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  • searching within a compressed sorted fixed width file

    - by user275455
    Assume I have a regular compressed fixed width file that is sorted on one of the fields. Given that I know the length of the records, I can use lseek to implement a binary search to records with fields that match a given value without having to read the entire file. Now the difficulty is that the file is gzipped. Is it possible to do this without completely inflating the file? If not with gzip. is there any compression that supports this kind of behavior?

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  • best practices question: How to save a collection of images and a java object in a single file? File

    - by Richard
    Hi all, I am making a java program that has a collection of flash-card like objects. I store the objects in a jtree composed of defaultmutabletreenodes. Each node has a user object attached to it with has a few string/native data type parameters. However, i also want each of these objects to have an image (typical formats, jpg, png etc). I would like to be able to store all of this information, including the images and the tree data to the disk in a single file so the file can be transferred between users and the entire tree, including the images and parameters for each object, can be reconstructed. I had not approached a problem like this before so I was not sure what the best practices were. I found XLMEncoder (http://java.sun.com/j2se/1.4.2/docs/api/java/beans/XMLEncoder.html) to be a very effective way of storing my tree and the native data type information. However I couldn't figure out how to save the image data itself inside of the XML file, and I'm not sure it is possible since the data is binary (so restricted characters would be invalid). My next thought was to associate a hash string instead of an image within each user object, and then gzip together all of the images, with the hash strings as the names and the XMLencoded tree in the same compmressed file. That seemed really contrived though. Does anyone know a good approach for this type of issue? THanks! Thanks!

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  • Program crashes after trying to use a recently created file. C#

    - by Jason T.
    So here is my code if (!File.Exists(pathName)) { File.Create(pathName); } StreamWriter outputFile = new StreamWriter(pathName,true); But whenever I run the program the first time the path with file gets created. However once I get to the StreamWriter line my program crashes because it says my fie is in use by another process. Is there something I'm missing between the File.Create and the StreamWriter statements?

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  • Python f.write() at beginning of file?

    - by kristus
    I'm doing it like this now, but i want it to write at the beginning of the file instead. f = open('out.txt', 'a') # or 'w'? f.write("string 1") f.write("string 2") f.write("string 3") f.close() so that the contenst of out.txt will be: string 3 string 2 string 1 and not (like this code does): string 1 string 2 string 3

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  • Read a file with 2048 bytes

    - by Suresh S
    Guys i have a file which has only one line. The file has no encoding it is a simple text file with single line. For every 2048 byte in a line , there is new record of 151 byte (totally 13*151 byte = 1945 records + 85 byte empty space). similarly for the next 2048 bytes. What is the best file i/o to use? i am thinking of reading 2048 bytes from file and storing it in an array . while (offset < fileLength &&(numRead=in.read(recordChunks, offset,alength)) >= 0) { } how can i get from the read statement only 2048 bytes at a time . i am getting IndexOutofBoundException.

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  • Improve performance writing 10 million records to text file using windows service

    - by user1039583
    I'm fetching more than 10 millions of records from database and writing to a text file. It takes hours of time to complete this operation. Is there any option to use TPL features here? It would be great if someone could get me started implementing this with the TPL. using (FileStream fStream = new FileStream("d:\\file.txt", FileMode.OpenOrCreate, FileAccess.ReadWrite)) { BufferedStream bStream = new BufferedStream(fStream); TextWriter writer = new StreamWriter(bStream); for (int i = 0; i < 100000000; i++) { writer.WriteLine(i); } bStream.Flush(); writer.Flush(); // empty buffer; fStream.Flush(); }

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  • how to write floating value accurately to a bin file.

    - by user319873
    Hi I am trying to dump the floating point values from my program to a bin file. Since I can't use any stdlib function, I am thinking of writting it char by char to a big char array which I am dumping in my test application to a file. It's like float a=3132.000001; I will be dumping this to a char array in 4 bytes. Code example would be:- if((a < 1.0) && (a > 1.0) || (a > -1.0 && a < 0.0)) a = a*1000000 // 6 bit fraction part. Can you please help me writting this in a better way.

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  • How to delete duplicate/aggregate rows faster in a file using Java (no DB)

    - by S. Singh
    I have a 2GB big text file, it has 5 columns delimited by tab. A row will be called duplicate only if 4 out of 5 columns matches. Right now, I am doing dduping by first loading each coloumn in separate List , then iterating through lists, deleting the duplicate rows as it encountered and aggregating. The problem: it is taking more than 20 hours to process one file. I have 25 such files to process. Can anyone please share their experience, how they would go about doing such dduping? This dduping will be a throw away code. So, I was looking for some quick/dirty solution, to get job done as soon as possible. Here is my pseudo code (roughly) Iterate over the rows i=current_row_no. Iterate over the row no. i+1 to last_row if(col1 matches //find duplicate && col2 matches && col3 matches && col4 matches) { col5List.set(i,get col5); //aggregate } Duplicate example A and B will be duplicate A=(1,1,1,1,1), B=(1,1,1,1,2), C=(2,1,1,1,1) and output would be A=(1,1,1,1,1+2) C=(2,1,1,1,1) [notice that B has been kicked out]

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  • Add up values from a text file

    - by Stanley
    Hi Guys I have a text file that contains Amounts at Substring (34, 47) of each line. I need to sum Up all the Values to the End of the File. I have this code that I had started to build but I do not know how to proceed from here: public class Addup { /** * @param args the command line arguments */ public static void main(String[] args) throws FileNotFoundException, IOException { // TODO code application logic here FileInputStream fs = new FileInputStream("C:/Analysis/RL004.TXT"); BufferedReader br = new BufferedReader(new InputStreamReader(fs)); String line; while((line = br.readLine()) != null){ String num = line.substring(34, 47); double i = Double.parseDouble(num); System.out.println(i); } } } The output is like this: 1.44576457E4 2.33434354E6 4.56875685E3 The Amount is in two decimal Places and I need the result also in the Two decimal Places. What Is the Best way to achieve this?

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  • StreamReader not working as expected

    - by Jon Preece
    Hi, I have written a simple utility that loops through all C# files in my project and updates the copyright text at the top. For example, a file may look like this; //Copyright My Company, © 2009-2010 The program should update the text to look like this; //Copyright My Company, © 2009-2010 However, the code I have written results in this; //Copyright My Company, � 2009-2011 Here is the code I am using; public bool ModifyFile(string filePath, List<string> targetText, string replacementText) { if (!File.Exists(filePath)) return false; if (targetText == null || targetText.Count == 0) return false; if (string.IsNullOrEmpty(replacementText)) return false; string modifiedFileContent = string.Empty; bool hasContentChanged = false; //Read in the file content using (StreamReader reader = File.OpenText(filePath)) { string file = reader.ReadToEnd(); //Replace any target text with the replacement text foreach (string text in targetText) modifiedFileContent = file.Replace(text, replacementText); if (!file.Equals(modifiedFileContent)) hasContentChanged = true; } //If we haven't modified the file, dont bother saving it if (!hasContentChanged) return false; //Write the modifications back to the file using (StreamWriter writer = new StreamWriter(filePath)) { writer.Write(modifiedFileContent); } return true; } Any help/suggestions are appreciated. Thanks!

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  • Windows equivalent of inb(), outb(), low level i/o

    - by Sebastian Dwornik
    I have some Linux code that monitors our hardware by collecting temperatures, voltages, and fan speeds, from the motherboard using inb(), outb(), inl(), etc. low level i/o functions. My challenge is to port that code over to run under Windows as a simple console app. But am puzzled in what functions Win32 (or .NET) provide that allow me permission to access direct memory mapped ports. I don't want to code a system driver either. My Windows tool preference is VS2008. (fyi) Is this possible?

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  • Can I set a timeout for a InputStream's read() function?

    - by Zombies
    I have a DataInputStream that I obtained from a Socket. Is there any way I can set a timeout for dis.read(...)? Currently I spawn a new thread to do the read. While the parent thread does a thread.join(timeout) to wait before interrupting it. I am aware of nio, but I don't think I want to refactor that much at this point. Thanks.

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  • RAKE won'tt create xml file

    - by user296507
    hi, i'm a bit lost here as to why my RAKE task will not create the desired XML file, however it works fine when i have the method 'build_xml' in the .RB file. require 'rubygems' require 'nokogiri' require 'open-uri' namespace :xml do desc "xml build test" task :xml_build => :environment do build_xml end end def build_xml #build xml docoument builder = Nokogiri::XML::Builder.new do |xml| xml.root { xml.location { xml.value "test" } } end File.open("test.xml", 'w') {|f| f.write(builder.to_xml) } end

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  • [NSData dataWithContentsOfFile:path] doesn't work

    - by Felics
    Hello, when I have the fallowing code to read a binary file: NSString* file = [NSString stringWithUTF8String:fileName]; NSString* filePath = resource ? [[NSBundle mainBundle] pathForResource:file ofType:nil] : [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0] stringByAppendingPathComponent: file]; NSData* fileData = [NSData dataWithContentsOfFile:filePath]; Where "fileName" and resource are load function parameters. "resource" is used to know if the file is located in application bundle or in Documents. Sometimes this code works well and sometimes it doesn't. As far I saw this problem is random. I can run the code 10 times in a row and it works fine and after that it gives me nil data without any modification. Does anybody knows what could be the problem? Could it be related with file extension or file name? Thank you. PS: I use this code on iPhone Simulator and the file exists in application bundle.

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  • Unable to write to a text file

    - by chrissygormley
    Hello, I am running some tests and need to write to a file. When I run the test's the open = (file, 'r+') does not write to the file. The test script is below: class GetDetailsIP(TestGet): def runTest(self): self.category = ['PTZ'] try: # This run's and return's a value result = self.client.service.Get(self.category) mylogfile = open("test.txt", "r+") print >>mylogfile, result result = ("".join(mylogfile.readlines()[2])) result = str(result.split(':')[1].lstrip("//").split("/")[0]) mylogfile.close() except suds.WebFault, e: assert False except Exception, e: pass finally: if 'result' in locals(): self.assertEquals(result, self.camera_ip) else: assert False When this test run's, no value has been entered into the text file and a value is returned in the variable result. I havw also tried mylogfile.write(result). If the file does not exist is claim's the file does not exist and doesn't create one. Could this be a permission problem where python is not allowed to create a file? I have made sure that all other read's to this file are closed so I the file should not be locked. Can anyone offer any suggestion why this is happening? Thanks

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  • Changing brightness in bufferedImage with DataBufferInt

    - by user2958025
    I must read some image and then I have to change brightness and contrast of this image I create main class and constructor where are panels, sliders and other stuff, I added changeListener to slider to take current value. My imagePanel is new Object of that class: public class Obrazek extends JPanel{ public static BufferedImage img = null; public Obrazek() { super(); try { img = ImageIO.read(new File("D:\\ja.jpg")); } catch (IOException e) {} } @Override public void paint(Graphics g) { g.drawImage(img, 0, 0, null); } } This is my load button private void przyciskWczytaj(java.awt.event.ActionEvent evt) { int odpowiedz = jFileChooser1.showOpenDialog(this); if (odpowiedz == jFileChooser1.APPROVE_OPTION) { File file = jFileChooser1.getSelectedFile(); try { BufferedImage im = ImageIO.read(new File(file.getAbsolutePath())); Obrazek.img = im; } catch (IOException ex) { System.out.println("Error"); } } } And now I want to create class where I will change that brightness. I have to use but I don't know how to use that thing: BufferedImage(256, 256, Bufferedmage.TYPE_INT_RGB) and to get each pixel of image I need to do something like: int rgb []=((DataBufferInt)img.getRaster().getDataBuffer()).getData(); And here I is next problem: How can I change the value of each r,g,b and show that new image on my panel

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  • Best directory to store application data with read\write rights for all users?

    - by Wodzu
    Hi guys. Until Windows Vista I was saving my application data into the directory where the program was located. The most common place was "C:\Program Files\MyApplication". As we know, under Vista and later the common user does't have rights to write under "Program Files" folder. So my first idea was to save the application data under "All Useres\Application Data" folder. But it seams that this folder has writing restrictions too! So to sum up, my requirements are: Folder should exist under Windows XP and above Microsoft's systems. All useres of the system should read\write\creation rights to this folder and it subfolders and files. I want to have only one copy of file\files for all useres. Thanks for your time.

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  • read chars from a file - c#

    - by Saskaaa
    How to read from a file array of numbers? I mean, how to read chars from a file? sorry for bad eng. upd: yes, i can :) just: "1 2 3 4 5 6 7 8" and etc. I just do not know how to read chars from a file.

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  • How to run a set of SQL queries from a file, in PHP?

    - by Harish Kurup
    I have some set of SQL queries which is in a file(i.e query.sql), and i want to run those queries in files using PHP, the code that i have wrote is not working, //database config's... $file_name="query.sql"; $query==file($file_name); $array_length=count($query); for($i=0;$i<$array_length;$i++) { $data .= $query[$i]; } echo $data; mysql_query($data); it echos the SQL Query from the file but throws an error at mysql_query() function...

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  • download large files using servlet

    - by niks
    I am using Apache Tomcat Server 6 and Java 1.6 and am trying to write large mp3 files to the ServletOutputStream for a user to download. Files are ranging from a 50-750MB at the moment. The smaller files aren't causing too much of a problem but with the larger files it and getting socket exception broken pipe. File fileMp3 = new File(objDownloadSong.getStrSongFolder() + "/" + strSongIdName); FileInputStream fis = new FileInputStream(fileMp3); response.setContentType("audio/mpeg"); response.setHeader("Content-Disposition", "attachment; filename=\"" + strSongName + ".mp3\";"); response.setContentLength((int) fileMp3.length()); OutputStream os = response.getOutputStream(); try { int byteRead = 0; while ((byteRead = fis.read()) != -1) { os.write(byteRead); } os.flush(); } catch (Exception excp) { downloadComplete = "-1"; excp.printStackTrace(); } finally { os.close(); fis.close(); }

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  • How to grab the lines AFTER a matched line in python

    - by toofly
    Hi All, I am an amateur using Python on and off for some time now. Sorry if this is a silly question, but I was wondering if anyone knew an easy way to grab a bunch of lines if the format in the input file is like this: " Heading 1 Line 1 Line 2 Line 3 Heading 2 Line 1 Line 2 Line 3 " I won't know how many lines are after each heading, but I want to grab them all. All I know is the name, or a regular expression pattern for the heading. The only way I know to read a file is the "for line in file:" way, but I don't know how to grab the lines AFTER the line I'm currently on. Hope this makes sense, and thanks for the help!

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  • write cache and write sequence order

    - by excanoe
    ok, here i have some weird question: let say we have some binary file (.log), and sequence of write operations, for example log1, log2, log3 and each has some block size n (raw data). question: can I be sure that log1,log2 and log3 sequences can be written in the correct order in ONE file, even if i have few cache levels (disk hardware and os level)? update very interested in what will be with records order (not with records) if we have software or hardware failure (reboot or another reason). update there can be some percent of write failures, but main question is: will write order stay correct?

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  • How to copy files without slowing down my app?

    - by Kevin Gebhardt
    I have a bunch of little files in my assets which need to be copied to the SD-card on the first start of my App. The copy code i got from here placed in an IntentService works like a charm. However, when I start to copy many litte files, the whole app gets increddible slow (I'm not really sure why by the way), which is a really bad experience for the user on first start. As I realised other apps running normal in that time, I tried to start a child process for the service, which didn't work, as I can't acess my assets from another process as far as I understood. Has anybody out there an idea how a) to copy the files without blocking my app b) to get through to my assets from a private process (process=":myOtherProcess" in Manifest) or c) solve the problem in a complete different way Edit: To make this clearer: The copying allready takes place in a seperate thread (started automaticaly by IntentService). The problem is not to separate the task of copying but that the copying in a dedicated thread somehow affects the rest of the app (e.g. blocking to many app-specific resources?) but not other apps (so it's not blocking the whole CPU or someting) Edit2: Problem solved, it turns out, there wasn't really a problem. See my answer below.

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