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Small strings compression library

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Statistics on smaz

Number of watchers on Github 634
Number of open issues 6
Average time to close an issue about 6 hours
Main language C
Open pull requests 4+
Closed pull requests 0+
Last commit over 8 years ago
Repo Created about 11 years ago
Repo Last Updated about 2 years ago
Size 212 KB
Organization / Authorantirez
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SMAZ - compression for very small strings

Smaz is a simple compression library suitable for compressing very short strings. General purpose compression libraries will build the state needed for compressing data dynamically, in order to be able to compress every kind of data. This is a very good idea, but not for a specific problem: compressing small strings will not work.

Smaz instead is not good for compressing general purpose data, but can compress text by 40-50% in the average case (works better with English), and is able to perform a bit of compression for HTML and urls as well. The important point is that Smaz is able to compress even strings of two or three bytes!

For example the string the is compressed into a single byte.

To compare this with other libraries, think that like zlib will usually not be able to compress text shorter than 100 bytes.


'This is a small string' compressed by 50% 'foobar' compressed by 34% 'the end' compressed by 58% 'not-a-g00d-Exampl333' enlarged by 15% 'Smaz is a simple compression library' compressed by 39% 'Nothing is more difficult, and therefore more precious, than to be able to decide' compressed by 49% 'this is an example of what works very well with smaz' compressed by 49% '1000 numbers 2000 will 10 20 30 compress very little' compressed by 10%

In general, lowercase English will work very well. It will suck with a lot of numbers inside the strings. Other languages are compressed pretty well too, the following is Italian, not very similar to English but still compressible by smaz:

'Nel mezzo del cammin di nostra vita, mi ritrovai in una selva oscura' compressed by 33% 'Mi illumino di immenso' compressed by 37% 'L'autore di questa libreria vive in Sicilia' compressed by 28%

It can compress URLS pretty well:

'http://google.com' compressed by 59% 'http://programming.reddit.com' compressed by 52% 'http://github.com/antirez/smaz/tree/master' compressed by 46%


The lib consists of just two functions:

int smaz_compress(char *in, int inlen, char *out, int outlen);

Compress the buffer 'in' of length 'inlen' and put the compressed data into 'out' of max length 'outlen' bytes. If the output buffer is too short to hold the whole compressed string, outlen+1 is returned. Otherwise the length of the compressed string (less then or equal to outlen) is returned.

int smaz_decompress(char *in, int inlen, char *out, int outlen);

Decompress the buffer 'in' of length 'inlen' and put the decompressed data into 'out' of max length 'outlen' bytes. If the output buffer is too short to hold the whole decompressed string, outlen+1 is returned. Otherwise the length of the compressed string (less then or equal to outlen) is returned. This function will not automatically put a nul-term at the end of the string if the original compressed string didn't included a nulterm.


Small was writte by Salvatore Sanfilippo and is released under the BSD license. Check the COPYING file for more information.

smaz open issues Ask a question     (View All Issues)
  • over 4 years Win32 Issues.
smaz open pull requests (View All Pulls)
  • Add smaz_fuzz.c for fuzzing.
  • Update smaz.h
  • Trie implementation of Smaz
  • Makefile: add check target
smaz questions on Stackoverflow (View All Questions)
  • How smaz compression library works?
  • How to aid Smaz in further compressing repeating characters?
smaz list of languages used
Other projects in C