reedsolo 0.1

Pure-Python Reed Solomon encoder/decoder

A pure-python Reed Solomon encoder/decoder, based on the wonderful tutorial at wikiversity, written by “Bobmath”.

I only consolidated the code a little and added exceptions and a simple API. To my understanding, the algorithm can correct up to nsym/2 of the errors in the message, where nsym is the number of bytes in the error correction code. The code should work on pretty much any reasonable version of python (2.4-3.2), but I’m only testing on 2.6-3.2.

Note

I claim no authorship of the code, and take no responsibility of the correctness of the algorithm. It’s way too much finite-field algebra for me :)

I’ve released this package as I needed an ECC codec for another project I’m working on, and I couldn’t find anything on the web (that still works).

>>> rs = RSCodec(10)
>>> rs.encode([1,2,3,4])
'\x01\x02\x03\x04,\x9d\x1c+=\xf8h\xfa\x98M'
>>> rs.encode("hello world")
'hello world\xed%T\xc4\xfd\xfd\x89\xf3\xa8\xaa'
>>> rs.decode(b'hello world\xed%T\xc4\xfd\xfd\x89\xf3\xa8\xaa')
'hello world'
>>> rs.decode(b'hello worXd\xed%T\xc4\xfd\xfd\x89\xf3\xa8\xaa')  # 1 error
'hello world'
>>> rs.decode(b'heXlo worXd\xed%T\xc4\xfdX\x89\xf3\xa8\xaa')     # 3 errors
'hello world'
>>> rs.decode(b'hXXlo worXd\xed%T\xc4\xfdX\x89\xf3\xa8\xaa')     # 4 errors
'hello world'
>>> rs.decode(b'hXXXo worXd\xed%T\xc4\xfdX\x89\xf3\xa8\xaa')     # 5 errors
'hello world'
>>> rs.decode(b'hXXXo worXd\xed%T\xc4\xfdXX\xf3\xa8\xaa')        # 6 errors - fail
Traceback (most recent call last):
  ...
ReedSolomonError: Could not locate error

>>> rs = RSCodec(12)
>>> rs.encode("hello world")
'hello world?Ay\xb2\xbc\xdc\x01q\xb9\xe3\xe2='
>>> rs.decode(b'hello worXXXXy\xb2XX\x01q\xb9\xe3\xe2=')         # 6 errors - ok
'hello world'