def encode(inputStream, outputStream, intervalLength, options):
Coder.checkInterval(intervalLength)
encoder = Encoder(inputStream, outputStream, options)
header = Long(Coder.HeaderValue.a, Coder.HeaderValue.b,
Coder.HeaderValue.c, Coder.HeaderValue.d)
for i in xrange(8):
outputStream.writeByte(header.a >> 8)
header.shl8()
packedOptions = options.toPacked()
for i in xrange(8):
outputStream.writeByte(packedOptions.a >> 8)
packedOptions.shl8()
Coder.doEncode(encoder, intervalLength)
def getOptions(inputStream):
header = Long(0, 0, 0, 0)
for i in xrange(8):
header.shl8()
inputByte = inputStream.readByte()
if inputByte == -1:
raise IOError("Unexpected end of file.")
header.d |= inputByte
if (header.a != Coder.HeaderValue.a) | (header.b
!= Coder.HeaderValue.b) | (header.c != Coder.HeaderValue.c) | (header.d
!= Coder.HeaderValue.d):
raise IOError("Wrong file header. Probably not a compressed file.")
return Coder.getOptionsHeaderless(inputStream)
def getOptionsHeaderless(inputStream):
packedOptions = Long(0, 0, 0, 0)
for i in xrange(8):
packedOptions.shl8()
inputByte = inputStream.readByte()
if inputByte == -1:
raise IOError("Unexpected end of file.")
packedOptions.d |= inputByte
result = Options.fromPacked(packedOptions)
if result is None:
raise ValueError("Invalid compression options.")
else:
return result
class Coder(object):
HeaderValue = Long(0x208b, 0xbb9f, 0x5b12, 0x98be)
@staticmethod
def getOptions(inputStream):
header = Long(0, 0, 0, 0)
for i in xrange(8):
header.shl8()
inputByte = inputStream.readByte()
if inputByte == -1:
raise IOError("Unexpected end of file.")
header.d |= inputByte
if (header.a != Coder.HeaderValue.a) | (header.b
!= Coder.HeaderValue.b) | (header.c != Coder.HeaderValue.c) | (header.d
!= Coder.HeaderValue.d):
raise IOError("Wrong file header. Probably not a compressed file.")
return Coder.getOptionsHeaderless(inputStream)
@staticmethod
def getOptionsHeaderless(inputStream):
packedOptions = Long(0, 0, 0, 0)
for i in xrange(8):
packedOptions.shl8()
inputByte = inputStream.readByte()
if inputByte == -1:
raise IOError("Unexpected end of file.")
packedOptions.d |= inputByte
result = Options.fromPacked(packedOptions)
if result is None:
raise ValueError("Invalid compression options.")
else:
return result
@staticmethod
def checkInterval(intervalLength):
if intervalLength <= 0:
raise ValueError("Interval length has to be positive.")
@staticmethod
def decode(inputStream, outputStream, intervalLength):
Coder.checkInterval(intervalLength)
options = Coder.getOptions(inputStream)
Coder.decodeRaw(inputStream, outputStream, intervalLength,
options)
@staticmethod
def decodeRaw(inputStream, outputStream, intervalLength, options):
Coder.checkInterval(intervalLength)
decoder = Decoder(inputStream, outputStream, options)
amountProcessed = 0
while not decoder.decode(intervalLength):
amountProcessed += intervalLength
@staticmethod
def encode(inputStream, outputStream, intervalLength, options):
Coder.checkInterval(intervalLength)
encoder = Encoder(inputStream, outputStream, options)
header = Long(Coder.HeaderValue.a, Coder.HeaderValue.b,
Coder.HeaderValue.c, Coder.HeaderValue.d)
for i in xrange(8):
outputStream.writeByte(header.a >> 8)
header.shl8()
packedOptions = options.toPacked()
for i in xrange(8):
outputStream.writeByte(packedOptions.a >> 8)
packedOptions.shl8()
Coder.doEncode(encoder, intervalLength)
@staticmethod
def encodeRaw(inputStream, outputStream, intervalLength, options):
Coder.checkInterval(intervalLength)
encoder = Encoder(inputStream, outputStream, options)
Coder.doEncode(encoder, intervalLength)
@staticmethod
def doEncode(encoder, intervalLength):
amountProcessed = 0
while not encoder.encode(intervalLength):
amountProcessed += intervalLength
encoder.flush()
