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• How can I run Ruby specs and/or tests in MacVim without locking up MacVim?

  - by Henry

  About 6 months ago I switched from TextMate to MacVim for all of my development work, which primarily consists of coding in Ruby, Ruby on Rails and JavaScript. With TextMate, whenever I needed to run a spec or a test, I could just command+R on the test or spec file and another window would open and the results would be displayed with the 'pretty' format applied. If the spec or test was a lengthy one, I could just continue working with the codebase since the test/spec was running in a separate process/window. After the test ran, I could click through the results directly to the corresponding line in the spec file. Tim Pope's excellent rails.vim plugin comes very close to emulating this behavior within the MacVim environment. Running :Rake when the current buffer is a test or spec runs the file then splits the buffer to display the results. You can navigate through the results and key through to the corresponding spot in the file. The problem with the rails.vim approach is that it locks up the MacVim window while the test runs. This can be an issue with big apps that might have a lot of setup/teardown built into the tests. Also, the visual red/green html results that TextMate displays (via --format pretty, I'm assuming) is a bit easier to scan than the split window. This guy came close about 18 mos ago: http://cassiomarques.wordpress.com/2009/01/09/running-rspec-files-from-vim-showing-the-results-in-firefox/ The script he has worked with a bit of hacking, but the tests still ran within MacVim and locked up the current window. Any ideas on how to fully replicate the TextMate behavior described above in MacVim? Thanks!

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• How can I render an in-memory UIViewController's view Landscape?

  - by Aaron

  I'm trying to render an in-memory (but not in hierarchy, yet) UIViewController's view into an in-memory image buffer so I can do some interesting transition animations. However, when I render the UIViewController's view into that buffer, it is always rendering as though the controller is in Portrait orientation, no matter the orientation of the rest of the app. How do I clue this controller in? My code in RootViewController looks like this: MyUIViewController* controller = [[MyUIViewController alloc] init]; int width = self.view.frame.size.width; int height = self.view.frame.size.height; int bitmapBytesPerRow = width * 4; unsigned char *offscreenData = calloc(bitmapBytesPerRow * height, sizeof(unsigned char)); CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); CGContextRef offscreenContext = CGBitmapContextCreate(offscreenData, width, height, 8, bitmapBytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast); CGContextTranslateCTM(offscreenContext, 0.0f, height); CGContextScaleCTM(offscreenContext, 1.0f, -1.0f); [(CALayer*)[controller.view layer] renderInContext:offscreenContext]; At that point, the offscreen memory buffers contents are portrait-oriented, even when the window is in landscape orientation. Ideas?

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• NASM - Load code from USB Drive

  - by new123456

  Hola, Would any assembly gurus know the argument (register dl) that signifies the first USB drive? I'm working through a couple of NASM tutorials, and would like to get a physical boot (I can get a clean one with qemu). This is the section of code that loads the "kernel" data from disk: loadkernel: mov si, LMSG ;; 'Loading kernel',13,10,0 call prints ;; ex puts() mov dl, 0x00 ;; The disk to load from mov ah, 0x02 ;; Read operation mov al, 0x01 ;; Sectors to read mov ch, 0x00 ;; Track mov cl, 0x02 ;; Sector mov dh, 0x00 ;; Head mov bx, 0x2000 ;; Buffer end mov es, bx mov bx, 0x0000 ;; Buffer start int 0x13 jc loadkernel mov ax, 0x2000 mov ds, ax jmp 0x2000:0x00 If it makes any difference, I'm running a stock Dell Inspiron 15 BIOS. Apparently, the correct value for me is 0x80. The BIOS loads the hard drives and labels them starting at 0x80 according to this answer. My particular BIOS decides to load the USB drive up as the first, for some reason, so I can boot from there.

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• How to do buffered intersection checks on an IPoint?

  - by Quigrim

  How would I buffer an IPoint to do an intersection check using IRelationalOperator? I have, for arguments sake: IPoint p1 = xxx; IPoint p2 = yyy; IRelationalOperator rel1 = (IRelationalOperator)p1; if (rel.Intersects (p2)) // Do something But now I want to add a tolerance to my check, so I assume the right way to do that is by either buffering p1 or p2. Right? How do I add such a buffer? Note: the Intersects method I am using is an extension method I wrote to simplify my code. Here it is: /// <summary> /// Returns true if the IGeometry is intersected. /// This method negates the Disjoint method. /// </summary> /// <param name="relOp">The rel op.</param> /// <param name="other">The other.</param> /// <returns></returns> public static bool Intersects ( this IRelationalOperator relOp, IGeometry other) { return (!relOp.Disjoint (other)); }

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• Improving I/O performance in C++ programs[external merge sort]

  - by Ajay

  I am currently working on a project involving external merge-sort using replacement-selection and k-way merge. I have implemented the project in C++[runs on linux]. Its very simple and right now deals with only fixed sized records. For reading & writing I use (i/o)fstream classes. After executing the program for few iterations, I noticed that I/O read blocks for requests of size more than 4K(typical block size). Infact giving buffer sizes greater than 4K causes performance to decrease. The output operations does not seem to need buffering, linux seemed to take care of buffering output. So I issue a write(record) instead of maintaining special buffer of writes and then flushing them out at once using write(records[]). But the performance of the application does not seem to be great. How could I improve the performance? Should I maintain special I/O threads to take care of reading blocks or are there existing C++ classes providing this abstraction already?(Something like BufferedInputStream in java)

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• How do I controll clipping with non-opaque graphics-item's in Qt?

  - by JJacobsson

  I have a bunch of QGraphicsSvgItem's in a QGraphicsScene that are drawn connected by QGraphicsLineItem's. This show's a graph of a tree-structure. What I want to do is provide a feature where everything but a selected sub-tree becomes transparent. A kind of "highlight this sub-tree" feature. That part was easy, but the results are ugly because now the lines can be seen through the semi-transparent svg's. I am looking for some way to still clip other QGraphicsItem's in the scene to the svg item's, giving the effect that the svg's are semi-transparent windows to the background. I know this code does not use svg's but I figure you can replace that yourself if you are so inclined. int main(int argc, char *argv[]) { QApplication app(argc, argv); QGraphicsScene scene; for( int i = 0; i < 10; ++i ) { QGraphicsLineItem* line = new QGraphicsLineItem; line->setLine( i * 25.0 + 1.0, 0, i * 25.0 + 23.0, 0 ); scene.addItem( line ); } for( int i = 0; i < 11; ++i ) { QGraphicsEllipseItem* ellipse = new QGraphicsEllipseItem; ellipse->setRect( (i * 25.0) - 9.0, -9.0, 18.0, 18.0f ); ellipse->setBrush( QBrush( Qt::green, Qt::SolidPattern ) ); ellipse->setOpacity( 0.5 ); scene.addItem( ellipse ); } QGraphicsView view( &scene ); view.show(); return app.exec(); } I would like the line's to not be seen behind the circle's. I have tried fiddling with the depth-buffer and the stencil buffer using opengl rendering to no avail. How do I get the QGraphicsSvgItem's (or QGraphicsEllipseItem's in the example code) to still clip the lines even though they are semi-transparent?

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• Why Does My Vector<PEVENTLOGRECORD> Mysteriously Get Cleared?

  - by Eric

  Hello everyone, I am making a program that reads and stores data from Windows EventLog files (.evt) in C++. I am using the calls OpenBackupEventLog(ServerName, FileName) and ReadEventLog(...). Also using this: PEVENTLOGRECORD Anyway, without supplying all of the code, here is the basic idea: 1. I get a handle to the .evt file using OpenBackupEventLog() and passing in a file name. 2. I then use ReadEventLog() to fill up a buffer with an unknown number of EventLog messages. 3. I traverse through the buffer and add each message to a vector 4. I keep filling up buffers (repeat steps 2 and 3) until I reach the end of the file. Here is my code for filling the vector: vector<PEVENTLOGRECORD> allRecords; while(_status == ERROR_SUCCESS) { if(!ReadEventLog(...)) CheckStatus(); else FillVectorFromBuffer(allRecords) } // Function FillVectorFromBuffer FillVectorFromBuffer(vector(PEVENTLOGRECORD) &allRecords) { int bytesExamined = 0; PBYTE pRecord = (PBYTE)_lpBuffer; // This is one of the params in ReadEventLog() while(bytesExamined < _pnBytesRead) // Another param from ReadEventLog { PEVENTLOGRECORD currentRecord = (PEVENTLOGRECORD)(pRecord); allRecords.push_back(currentRecord); pRecord += currentRecord->Length; bytesExamined += currentRecord->Length; } } Anyway, whenever I run this, it will get all the EventLogs in the file, and the vector will have everything I want it to. But as soon as this line: if(!ReadEventLog()) gets called and returns true (aka ReadEventLog() returns false), then every field in my vector gets set to zero. The vector will still contain the correct number of elements, it's just that all of the fields in the PEVENTLOGRECORD struct are now zero. Anyone with better debugging experience have any ideas? Thanks.

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• Multi-reader IPC solution?

  - by gct

  I'm working on a framework in C++ (just for fun for now), that lets the user write plugins that use a standard API to stream data between each other. There's going to be three basic transport mechanisms for the data: files, sockets, and some kind of IPC piping system. The system is set up so that for the non-file transport, each stream can have multiple readers. IE once a server socket it setup, multiple computers can connect and stream the data. I'm a little stuck at the multi-reader IPC system though. All my plugins run in threads so they live in the same address space, so some kind of shared memory system would work fine, I was thinking I'd write my own circular buffer with a write pointer and read pointers chassing it around the buffer, but I have my doubts that I can achieve the same performance as something like linux pipes. I'm curious what people would suggest for a multi-reader solution to something like this? Is the overhead for pipes or domain sockets low enough that I could just open a connection to each reader and issue separate writes to each reader? This is intended to be significant volumes of data (tens of mega-samples/sec), so performance is a must.

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• java url connection, wait for data being sent through the outputstream

  - by Mateu

  I'm writting a java class that tests uploading speed connection to a server. I want to check how many data can be send in 5 seconds. I've written a class which creates a URL, creates a connection, and sends data trough the outPutStream. There is a loop where I writte data to the stream for 5 seconds. However I'm not able to see when data has been send (I writte data to the output stream, but data is not send yet). How can I wait untill data is really sent to the server? Here goes my code (which does not work): URL u = new URL(url) HttpURLConnection uc = (HttpURLConnection) u.openConnection(); uc.setDoOutput(true); uc.setDoInput(true); uc.setUseCaches(false); uc.setDefaultUseCaches(false); uc.setRequestMethod("POST"); uc.setRequestProperty("Content-Type", "application/octet-stream"); uc.connect(); st.start(); // Send the request OutputStream os = uc.getOutputStream(); //This while is incorrect cause it does not wait for data beeing sent while (st.getElapsedTime() < miliSeconds) { os.write(buffer); os.flush(); st.addSize(buffer.length); } os.close(); Thanks

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• x86 Assembly: Before Making a System Call on Linux Should You Save All Registers?

  - by mudge

  I have the below code that opens up a file, reads it into a buffer and then closes the file. The close file system call requires that the file descriptor number be in the ebx register. The ebx register gets the file descriptor number before the read system call is made. My question is should I save the ebx register on the stack or somewhere before I make the read system call, (could int 80h trash the ebx register?). And then restore the ebx register for the close system call? Or is the code I have below fine and safe? I have run the below code and it works, I'm just not sure if it is generally considered good assembly practice or not because I don't save the ebx register before the int 80h read call. ;; open up the input file mov eax,5 ; open file system call number mov ebx,[esp+8] ; null terminated string file name, first command line parameter mov ecx,0o ; access type: O_RDONLY int 80h ; file handle or negative error number put in eax test eax,eax js Error ; test sign flag (SF) for negative number which signals error ;; read in the full input file mov ebx,eax ; assign input file descripter mov eax,3 ; read system call number mov ecx,InputBuff ; buffer to read into mov edx,INPUT_BUFF_LEN ; total bytes to read int 80h test eax,eax js Error ; if eax is negative then error jz Error ; if no bytes were read then error add eax,InputBuff ; add size of input to the begining of InputBuff location mov [InputEnd],eax ; assign address of end of input ;; close the input file ;; file descripter is already in ebx mov eax,6 ; close file system call number int 80h

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• C++ Suppress Automatic Initialization and Destruction

  - by Travis G

  How does one suppress the automatic initialization and destruction of a type? While it is wonderful that T buffer[100] automatically initializes all the elements of buffer, and destroys them when they fall out of scope, this is not the behavior I want. #include <iostream> static int created = 0, destroyed = 0; struct S { S() { ++created; } ~S() { ++destroyed; } }; template <typename T, size_t KCount> class Array { private: T m_buffer[KCount]; public: Array() { // some way to suppress the automatic initialization of m_buffer } ~Array() { // some way to suppress the automatic destruction of m_buffer } }; int main() { { Array<S, 100> arr; } std::cout << "Created:\t" << created << std::endl; std::cout << "Destroyed:\t" << destroyed << std::endl; return 0; } The output of this program is: Created: 100 Destroyed: 100 I would like it to be: Created: 0 Destroyed: 0 My only idea is to make m_buffer some trivially constructed and destructed type like char and then rely on operator[] to wrap the pointer math for me, although this seems like a horribly hacked solution. Another solution would be to use malloc and free, but that gives a level of indirection that I do not want.

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• StreamReader returning another char

  - by Fernando

  I'm trying to read the content of a file with a StreamReader, that receives a FileStream. The file has some spaces inside (char 32) and the StreamReader is reading them as 0 (char 48). The screenshot shows the FileStream buffer and the StreamReader buffer. Both have the value 32, but when I call Read(), it returns 48. Am I missing something here? By the way, the code is running under .NET Compact Framework. The code that reads the data: public void Read() { using (StreamReader reader = new StreamReader(InputStream, Encoding.ASCII)) { foreach (var property in DataObject.EnumerateProperties()) { OffsetInfo offset = property.GetTextOffset(); reader.BaseStream.Position = offset.Start - 1; StringBuilder builder = new StringBuilder(offset.Size); int count = 0; while (reader.Peek() >= 0 && count < offset.Size) { char c = (char)reader.Read(); if ((int)c != 32 && c != '\r' && c != '\n') { builder.Append(c); count++; } else { reader.BaseStream.Position++; } } property.SetValue(DataObject, Convert.ChangeType(builder.ToString(), property.PropertyType, CultureInfo.CurrentCulture), null ); } } }

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• How to control virtual memory management in linux?

  - by chmike

  I'm writing a program that uses an mmap file to hold a huge buffer organized as an array of 64 MB blocks. The blocks are used to aggregate data received from different hosts through the network. As a consequence the total data size written in each block is not known in advance. Most of the time it is only 2MB but in some cases it can be up to 20MB or more. The data doesn't stay long in the buffer. 90% is deleted after less than a second and the rest is transmitted to another host. I would like to know if there is a way to tell the virtual memory manager that ram pages are not dirty anymore when data is deleted. Should I use mmap and munmap when a block is used and released to control the virtual memory ? What would be the overhead of doing this ? Also, some colleagues expressed concerns about the performance impact of allocating such a big mmap space. I expect it to behave like a swap file so that only dirty pages are to be considered.

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• Is there a general-purpose printf-ish routine defined in any C standard

  - by supercat

  In many C libraries, there is a printf-style routine which is something like the following: int __vgprintf(void *info, (void)(*print_function(void*, char)), const char *format, va_list params); which will format the supplied string and call print_function with the passed-in info value and each character in sequence. A function like fprintf will pass __vgprintf the passed-in file parameter and a pointer to a function which will cast its void* to a FILE* and output the passed-in character to that file. A function like snprintf will create a struct holding a char* and length, and pass the address of that struct to a function which will output each character in sequence, space permitting. Is there any standard for such a function, which could be used if e.g. one wanted a function to output an arbitrary format to a TCP port? A common approach is to allocate a buffer one hopes is big enough, use snprintf to put the data there, and then output the data from the buffer. It would seem cleaner, though, if there were a standard way to to specify that the print formatter should call a user-supplied routine with each character.

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• sendto is returning ENOBUF

  - by user338159

  Hi, I am currently running an old system on Tru64 which involves lots of UDP sockets using the sendto() function. The sockets are used in our code to send messages to/from various processes and then eventually on to a thick client app that is connected remotely. Occasionally the socket to the thick client gets stuck, this can cause some of these messages to get built up. My question is how can I determine the current buffer size, and how do I determine the maximum message buffer. The code below gives a snippet of how I set up the port and use the sendto function. /* need to adjust the maximum size we can send on this / / as it needs to be able to cope with the biggest / / messages we send / lenlen = sizeof(len) ; / allow double for when the system is under load */ len = 2 * C_MAX_MESSAGE_DATA_SIZE ; lpos_setsockopt(FATAL, msg_socket,SOL_SOCKET, SO_SNDBUF, &len, lenlen, &error_no) ; result = sendto( msg_socket, (char *)message, (int)message_len, flags, dest_addr, addrlen); Note. We have ported this application to Linux and the problem does not seem to appear there. Any help would be greatly appreciated. Regards

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• Circumvent c++ null-terminated string frustration

  - by ypnos

  I'm using boost::program_options and it suffers from the same as many other c++ libs, even std itself: It still uses C-style null-terminated strings, because nobody really likes the weak std::string. The method in question is: options_description_easy_init& operator()(const char* name, const value_semantic* s, const char* description); The typical use case is just fine: options.add_options() ("graphical", bool_switch(&isGraphical)->default_value(false), "Show any graphical output during runtime") However, I need the name of the option to be set dynamically. The reason is that in some cases I nead a custom prefix, which is added to the string by my function std::string key(const std::string& k): options.add_options() (key("graphical"), bool_switch(&isGraphical)->default_value(false), "Show any graphical output during runtime") This fails. I could now use c_str() on the std::string but that's evil -- I don't know how long program_options keeps the variable around and if my string is still alive when needed. I could also reserve memory in a buffer etc. and hand in that. The buffer is never freed and it sucks/is evil. Is there anything else I can do to circumvent the C-style string mess in this situation?

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• Response as mail attachment

  - by el ninho

  using (MemoryStream stream = new MemoryStream()) { compositeLink.PrintingSystem.ExportToPdf(stream); Response.Clear(); Response.Buffer = false; Response.AppendHeader("Content-Type", "application/pdf"); Response.AppendHeader("Content-Transfer-Encoding", "binary"); Response.AppendHeader("Content-Disposition", "attachment; filename=test.pdf"); Response.BinaryWrite(stream.GetBuffer()); Response.End(); } I got this working fine. Next step is to send this pdf file to mail, as attachment using (MemoryStream stream = new MemoryStream()) { compositeLink.PrintingSystem.ExportToPdf(stream); Response.Clear(); Response.Buffer = false; Response.AppendHeader("Content-Type", "application/pdf"); Response.AppendHeader("Content-Transfer-Encoding", "binary"); Response.AppendHeader("Content-Disposition", "attachment; filename=test.pdf"); Response.BinaryWrite(stream.GetBuffer()); System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage(); message.To.Add("[email protected]"); message.Subject = "Subject"; message.From = new System.Net.Mail.MailAddress("[email protected]"); message.Body = "Body"; message.Attachments.Add(Response.BinaryWrite(stream.GetBuffer())); System.Net.Mail.SmtpClient smtp = new System.Net.Mail.SmtpClient("192.168.100.100"); smtp.Send(message); Response.End(); } I have problem with this line: message.Attachments.Add(Response.BinaryWrite(stream.GetBuffer())); Any help how to get this to work? Thanks

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• Is there a way to receive data as unsigned char over UDP on Qt?

  - by user269037

  I need to send floating point numbers using a UDP connection to a Qt application. Now in Qt the only function available is qint64 readDatagram ( char * data, qint64 maxSize, QHostAddress * address = 0, quint16 * port = 0 ) which accepts data in the form of signed character buffer. I can convert my float into a string and send it but it will obviously not be very efficient converting a 4 byte float into a much longer sized character buffer. I got hold of these 2 functions to convert a 4 byte float into an unsinged 32 bit integer to transfer over network which works fine for a simple C++ UDP program but for Qt I need to receive the data as unsigned char. Is it possible to avoid converting the floatinf point data into a string and then sending it? uint32_t htonf(float f) { uint32_t p; uint32_t sign; if (f < 0) { sign = 1; f = -f; } else { sign = 0; } p = ((((uint32_t)f)&0x7fff)<<16) | (sign<<31); // Whole part and sign. p |= (uint32_t)(((f - (int)f) * 65536.0f))&0xffff; // Fraction. return p; } float ntohf(uint32_t p) { float f = ((p>>16)&0x7fff); // Whole part. f += (p&0xffff) / 65536.0f; // Fraction. if (((p>>31)&0x1) == 0x1) { f = -f; } // Sign bit set. return f; }

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• C++, Ifstream opens local file but not file on HTTP Server

  - by fammi

  Hi, I am using ifstream to open a file and then read from it. My program works fine when i give location of the local file on my system. for eg /root/Desktop/abc.xxx works fine But once the location is on the http server the file fails to open. for eg http://192.168.0.10/abc.xxx fails to open. Is there any alternate for ifstream when using a URL address? thanks. part of the code where having problem: bool readTillEof = (endIndex == -1) ? true : false; // Open the file in binary mode and seek to the end to determine file size ifstream file ( fileName.c_str ( ), ios::in|ios::ate|ios::binary ); if ( file.is_open ( ) ) { long size = (long) file.tellg ( ); long numBytesRead; if ( readTillEof ) { numBytesRead = size - startIndex; } else { numBytesRead = endIndex - startIndex + 1; } // Allocate a new buffer ptr to read in the file data BufferSptr buf (new Buffer ( numBytesRead ) ); mpStreamingClientEngine->SetResponseBuffer ( nextRequest, buf ); // Seek to the start index of the byte range // and read the data file.seekg ( startIndex, ios::beg ); file.read ( (char *)buf->GetData(), numBytesRead ); // Pass on the data to the SCE // and signal completion of request mpStreamingClientEngine->HandleDataReceived( nextRequest, numBytesRead); mpStreamingClientEngine->MarkRequestCompleted( nextRequest ); // Close the file file.close ( ); } else { // Report error to the Streaming Client Engine // as unable to open file AHS_ERROR ( ConnectionManager, " Error while opening file \"%s\"\n", fileName.c_str ( ) ); mpStreamingClientEngine->HandleRequestFailed( nextRequest, CONNECTION_FAILED ); } }

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• no default constructor exists for class

  - by MixedCoder

  #include "Includes.h" enum BlowfishAlgorithm { ECB, CBC, CFB64, OFB64, }; class Blowfish { public: struct bf_key_st { unsigned long P[18]; unsigned long S[1024]; }; Blowfish(BlowfishAlgorithm algorithm); void Dispose(); void SetKey(unsigned char data[]); unsigned char Encrypt(unsigned char buffer[]); unsigned char Decrypt(unsigned char buffer[]); char EncryptIV(); char DecryptIV(); private: BlowfishAlgorithm _algorithm; unsigned char _encryptIv[200]; unsigned char _decryptIv[200]; int _encryptNum; int _decryptNum; }; class GameCryptography { public: Blowfish _blowfish; GameCryptography(unsigned char key[]); void Decrypt(unsigned char packet[]); void Encrypt(unsigned char packet[]); Blowfish Blowfish; void SetKey(unsigned char k[]); void SetIvs(unsigned char i1[],unsigned char i2[]); }; GameCryptography::GameCryptography(unsigned char key[]) { } Error:IntelliSense: no default constructor exists for class "Blowfish" ???!

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• What would happen if a same file being read and appended at the same time(python programming)?

  - by Shane

  I'm writing a script using two separate thread one doing file reading operation and the other doing appending, both threads run fairly frequently. My question is, if one thread happens to read the file while the other is just in the middle of appending strings such as "This is a test" into this file, what would happen? I know if you are appending a smaller-than-buffer string, no matter how frequently you read the file in other threads, there would never be incomplete line such as "This i" appearing in your read file, I mean the os would either do: append "This is a test" - read info from the file; or: read info from the file - append "This is a test" to the file; and such would never happen: append "This i" - read info from the file - append "s a test". But if "This is a test" is big enough(assuming it's a bigger-than-buffer string), the os can't do appending job in one operation, so the appending job would be divided into two: first append "This i" to the file, then append "s a test", so in this kind of situation if I happen to read the file in the middle of the whole appending operation, would I get such result: append "This i" - read info from the file - append "s a test", which means I might read a file that includes an incomplete string?

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• Is it possible to anti alias using Copy swap effect?

  - by Nor

  I'm developing an application in VB.Net using Managed DirectX that runs in windowed mode and renders onto a picture box that is smaller than the form. Whenever I resize the form, the back buffer is streched to fit the picture box. This is not what I would like. The backbuffer size is the same as screen size, however, I only want to render a part of the back buffer, whose size is controlled by the size of the picture box into which I'm rendering. Resetting the device with new presentation parameters is something I would like to avoid. I'm aware that I can use an overload of Device.Present if I set the swap effect to copy, but this doesn't allow me to use Multi Sample Anti Alias (which requires the Discard swap effect). It seems to me that the overload Device.Present is not usable with any other swap effect than copy, and throws an exception. An other alternative I considered is the PresentFlags.DeviceClip, however it seems that it works only for Windows XP. I'm using Windows 7 and it doesn't seem to be doing anything. So, is it even possible that I use anti-aliasing in this situation?

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• Need help implementing this algorithm with map reduce(hadoop)

  - by Julia

  Hi all! i have algorithm that will go through a large data set read some text files and search for specific terms in those lines. I have it implemented in Java, but I didnt want to post code so that it doesnt look i am searching for someone to implement it for me, but it is true i really need a lot of help!!! This was not planned for my project, but data set turned out to be huge, so teacher told me I have to do it like this. I was reading about MapReduce and thaught that i first do the standard implementation and then it will be more/less easier to do it with mapreduce. But didnt happen, since algorithm is quite stupid and nothing special, and map reduce...i cant wrap my mind around it. So here is shortly pseudo code of my algorithm LIST termList (there is method that creates this list from lucene index) FOLDER topFolder INPUT topFolder IF it is folder and not empty list files (there are 30 sub folders inside) FOR EACH sub folder GET file "CheckedFile.txt" analyze(CheckedFile) ENDFOR END IF Method ANALYZE(CheckedFile) read CheckedFile WHILE CheckedFile has next line GET line FOR(loops through termList) GET third word from line IF third word = term from list append whole line to string buffer ENDIF ENDFOR END WHILE OUTPUT string buffer to file Also, as you can see, each time when "analyze" is called, new file has to be created, i understood that map reduce is difficult to write to many outputs??? I understand mapreduce intuition, and my example seems perfectly suited for mapreduce, but when it comes to do this, obviously I do not know enough and i am STUCK! Please please help.

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• Multithreading: Read from / write to a pipe

  - by Tero Jokinen

  I write some data to a pipe - possibly lots of data and at random intervals. How to read the data from the pipe? Is this ok: in the main thread (current process) create two more threads (2, 3) the second thread writes sometimes to the pipe (and flush-es the pipe?) the 3rd thread has infinite loop which reads the pipe (and then sleeps for some time) Is this so far correct? Now, there are a few thing I don't understand: do I have to lock (mutex?) the pipe on write? IIRC, when writing to pipe and its buffer gets full, the write end will block until I read the already written data, right? How to check for read data in the pipe, not too often, not too rarely? So that the second thread wont block? Is there something like select for pipes? It is possible to set the pipe to unbuffered more or I have to flush it regularly - which one is better? Should I create one more thread, just for flushing the pipe after write? Because flush blocks as well, when the buffer is full, right? I just don't want the 1st and 2nd thread to block.... [Edit] Sorry, I thought the question is platform agnostic but just in case: I'm looking at this from Win32 perspective, possibly MinGW C...

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• Testing for a closed socket

  - by Robert S. Barnes

  I'm trying to test for a closed socket that has been gracefully closed by the peer without incurring the latency hit of a double send to induce a SIGPIPE. One of the assumptions here is that the socket if closed was gracefully closed by the peer immediately after it's last write / send. Actual errors like a premature close are dealt with else where in the code. If the socket is still open, there will be 0 or more bytes data which I don't actually want to pull out of the socket buffer yet. I was thinking that I could call int ret = recv(sockfd, buf, 1, MSG_DONTWAIT | MSG_PEEK); to determine if the socket is still connected. If it's connected but there's no data in the buffer I'll get a return of -1 with errno == EAGAIN and return the sockfd for reuse. If it's been gracefully closed by the peer I'll get ret == 0 and open a new connection. I've tested this and it seems to work. However, I suspect there is a small window between when I recv the last bit of my data and when the peer FIN arrives in which I could get a false-positive EAGAIN from my test recv. Is this going to bite me, or is there a better way of doing this?

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