Description

This documents present CGZip, C++ class wrapper for the gzip methods, which are included in the zlib library. The intention of this class is to have a simple class for zipping-unzipping buffers.

The main features of the class are:

  • Compress, decompress LPCTSTR to file
  • Compress, decompress memory buffer to file
  • Non-MFC
  • Hides zlib so you don't have to distribute the zlib headers
  • UNICODE compliant,

Examples

In the examples, we shall consider the following code snippet to be present on top:

// CGZip is in the zlib namespaceusing namespace zlib;CGZip gzip;

Zipping a memory buffer or a string

First of all, let's open a file for writing:

if(!gzip.Open(_T("myFile.gz"), CGZip::ArchiveModeWrite))){        // the file could not be opened...}

As you can see, Open returns true if success and false otherwise. All the methods (almost) have this behavior.

Now we can send data and strings to the file:

Strings:

LPCTSTR szString = _T("This is a test string\n");// writing stringgzip.WriteString(szString);

Buffers:

void* pBuffer; // a memory bufferint len;       // size in bytes of the memory buffer// writing buffergzip.WriteBuffer(pBuffer,len);

When done, you must close the file:

gzip.Close();

Note that if gzip goes out of scope, it is automatically closed.

Unzipping a buffer or a string

The reading behaves pretty much like the writing. First of all, open a file for reading:

if(!gzip.Open(_T("myFile.gz"), CGZip::ArchiveModeRead))){        // the file could not be opened...}

Now, you can read a buffer with fixed length or the whole file:

The whole file:

void* pBuffer=NULL;int len=0;// reads and unzip the hole file, len contains the resulting size of pBuffergzip.ReadBuffer(&pBuffer,&len);// pBuffer now contains len read bytes...// don't forget to delete pBufferif (pBuffer)   delete[] pBuffer;

A fixed length buffer:

int len;char* pBuffer[len];// reads and unzip the hole file, len contains the resulting size of pBuffergzip.ReadBufferSize(pBuffer,len);

Class reference

A detailed class reference is available as compressed HTML (generated by Doxygen).

GZip license

This piece of code is totally, utterly free for commercial and non-commercial use. However, it uses zlib so you should check the zlib license before using it. It is included in the source code but here it is:

//zlib.h -- interface of the 'zlib' general purpose compression library//version 1.1.4, March 11th, 2002//Copyright (C) 1995-2002 Jean-loup Gailly and Mark Adler//This software is provided 'as-is', without any express or implied//warranty.  In no event will the authors be held liable for any damages//arising from the use of this software.//Permission is granted to anyone to use this software for any purpose,//including commercial applications, and to alter it and redistribute it//freely, subject to the following restrictions://1. The origin of this software must not be misrepresented; you must not//   claim that you wrote the original software. If you use this software//   in a product, an acknowledgment in the product documentation would be//   appreciated but is not required.//2. Altered source versions must be plainly marked as such, and must not be//   misrepresented as being the original software.//3. This notice may not be removed or altered from any source distribution.//Jean-loup Gailly        Mark Adler//jloup@gzip.org          madler@alumni.caltech.edu//The data format used by the zlib library is described by RFCs (Request for//Comments) 1950 to 1952 in the files ftp://ds.internic.net/rfc/rfc1950.txt//(zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).