obfuslate/README at master · choobin/obfuslate · GitHub

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obfuslate, a tiny gzip decoder.

A short almost incomprehensible implementation of inflate capable of decoding gzip files using no hard-coded tables.

Two test scripts are provided. test-obfuslate is used to test a binary against a number of artificial, pseudo-real and real compressed texts from the Repetitive Corpus (see references). test-btypes tests decoding of each DEFLATE block type using specially formatted archives.

Implementation notes.

Supports all three DEFLATE block types; no compression, fixed and dynamic Huffman code tables.

Skips ID1 and ID2 check.

Assumes CM == 8 (deflate).

Skips FHCRC, FEXTRA, FNAME and FCOMMENT (if they exist).

Skips the final CRC32 check.

Requires a compiler that supports statement expressions.

Tested on:

gcc version 4.8.1 x86_64-unknown-linux-gnu
gcc version 4.7.2 x86_64-unknown-linux-gnu
icc version 12.1.3 (gcc version 4.6.0 compatibility)
pgcc 12.10-0 64-bit target on x86-64 Linux -tp sandybridge
clang version 3.3 (tags/RELEASE_33/final) x86_64-unknown-linux-gnu
tcc version 0.9.26 (x86-64 Linux)
gcc version 4.3.1 sparc-sun-solaris2.10
cc: Sun C 5.9 SunOS_sparc Patch 124867-09 2008/11/25

References.

DEFLATE Compressed Data Format Specification version 1.3
http://www.ietf.org/rfc/rfc1951.txt

GZIP file format specification version 4.3
http://www.ietf.org/rfc/rfc1952.txt

An Explanation of the Deflate Algorithm
http://zlib.net/feldspar.html

Repetitive Corpus
http://pizzachili.dcc.uchile.cl/repcorpus.html