Overview

tinf - tiny inflate library

Version 1.00

Copyright (c) 2003 Joergen Ibsen

http://www.ibsensoftware.com/

About

tinf is a small library implementing the decompression algorithm for the deflate compressed data format (called 'inflate'). Deflate compression is used in e.g. zlib, gzip, zip and png.

I wrote it because I needed a small in-memory zlib decompressor for a self- extracting archive, and the zlib library added 15k to my program. The tinf code added only 2k.

Naturally the size difference is insignificant in most cases. Also, the zlib library has many more features, is more secure, and mostly faster. But if you have a project that calls for a small and simple deflate decompressor, give it a try :-)

While the implementation should be fairly compliant, it does assume it is given valid compressed data, and that there is sufficient space for the decompressed data.

Simple wrappers for decompressing zlib streams and gzip'ed data in memory are supplied.

tgunzip, an example command-line gzip decompressor in C, is included.

The inflate algorithm and data format are from 'DEFLATE Compressed Data Format Specification version 1.3' (RFC 1951).

The zlib data format is from 'ZLIB Compressed Data Format Specification version 3.3' (RFC 1950).

The gzip data format is from 'GZIP file format specification version 4.3' (RFC 1952).

Ideas for future versions:

  • the fixed Huffman trees could be built by tinf_decode_trees() using a small table
  • memory for the TINF_DATA object should be passed, to avoid using more than 1k of stack space
  • wrappers for unpacking zip archives and png images
  • implement more in x86 assembler
  • more sanity checks
  • in tinf_uncompress, the (entry value of) destLen and sourceLen are not used
  • blocking of some sort, so everything does not have to be in memory
  • optional table-based huffman decoder

Functionality

void tinf_init();

Initialise the global uninitialised data used by the decompression code. This function must be called once before any calls to the decompression functions.

int tinf_uncompress(void *dest,
                    unsigned int *destLen,
                    const void *source,
                    unsigned int sourceLen);

Decompress data in deflate compressed format from source[] to dest[]. destLen is set to the length of the decompressed data. Returns TINF_OK on success, and TINF_DATA_ERROR on error.

int tinf_gzip_uncompress(void *dest,
                         unsigned int *destLen,
                         const void *source,
                         unsigned int sourceLen);

Decompress data in gzip compressed format from source[] to dest[]. destLen is set to the length of the decompressed data. Returns TINF_OK on success, and TINF_DATA_ERROR on error.

int tinf_zlib_uncompress(void *dest,
                         unsigned int *destLen,
                         const void *source,
                         unsigned int sourceLen);

Decompress data in zlib compressed format from source[] to dest[]. destLen is set to the length of the decompressed data. Returns TINF_OK on success, and TINF_DATA_ERROR on error.

unsigned int tinf_adler32(const void *data,
                          unsigned int length);

Computes the Adler-32 checksum of length bytes starting at data. Used by tinf_zlib_uncompress().

unsigned int tinf_crc32(const void *data,
                        unsigned int length);

Computes the CRC32 checksum of length bytes starting at data. Used by tinf_gzip_uncompress().

Source Code

The source code is ANSI C, and assumes that int is 32-bit. It has been tested on the x86 platform under Windows and Linux.

The decompression functions should be endian-neutral, and also reentrant and thread-safe (not tested).

In src/nasm there are 32-bit x86 assembler (386+) versions of some of the files.

Makefiles (GNU Make style) for a number of compilers are included.

Frequently Asked Questions

Q: Is it really free? Can I use it in my commercial ExpenZip software?

A: It's open-source software, available under the zlib license (see later), which means you can use it for free -- even in commercial products. If you do, please be kind enough to add an acknowledgement.

Q: Did you just strip stuff from the zlib source to make it smaller?

A: No, tinf was written from scratch, using the RFC documentation of the formats it supports.

Q: What do you mean by: 'the zlib library .. is more secure'?

A: The zlib decompression code checks the compressed data for validity while decompressing, so even on corrupted data it will not crash. The tinf code assumes it is given valid compressed data.

Q: I'm a Delphi programmer, can I use tinf?

A: Sure, the object files produced by both Borland C and Watcom C should be linkable with Delphi.

Q: Will tinf work on UltraSTRANGE machines running WhackOS?

A: I have no idea .. please try it out and let me know!

Q: Why are all the makefiles in GNU Make style?

A: I'm used to GNU Make, and it has a number of features that are missing in some of the other Make utilities.

Q: This is the first release, how can there be frequently asked questions?

A: Ok, ok .. I made the questions up ;-)

License

tinf - tiny inflate library

Copyright (c) 2003 Joergen Ibsen

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.