CGZip, a C++ wrapper for gzip methods






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Nov 18, 2002
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A minimal class for handling gzip methods included in the zlib library.
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).