示例#1
0
def compress(dic, consts):
  bitstream.start(sys.argv[2], sys.argv[3])
  buf = bitstream.read(consts['max'])
  while buf != []:
    # find matches and encode
    match = match_buffers(dic, buf)
    length = encode(match[0], match[1], dic, buf, consts)
    # slide the window
    del dic[:length]
    dic.extend(buf[:length])
    del buf[:length]
    buf.extend(bitstream.read(length))
示例#2
0
def decompress(dic, consts):
  bitstream.start(sys.argv[2], sys.argv[3])
  buf = ['filler']
  while buf != []:
    flag = bitstream.read(1)
    if flag == [47]: #unencoded
      buf = bitstream.read(consts['max'])
    else: # encoded
      break
    # slide the window
    del dic[:len(buf)]
    dic.extend(buf)
    bitstream.write(buf)
示例#3
0
def decompress(dic, consts):
  bitstream.start(sys.argv[2], sys.argv[3])
  buf = ['filler']
  while buf != []:
    flag = bitstream.read(1)
    if flag == [47]: #unencoded
      buf = bitstream.read(consts['max'])
    else: # encoded
      break
    # slide the window
    del dic[:len(buf)]
    dic.extend(buf)
    bitstream.write(buf)

consts = {'min':16, # minimum match size; any less is not worth encoding
          'max':23, # maximum match size
          'dic':4096, # dictionary size
          'posbits':12, # number of bits to encode position
          'lenbits':3, # of bits to encode range
          'uncoded':47, # uncoded flag
          'coded':46,} # encoded flag
bitstream.start('dictionary', None)
dic = bitstream.read(consts['dic'])

if sys.argv[1] == '-c':
  compress(dic, consts)
elif sys.argv[1] == '-d':
  decompress(dic, consts)
else:
  print('Usage: {0} -(c/d) <infile> <outfile>'.format(sys.argv[0]))