encoding.py 文件源码

def compress(body, compress_level):
    """Compress 'body' at the given compress_level."""
    import zlib

    # See http://www.gzip.org/zlib/rfc-gzip.html
    yield ntob('\x1f\x8b')       # ID1 and ID2: gzip marker
    yield ntob('\x08')           # CM: compression method
    yield ntob('\x00')           # FLG: none set
    # MTIME: 4 bytes
    yield struct.pack('<L', int(time.time()) & int('FFFFFFFF', 16))
    yield ntob('\x02')           # XFL: max compression, slowest algo
    yield ntob('\xff')           # OS: unknown

    crc = zlib.crc32(ntob(''))
    size = 0
    zobj = zlib.compressobj(compress_level,
                            zlib.DEFLATED, -zlib.MAX_WBITS,
                            zlib.DEF_MEM_LEVEL, 0)
    for line in body:
        size += len(line)
        crc = zlib.crc32(line, crc)
        yield zobj.compress(line)
    yield zobj.flush()

    # CRC32: 4 bytes
    yield struct.pack('<L', crc & int('FFFFFFFF', 16))
    # ISIZE: 4 bytes
    yield struct.pack('<L', size & int('FFFFFFFF', 16))