine("closing listening socket"); } catch (Exception exc) { Console.WriteLine("Listening socket error: \"" + exc.Message + "\""); } } There are packets sent to the broadcast ipaddress (239.255.255.255) which I can see in Commview tool, but can't receive them from the code... Can anybody help me out please? Thanking you in advance, Prasad Kancharla.

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• Benchmarking a UDP server

  - by Nicolas

  I am refactoring a UDP listener from Java to C. It needs to handle between 1000 and 10000 UDP messages per second, with an average data length of around 60 bytes. There is no reply necessary. Data cannot be lost (Don't ask why UDP was decided). I fork off a process to deal with the incoming data so that I can recvfrom as quickly as possible - without filling up my kernel buffers. The child then handles the data received. In short, my algo is: Listen for data. When data is received, check for errors. Fork off a child. If I'm a child, do what I with the data and exit. If I'm a parent, reap any zombie children waitpid(-1, NULL, WNOHANG). Repeat. Firstly, any comments about the above? I'm creating the socket with socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP), binding with AF_INET and INADDR_ANY and recvfrom with no flags. Secondly, can anyone suggest something that I can use to test that this application (or at least the listener) can handle more messages than what I am expecting? Or, would I need to hack something together to do this. I'd guess the latter would be better, so that I can compare data that is generated versus data that is received. But, comments would be appreciated.

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• Asynchronous NSURLConnection Throws EXC_BAD_ACCESS

  - by Sheehan Alam

  I'm not really sure why my code is throwing a EXC_BAD_ACCESS, I have followed the guidelines in Apple's documentation: -(void)getMessages:(NSString*)stream{ NSString* myURL = [NSString stringWithFormat:@"http://www.someurl.com"]; NSURLRequest *theRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:myURL]]; NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self]; if (theConnection) { receivedData = [[NSMutableData data] retain]; } else { NSLog(@"Connection Failed!"); } } And my delegate methods #pragma mark NSURLConnection Delegate Methods - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { // This method is called when the server has determined that it // has enough information to create the NSURLResponse. // It can be called multiple times, for example in the case of a // redirect, so each time we reset the data. // receivedData is an instance variable declared elsewhere. [receivedData setLength:0]; } - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { // Append the new data to receivedData. // receivedData is an instance variable declared elsewhere. [receivedData appendData:data]; } - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error { // release the connection, and the data object [connection release]; // receivedData is declared as a method instance elsewhere [receivedData release]; // inform the user NSLog(@"Connection failed! Error - %@ %@", [error localizedDescription], [[error userInfo] objectForKey:NSErrorFailingURLStringKey]); } - (void)connectionDidFinishLoading:(NSURLConnection *)connection { // do something with the data // receivedData is declared as a method instance elsewhere NSLog(@"Succeeded! Received %d bytes of data",[receivedData length]); // release the connection, and the data object [connection release]; [receivedData release]; } I get an EXC_BAD_ACCESS on didReceiveData. Even if that method simply contains an NSLog, I get the error. Note: receivedData is an NSMutableData* in my header file

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• GZipStream not reading the whole file

  - by Ed

  I have some code that downloads gzipped files, and decompresses them. The problem is, I can't get it to decompress the whole file, it only reads the first 4096 bytes and then about 500 more. Byte[] buffer = new Byte[4096]; int count = 0; FileStream fileInput = new FileStream("input.gzip", FileMode.Open, FileAccess.Read, FileShare.Read); FileStream fileOutput = new FileStream("output.dat", FileMode.Create, FileAccess.Write, FileShare.None); GZipStream gzipStream = new GZipStream(fileInput, CompressionMode.Decompress, true); // Read from gzip steam while ((count = gzipStream.Read(buffer, 0, buffer.Length)) > 0) { // Write to output file fileOutput.Write(buffer, 0, count); } // Close the streams ... I've checked the downloaded file; it's 13MB when compressed, and contains one XML file. I've manually decompressed the XML file, and the content is all there. But when I do it with this code, it only outputs the very beginning of the XML file. Anyone have any ideas why this might be happening?

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