def compress(inp, bitout):
# Set up encoder and model. In this PPM model, symbol 256 represents EOF;
# its frequency is 1 in the order -1 context but its frequency
# is 0 in all other contexts (which have non-negative order).
enc = arithmeticcoding.ArithmeticEncoder(bitout)
model = ppmmodel.PpmModel(MODEL_ORDER, 257, 256)
history = []
while True:
# Read and encode one byte
symbol = inp.read(1)
if len(symbol) == 0:
break
symbol = symbol[0] if python3 else ord(symbol)
encode_symbol(model, history, symbol, enc)
model.increment_contexts(history, symbol)
if model.model_order >= 1:
# Append current symbol or shift back by one
if len(history) == model.model_order:
del history[0]
history.append(symbol)
encode_symbol(model, history, 256, enc) # EOF
enc.finish() # Flush remaining code bits
def compress(inp, bitout):
"""
Set up encoder and model. In this PPM model, symbol 256 represents EOF. Its frequency is 1 in the order -1
context but its frequency is 0 in all other contexts (which have non-negative order).
"""
enc = arithmeticcoding.ArithmeticEncoder(32, bitout)
model = ppmmodel.PpmModel(MODEL_ORDER, 257, 256)
history = []
while True:
# Read and encode one byte
symbol = inp.read(1)
if len(symbol) == 0:
break
symbol = symbol[0]
encode_symbol(model, history, symbol, enc)
model.increment_contexts(history, symbol)
if model.model_order >= 1:
# Prepend current symbol, dropping oldest symbol if necessary
if len(history) == model.model_order:
history.pop()
history.insert(0, symbol)
encode_symbol(model, history, 256, enc) # EOF
# Flush remaining code bits
enc.finish()
def decompress(bitin, out):
# Set up decoder and model
dec = arithmeticcoding.ArithmeticDecoder(bitin)
model = ppmmodel.PpmModel(MODEL_ORDER, 257, 256)
history = []
while True:
# Decode and write one byte
symbol = decode_symbol(dec, model, history)
if symbol == 256: # EOF symbol
break
out.write(bytes((symbol, )) if python3 else chr(symbol))
model.increment_contexts(history, symbol)
if model.model_order >= 1:
# Append current symbol or shift back by one
if len(history) == model.model_order:
del history[0]
history.append(symbol)
def decompress(bitin, out): # Set up decoder and model. In this PPM model, symbol 256 represents EOF; # its frequency is 1 in the order -1 context but its frequency # is 0 in all other contexts (which have non-negative order). dec = arithmeticcoding.ArithmeticDecoder(32, bitin) model = ppmmodel.PpmModel(MODEL_ORDER, 257, 256) history = [] while True: # Decode and write one byte symbol = decode_symbol(dec, model, history) if symbol == 256: # EOF symbol break out.write(bytes((symbol,)) if python3 else chr(symbol)) model.increment_contexts(history, symbol) if model.model_order >= 1: # Prepend current symbol, dropping oldest symbol if necessary if len(history) == model.model_order: history.pop() history.insert(0, symbol)
def compress(inp, bitout):
# Set up encoder and model
enc = arithmeticcoding.ArithmeticEncoder(bitout)
model = ppmmodel.PpmModel(MODEL_ORDER, 257, 256)
history = []
while True:
# Read and encode one byte
symbol = inp.read(1)
if len(symbol) == 0:
break
symbol = symbol[0] if python3 else ord(symbol)
encode_symbol(model, history, symbol, enc)
model.increment_contexts(history, symbol)
if model.model_order >= 1:
# Append current symbol or shift back by one
if len(history) == model.model_order:
del history[0]
history.append(symbol)
encode_symbol(model, history, 256, enc) # EOF
enc.finish() # Flush remaining code bits