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There are four functions, allowing compression and decompression in the two formats we support so far. The functions will accept bytes or unicode strings which are treated as utf-8. The LZ77+Huffman decompression algorithm requires an exact target length to decompress, so this is mandatory. The plain decompression algorithm does not need an exact length, but you can provide one to help it know how much space to allocate. As currently written, you can provide a short length and it will often succeed in decompressing to a different shorter string. These bindings are intended to make ad-hoc investigation easier, not for production use. This is reflected in the guesses about output size that plain_decompress() makes if you don't supply one -- either they are stupidly wasteful or ridiculously insufficient, depending on whether or not you were trying to decompress a 20MB string. >>> a = '12345678' >>> import compression >>> b = compression.huffman_compress(a) >>> b b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00 #.... >>> len(b) 262 >>> c = compression.huffman_decompress(b, len(a)) >>> c b'12345678' # note, c is bytes, a is str >>> a '12345678' >>> d = compression.plain_compress(a) >>> d b'\xff\xff\xff\x0012345678' >>> compression.plain_decompress(d) # no size specified, guesses b'12345678' >>> compression.plain_decompress(d,5) b'12345' >>> compression.plain_decompress(d,0) # 0 for auto b'12345678' >>> compression.plain_decompress(d,1) b'1' >>> compression.plain_decompress(a,444) Traceback (most recent call last): compression.CompressionError: unable to decompress data into a buffer of 444 bytes. >>> compression.plain_decompress(b,444) b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00 #... That last one decompresses the Huffman compressed file with the plain compressor; pretty much any string is valid for plain decompression. Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz> Reviewed-by: Jeremy Allison <jra@samba.org> |
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| .. | ||
| tests | ||
| lzxpress_huffman.c | ||
| lzxpress_huffman.h | ||
| lzxpress.c | ||
| lzxpress.h | ||
| pycompression.c | ||
| wscript_build | ||