#

UTF-8? ✓

import bz2

import snappy

#

Exceptions

#

class UnknownCompressor(Exception):
    pass

#

Compressor Classes

#

Compressor classes adapt compression APIs from python libraries to what the CAS class cas.py needs.

#

Base Class / No Compression

#

Compression / Decompression wrapper CAS <-> python

class Compressor(object):

#

Each class has an identifier attribute by which CAS selects the compressor

    identifier = "no"

#

Compress

#

Compress data and return it with additional metadata for CAS.py

    @staticmethod
    def compress(data):

#

        meta = {
            "compression": "no",
            "orig_size": len(data)
        }
        return meta, data

#

Decompress

#

Decompress data

    @staticmethod
    def decompress(data):

#

        return data

#

Select

#

Select compressor class by identifier. Return class object

    @staticmethod
    def select(identifier):

#

        for cls in Compressor.__subclasses__():
            if cls.identifier == identifier:
                return cls

        if Compressor.identifier == identifier:
            return Compressor

        raise UnknownCompressor("Compressor unknown: " + identifier)

#

Supported

#

Return list of supported compressors

    @staticmethod
    def supported():

#

        return [cls.identifier for cls in Compressor.__subclasses__()] + [Compressor.identifier]

#

Snappy Compressor

#

class SnappyCompressor(Compressor):
    identifier = "snappy"

#

    @staticmethod
    def compress(data):
        meta = {
            "compression": "snappy",
            "orig_size": len(data)
        }

        compressed_data = snappy.compress(data)
        return meta, compressed_data

    @staticmethod
    def decompress(compressed_data):
        data = snappy.uncompress(compressed_data)
        return data

#

BZ2 Compressor

#

class BZ2Compressor(Compressor):
    identifier = "bz2"

#

    @staticmethod
    def compress(data):
        meta = {
            "compression": "bz2",
            "orig_size": len(data),
            "compresslevel": 9
        }

        compressed_data = bz2.compress(data, 9)
        return meta, compressed_data

    @staticmethod
    def decompress(compressed_data):
        data = bz2.decompress(compressed_data)
        return data

compressor.py