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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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• 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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• How to exploit Diffie-hellman to perform a man in the middle attack

  - by jfisk

  Im doing a project where Alice and Bob send each other messages using the Diffie-Hellman key-exchange. What is throwing me for a loop is how to incorporate the certificate they are using in this so i can obtain their secret messages. From what I understand about MIM attakcs, the MIM acts as an imposter as seen on this diagram: Below are the details for my project. I understand that they both have g and p agreed upon before communicating, but how would I be able to implement this with they both having a certificate to verify their signatures? Alice prepares ?signA(NA, Bob), pkA, certA? where signA is the digital signature algorithm used by Alice, “Bob” is Bob’s name, pkA is the public-key of Alice which equals gx mod p encoded according to X.509 for a fixed g, p as specified in the Diffie-Hellman key- exchange and certA is the certificate of Alice that contains Alice’s public-key that verifies the signature; Finally, NA is a nonce (random string) that is 8 bytes long. Bob checks Alice's signature, and response with ?signB{NA,NB,Alice},pkB,certB?. Alice gets the message she checks her nonce NA and calculates the joint key based on pkA, pkB according to the Diffie-Hellman key exchange. Then Alice submits the message ?signA{NA,NB,Bob},EK(MA),certA? to Bob and Bobrespondswith?SignB{NA,NB,Alice},EK(MB),certB?. where MA and MB are their corresponding secret messages.

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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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• 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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• 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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• 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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• 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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• (PL/SQL)Oracle stored procedure parameter size limit(VARCHAR2)

  - by Jude Lee

  Hello, there. I have an problem with my oracle stored procedure as following. codes : CREATE OR REPLACE PROCEDURE APP.pr_ap_gateway ( aiov_req IN OUT VARCHAR2, aov_rep01 OUT VARCHAR2, aov_rep02 OUT VARCHAR2, aov_rep03 OUT VARCHAR2, aov_rep04 OUT VARCHAR2, aov_rep05 OUT VARCHAR2 ) IS v_header VARCHAR (100); v_case VARCHAR (4); v_err_no_case VARCHAR (5) := '00004'; BEGIN DBMS_OUTPUT.ENABLE (1000000); aov_rep01 := lpad(' ', 190, ' '); dbms_output.put_line('>> ['||length(aov_rep01)||']'); aov_rep01 := lpad(' ', 199, ' '); dbms_output.put_line('>> ['||length(aov_rep01)||']'); aov_rep01 := lpad(' ', 200, ' '); dbms_output.put_line('>> ['||length(aov_rep01)||']'); aov_rep01 := lpad(' ', 201, ' '); dbms_output.put_line('>> ['||length(aov_rep01)||']'); END pr_ap_gateway; / results : >> [190] >> [199] >> [200] and then error 'buffer overflow' ORA-06502: PL/SQL: ?? ?? ? ??: ??? ??? ?? ???? I know that VARCHAR2 type can contain 32KB in PL/SQL. But, in my test, VARCHAR2 parameter contains only 200 Bytes. What's wrong with this situation? This procedure will called by java daemon program. So, There's no declaration of parameters size before calling procedure. Thanks in advance for your reply.

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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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• 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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• 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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• 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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• Binary file email attachment problem

  - by Alan Harris-Reid

  Hi there, Using Python 3.1.2 I am having a problem sending binary attachment files (jpeg, pdf, etc.) - MIMEText attachments work fine. The code in question is as follows... for file in self.attachments: part = MIMEBase('application', "octet-stream") part.set_payload(open(file,"rb").read()) encoders.encode_base64(part) part.add_header('Content-Disposition', 'attachment; filename="%s"' % file) msg.attach(part) # msg is an instance of MIMEMultipart() server = smtplib.SMTP(host, port) server.login(username, password) server.sendmail(from_addr, all_recipients, msg.as_string()) However, way down in the calling-stack (see traceback below), it looks as though msg.as_string() has received an attachment which creates a payload of 'bytes' type instead of string. Has anyone any idea what might be causing the problem? Any help would be appreciated. Alan builtins.TypeError: string payload expected: File "c:\Dev\CommonPY\Scripts\email_send.py", line 147, in send server.sendmail(self.from_addr, all_recipients, msg.as_string()) File "c:\Program Files\Python31\Lib\email\message.py", line 136, in as_string g.flatten(self, unixfrom=unixfrom) File "c:\Program Files\Python31\Lib\email\generator.py", line 76, in flatten self._write(msg) File "c:\Program Files\Python31\Lib\email\generator.py", line 101, in _write self._dispatch(msg) File "c:\Program Files\Python31\Lib\email\generator.py", line 127, in _dispatch meth(msg) File "c:\Program Files\Python31\Lib\email\generator.py", line 181, in _handle_multipart g.flatten(part, unixfrom=False) File "c:\Program Files\Python31\Lib\email\generator.py", line 76, in flatten self._write(msg) File "c:\Program Files\Python31\Lib\email\generator.py", line 101, in _write self._dispatch(msg) File "c:\Program Files\Python31\Lib\email\generator.py", line 127, in _dispatch meth(msg) File "c:\Program Files\Python31\Lib\email\generator.py", line 155, in _handle_text raise TypeError('string payload expected: %s' % type(payload))

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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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• Sync Vs. Async Sockets Performance in .NET

  - by Michael Covelli

  Everything that I read about sockets in .NET says that the asynchronous pattern gives better performance (especially with the new SocketAsyncEventArgs which saves on the allocation). I think this makes sense if we're talking about a server with many client connections where its not possible to allocate one thread per connection. Then I can see the advantage of using the ThreadPool threads and getting async callbacks on them. But in my app, I'm the client and I just need to listen to one server sending market tick data over one tcp connection. Right now, I create a single thread, set the priority to Highest, and call Socket.Receive() with it. My thread blocks on this call and wakes up once new data arrives. If I were to switch this to an async pattern so that I get a callback when there's new data, I see two issues The threadpool threads will have default priority so it seems they will be strictly worse than my own thread which has Highest priority. I'll still have to send everything through a single thread at some point. Say that I get N callbacks at almost the same time on N different threadpool threads notifying me that there's new data. The N byte arrays that they deliver can't be processed on the threadpool threads because there's no guarantee that they represent N unique market data messages because TCP is stream based. I'll have to lock and put the bytes into an array anyway and signal some other thread that can process what's in the array. So I'm not sure what having N threadpool threads is buying me. Am I thinking about this wrong? Is there a reason to use the Async patter in my specific case of one client connected to one server?

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• NSKeyedArchiver on NSArray has large size overhead

  - by redguy

  I'm using NSKeyedArchiver in Mac OS X program which generates data for iPhone application. I found out that by default, resulting archives are much bigger than I expected. Example: NSMutableArray * ar = [NSMutableArray arrayWithCapacity:10]; for (int i = 0; i < 100000; i++) { NSString * s = [NSString stringWithFormat:@"item%06d", i]; [ar addObject:s]; } [NSKeyedArchiver archiveRootObject:ar toFile: @"NSKeyedArchiver.test"]; This stores 10 * 100000 = 1M bytes of useful data, yet the size of the resulting file is almost three megabytes. The overhead seems to be growing with number of items in the array. In this case, for 1000 items, the file was about 22k. "file" reports that it is a "Apple binary property list" (not the XML format). Is there an simple way to prevent this huge overhead? I wanted to use the NSKeyedArchiver for the simplicity it provides. I can write data to my own, non-generic, binary format, but that's not very elegant. Also, aggregating the data into large chunks and feeding these to the NSKeyedArchiver should work, but again, that kinda beats the point of using simple&easy&ready to use archiver. Am I missing some method call or usage pattern that would reduce this overhead?

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• Add Hexidecimal Header Info to JPEG File Using Java

  - by jboyd

  I need to add header info to a JPEG file in order to get it to work properly when shared on some websites, I've tracked down the correct info through a lot of Hex digging, but now I'm kind of stuck trying to get it into the file. I know where in the file it needs to go, and I know how long it is, my problem is that RandomAccessFile just overwrites existing data in the file and FileOutputStream appends the data to the end. I don't want either, I want to INSERT data starting at the third byte. My example code: File fileToChange = new File("someimage.jpg"); byte[] i = new byte[2]; i[0] = (byte)Integer.decode("0xcc"); i[1] = (byte)Integer.decode("0xcc"); RandomAccessFile f = new RandomAccessFile(new File("videothing.jpg"), "rw"); long aPositionWhereIWantToGo = 2; f.seek(aPositionWhereIWantToGo); // this basically reads n bytes in the file f.write((byte[])i); f.close(); So this doesn't work because it overwrites, and does not insert, I can't find any way to just insert data into a file

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• Can't build pyxpcom on OS X 10.6

  - by Gj

  I've been following these instructions at https://developer.mozilla.org/en/Building_PyXPCOM but getting this: $ make make export make[2]: Nothing to be done for `export'. make[4]: Nothing to be done for `export'. make[4]: Nothing to be done for `export'. /opt/local/bin/python2.5 ../../../src/config/nsinstall.py -L /usr/local/pyxpcom/build/xpcom/src -m 644 ../../../src/xpcom/src/PyXPCOM.h ../../dist/include make[3]: Nothing to be done for `export'. /opt/local/bin/python2.5 ../../../../src/config/nsinstall.py -D ../../../dist/idl /opt/local/bin/python2.5 ../../../../src/config/nsinstall.py -D ../../../dist/idl make[4]: *** No rule to make target `_xpidlgen/py_test_component.h', needed by `export'. Stop. make[3]: *** [export] Error 2 make[2]: *** [export] Error 2 make[1]: *** [export] Error 2 make: *** [default] Error 2 Any ideas? An interesting anomaly is that despite me setting the PYTHON env variable to Python 2.6, the configure and make both seem to go after the 2.5... Thanks for any advice! PS here's the configure output: $ ../src/configure --with-libxul-sdk=/Users/me/xulrunner-sdk/ loading cache ./config.cache checking host system type... i386-apple-darwin10.3.0 checking target system type... i386-apple-darwin10.3.0 checking build system type... i386-apple-darwin10.3.0 checking for mawk... (cached) gawk checking for perl5... (cached) /opt/local/bin/perl5 checking for gcc... (cached) gcc checking whether the C compiler (gcc ) works... yes checking whether the C compiler (gcc ) is a cross-compiler... no checking whether we are using GNU C... (cached) yes checking whether gcc accepts -g... (cached) yes checking for c++... (cached) c++ checking whether the C++ compiler (c++ ) works... yes checking whether the C++ compiler (c++ ) is a cross-compiler... no checking whether we are using GNU C++... (cached) yes checking whether c++ accepts -g... (cached) yes checking for ranlib... (cached) ranlib checking for as... (cached) /usr/bin/as checking for ar... (cached) ar checking for ld... (cached) ld checking for strip... (cached) strip checking for windres... no checking whether gcc and cc understand -c and -o together... (cached) yes checking how to run the C preprocessor... (cached) gcc -E checking how to run the C++ preprocessor... (cached) c++ -E checking for a BSD compatible install... (cached) /usr/bin/install -c checking whether ln -s works... (cached) yes checking for minimum required perl version >= 5.006... 5.008009 checking for full perl installation... yes checking for /opt/local/bin/python... (cached) /opt/local/bin/python2.5 checking for doxygen... (cached) : checking for whoami... (cached) /usr/bin/whoami checking for autoconf... (cached) /opt/local/bin/autoconf checking for unzip... (cached) /usr/bin/unzip checking for zip... (cached) /usr/bin/zip checking for makedepend... (cached) /opt/local/bin/makedepend checking for xargs... (cached) /usr/bin/xargs checking for pbbuild... (cached) /usr/bin/xcodebuild checking for sdp... (cached) /usr/bin/sdp checking for gmake... (cached) /opt/local/bin/gmake checking for X... (cached) no checking whether the compiler supports -Wno-invalid-offsetof... yes checking whether ld has archive extraction flags... (cached) no checking that static assertion macros used in autoconf tests work... (cached) yes checking for 64-bit OS... yes checking for minimum required Python version >= 2.4... yes checking for -dead_strip option to ld... yes checking for ANSI C header files... (cached) yes checking for working const... (cached) yes checking for mode_t... (cached) yes checking for off_t... (cached) yes checking for pid_t... (cached) yes checking for size_t... (cached) yes checking for st_blksize in struct stat... (cached) yes checking for siginfo_t... (cached) yes checking for int16_t... (cached) yes checking for int32_t... (cached) yes checking for int64_t... (cached) yes checking for int64... (cached) no checking for uint... (cached) yes checking for uint_t... (cached) no checking for uint16_t... (cached) no checking for uname.domainname... (cached) no checking for uname.__domainname... (cached) no checking for usable char16_t (2 bytes, unsigned)... (cached) no checking for usable wchar_t (2 bytes, unsigned)... (cached) no checking for compiler -fshort-wchar option... (cached) yes checking for visibility(hidden) attribute... (cached) yes checking for visibility(default) attribute... (cached) yes checking for visibility pragma support... (cached) yes checking For gcc visibility bug with class-level attributes (GCC bug 26905)... (cached) yes checking For x86_64 gcc visibility bug with builtins (GCC bug 20297)... (cached) no checking for dirent.h that defines DIR... (cached) yes checking for opendir in -ldir... (cached) no checking for sys/byteorder.h... (cached) no checking for compat.h... (cached) no checking for getopt.h... (cached) yes checking for sys/bitypes.h... (cached) no checking for memory.h... (cached) yes checking for unistd.h... (cached) yes checking for gnu/libc-version.h... (cached) no checking for nl_types.h... (cached) yes checking for malloc.h... (cached) no checking for X11/XKBlib.h... (cached) yes checking for io.h... (cached) no checking for sys/statvfs.h... (cached) yes checking for sys/statfs.h... (cached) no checking for sys/vfs.h... (cached) no checking for sys/mount.h... (cached) yes checking for sys/quota.h... (cached) yes checking for mmintrin.h... (cached) yes checking for new... (cached) yes checking for sys/cdefs.h... (cached) yes checking for gethostbyname_r in -lc_r... (cached) no checking for dladdr... (cached) yes checking for socket in -lsocket... (cached) no checking whether mmap() sees write()s... yes checking whether gcc needs -traditional... (cached) no checking for 8-bit clean memcmp... (cached) yes checking for random... (cached) yes checking for strerror... (cached) yes checking for lchown... (cached) yes checking for fchmod... (cached) yes checking for snprintf... (cached) yes checking for statvfs... (cached) yes checking for memmove... (cached) yes checking for rint... (cached) yes checking for stat64... (cached) yes checking for lstat64... (cached) yes checking for truncate64... (cached) no checking for statvfs64... (cached) no checking for setbuf... (cached) yes checking for isatty... (cached) yes checking for flockfile... (cached) yes checking for getpagesize... (cached) yes checking for localtime_r... (cached) yes checking for strtok_r... (cached) yes checking for wcrtomb... (cached) yes checking for mbrtowc... (cached) yes checking for res_ninit()... (cached) no checking for gnu_get_libc_version()... (cached) no ../src/configure: line 9881: AM_LANGINFO_CODESET: command not found checking for an implementation of va_copy()... (cached) yes checking for an implementation of __va_copy()... (cached) yes checking whether va_lists can be copied by value... (cached) no checking for C++ exceptions flag... (cached) -fno-exceptions checking for gcc 3.0 ABI... (cached) yes checking for C++ "explicit" keyword... (cached) yes checking for C++ "typename" keyword... (cached) yes checking for modern C++ template specialization syntax support... (cached) yes checking whether partial template specialization works... (cached) yes checking whether operators must be re-defined for templates derived from templates... (cached) no checking whether we need to cast a derived template to pass as its base class... (cached) no checking whether the compiler can resolve const ambiguities for templates... (cached) yes checking whether the C++ "using" keyword can change access... (cached) yes checking whether the C++ "using" keyword resolves ambiguity... (cached) yes checking for "std::" namespace... (cached) yes checking whether standard template operator!=() is ambiguous... (cached) unambiguous checking for C++ reinterpret_cast... (cached) yes checking for C++ dynamic_cast to void*... (cached) yes checking whether C++ requires implementation of unused virtual methods... (cached) yes checking for trouble comparing to zero near std::operator!=()... (cached) no checking for LC_MESSAGES... (cached) yes checking for tar archiver... checking for gnutar... (cached) gnutar gnutar checking for wget... checking for wget... (cached) wget wget checking for valid optimization flags... yes checking for gcc -pipe support... yes checking whether compiler supports -Wno-long-long... yes checking whether C compiler supports -fprofile-generate... yes checking for correct temporary object destruction order... yes checking for correct overload resolution with const and templates... no Building Python extensions using python-2.5 from /opt/local/Library/Frameworks/Python.framework/Versions/2.5 creating ./config.status creating config/autoconf.mk creating Makefile creating xpcom/Makefile creating xpcom/src/Makefile creating xpcom/src/loader/Makefile creating xpcom/src/module/Makefile creating xpcom/components/Makefile creating xpcom/test/Makefile creating xpcom/test/test_component/Makefile creating dom/Makefile creating dom/src/Makefile creating dom/test/Makefile creating dom/test/pyxultest/Makefile creating dom/nsdom/Makefile creating dom/nsdom/test/Makefile

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• valgrind complains doing a very simple strtok in c

  - by monkeyking

  Hi I'm trying to tokenize a string by loading an entire file into a char[] using fread. For some strange reason it is not always working, and valgrind complains in this very small sample program. Given an input like test.txt first second And the following program #include <stdio.h> #include <string.h> #include <stdlib.h> #include <sys/stat.h> //returns the filesize in bytes size_t fsize(const char* fname){ struct stat st ; stat(fname,&st); return st.st_size; } int main(int argc, char *argv[]){ FILE *fp = NULL; if(NULL==(fp=fopen(argv[1],"r"))){ fprintf(stderr,"\t-> Error reading file:%s\n",argv[1]); return 0; } char buffer[fsize(argv[1])]; fread(buffer,sizeof(char),fsize(argv[1]),fp); char *str = strtok(buffer," \t\n"); while(NULL!=str){ fprintf(stderr,"token is:%s with strlen:%lu\n",str,strlen(str)); str = strtok(NULL," \t\n"); } return 0; } compiling like gcc test.c -std=c99 -ggdb running like ./a.out test.txt thanks

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• How to write PIL image filter for plain pgm format?

  - by Juha

  How can I write a filter for python imaging library for pgm plain ascii format (P2). Problem here is that basic PIL filter assumes constant number of bytes per pixel. My goal is to open feep.pgm with Image.open(). See http://netpbm.sourceforge.net/doc/pgm.html or below. Alternative solution is that I find other well documented ascii grayscale format that is supported by PIL and all major graphics programs. Any suggestions? br, Juha feep.pgm: P2 # feep.pgm 24 7 15 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 3 3 3 0 0 7 7 7 7 0 0 11 11 11 11 0 0 15 15 15 15 0 0 3 0 0 0 0 0 7 0 0 0 0 0 11 0 0 0 0 0 15 0 0 15 0 0 3 3 3 0 0 0 7 7 7 0 0 0 11 11 11 0 0 0 15 15 15 15 0 0 3 0 0 0 0 0 7 0 0 0 0 0 11 0 0 0 0 0 15 0 0 0 0 0 3 0 0 0 0 0 7 7 7 7 0 0 11 11 11 11 0 0 15 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 edit: Thanks for the answer, I works... but I need a solution that uses Image.open(). Most of python programs out there use PIL for graphics manipulation (google: python image open). Thus, I need to be able to register a filter to PIL. Then, I can use any software that uses PIL. I now think mostly scipy, pylab, etc. dependent programs.

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• Trouble with Berkeley DB JE Base API Secondary Databases and Sequences

  - by milosz

  I have a class Document which consists of Id (int) and Url (String). I would like to have a primary index on Id and secondary index on Url. I would also like to have a sequence for Id auto-incrementation. So I create a SecondaryDatabase and then I create a Sequence. During initialisation of the Sequence I get an exception: Exception in thread "main" java.lang.IllegalArgumentException at com.sleepycat.util.UtfOps.getCharLength(UtfOps.java:137) at com.sleepycat.util.UtfOps.bytesToString(UtfOps.java:259) at com.sleepycat.bind.tuple.TupleInput.readString(TupleInput.java:152) at pl.edu.mimuw.zbd.berkeley.zadanie.rozwiazanie.MyDocumentBiding.entryToObject(MyDocumentBiding.java:12) at pl.edu.mimuw.zbd.berkeley.zadanie.rozwiazanie.MyDocumentBiding.entryToObject(MyDocumentBiding.java:1) at com.sleepycat.bind.tuple.TupleBinding.entryToObject(TupleBinding.java:76) at pl.edu.mimuw.zbd.berkeley.zadanie.rozwiazanie.UrlKeyCreator.createSecondaryKey(UrlKeyCreator.java:20) at com.sleepycat.je.SecondaryDatabase.updateSecondary(SecondaryDatabase.java:835) at com.sleepycat.je.SecondaryTrigger.databaseUpdated(SecondaryTrigger.java:42) at com.sleepycat.je.Database.notifyTriggers(Database.java:2004) at com.sleepycat.je.Cursor.putNotify(Cursor.java:1692) at com.sleepycat.je.Cursor.putInternal(Cursor.java:1616) at com.sleepycat.je.Cursor.putNoOverwrite(Cursor.java:663) at com.sleepycat.je.Sequence.<init>(Sequence.java:188) at com.sleepycat.je.Database.openSequence(Database.java:546) at pl.edu.mimuw.zbd.berkeley.zadanie.rozwiazanie.MyFullTextSearchEngine.init(MyFullTextSearchEngine.java:131) at pl.edu.mimuw.zbd.berkeley.zadanie.testy.MyFullTextSearchEngineTest.main(MyFullTextSearchEngineTest.java:18) It seems that during the initialisation of the sequence the secondary database is forced to update. When I debug the entryToObject method of MyDocumentBiding the bytes that it tries to convert to object seem random. What am I doing wrong?

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• Python: Seeing all files in Hex.

  - by Recursion

  I am writing a python script which looks at common computer files and examines them for similar bytes, words, double word's. Though I need/want to see the files in Hex, ande cannot really seem to get python to open a simple file in python. I have tried codecs.open with hex as the encoding, but when I operate on the file descriptor it always spits back File "main.py", line 41, in <module> main() File "main.py", line 38, in main process_file(sys.argv[1]) File "main.py", line 27, in process_file seeker(line.rstrip("\n")) File "main.py", line 15, in seeker for unit in f.read(2): File "/usr/lib/python2.6/codecs.py", line 666, in read return self.reader.read(size) File "/usr/lib/python2.6/codecs.py", line 472, in read newchars, decodedbytes = self.decode(data, self.errors) File "/usr/lib/python2.6/encodings/hex_codec.py", line 50, in decode return hex_decode(input,errors) File "/usr/lib/python2.6/encodings/hex_codec.py", line 42, in hex_decode output = binascii.a2b_hex(input) TypeError: Non-hexadecimal digit found def seeker(_file): f = codecs.open(_file, "rb", "hex") for LINE in f.read(): print LINE f.close() I really just want to see files, and operate on them as if it was in a hex editor like xxd. Also is it possible to read a file in increments of maybe a word at a time. No this is not homework.

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• Download, pause and resume an download using Indy components

  - by Salvador

  Actually i'm using the TIdHTTP component for download a file from internet. i'm wondering if is possible pause and resume the download using this component o maybe another indy component. this is my current code, this works ok for download a file (without resume), but . now i want pause the download close my app ,and when my app restart then resume the download from the last position saved. var Http: TIdHTTP; MS : TMemoryStream; begin Result:= True; Http := TIdHTTP.Create(nil); MS := TMemoryStream.Create; try try Http.OnWork:= HttpWork;//this event give me the actual progress of the download process Http.Head(Url); FSize := Http.Response.ContentLength; AddLog('Downloading File '+GetURLFilename(Url)+' - '+FormatFloat('#,',FSize)+' Bytes'); Http.Get(Url, MS); MS.SaveToFile(LocalFile); except on E : Exception do Begin Result:=False; AddLog(E.Message); end; end; finally Http.Free; MS.Free; end; end;

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• Reloading a JTree during runtime

  - by Patrick Kiernan

  I create a JTree and model for it out in a class separate to the GUI class. The data for the JTree is extracted from a file. Now in the GUI class the user can add files from the file system to an AWT list. After the user clicks on a file in the list I want the JTree to update. The variable name for the JTree is schemaTree. I have the following code for the when an item in the list is selected: private void schemaListItemStateChanged(java.awt.event.ItemEvent evt) { int selection = schemaList.getSelectedIndex(); File selectedFile = schemas.get(selection); long fileSize = selectedFile.length(); fileInfoLabel.setText("Size: " + fileSize + " bytes"); schemaParser = new XSDParser(selectedFile.getAbsolutePath()); TreeModel model = schemaParser.generateTreeModel(); schemaTree.setModel(model); } I've updated the code to correspond to the accepted answer. The JTree now updates correctly based on which file I select in the list.

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