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• How to have a soft-real-time process in presense of heavily swapping IO-intensive background load?

  - by Vi

  schedtool: PID 32301: PRIO 4, POLICY R: SCHED_RR , NICE -20, AFFINITY 0xf ionice: realtime: prio 4 But the music is stumbling anyway. Background load is low prio (SCHED_IDLEPRIO, idle ionice), but uses a lot of memory (more than is physically available) and does a lot of IO and calculations. Latencytop shows about 1500ms for: Following symlink Writing buffer to disk (sync) Page fault Writing a page to disk both for the bg load and for unrelated processes. Load average is 10 and counting. Why cannot it allocate, for example, 200MHZ of one of the cores and 32M of memory and not less than once per second opportunity for IO for mplayer to make it happy while continuing calculations on the background? Or: why it cannot leave background task and swap loving each other but keeping the rest of the system as if there were no background load? How to have RT processes AND heavy bg load simultaneously (without of virtual machines)?

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• Android File Picker

  - by GuyNoir

  Is there a good solution for picking a file in an android application? I need the user to be able to browse their SD card for a file they would like to load. However, it cannot use an outside application (like andExplorer). It must stay contained inside my application. I saw one a while ago that's hosted on google code and used by the Gameboid, SNESoid and other similar emulators to pick roms. If any one can point me to that one that'd be just as great. Thanks!

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• File path for J2ME FileConnection?

  - by Kilnr

  Hi, I'm writing a MIDlet which needs to write file. I'm using FileConnection from JSR-75 to accomplish this. The intention is to have this MIDlet runnning on as much devices as possible (all MIDP 2.0 devices with JSR-75 support, ideally). On several emulators and an HTC Touch Pro2, I can perfectly use the following code to get the root of the filesystem: Enumeration drives = FileSystemRegistry.listRoots(); String root = (String) drives.nextElement(); String path = "file:///" + root; However, on a Nokia S60 5th edition emulator, trying to open a FileConnection to this path throws a java.lang.SecurityException. Apparently S60 devices do not allow connections to the root of the filesystem. I realise I can use something like System.getProperty("fileconn.dir.photos"), but that isn't supported on all devices either. So, my actual question: what is the best approach to get a path to create a FileConnection with, that allows for maximum portability? Thanks. Edit: I suppose I could iterate over all the roots in the Enumeration, and check for a writable one, but that's hardly optimal for two reasons. First, there aren't necessarily any writable roots. Second, this could be the phone memory or a memory card, so the storage method wouldn't be consistent across devices, which is rather ugly.

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• How to convert binary read/write to non-binary read/write in C++

  - by Phenom

  I have some C++ code from somewhere that reads and writes data in binary format. I want to see what it's reading and writing in the file, so I want to convert it's binary read and write to non-binary read and write. Also, when I convert the binary write to non-binary write, I want it to still be able to read in the information correctly. How can this be done? The write function: int btwrite(short rrn, BTPAGE *page_ptr) { // long lseek(), addr; long addr; addr = (long) rrn * (long) PAGESIZE + HEADERSIZE; lseek(btfd, addr, 0); return (write(btfd, page_ptr, PAGESIZE)); } The read function: int btread(short rrn, BTPAGE *page_ptr) { // long lseek(), addr; long addr; addr = (long)rrn * (long)PAGESIZE + HEADERSIZE; lseek(btfd, addr, 0); return ( read(btfd, page_ptr, PAGESIZE) ); }

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• Non-blocking read on a stream in python.

  - by Mathieu Pagé

  Hi, I'm using the subprocess module to start a subprocess and connect to it's output stream (stdout). I want to be able to execute non-blocking reads on its stdout. Is there a way to make .readline non-bloking or to check if there is data on the stream before I invoke .readline? I'd like this to be portable or at least work under Windows and Linux. here is how I do it for now (It's blocking on the .readline if no data is avaible): p = subprocess.Popen('myprogram.exe', stdout = subprocess.PIPE) str = p.stdout.readline() Thanks for your help.

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• iPad: CFBundleDocumentTypes & UIFileSharingEnabled issues

  - by carloe

  Has anyone gotten UIFileSharingEnabled or CFBundleDocumentTypes to work? I added UIFileSharingEnabled as true to my plist and used Apple's example from the link below for CFBundleDocumentTypes, but can't seem to get it to work. I don't see my app under file sharing in iTunes, and I do not get the option to open documents I registered in my app when I click on them in the mail.app http://developer.apple.com/iphone/library/documentation/General/Conceptual/iPadProgrammingGuide/CoreApplication/CoreApplication.html

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• How to do proper Unicode and ANSI output redirection on cmd.exe?

  - by Sorin Sbarnea

  If you are doing automation on windows and you are redirecting the output of different commands (internal cmd.exe or external, you'll discover that your log files contains combined Unicode and ANSI output (meaning that they are invalid and will not load well in viewers/editors). Is it is possible to make cmd.exe work with UTF-8? This question is not about display, s about stdin/stdout/stderr redirection and Unicode. I am looking for a solution that would allow you to: redirect the output of the internal commands to a file using UTF-8 redirect output of external commands supporting Unicode to the files but encoded as UTF-8. If it is impossible to obtain this kind of consistence using batch files, is there another way of solving this problem, like using python scripting for this? In this case, I would like to know if it is possible to do the Unicode detection alone (user using the scripting should not remember if the called tools will output Unicode or not, it will just expect to convert the output to UTF-8. For simplicity we'll assume that if the tool output is not-Unicode it will be considered as UTF-8 (no codepage conversion).

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• how to copy files from folder to another folder

  - by AmRoSH

  I have Folder this Folder have some files and folders i need to copy just files from this folder to another one without coping the folders. if anyone understood that please i need some help.

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• Lots of questions about file I/O (reading/writing message strings)

  - by Nazgulled

  Hi, For this university project I'm doing (for which I've made a couple of posts in the past), which is some sort of social network, it's required the ability for the users to exchange messages. At first, I designed my data structures to hold ALL messages in a linked list, limiting the message size to 256 chars. However, I think my instructors will prefer if I save the messages on disk and read them only when I need them. Of course, they won't say what they prefer, I need to make a choice and justify the best I can why I went that route. One thing to keep in mind is that I only need to save the latest 20 messages from each user, no more. Right now I have an Hash Table that will act as inbox, this will be inside the user profile. This Hash Table will be indexed by name (the user that sent the message). The value for each element will be a data structure holding an array of size_t with 20 elements (20 messages like I said above). The idea is to keep track of the disk file offsets and bytes written. Then, when I need to read a message, I just need to use fseek() and read the necessary bytes. I think this could work nicely... I could use just one single file to hold all messages from all users in the network. I'm saying one single file because a colleague asked an instructor about saving the messages from each user independently which he replied that it might not be the best approach cause the file system has it's limits. That's why I'm thinking of going the single file route. However, this presents a problem... Since I only need to save the latest 20 messages, I need to discard the older ones when I reach this limit. I have no idea how to do this... All I know is about fread() and fwrite() to read/write bytes from/to files. How can I go to a file offset and say "hey, delete the following X bytes"? Even if I could do that, there's another problem... All offsets below that one will be completely different and I would have to process all users mailboxes to fix the problem. Which would be a pain... So, any suggestions to solve my problems? What do you suggest?

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• Synchronization requirements for FileStream.(Begin/End)(Read/Write)

  - by Doug McClean

  Is the following pattern of multi-threaded calls acceptable to a .Net FileStream? Several threads calling a method like this: ulong offset = whatever; // different for each thread byte[] buffer = new byte[8192]; object state = someState; // unique for each call, hence also for each thread lock(theFile) { theFile.Seek(whatever, SeekOrigin.Begin); IAsyncResult result = theFile.BeginRead(buffer, 0, 8192, AcceptResults, state); } if(result.CompletedSynchronously) { // is it required for us to call AcceptResults ourselves in this case? // or did BeginRead already call it for us, on this thread or another? } Where AcceptResults is: void AcceptResults(IAsyncResult result) { lock(theFile) { int bytesRead = theFile.EndRead(result); // if we guarantee that the offset of the original call was at least 8192 bytes from // the end of the file, and thus all 8192 bytes exist, can the FileStream read still // actually read fewer bytes than that? // either: if(bytesRead != 8192) { Panic("Page read borked"); } // or: // issue a new call to begin read, moving the offsets into the FileStream and // the buffer, and decreasing the requested size of the read to whatever remains of the buffer } } I'm confused because the documentation seems unclear to me. For example, the FileStream class says: Any public static members of this type are thread safe. Any instance members are not guaranteed to be thread safe. But the documentation for BeginRead seems to contemplate having multiple read requests in flight: Multiple simultaneous asynchronous requests render the request completion order uncertain. Are multiple reads permitted to be in flight or not? Writes? Is this the appropriate way to secure the location of the Position of the stream between the call to Seek and the call to BeginRead? Or does that lock need to be held all the way to EndRead, hence only one read or write in flight at a time? I understand that the callback will occur on a different thread, and my handling of state, buffer handle that in a way that would permit multiple in flight reads. Further, does anyone know where in the documentation to find the answers to these questions? Or an article written by someone in the know? I've been searching and can't find anything. Relevant documentation: FileStream class Seek method BeginRead method EndRead IAsyncResult interface

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• One row is skipped each time the program scans a matrix from file !

  - by ZaZu

  Hello there, I had this code working yesterday, but it seems like I edited it a bit and lost the working version. I cant get this to work anymore. I basically want to scan a matrix from a .txt file. But each time it scans the first row, the second one is skipped, and it reads the third instead :( Here is my code : for(i=0;i<=test->rowmat1;i++){ for(j=0;j<=test->colmat1;j++){ fscanf(fin,"%f\t",&test->mat[i][j]); } fscanf(fin,"%*[^\n]",&test->mat[i][j]); } For example, for a matrix of : 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 If I extract 3 rows and 3 cols, I get : 1.00 2.00 3.00 7.00 8.00 9.00 Then fails, it wants to skip over the second line but there is nothing after 10 11 12 Why did it stop working ? What do I have wrong ? Please help, Thanks in advance.

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• safely lock a file then move? windows

  - by acidzombie24

  I have a file and need to ensure it exist before inserting a row into the db. After i insert i need to use the PK as part of the filename and move it into another location. How do i check if it exist then lock it so it cant be deleted until i can insert into the db then proceed to move the file without it being deleted upon releasing the lock? also the file may be in use. I am thinking of copying the file into a safe location then moving that file away. In this case i need to copy a file that is being used for reading. How can i do the above steps safely? Using .NET

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• listFiles() of File not working on symbolic links?

  - by Joset

  I have the following File object pointing to a directory via symbolic link, File directory = new File("/path/symlink/foo/bar"); String[] files = directory.listFiles(); listFiles() returns null, is this because of the symlink? if yes, how will I go about this if I really want to list the files in bar using the path that contains a symlink?

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• Maintain file permissions when extracting from a zip file using JDK 5 api

  - by Raymond

  I am using java.util.Zip and java.util.ZipEntry to successfully extra a zip file's contents to disk. I would like to maintain the file permissions set when extracting on a *nix file-system. Can anyone point me to the "correct" way to do this?

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• Android: How to copy a SQLite database from one application to another

  - by mahdaeng

  I have a lite version of an application that uses a SQLite database. I want to copy that database over to the full version of the application when the user installs the full version. I have written some code to perform the file copy, but the lite database file always comes up as unreadable. The file is there and I can point to it, but I can't read it to perform the copy. In the Android documentation, we read: You can save files directly on the device's internal storage. By default, files saved to the internal storage are private to your application and other applications cannot access them (nor can the user). Note the words, "by default". Is there a way that I can override that default and make the SQLite file readable by my other application? Thank you.

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• How can I insert or remove bytes from the middle of a large file in .NET

  - by Eric

  Is it possible to efficiently insert or remove bytes from the middle of a large file, and if so how? Or am I stuck rewriting the entire file after the point where the data was inserted or removed? [A lot of Bytes][Unwanted Bytes][A lot of Bytes] - > [A lot of Bytes][A lot of Bytes] or [A lot of Bytes][A lot of Bytes] - > [A loto f Bytes][New Inserted Bytes][A lot of Bytes]

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• Android: writing a file to sdcard

  - by Sumit M Asok

  I'm trying to write a file from an Http post reply to a file on the sdcard. Everything works fine until the byte array of data is retrieved. I've tried setting WRITE_EXTERNAL_STORAGE permission in the manifest and tried many different combinations of tutorials I found on the net. All I could find was using the openFileOutput("",MODE_WORLD_READABLE) method, of the activity but how my app writes file is by using a thread. Specifically, a thread is invoked from another thread when a file has to be written, so giving an activity object didn't work even though I tried it. The app has come a long way and I cannot change how the app is currently written. Please, someone help me? CODE: File file = new File(bgdmanip.savLocation); FileOutputStream filecon = null; filecon = new FileOutputStream(file); // bgdmanip.savLocation holds the whole files path byte[] myByte; myByte = Base64Coder.decode(seReply); Log.d("myBytes", String.valueOf(myByte)); bos.write(myByte); filecon.write(myByte); myvals = x * 11024; seReply is a string reply from HttpPost response. the second set of code is looped with reference to x. the file is created but remains 0 bytes

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• Java: Send BufferedImage through Socket with a low bitdepth

  - by Martijn Courteaux

  Hi, The title says enough I think. I have a full quality BufferedImage and I want to send it through an OutputStream with a low bitdepth. I don't want an algorithm to change pixel by pixel the quality, so it is still a full-quality. So, the goal is to write the image (with the full resolution) through the OuputStream with a very small size. Thanks, Martijn

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• How can I walk through two files simultaneously in Perl?

  - by Alex Reynolds

  I have two text files that contain columnar data of the variety position-value, sorted by position. Here is an example of the first file (file A): 100 1 101 1 102 0 103 2 104 1 ... Here is an example of the second file (B): 20 0 21 0 ... 100 2 101 1 192 3 193 1 ... Instead of reading one of the two files into a hash table, which is prohibitive due to memory constraints, what I would like to do is walk through two files simultaneously, in a stepwise fashion. What this means is that I would like to stream through lines of either A or B and compare position values. If the two positions are equal, then I perform a calculation on the values associated with that position. Otherwise, if the positions are not equal, I move through lines of file A or file B until the positions are equal (when I again perform my calculation) or I reach EOF of both files. Is there a way to do this in Perl?

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• Is it possible to stream a file to and from servers without holding the data in ram?

  - by Chris Denman

  Hi everyone! PHP question (new to PHP after 10 years of Perl, arrggghhh!). I have a 100mb file that I want to send to another server. I have managed to read the file in and "post" it without curl (cannot use curl for this app). Everything is working fine on smaller files. However, with the larger files, PHP complains about not being able to allocate memory. Is there a way to open a file, line by line, and send it as a post ALSO line by line? This way nothing is held in ram thus preventing my errors and getting around strict limitations. Chris

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• C# File Exception: cannot access the file because it is being used by another process

  - by Lirik

  I'm trying to download a file from the web and save it locally, but I get an exception: C# The process cannot access the file 'blah' because it is being used by another process. This is my code: File.Create("data.csv"); // create the file request = (HttpWebRequest)WebRequest.CreateDefault(new Uri(url)); request.Timeout = 30000; response = (HttpWebResponse)request.GetResponse(); using (Stream file = File.OpenWrite("data.csv"), // <-- Exception here input = response.GetResponseStream()) { // Save the file using Jon Skeet's CopyStream method CopyStream(input, file); } I've seen numerous other questions with the same exception, but none of them seem to apply here. Any help?

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• .NET: IOException for permissions when creating new file?

  - by Rosarch

  I am trying to create a new file and write XML to it: FileStream output = File.Create(Path.Combine(PATH_TO_DATA_DIR, fileName)); The argument evaluates to: C:\path\to\Data\test.xml The exception is: The process cannot access the file 'C:\path\to\Data\test.xml' because it is being used by another process. What am I doing wrong here? UPDATE: This code throws the same exception: StreamWriter writer = new StreamWriter(Path.Combine(PATH_TO_DATA_DIR, fileName)); UPDATE 2: The file I am trying to create does not exist in the file system. So how can be it in use?

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• lseek/write suddenly returns -1 with errno = 9 (Bad file descriptor)

  - by Ger Teunis

  My application uses lseek to seek the desired position to write data. The file is opened using open() command successfully and my application was able to use lseek and wite lots of times. At a given time, for some users and not easily reproducible the lseek returns -1 with an errno of 9. File is not closed before this and the filehandle (int) isn't reset. After this an other file is created open is okay again and lseek and write works again. To make it even worse, this user tried the complete sequence again and all was well. So my question is, can the OS close the file handle for me for some reason? What could cause this? A file indexer or file scanner of some sort? What is the best way to solve this; is this pseudo code the best solution? (never mind the code layout, will create functions for it) int fd=open(...); if (fd>-1) { long result = lseek(fd,....); if (result == -1 && errno==9) { close(fd..); //make sure we try to close nicely fd=open(...); result = lseek(fd,....); } } Anybody experience with something similar? Summary: file seek and write works okay for a given fd and suddenly gives back errno=9 without a reason.

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• Possible to open a text file in a MYSQL stored procedure?

  - by futureelite7

  Is it possible to open and read from a text file in a MYSQL stored procedure? I have a text file with a list of about 50k telephone numbers, and want to write a stored procedure that will open the file, read the 50k lines and store it as rows in a table. I cannot load the file directly using LOAD IN FILE as the table has additional columns that I have to set. Thanks!

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• C# .Net file in use issue

  - by Dan

  I'm having an issue opening files that have recently been closed by the .Net framework. Basically, what happens is the following: -Read in an XML file using DataSet.ReadXml() -Make some changes to the data -Write out the XML file using DataSet.WriteXml() -Copy the XML file to a new location using File.Copy -FTP the file using a custom control This sequence can intermittently fail either after the WriteXML or the File.Copy with a file in use exception. I'm guessing it could be the Windows write cache not flushing right away. Can anyone confirm that this could be causing my issue? Any solutions to suggest? Thanks, Dan

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