def lzw_encode(seq):
seq = list(seq) # make a copy
seq.reverse(
) # For efficiency, we will reverse the list and get data from the end
output = []
dictionary = {str(s): s for s in range(256)}
i = 256
try:
s = seq.pop()
except IndexError:
return int_seq_to_bin_seq(output, 255)
# dictionary = [] # TODO: Set a default set of values for the dictionary
while True:
try:
c = seq.pop()
except IndexError:
break
if (s + c) in dictionary:
s = s + c
else:
output.append(dictionary[s])
dictionary[s + c] = i
i += 1
s = c
if s in dictionary:
output.append(dictionary[s])
else:
output.append(i)
return int_seq_to_bin_seq(output, len(dictionary))
def lzw_encode(seq):
seq = list(seq) # make a copy
seq.reverse() # For efficiency, we will reverse the list and get data from the end
output = []
dictionary = {str(s) : s for s in range(256)}
i = 256
try:
s = seq.pop()
except IndexError:
return int_seq_to_bin_seq(output, 255)
# dictionary = [] # TODO: Set a default set of values for the dictionary
while True:
try:
c = seq.pop()
except IndexError:
break
if (s + c) in dictionary:
s = s + c
else:
output.append(dictionary[s])
dictionary[s + c] = i
i += 1
s = c
if s in dictionary:
output.append(dictionary[s])
else:
output.append(i)
return int_seq_to_bin_seq(output, len(dictionary))
def encode( chan, opcode):
if( opcode == ENCODING_SCHEME_VARLEN):
return shanfan_encode(chan)[0]
if( opcode == ENCODING_SCHEME_DICT):
chan = [str(s) for s in chan]
return lzw_encode(chan)
else:
return int_seq_to_bin_seq(chan, 255)
