# Gzstream Library Home Page

- Introduction
- Supported Systems
- Installation
- Documentation
- What's Missing
- Download
- Links

## Introduction

Gzstream is a small C++ library, basically just a wrapper, that provides the functionality of the zlib C-library in a C++ iostream. It is freely available under the LGPL license.

Gzstream has been written by Deepak Bandyopadhyay and Lutz Kettner at the Computational Geometry Group at UNC Chapel Hill.

## Supported Systems

Gzstream requires a standard compliant C++ compiler (we use the new header file conventions and the new iostream in the std:: name space) and, of course, zlib. We used zlib 1.1.3 so far, but see the zlib home page for why you should upgrade to zlib 1.1.4. So, in theory, the provided sources could run on many platforms. However, we used only the following few platforms.

- PC Linux, RedHat 6.1, g++ version 2.95.2
- PC Linux, Debian, g++ version 2.95.2 and 3.1
- SGI Irix 6.5, MIPSpro CC version 7.30

## Installation

Either compile `gzstream.C` by hand, place it in some library, and move `gzstream.h` into the include search path of your compiler. Or use the provided `Makefile`, adapt its variables, and follow the remarks in the `Makefile`. Two test programs are provided, `test_gzip.C` and `test_gunzip.C`. The `Makefile` contains a rule that performs a small test with these programs.

## Documentation

The library provides two classes, `igzstream` and `ogzstream`, that can be used analogously to `ifstream` and `ofstream` respectively.

The classes are by default in the global name space. This can be changed by setting the macro `GZSTREAM_NAMESPACE` to the desired name space, e.g., by setting the option -DGZSTREAM_NAMESPACE=gz in the `Makefile`. However, this needs to be consistent for both, the library compilation and the application that uses the library.

## What's Missing

- Seek. The zlib library provides the necessary functionality, but we have not realized that in the wrapper (yet? ;-).
- Both streams are based on the same streambuffer. So, they cannot be used to derive an iogzstream class that would allow simultaneous reading and writing to the same file.

## Download and Release Notes

- Gzstream library 1.5 (08 Apr 2003): gzstream.tgz
  Fixed bug that did not set the state correctly on failure to open or close a file.
  Fixed bug in the indexing of the write buffer that caused the write buffer to shrink continously and finally caused wrong results when writing compressed files (only observed on some platforms).

- Gzstream library 1.4 (27 Apr 2002):
  Fixed a bug that stopped stream output after calling `flush()` or using `std::endl`.

- Gzstream library 1.3 (06 Nov 2001):
  Fixed unsigned char -- signed char bug. Increased buffer size for better performance.

- Gzstream library 1.2 (04 Oct 2001):
  Initial release as gzstream, renamed from zipstream.

- Zipstream library 1.1 (09 Sep 2001):
  Initial release.

## Acknowledgements

Credits for finding bugs and improving this software go to: Vincent Ricard, Peter Milley, Peter J. Torelli, and Ares Lagae.

## Links

- zlib C-library
- Deepak Bandyopadhyay
- Lutz Kettner
- The Computational Geometry Group at UNC Chapel Hill