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  • What is the fastest way for reading huge files in Delphi?

    - by dummzeuch
    My program needs to read chunks from a huge binary file with random access. I have got a list of offsets and lengths which may have several thousand entries. The user selects an entry and the program seeks to the offset and reads length bytes. The program internally uses a TMemoryStream to store and process the chunks read from the file. Reading the data is done via a TFileStream like this: FileStream.Position := Offset; MemoryStream.CopyFrom(FileStream, Size); This works fine but unfortunately it becomes increasingly slower as the files get larger. The file size starts at a few megabytes but frequently reaches several tens of gigabytes. The chunks read are around 100 kbytes in size. The file's content is only read by my program. It is the only program accessing the file at the time. Also the files are stored locally so this is not a network issue. I am using Delphi 2007 on a Windows XP box. What can I do to speed up this file access?

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  • MFC: Reading entire file to buffer...

    - by deostroll
    I've meddled with some code but I am unable to read the entire file properly...a lot of junk gets appended to the output. How do I fix this? // wmfParser.cpp : Defines the entry point for the console application. // #include "stdafx.h" #include "wmfParser.h" #include <cstring> #ifdef _DEBUG #define new DEBUG_NEW #endif // The one and only application object CWinApp theApp; using namespace std; int _tmain(int argc, TCHAR* argv[], TCHAR* envp[]) { int nRetCode = 0; // initialize MFC and print and error on failure if (!AfxWinInit(::GetModuleHandle(NULL), NULL, ::GetCommandLine(), 0)) { // TODO: change error code to suit your needs _tprintf(_T("Fatal Error: MFC initialization failed\n")); nRetCode = 1; } else { // TODO: code your application's behavior here. CFile file; CFileException exp; if( !file.Open( _T("c:\\sample.txt"), CFile::modeRead, &exp ) ){ exp.ReportError(); cout<<'\n'; cout<<"Aborting..."; system("pause"); return 0; } ULONGLONG dwLength = file.GetLength(); cout<<"Length of file to read = " << dwLength << '\n'; /* BYTE* buffer; buffer=(BYTE*)calloc(dwLength, sizeof(BYTE)); file.Read(buffer, 25); char* str = (char*)buffer; cout<<"length of string : " << strlen(str) << '\n'; cout<<"string from file: " << str << '\n'; */ char str[100]; file.Read(str, sizeof(str)); cout << "Data : " << str <<'\n'; file.Close(); cout<<"File was closed\n"; //AfxMessageBox(_T("This is a test message box")); system("pause"); } return nRetCode; }

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  • Read File/Directory properties with java

    - by Pizza
    How can I read the file information (for example size, line count, last modification, etc) from a file in the file-system or the directory content with JAVA? I need it for a linux operating system. Thanks Ps. This is my first question, althought I have user this forum for a while so please be kind :P

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  • Java how to copy part of a file

    - by user3479074
    I have to read a file and depending of the content of the last lines, I have to copy most of its content into a new file. Unfortunately I didn't found a way to copy first n lines or chars of a file in java. The only way I found, is copying the file using nio FileChannels where I can specifiy the length in bytes. However, therefore I would need to know how many bytes the stuff I read needed in the source-file. Does anyone know a solution for one of these problems?

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  • How to store a scaleable sized extensible event log?

    - by firoso
    Hello everyone! I've been contemplating writing a simple "event log" that takes a paramater list and stores event messages in a log file, trouble is, I forsee this file growing to be rather large (assume 1M entries or more) the question is, how can I implement this system without pulling teeth, I know that SQL would be a possible way to go. XML would be ideal but not really practical for scaleability if i'm not going nuts. Example Log Entry -----Time Date-------- ---------Sender----------------------- ---------Tags---------- --Message---------- 12/24/2008 24:00:00 $DOMAIN\SYSTEM\Application$ :Trivial: :Notification: It's Christmas in 1s

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  • c++ File input/output

    - by Myx
    Hi: I am trying to read from a file using fgets and sscanf. In my file, I have characters on each line of the while which I wish to put into a vector. So far, I have the following: FILE *fp; fp = fopen(filename, "r"); if(!fp) { fprintf(stderr, "Unable to open file %s\n", filename); return 0; } // Read file int line_count = 0; char buffer[1024]; while(fgets(buffer, 1023, fp)) { // Increment line counter line_count++; char *bufferp = buffer; ... while(*bufferp != '\n') { char *tmp; if(sscanf(bufferp, "%c", tmp) != 1) { fprintf(stderr, "Syntax error reading axiom on " "line %d in file %s\n", line_count, filename); return 0; } axiom.push_back(tmp); printf("put %s in axiom vector\n", axiom[axiom.size()-1]); // increment buffer pointer bufferp++; } } my axiom vector is defined as vector<char *> axiom;. When I run my program, I get a seg fault. It happens when I do the sscanf. Any suggestions on what I'm doing wrong?

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  • Search a string in a file and write the matched lines to another file in Java

    - by Geeta
    For searching a string in a file and writing the lines with matched string to another file it takes 15 - 20 mins for a single zip file of 70MB(compressed state). Is there any ways to minimise it. my source code: getting Zip file entries zipFile = new ZipFile(source_file_name); entries = zipFile.entries(); while (entries.hasMoreElements()) { ZipEntry entry = (ZipEntry)entries.nextElement(); if (entry.isDirectory()) { continue; } searchString(Thread.currentThread(),entry.getName(), new BufferedInputStream (zipFile.getInputStream(entry)), Out_File, search_string, stats); } zipFile.close(); Searching String public void searchString(Thread CThread, String Source_File, BufferedInputStream in, File outfile, String search, String stats) throws IOException { int count = 0; int countw = 0; int countl = 0; String s; String[] str; BufferedReader br2 = new BufferedReader(new InputStreamReader(in)); System.out.println(CThread.currentThread()); while ((s = br2.readLine()) != null) { str = s.split(search); count = str.length - 1; countw += count; //word count if (s.contains(search)) { countl++; //line count WriteFile(CThread,s, outfile.toString(), search); } } br2.close(); in.close(); } -------------------------------------------------------------------------------- public void WriteFile(Thread CThread,String line, String out, String search) throws IOException { BufferedWriter bufferedWriter = null; System.out.println("writre thread"+CThread.currentThread()); bufferedWriter = new BufferedWriter(new FileWriter(out, true)); bufferedWriter.write(line); bufferedWriter.newLine(); bufferedWriter.flush(); } Please help me. Its really taking 40 mins for 10 files using threads and 15 - 20 mins for a single file of 70MB after being compressed. Any ways to minimise the time.

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  • Is there a concise way to create an InputSupplier for an InputStream in Google Guava?

    - by Fabian Steeg
    There are a few factory methods in Google Guava to create InputSuppliers, e.g. from a byte[]: ByteStreams.newInputStreamSupplier(bytes); Or from a File: Files.newInputStreamSupplier(file); Is there a similar way to to create an InputSupplier for a given InputStream? That is, a way that's more concise than an anonymous class: new InputSupplier<InputStream>() { public InputStream getInput() throws IOException { return inputStream; } }; Background: I'd like to use InputStreams with e.g. Files.copy(...) or ByteStreams.equal(...).

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  • How to append text into text file dynamically

    - by niraj deshmukh
    [12] key1=val1 key2=val2 key3=val3 key4=val4 key5=val5 [13] key1=val1 key2=val2 key3=val3 key4=val4 key5=xyz [14] key1=val1 key2=val2 key3=val3 key4=val4 key5=val5 I want to update key5=val5 where [13]. try { br = new BufferedReader(new FileReader(oldFileName)); bw = new BufferedWriter(new FileWriter(tmpFileName)); String line; while ((line = br.readLine()) != null) { System.out.println(line); if (line.contains("[13]")) { while (line.contains("key5")) { if (line.contains("key5")) { line = line.replace("key5", "key5= Val5"); bw.write(line+"\n"); } } } } } catch (Exception e) { return; } finally { try { if(br != null) br.close(); } catch (IOException e) { // } try { if(bw != null) bw.close(); } catch (IOException e) { // } }

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  • Error copying file from app bundle

    - by Michael Chen
    I used the FireFox add-on SQLite Manager, created a database, which saved to my desktop as "DB.sqlite". I copied the file into my supporting files for the project. But when I run the app, immediately I get the error "Assertion failure in -[AppDelegate copyDatabaseIfNeeded], /Users/Mac/Desktop/Note/Note/AppDelegate.m:32 2014-08-19 23:38:02.830 Note[28309:60b] Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Failed to create writable database file with message 'The operation couldn’t be completed. (Cocoa error 4.)'.' First throw call stack: "... Here is the App Delegate Code where the error takes place -(void) copyDatabaseIfNeeded { NSFileManager *fileManager = [NSFileManager defaultManager]; NSError *error; NSString *dbPath = [self getDBPath]; BOOL success = [fileManager fileExistsAtPath:dbPath]; if (!success) { NSString *defaultDBPath = [[ [NSBundle mainBundle ] resourcePath] stringByAppendingPathComponent:@"DB.sqlite"]; success = [fileManager copyItemAtPath:defaultDBPath toPath:dbPath error:&error]; if (!success) NSAssert1(0, @"Failed to create writable database file with message '%@'.", [error localizedDescription]); } } I am very new to Sqlite, so I maybe I didn't create a database correctly in the FireFox Sqlite manager, or maybe I didn't "properly" copy the .sqlite file in? (I did check the target membership in the sqlite and it correctly has my project selected. Also, the .sqlite file names all match up perfectly.)

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  • Homemade fstat to get file size, always return 0 length.

    - by Fred
    Hello, I am trying to use my own function to get the file size from a file. I'll use this to allocate memory for a data structure to hold the information on the file. The file size function looks like this: long fileSize(FILE *fp){ long start; fflush(fp); rewind(fp); start = ftell(fp); return (fseek(fp, 0L, SEEK_END) - start); } Any ideas what I'm doing wrong here?

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  • Read whole ASCII file into C++ std::string

    - by Arrieta
    Hello, I need to read a whole file into memory and place it in a C++ std::string. If I were to read it into a char, the answer would be very simple: std::ifstream t; int lenght; t.open("file.txt", "r"); // open input file t.seekg(0, std::ios::end); // go to the end length = t.tellg(); // report location (this is the lenght) t.seekg(0, std::ios::beg); // go back to the beginning buffer = new char[length]; // allocate memory for a buffer of appropriate dimension t.read(buffer, length); // read the whole file into the buffer t.close(); // close file handle // ... do stuff with buffer here ... Now, I want to do the exact same thing, but using a std::string instead of a char. I want to avoid loops, i. e., I don't want to: std::ifstream t; t.open("file.txt", "r"); std::string buffer; std::string line; while(t){ std::getline(t, line); // ... append line to buffer and go on } t.close() any ideas?

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  • Java I/O: How to append to an already existing text file.

    - by Joe
    Hi I am having no problem writing to or appending to a file, the only problem is that as soon as I quit the program and then run it again, it creates a new file overwriting my original file. This is a problem, as I am using the text file to keep a running tally. Is there a way to get an already created text file as an object and then append to it? Thanks in advance.

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  • Most efficient way to write over file after reading

    - by Ryan McClure
    I'm reading in some data from a file, manipulating it, and then overwriting it to the same file. Until now, I've been doing it like so: open (my $inFile, $file) or die "Could not open $file: $!"; $retString .= join ('', <$inFile>); ... close ($inFile); open (my $outFile, $file) or die "Could not open $file: $!"; print $outFile, $retString; close ($inFile); However I realized I can just use the truncate function and open the file for read/write: open (my $inFile, '+<', $file) or die "Could not open $file: $!"; $retString .= join ('', <$inFile>); ... truncate $inFile, 0; print $inFile $retString; close ($inFile); I don't see any examples of this anywhere. It seems to work well, but am I doing it correctly? Is there a better way to do this?

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  • Batch backup a harddrive without modifying access times C#

    - by johnathan-doena
    I'm trying to write a simple program that will backup my flash drive. I want it to work automatically and silently in the background, and I also want it to be as quick as possible. The thing is, resetting all the access times is useless to me, and something I want to avoid. I know I can read the access times and set them back, but I bet it will fail one day in the future. It would be much simpler to read the files without ever changing it. Also, what is the fastest way to do this? What differences would there be between, say, a flash drive and an external hard drive. I am writing this in C#, as it is the simplest way to do it and it will probably last more generations of Windows..

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  • Embarrassingly parallel workflow creates too many output files

    - by Hooked
    On a Linux cluster I run many (N > 10^6) independent computations. Each computation takes only a few minutes and the output is a handful of lines. When N was small I was able to store each result in a separate file to be parsed later. With large N however, I find that I am wasting storage space (for the file creation) and simple commands like ls require extra care due to internal limits of bash: -bash: /bin/ls: Argument list too long. Each computation is required to run through a qsub scheduling algorithm so I am unable to create a master program which simply aggregates the output data to a single file. The simple solution of appending to a single fails when two programs finish at the same time and interleave their output. I have no admin access to the cluster, so installing a system-wide database is not an option. How can I collate the output data from embarrassingly parallel computation before it gets unmanageable?

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  • best way to output a full precision double into a text file

    - by flevine100
    Hi, I need to use an existing text file to store some very precise values. When read back in, the numbers essentially need to be exactly equivalent to the ones that were originally written. Now, a normal person would use a binary file... for a number of reasons, that's not possible in this case. So... do any of you have a good way of encoding a double as a string of characters (aside from increasing the precision). My first thought was to cast the double to a char[] and write out the chars. I don't think that's going to work because some of the characters are not visible, produce sounds, and even terminate strings ('\0'... I'm talkin to you!) Thoughts?

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  • Explained shell statement

    - by Mats Stijlaart
    The following statement will remove line numbers in a txt file: cat withLineNumbers.txt | sed 's/^.......//' >> withoutLineNumbers.txt The input file is created with the following statement (this one i understand): nl -ba input.txt >> withLineNumbers.txt I know the functionality of cat and i know the output is written to the 'withoutLineNumbers.txt' file. But the part of '| sed 's/^.......//'' is not really clear to me. Thanks for your time.

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