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nodemcu-firmware/app/uzlib
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Johny Mattsson 526d21dab4 Major cleanup - c_whatever is finally history. (#2838) 
The PR removed the bulk of non-newlib headers from the NodeMCU source base.  
app/libc has now been cut down to the bare minimum overrides to shadow the 
corresponding functions in the SDK's libc. The old c_xyz.h headerfiles have been 
nuked in favour of the standard <xyz.h> headers, with a few exceptions over in 
sdk-overrides. Again, shipping a libc.a without headers is a terrible thing to do. We're 
still living on a prayer that libc was configured the same was as a default-configured
xtensa gcc toolchain assumes it is. That part I cannot do anything about, unfortunately, 
but it's no worse than it has been before.

This enables our source files to compile successfully using the standard header files, 
and use the typical malloc()/calloc()/realloc()/free(), the strwhatever()s and 
memwhatever()s. These end up, through macro and linker magic, mapped to the 
appropriate SDK or ROM functions.
 		2019-07-22 00:58:21 +03:00
..
host trailing spaces cleanup (#2659) 2019-02-17 18:26:29 +00:00
Makefile trailing spaces cleanup (#2659) 2019-02-17 18:26:29 +00:00
README.md Add compression to LFS images (#2448) 2018-09-29 16:57:51 +03:00
crc32.c Add compression to LFS images (#2448) 2018-09-29 16:57:51 +03:00
uzlib.h Major cleanup - c_whatever is finally history. (#2838) 2019-07-22 00:58:21 +03:00
uzlib_deflate.c trailing spaces cleanup (#2659) 2019-02-17 18:26:29 +00:00
uzlib_inflate.c Major cleanup - c_whatever is finally history. (#2838) 2019-07-22 00:58:21 +03:00

README.md

uzlib - Deflate/Zlib-compatible LZ77 compression library

This is a heavily modified and cut down version of Paul Sokolovsky's uzlib library. This library has exported routines which

  • Can compress data to a Deflate-compatible bitstream, albeit with lower compression ratio than the Zlib Deflate algorithm as a static Deflate Huffman tree encoding is used for bitstream). Note that since this compression is in RAM and requires ~4 bytes per byte of the input record, should only be called for compressing small records on the ESP8266.

  • Can decompress any valid Deflate, Zlib, and Gzip (further called just "Deflate") bitstream less than 16Kb, and any arbitrary length stream compressed by the uzlib compressor.

uzlib aims for minimal code size and runtime memory requirements, and thus is suitable for embedded systems and IoT devices such as the ESP8266.

uzlib is based on:

  • tinf library by Joergen Ibsen (Deflate decompression)
  • Deflate Static Huffman tree routines by Simon Tatham
  • LZ77 compressor by Paul Sokolovsky provided my initial inspiration, but I ended up rewriting this following RFC 1951 to get improved compression performance.

The above 16Kb limitation arises from the RFC 1951 use of a 32Kb dictionary, which is impractical on a chipset with only ~40 Kb RAM avialable to applications.

The relevant copyright statements are provided in the source files which use this code.

uzlib library is licensed under Zlib license.