CGZip, a C++ wrapper for gzip methods

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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 namespace

using 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 string

gzip.WriteString(szString);

Buffers:

void* pBuffer; // a memory buffer

int len;       // size in bytes of the memory buffer

// writing buffer

gzip.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 pBuffer

gzip.ReadBuffer(&pBuffer,&len);
// pBuffer now contains len read bytes

...
// don't forget to delete pBuffer

if (pBuffer)
   delete[] pBuffer;

A fixed length buffer:

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

gzip.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).