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  • What influences running time of reading a bunch of images?

    - by remi
    I have a program where I read a handful of tiny images (50000 images of size 32x32). I read them using OpenCV imread function, in a program like this: std::vector<std::string> imageList; // is initialized with full path to the 50K images for(string s : imageList) { cv::Mat m = cv::imread(s); } Sometimes, it will read the images in a few seconds. Sometimes, it takes a few minutes to do so. I run this program in GDB, with a breakpoint further away than the loop for reading images so it's not because I'm stuck in a breakpoint. The same "erratic" behaviour happens when I run the program out of GDB. The same "erratic" behaviour happens with program compiled with/without optimisation The same "erratic" behaviour happens while I have or not other programs running in background The images are always at the same place in the hard drive of my machine. I run the program on a Linux Suse distrib, compiled with gcc. So I am wondering what could affect the time of reading the images that much?

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  • 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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  • Generic file container for quick read of data

    - by DreamCodeR
    Since there are some major privacy issues with alot of social networking sites I am trying to think about alternatives. One is to let the user keep all the information stored in some kind of file container. Now, I haven't found a single type of container that can hold "generic" information. Only for audio/video. What I want is a container that can be read by PHP with some kind of index file that lists up the users pictures in a image/ directory in the container, FOAF files (or some alternative XML-file describing users information and friends, etc.). My thoughts was to let the user keep all their information and data stored in a container that can be imported/exported and deleted from my server (the prototype social networking site I am trying to create), and then uploaded to another site that might use the same format (not that I think that will ever happen, but the user still keeps all their pictures, data, comments, messages, etc). The only thing I have come up with yet is to create a tar archive with the Archive_tar library which extracts and creates Tar-archives with an index-file describing which files are holding the messages (there might be several so each file won't be so large), what pictures are in the image/ folder and what are their names and what comments they have gotten etc. Maybe also the permissions for viewing each type of content. Does there exist any generic file format of a container that I can use to keep all this information in one file with a tree-like index file? Or must i try and create something like this myself?

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  • Why are some programs writing on stderr instead of stdout their output?

    - by Zagorax
    I've recently added to my .bashrc file an ssh-add command. I found that ssh-add $HOME/.ssh/id_rsa_github > /dev/null results on a message "identity added and something else" every time I open a shell. While ssh-add $HOME/.ssh/id_rsa_github > /dev/null 2>&1 did the trick and my shell is now 'clean'. Reading on internet, I found that other command do it, (for example time). Could you please explain why it's done?

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  • which one consume less resources? opening text file or make an sql query,both a thousand times ?

    - by imin
    hi I've a php website which displays recipes www.trymasak.my, to be exact. The recipes being displayed at the index page is updated about once a day. To get the latest recipes, I just use a mysql query which is something like "select recipe_name, page_views, image from table order by last_updated". So if I got 10000 visitors a day, obviously the query would be made 10000 times a day. A friend told me a better way (in terms of reducing server load) is when I update the recipes, I just put in the latest recipe details (names,images etc) into a text file, and make my page instead of querying a same query for 10,000 times, just get the data from the text file. Is his suggestion really better? If yes, which is the best php command should I use to open, read and close the text file? thanks

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  • Enter custom file name to be read ?

    - by ZaZu
    Hello, I want to allow users to type the name of any .txt file to be read/written. This is my code : printf("Enter .txt file name\n"); scanf("%s",&fname); FILE *inputf; inputf=fopen(&fname,"w"); Problem is this method does not work (having &fname) as a parameter. I can imagine its because C needs "filename.txt" for it work ... even if I enter for example : "custom.txt", the program returns an error of "Storage block not big enough for this operation" What is the correct method to accomplish this ? Im using C and im pretty much using basic commands .. (not too advanced) Thanks alot !!!

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  • Writing at the end of file

    - by user342534
    Hi, I'm working on a system that requires high file I/O performance (with C#). Basically, I'm filling up large files (~100MB) from the start of the file until the end of the file. Every ~5 seconds I'm adding ~5MB to the file (sequentially from the start of the file), on every bulk I'm flushing the stream. Every few minutes I need to update a structure which I write at the end of the file (some kind of metadata). When flushing each one of the bulks I have no performance issue. However, when updating the metadata at the end of the file I get really low performance. My guess is that when creating the file (which also should be done extra fast), the file doesn't really allocates the entire 100MB on the disk and when I flush the metadata it must allocates all space until the end of file. Guys/Girls, any Idea how I can overcome this problem? Thanks a lot!

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  • How can I modify the application file of an application that is currently running (on Linux)?

    - by Hach-Que
    I have an application running called AppFS. This application has an ext2 filesystem just attached to the end of the file (it's positioned so that the application binary exists in a 1MB spacing area, followed by the ext2 data). Now I've got FUSE embedded in the program and I've managed to extract the filesystem out of the application data into a temporary file so that FUSE can mount / use it. The problem I have now is writing the temporary file back into the application file. I get "Text file busy" presumably because the application has locked itself and won't let writes occur. Is there a way I can force the file to become unlocked so I can write data to it? (It's important to note that I'm not changing the application binary area - just rewriting the ext2 component.) It needs to be unlocked without requiring root permissions (unlocked by the same user who started the application).

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  • Parsing C# Script into Java

    - by pantaryl
    I'm looking for a way to easily read in a C# file and place it into a Java Object for database storage (storing the class name, functions, variables, etc). I'm making a Hierarchical State Machine AI Building Tool for a game I'm creating and need to be able to import an existing C# file and store it in a database for retrieval in the future. Does anyone know of any preexisting libraries for parsing C# files? Something similar to JavaParser? Thanks everyone! EDIT: This needs to be part of my Java Project. I'll be loading in the C# files through my Java Application and saving it into my db4o database.

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  • Naming a file downloaded from url in iPhone

    - by hgpc
    I would like to save a file downloaded from the internet in iPhone. Can I use the url as the file name? If not, what transformation should I apply to the url to obtain a valid file name? I need to find the local copy of the file later using its url.

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  • How do I read and write to a file using threads in java?

    - by WarmWaffles
    I'm writing an application where I need to read blocks in from a single file, each block is roughly 512 bytes. I am also needing to write blocks simultaneously. One of the ideas I had was BlockReader implements Runnable and BlockWriter implements Runnable and BlockManager manages both the reader and writer. The problem that I am seeing with most examples that I have found was locking problems and potential deadlock situations. Any ideas how to implement this?

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  • Java: GatheringByteChannel advantages?

    - by Jason S
    I'm wondering when the GatheringByteChannel's write methods (taking in an array of ByteBuffers) have advantages over the "regular" WritableByteChannel write methods. I tried a test where I could use the regular vs. the gathering write method on a FileChannel, with approx 400KB/sec total in ByteBuffers of between 23-27 bytes in length in both cases. Gathering writes used an array of 64. The regular method used up approx 12% of my CPU, and the gathering method used up approx 16% of my CPU (worse than the regular method!) This tells me it's NOT useful to use gathering writes on a FileChannel around this range of operating parameters. Why would this be the case, and when would you ever use GatheringByteChannel? (on network I/O?) Relevant differences here: public void log(Queue<Packet> packets) throws IOException { if (this.gather) { int Nbuf = 64; ByteBuffer[] bbufs = new ByteBuffer[Nbuf]; int i = 0; Packet p; while ((p = packets.poll()) != null) { bbufs[i++] = p.getBuffer(); if (i == Nbuf) { this.fc.write(bbufs); i = 0; } } if (i > 0) { this.fc.write(bbufs, 0, i); } } else { Packet p; while ((p = packets.poll()) != null) { this.fc.write(p.getBuffer()); } } }

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  • Read file structure into an array, but only specific files.

    - by dmackerman
    I have a directory structure that looks like this: /expandables - folder - folder - folder - folder - BannerInfo.txt - index.html Each one of the folder has the same exact stucture. One file named BannerInfo.txt and index.html. There are about 250 of these folders if that matters. I want to loop through these folders and store each of the index.html files into an array. Inside of the index.html file is just some simple HTML and Javascript of which I want to read into a string to be displayed later on. I'm struggling with how to filter out only the index.html file from the individual folders. The purpose of this is because I want to randomly select an index.html file and put the contents into a textarea. I thought I could do a simple array_rand() on the returned array and spit out the string. Any ideas?

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  • USB device Set Attribute in C#

    - by p19lord
    I have this bit of code: DriveInfo[] myDrives = DriveInfo.GetDrives(); foreach (DriveInfo myDrive in myDrives) { if (myDrive.DriveType == DriveType.Removable) { string path = Convert.ToString(myDrive.RootDirectory); DirectoryInfo mydir = new DirectoryInfo(path); String[] dirs = new string[] {Convert.ToString(mydir.GetDirectories())}; String[] files = new string[] {Convert.ToString(mydir.GetFiles())}; foreach (var file in files) { File.SetAttributes(file, ~FileAttributes.Hidden); File.SetAttributes(file, ~FileAttributes.ReadOnly); } foreach (var dir in dirs) { File.SetAttributes(dir, ~FileAttributes.Hidden); File.SetAttributes(dir, ~FileAttributes.ReadOnly); } } } I have a problem. It is trying the code for Floppy Disk drive first which and because no Floppy disk in it, it threw the error The device is not ready. How can I prevent that?

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  • FileInput Help/Advice

    - by user559142
    I have a fileinput class. It has a string parameter in the constructor to load the filename supplied. However it just exits if the file doesn't exist. I would like it to output a message if the file doesn't exist - but not sure how.... Here is the class: public class FileInput extends Input { /** * Construct <code>FileInput</code> object given a file name. */ public FileInput(final String fileName) { try { scanner = new Scanner(new FileInputStream(fileName)); } catch (FileNotFoundException e) { System.err.println("File " + fileName + " could not be found."); System.exit(1); } } /** * Construct <code>FileInput</code> object given a file name. */ public FileInput(final FileInputStream fileStream) { super(fileStream); } } And its implementation: private void loadFamilyTree() { out.print("Enter file name: "); String fileName = in.nextLine(); FileInput input = new FileInput(fileName); family.load(input); input.close(); }

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  • Using FILE_FLAG_NO_BUFFERING will return noticeable speed gain?

    - by 9dan
    Recently noticed detail description of FILE_FLAG_NO_BUFFERING flag in MSDN, and read several Google search results about unbuffered I/O in Windows. http://msdn.microsoft.com/en-us/library/aa363858(v=vs.85).aspx I wondering now, is it really important to consider unbuffered option in file I/O programming? Because many programs use plain old C stream I/O or C++ iostream, I didn't gave any attention to FILE_FLAG_NO_BUFFERING flag before. Let's say we are developing photo explorer program like Picasa. If we implement unbuffered I/O, could thumbnail display speed show noticeable difference in ordinary users?

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  • C++ how to store integer into a binary file??

    - by blaxc
    i gt a struct with 2 integer, i want to store them in a binary file and read it again... here is my code... struct pw { int a; int b; }; void main(){ pw* p = new pw(); pw* q = new pw(); std::ofstream fout(ADMIN_FILE, ios_base::out | ios_base::binary | ios_base::trunc); std::ifstream fin(ADMIN_FILE, ios_base::in | ios_base::binary); p->a=123; p->b=321; fout.write((const char*)p, sizeof(pw)); fin.write((char*)q, sizeof(pw)); fin.close(); cout<< q->a << endl;} my output is 0. anyone can tell me what is the problem?

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  • Operator Overloading << in c++

    - by thlgood
    I'm a fresh man in C++. I write this simple program to practice Overlaoding. This is my code: #include <iostream> #include <string> using namespace std; class sex_t { private: char __sex__; public: sex_t(char sex_v = 'M'):__sex__(sex_v) { if (sex_v != 'M' && sex_v != 'F') { cerr << "Sex type error!" << sex_v << endl; __sex__ = 'M'; } } const ostream& operator << (const ostream& stream) { if (__sex__ == 'M') cout << "Male"; else cout << "Female"; return stream; } }; int main(int argc, char *argv[]) { sex_t me('M'); cout << me << endl; return 0; } When I compiler it, It print a lots of error message: The error message was in a mess. It's too hard for me to found useful message sex.cpp: ???‘int main(int, char**)’?: sex.cpp:32:10: ??: ‘operator<<’?‘std::cout << me’????? sex.cpp:32:10: ??: ???: /usr/include/c++/4.6/ostream:110:7: ??: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostre

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  • Split a binary file into chunks c++

    - by L4nce0
    I've been bashing my head against trying to first divide up a file into chunks, for the purpose of sending over sockets. I can read / write a file easily without splitting it into chunks. The code below runs, works, kinda. It will write a textfile and has a garbage character. Which if this was just for txt, no problem. Jpegs aren't working with said garbage. Been at it for a few days, so I've done my research, and it's time to get some help. I do want to stick strictly to binary readers, as this need to handle any file. I've seen a lot of slick examples out there. (none of them worked for me with jpgs) Mostly something along the lines of while(file)... I subscribe to the, if you know the size, use a for-loop, not a while-loop camp. Thank you for the help!! vector<char*> readFile(const char* fn){ vector<char*> v; ifstream::pos_type size; char * memblock; ifstream file; file.open(fn,ios::in|ios::binary|ios::ate); if (file.is_open()) { size = fileS(fn); file.seekg (0, ios::beg); int bs = size/3; // arbitrary. Actual program will use the socket send size int ws = 0; int i = 0; for(i = 0; i < size; i+=bs){ if(i+bs > size) ws = size%bs; else ws = bs; memblock = new char [ws]; file.read (memblock, ws); v.push_back(memblock); } } else{ exit(-4); } return v; } int main(int argc, char **argv) { vector<char*> v = readFile("foo.txt"); ofstream myFile ("bar.txt", ios::out | ios::binary); for(vector<char*>::iterator it = v.begin(); it!=v.end(); ++it ){ myFile.write(*it,strlen(*it)); } }

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  • problem with f.readline()?

    - by kaushik
    I am reading one line at a time from a file, but at the end of each line it adds a '\n'. example: line is: 094 234 hii but my input is: 094 234 hii\n I want to read line by linem but I don't need to keep the newlines... My goal is to read a list from every line: I need ['094','234','hii'], not ['094','234','hii\n'] Any advice?

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  • Writing different structs to a file in C++? [on hold]

    - by user58053
    I need a way to write structures of three different kinds to a binary file, which later has to be searched. (As in, for example, struct A has two fields, an int and a char; struct B has int and a long; I need to output all structures whose int equals the one given from keyboard). I understand how to write structs of the same kind to a file and how to search them, but here I am just lost, best thing I came up with is declaring a struct containing all possibly needed fields and leaving the ones I don't need empty, but it really feels wrong, there HAS to be a better way to do that. I've read about binary files and could not find anything relevant, most examples and tutorials deal with writing one data type. Could anyone point me in the right direction? EDIT: I am looking for what @Jerry_coffin called database mode, and will probably use one of the existing database systems for that, best way to go, probably. Thank you everybody for the suggestions

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  • related to java file handling.

    - by sadia
    In Java how can I take the data of my file on my display screen? I want to use data in my file and also want that data to be displayed on my output screen when I execute my program. Can any body please help by providing me such example in Java language. Thank you!

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