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  • Simple binary File I/O problem with cstdio(c++)

    - by Atilla Filiz
    The c++ program below fails to read the file. I know using cstdio is not good practice but that what I am used to and it should work anyway. $ ls -l l.uyvy -rw-r--r-- 1 atilla atilla 614400 2010-04-24 18:11 l.uyvy $ ./a.out l.uyvy Read 0 bytes out of 614400, possibly wrong file code: #include<cstdio> int main(int argc, char* argv[]) { FILE *fp; if(argc<2) { printf("usage: %s <input>\n",argv[0]); return 1; } fp=fopen(argv[1],"rb"); if(!fp) { printf("erör, cannot open %s for reading\n",argv[1]); return -1; } int bytes_read=fread(imgdata,1,2*IMAGE_SIZE,fp); //2bytes per pixel fclose(fp); if(bytes_read < 2*IMAGE_SIZE) { printf("Read %d bytes out of %d, possibly wrong file\n", bytes_read, 2*IMAGE_SIZE); return -1; } return 0; }

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  • Loading specific files from arbitrary directories?

    - by Haydn V. Harach
    I want to load foo.txt. foo.txt might exist in the data/bar/ directory, or it might exist in the data/New Folder/ directory. There might be a different foo.txt in both of these directories, in which case I would want to either load one and ignore the other according to some order that I've sorted the directories by (perhaps manually, perhaps by date of creation), or else load them both and combine the results somehow. The latter (combining the results of both/all foo.txt files) is circumstantial and beyond the scope of this question, but something I want to be able to do in the future. I'm using SDL and boost::filesystem. I want to keep my list of dependencies as small as possible, and as cross-platform as possible. I'm guessing that my best bet would be to get a list of every directory (within the data/ folder), sort/filter this list, then when I go to load foo.txt, I search for it in each potential directory? This sounds like it would be very inefficient, if I have dozens of potential directories to search through every time. What's the best way to go about accomplishing this? Bonus: What if I want some of the directories to be archives? ie. considering both data/foo/ and data/bar.zip to both be valid, and pull foobar.txt from either one without caring.

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  • close file with fclose() but file still in use

    - by Marco
    Hi all, I've got a problem with deleting/overwriting a file using my program which is also being used(read) by my program. The problem seems to be that because of the fact my program is reading data from the file (output.txt) it puts the file in a 'in use' state which makes it impossible to delete or overwrite the file. I don't understand why the file stays 'in use' because I close the file after use with fclose(); this is my code: bool bBool = true while(bBool){ //Run myprogram.exe tot generate (a new) output.txt //Create file pointer and open file FILE* pInputFile = NULL; pInputFile = fopen("output.txt", "r"); // //then I do some reading using fscanf() // //And when I'm done reading I close the file using fclose() fclose(pInputFile); //The next step is deleting the output.txt if( remove( "output.txt" ) == -1 ){ //ERROR }else{ //Succesfull } } I use fclose() to close the file but the file remains in use by my program until my program is totally shut down. What is the solution to free the file so it can be deleted/overwrited? In reality my code isn't a loop without an end ; ) Thanks in advance! Marco Update Like ask a part of my code which also generates the file 'in use'. This is not a loop and this function is being called from the main(); Here is a piece of code: int iShapeNr = 0; void firstRun() { //Run program that generates output.txt runProgram(); //Open Shape data file FILE* pInputFile = NULL; int iNumber = 0; pInputFile = fopen("output.txt", "r"); //Put all orientations of al detected shapes in an array int iShapeNr = 0; int iRotationBuffer[1024];//1024 is maximum detectable shapes, can be changed in RoboRealm int iXMinBuffer[1024]; int iXMaxBuffer[1024]; int iYMinBuffer[1024]; int iYMaxBuffer[1024]; while(feof(pInputFile) == 0){ for(int i=0;i<9;i++){ fscanf(pInputFile, "%d", &iNumber); fscanf(pInputFile, ","); if(i == 1) { iRotationBuffer[iShapeNr] = iNumber; } if(i == 3){//xmin iXMinBuffer[iShapeNr] = iNumber; } if(i == 4){//xmax iXMaxBuffer[iShapeNr] = iNumber; } if(i == 5){//ymin iYMinBuffer[iShapeNr] = iNumber; } if(i == 6){//ymax iYMaxBuffer[iShapeNr] = iNumber; } } iShapeNr++; } fflush(pInputFile); fclose(pInputFile); } The while loop parses the file. The output.txt contains sets of 9 variables, the number of sets is unknown but always in sets of 9. output.txt could contain for example: 0,1,2,3,4,5,6,7,8,8,7,6,5,4,1,2,3,0

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  • Read char from txt file in C++

    - by Jack in the Box
    I have a program that will read the number of rows and columns from a txt file. Also, the program has to read the contents of a 2D array from the same file. Here is the txt file 8 20 * * *** *** 8 and 20 are the number of rows and columns respectively. The spaces and asterisks are the contents of the array, Array[8][20] For example, Array[0][1] = '*' I did make the program reading 8 and 20 as follow: ifstream myFile; myFile.open("life.txt"); if(!myFile) { cout << endl << "Failed to open file"; return 1; } myFile >> rows >> cols; myFile.close(); grid = new char*[rows]; for (int i = 0; i < rows; i++) { grid[i] = new char[cols]; } Now, how to assign the spaces and the asterisks to to the fields in the array? I hope you got the point.

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  • How can I determine if a file is read-only for my process on *nix?

    - by user109078
    Using the stat function, I can get the read/write permissions for: owner user other ...but this isn't what I want. I want to know the read/write permissions of a file for my process (i.e. the application I'm writing). The owner/user/other is only helpful if I know if my process is running as the owner/user/other of the file...so maybe that's the solution but I'm not sure of the steps to get there.

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  • Out-of-memory algorithms for addressing large arrays

    - by reve_etrange
    I am trying to deal with a very large dataset. I have k = ~4200 matrices (varying sizes) which must be compared combinatorially, skipping non-unique and self comparisons. Each of k(k-1)/2 comparisons produces a matrix, which must be indexed against its parents (i.e. can find out where it came from). The convenient way to do this is to (triangularly) fill a k-by-k cell array with the result of each comparison. These are ~100 X ~100 matrices, on average. Using single precision floats, it works out to 400 GB overall. I need to 1) generate the cell array or pieces of it without trying to place the whole thing in memory and 2) access its elements (and their elements) in like fashion. My attempts have been inefficient due to reliance on MATLAB's eval() as well as save and clear occurring in loops. for i=1:k [~,m] = size(data{i}); cur_var = ['H' int2str(i)]; %# if i == 1; save('FileName'); end; %# If using a single MAT file and need to create it. eval([cur_var ' = cell(1,k-i);']); for j=i+1:k [~,n] = size(data{j}); eval([cur_var '{i,j} = zeros(m,n,''single'');']); eval([cur_var '{i,j} = compare(data{i},data{j});']); end save(cur_var,cur_var); %# Add '-append' when using a single MAT file. clear(cur_var); end The other thing I have done is to perform the split when mod((i+j-1)/2,max(factor(k(k-1)/2))) == 0. This divides the result into the largest number of same-size pieces, which seems logical. The indexing is a little more complicated, but not too bad because a linear index could be used. Does anyone know/see a better way?

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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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  • How can I speed up line by line reading of an ASCII file? (C++)

    - by Jon
    Here's a bit of code that is a considerable bottleneck after doing some measuring: //----------------------------------------------------------------------------- // Construct dictionary hash set from dictionary file //----------------------------------------------------------------------------- void constructDictionary(unordered_set<string> &dict) { ifstream wordListFile; wordListFile.open("dictionary.txt"); string word; while( wordListFile >> word ) { if( !word.empty() ) { dict.insert(word); } } wordListFile.close(); } I'm reading in ~200,000 words and this takes about 240 ms on my machine. Is the use of ifstream here efficient? Can I do better? I'm reading about mmap() implementations but I'm not understanding them 100%. The input file is simply text strings with *nix line terminations.

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  • FileNotFound exception

    - by Pratik
    I am trying to read a file in a servlet. I am using eclipse IDE. I get a FileNotFoundException if I provide relative file name. List<String> ls=new ArrayList<String>(); Scanner input = new Scanner(new File("Input.txt")); while(input.hasNextLine()) { ls.add(input.nextLine()); } The same code works if I put the absolute path like this: Scanner input = new Scanner(new File("F:/Spring and other stuff/AjaxDemo/src/com/pdd/ajax/Input.txt")); The Java file and text file are there in the same folder. Does it searches text file in some other folder ?

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  • Optimizing memory usage and changing file contents with PHP

    - by errata
    In a function like this function download($file_source, $file_target) { $rh = fopen($file_source, 'rb'); $wh = fopen($file_target, 'wb'); if (!$rh || !$wh) { return false; } while (!feof($rh)) { if (fwrite($wh, fread($rh, 1024)) === FALSE) { return false; } } fclose($rh); fclose($wh); return true; } what is the best way to rewrite last few bytes of a file with my custom string? Thanks!

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  • Reading a simple Avro file from HDFS

    - by John Galt... who
    I am trying to do a simple read of an Avro file stored in HDFS. I found out how to read it when it is on the local file system.... FileReader reader = DataFileReader.openReader(new File(filename), new GenericDatumReader()); for (GenericRecord datum : fileReader) { String value = datum.get(1).toString(); System.out.println("value = " value); } reader.close(); My file is in HDFS, however. I cannot give the openReader a Path or an FSDataInputStream. How can I simply read an Avro file in HDFS? EDIT: I got this to work by creating a custom class (SeekableHadoopInput) that implements SeekableInput. I "stole" this from "Ganglion" on github. Still, seems like there would be a Hadoop/Avro integration path for this. Thanks

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  • Python text file processing speed issues

    - by Anonymouslemming
    Hi all, I'm having a problem with processing a largeish file in Python. All I'm doing is f = gzip.open(pathToLog, 'r') for line in f: counter = counter + 1 if (counter % 1000000 == 0): print counter f.close This takes around 10m25s just to open the file, read the lines and increment this counter. In perl, dealing with the same file and doing quite a bit more (some regular expression stuff), the whole process takes around 1m17s. Perl Code: open(LOG, "/bin/zcat $logfile |") or die "Cannot read $logfile: $!\n"; while (<LOG>) { if (m/.*\[svc-\w+\].*login result: Successful\.$/) { $_ =~ s/some regex here/$1,$2,$3,$4/; push @an_array, $_ } } close LOG; Can anyone advise what I can do to make the Python solution run at a similar speed to the Perl solution? I've tried just uncompressing the file and dealing with it using open instead of gzip.open, but that made a very small difference to the overall time.

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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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  • What is a good way of coding a file processing program, which accepts multisource data in Java

    - by jjepsuomi
    I'm making a data prosessing system, which currently is using csv-data as input and output form. In the future I might want to add support for example database-, xml-, etc. typed input and output forms. How should I desing my program so that it would be easy to add support for new type of data sources? Should simply make for example an abstract data class (which would contain the basic file prosessing methods) and then inherit this class for database, xml, etc. cases? Hope my question is clear =) In other words my question is: "How to desing a file prosessing system, which can be easily updated to accept input data from different sources (database, XML, Excel, etc.)".

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  • unbuffered I/O in Linux

    - by stuck
    I'm writing lots and lots of data that will not be read again for weeks - as my program runs the amount of free memory on the machine (displayed with 'free' or 'top') drops very quickly, the amount of memory my app uses does not increase - neither does the amount of memory used by other processes. This leads me to believe the memory is being consumed by the filesystems cache - since I do not intend to read this data for a long time I'm hoping to bypass the systems buffers, such that my data is written directly to disk. I dont have dreams of improving perf or being a super ninja, my hope is to give a hint to the filesystem that I'm not going to be coming back for this memory any time soon, so dont spend time optimizing for those cases. On Windows I've faced similar problems and fixed the problem using FILE_FLAG_NO_BUFFERING|FILE_FLAG_WRITE_THROUGH - the machines memory was not consumed by my app and the machine was more usable in general. I'm hoping to duplicate the improvements I've seen but on Linux. On Windows there is the restriction of writing in sector sized pieces, I'm happy with this restriction for the amount of gain I've measured. is there a similar way to do this in Linux?

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  • fopen() fails to open stream: permission denied, yet permissions should be valid

    - by about blank
    So, I have this error: Warning: fopen(/path/to/test-in.txt) [function.fopen]: failed to open stream: Permission denied Performing ls -l in the directory where test-in.txt is produces the following output: -rw-r--r-- 1 $USER $USER 1921 Sep 6 20:09 test-in.txt -rw-r--r-- 1 $USER $USER 0 Sep 6 20:08 test-out.txt In order to get past this, I decided to perform the following: chgrp -R www-data /path/to/php/webroot And then did: chmod g+rw /path/to/php/webroot Yet, I still get this error when I run my php5 script to open the file. Why is this happening? I've tried this using LAMP as well as cherokee through CGI, so it can't be this. Is there a solution of some sort? Edit I'll also add that I'm just developing via localhost right now. Update - PHP fopen() line $fullpath = $this->fileRoot . $this->fileInData['fileName']; $file_ptr = fopen( $fullpath, 'r+' ); I should also mention I'd like to stick with Cherokee if possible. What's this deal about setting file permissions for Apache/Cherokee?

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  • write 2d array to a file in C (Operating system)

    - by Bobj-C
    Hello All, I used to use the code below to Write an 1D array to a File: FILE *fp; float floatValue[5] = { 1.1F, 2.2F, 3.3F, 4.4F, 5.5F }; int i; if((fp=fopen("test", "wb"))==NULL) { printf("Cannot open file.\n"); } if(fwrite(floatValue, sizeof(float), 5, fp) != 5) printf("File read error."); fclose(fp); /* read the values */ if((fp=fopen("test", "rb"))==NULL) { printf("Cannot open file.\n"); } if(fread(floatValue, sizeof(float), 5, fp) != 5) { if(feof(fp)) printf("Premature end of file."); else printf("File read error."); } fclose(fp); for(i=0; i<5; i++) printf("%f ", floatValue[i]); My question is if i want to write and read 2D array ??

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  • threading in Python taking up too much CPU

    - by KevinShaffer
    I wrote a chat program and have a GUI running using Tkinter, and to go and check when new messages have arrived, I create a new thread so Tkinter keeps doing its thing without locking up while the new thread goes and grabs what I need and updates the Tkinter window. This however becomes a huge CPU hog, and my guess is that it has to do somehow with the fact that the Thread is started and never really released when the function is done. Here's the relevant code (it's ugly and not optimized at the moment, but it gets the job done, and itself does not use too much processing power, as when I run it not threaded, it doesn't take up much CPU but it locks up Tkinter) Note: This is inside of a class, hence the extra tab. def interim(self): threading.Thread(target=self.readLog).start() self.after(5000,self.interim) def readLog(self): print 'reading' try: length = len(str(self.readNumber)) f = open('chatlog'+str(myport),'r') temp = f.readline().replace('\n','') while (temp[:length] != str(self.readNumber)) or temp[0] == '<': temp = f.readline().replace('\n','') while temp: if temp[0] != '<': self.updateChat(temp[length:]) self.readNumber +=1 else: self.updateChat(temp) temp = f.readline().replace('\n','') f.close() Is there a way to better manage the threading so I don't consume 100% of the CPU very quickly?

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  • [FIXED] Scan file contents into an array of a structure.

    - by ZaZu
    Hello, I have a structure in my program that contains a particular array. I want to scan a random file with numbers and put the contents into that array. This is my code : ( NOTE : This is a sample from a bigger program, so I need the structure and arrays as declared ) The contents of the file are basically : 5 4 3 2 5 3 4 2 #include<stdio.h> #define first 500 #define sec 500 struct trial{ int f; int r; float what[first][sec]; }; int trialtest(trial *test); main(){ trial test; trialtest(&test); } int trialtest(trial *test){ int z,x,i; FILE *fin; fin=fopen("randomfile.txt","r"); for(i=0;i<5;i++){ fscanf(fin,"%5.2f\t",(*test).what[z][x]); } fclose(fin); return 0; } But the problem is, whenever this I run this code, I get this error : (25) : warning 508 - Data of type 'double' supplied where a pointer is required I tried adding do{ for(i=0;i<5;i++){ q=fscanf(fin,"%5.2f\t",(*test).what[z][x]); } }while(q!=EOF); But that didnt work either, it gives the same error. Does anyone have a solution to this problem ?

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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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