DecompressLibrary - a general library to decompress a zip, gz, or tar.gz file into a memory buffer

• Download demo project - 307 Kb
• Download source - 145 Kb

Introduction

I developed this class because I needed a general class that will detect internally if a file is an archive, and then read the compressed files contained in the archive. For Zip and gz archives, I found the source code on CodeProject, in the articles of Hans Dietrich and Jonathan de Halleux.

I also implemented in the class the possibility of detecting & reading from tar files.

Using the code

The class provides methods for: detecting and opening an archive, returning the number of files in an archive, and reading files from archives based on file position. In the header file we have the methods and their description.

/***********************************************************************
Open a compressed file.
Parameters
    pszCompressedFile - name of the file
Return values:
    TRUE - file opened
    FALSE - file could not be opened 
            (use GetErrorText() to find the errror)\
Note:
    The archive file must have one of these extensions:
    - .zip
    - .gz
    - .tar.gz
    - .tgz
***********************************************************************/
BOOL    OpenArchive(IN const char* pszArchiveFile);

/***********************************************************************
Closes the archive, destroys all the internal objects
***********************************************************************/
void    CloseArchive();

/***********************************************************************
Get number of files in the archive
Return values:
    Number of files in the archive.
    -1 if there are errors.
***********************************************************************/
int        GetCompressedFilesCount();

/***********************************************************************
Get a buffer that contain the file in archive at a specific position
Params:
    nFileIndex - file position in archive
    pszFileBuffer - buffer containg the file data
    nFileSize - file size
    fIsFile - TRUE if this is a regular file, 
              FALSE otherwise (directory, link, etc)
    szFileName - name of the file
Return values:
    TRUE - file found and buffer filled correctly
    FALSE - some error (use GetErrorText() to find the error)
Note:
    All data buffers will be allocated/deleted internally in this class,
    they should not be changed from outside !
***********************************************************************/
BOOL    GetArchiveFile( IN int nFileIndex, 
                        OUT char** pszFileBuffer, 
                        OUT int& nFileSize,
                        OUT BOOL& fIsFile,
                        OUT CString& szFileName);


/***********************************************************************
Get last error if there were any problems
***********************************************************************/
CString    GetErrorText();
BOOL    OpenArchive(IN const char* pszArchiveFile);

How to use

Include the DecompressLibrary project in your workspace. Next include the DecompressClass.h header file. Sample usage:

CDecompressClass testObj;
// open archive

testObj.OpenArchive("archivefile.zip");
// if we opened ok, read each file from the archive

for (int i=0; i < testObj.GetCompressedFilesCount(); i++)
{
    // will contain the file buffer

    char* pszFileBuffer;
    // will contain the file length

    int nFileLength;
    // will contain the file name

    CString szFileName;
    // flag if is a file or not (directory, link, etc)

    BOOL fIsFile;
    
    testObj.GetArchiveFile(i,    /*position in archive*/
                &pszFileBuffer,  /*will point to the memory buffer 
                                   containing the file content*/
                nFileLength,     /*will contain the file length*/
                fIsFile,         /*will show if it's a file or not*/
                szFileName       /*name of the file*/
                );            
}

History

• Version 1.0 - 2005 Nov 14, first implementation of the class.

Demo app

You will find a test dialog used to test the class:

Usage

This software is released into the public domain. You are free to use it in any way you like. If you modify it or extend it, please to consider posting new code here for everyone to share. This software is provided "as is" with no expressed or implied warranty. I accept no liability for any damage or loss of business that this software may cause.