def main():
symb = [(.07,'a'), (.09,'b'),(.12,'c'),(.22,'d'),(.23,'e'),(.27,'f')]
tree = huff.makeHuff(symb)
if tree.left.left != 'd' or \
tree.left.right != 'e' or \
tree.right.left != 'f' or \
tree.right.right.left !='c' or \
tree.right.right.right.left !='a' or \
tree.right.right.right.right != 'b':
passed = False
else:
passed = True
testPass("makeHuff",passed)
passed = True
result = huff.encode(tree)
expected = {'a':'1110','c':'110','b':'1111','e':'01','d':'00','f':'10'}
if result != expected:
passed = False
print "symb | prob | code"
for i in sorted(symb):
print i[1], " |", (i[0]), "| ", result[i[1]]
testPass("encode",passed)
def test_same(self):
seq = [0] * 16
from collections import Counter
freqs = Counter(seq)
coding, root = huff.generate_coding(freqs)
encode = huff.encode(seq, coding)
decode = huff.decode("".join(encode), root)
self.assertEqual(list(seq), decode)
def test_mix(self):
seq = [1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 5, 5, 5]
random.shuffle(seq)
from collections import Counter
freqs = Counter(seq)
expect = {1: "10", 2: "01", 3: "11", 4: "001", 5: "000"}
coding, root = huff.generate_coding(freqs)
self.assertDictEqual(expect, coding)
encode = huff.encode(seq, coding)
decode = huff.decode("".join(encode), root)
self.assertEqual(seq, decode)
def compress(f, compf, block = None):
"""
Compress a file by bwt-mtf-huff processes.
f: a file-like object, content for compressing
compf: compression result
"""
# craete alphabet for move-to-front
content = f.read()
alphabet_set = set(content)
alphabet = [''] + list(alphabet_set)
# dump alphabet
cPickle.dump(alphabet, compf, 2)
content = None
f.seek(0)
count = 0
while True:
data = f.read(BLOCK_SIZE)
if data == '':
break
if block == None or block == count:
print "block %r:" % count
bwt_encode, I = bwt.encode(data)
mtf_encode = mtf.encode(alphabet, bwt_encode)
# create Huffman tree
freqs = Counter(mtf_encode)
if block:
print freqs
coding, root = huff.generate_coding(freqs)
if block:
print coding
# encoding
huff_encode = ''.join(huff.encode(mtf_encode, coding))
#print "huff_encode:\n%r" % huff_encode
nbits = len(huff_encode)
huff_bytes = tobytes(huff_encode)
compf.write(struct.pack(">2I", nbits, I))
dump_freqs(compf, freqs)
compf.write(huff_bytes)
print "nbits = %r, I = %r, length = %r" % (nbits, I, len(data))
count = count + 1
def main():
symb = [(.07, 'a'), (.09, 'b'), (.12, 'c'), (.22, 'd'), (.23, 'e'),
(.27, 'f')]
tree = huff.makeHuff(symb)
if tree.left.left != 'd' or \
tree.left.right != 'e' or \
tree.right.left != 'f' or \
tree.right.right.left !='c' or \
tree.right.right.right.left !='a' or \
tree.right.right.right.right != 'b':
passed = False
else:
passed = True
testPass("makeHuff", passed)
passed = True
result = huff.encode(tree)
expected = {
'a': '1110',
'c': '110',
'b': '1111',
'e': '01',
'd': '00',
'f': '10'
}
if result != expected:
passed = False
print "symb | prob | code"
for i in sorted(symb):
print i[1], " |", (i[0]), "| ", result[i[1]]
testPass("encode", passed)
