def decompress(compressed, uncompressed):
'''First, read a Huffman tree from the 'compressed' stream using your
read_tree function. Then use that tree to decode the rest of the
stream and write the resulting symbols to the 'uncompressed'
stream.
Args:
compressed: A file stream from which compressed input is read.
uncompressed: A writable file stream to which the uncompressed
output is written.
'''
# read the tree from the compressed file
tree = read_tree(compressed)
# initialize bit reading
readin = bitio.BitReader(compressed)
not_end_file = True
# initialize new file for bit writing
writeout = bitio.BitWriter(uncompressed)
while not_end_file:
try:
# recursively decode one byte
byte = decode_byte(tree, readin)
if byte != None:
writeout.writebits(byte, 8)
except EOFError:
not_end_file = False
# push changes to file
writeout.flush()
writeout.flush()
def decompress(compressed, uncompressed):
'''First, read a Huffman tree from the 'compressed' stream using your
read_tree function. Then use that tree to decode the rest of the
stream and write the resulting symbols to the 'uncompressed'
stream.
Args:
compressed: A file stream from which compressed input is read.
uncompressed: A writable file stream to which the uncompressed
output is written.
'''
bitreader = bitio.BitReader(compressed)
bitwriter = bitio.BitWriter(uncompressed)
# read the tree from the compressed stream
tree = read_tree(bitreader)
# keep decoding bytes and writing to the uncompressed stream until the
# EOF symbol is reached
while True:
decoded = decode_byte(tree, bitreader)
if decoded == None:
break
bitwriter.writebits(decoded, 8)
def compress(tree, uncompressed, compressed):
'''First write the given tree to the stream 'compressed' using the
write_tree function. Then use the same tree to encode the data
from the input stream 'uncompressed' and write it to 'compressed'.
If there are any partially-written bytes remaining at the end,
write 0 bits to form a complete byte.
Flush the bitwriter after writing the entire compressed file.
Args:
tree: A Huffman tree.
uncompressed: A file stream from which you can read the input.
compressed: A file stream that will receive the tree description
and the coded input data.
'''
write_tree(tree, compressed)
table = huffman.make_encoding_table(tree) # make encoding table from tree
writing = bitio.BitWriter(compressed)
for z in uncompressed:
for asciChar in z: # go through each asci character in the line and find it on the table which would give the corrosponding binaries
binary = table[asciChar]
for singleBit in binary: # go through each binary and write it, true = 1 false =0
if singleBit == 1:
writing.writebit(True)
elif singleBit == 0:
writing.writebit(False)
for singleBit in table[
None]: # table[None] = EOF binary which was not included in the above for loop.
if singleBit == 1:
writing.writebit(True)
elif singleBit == 0:
writing.writebit(False)
writing.flush()
def compress(tree, uncompressed, compressed): write_tree(tree, compressed) encoding_table = huffman.make_encoding_table(tree) values_table = list(encoding_table.values()) keys_table = list(encoding_table.keys()) mybytereader = bitio.BitReader(uncompressed) endoffile = False list1 = [] while not endoffile: try: mybyte = mybytereader.readbits(8) list1.append(mybyte) except EOFError: endoffile = True mybitwriter = bitio.BitWriter(compressed) for i in list1: if i in encoding_table.keys(): code = encoding_table[i] for h in code: mybitwriter.writebit(h) mybitwriter.writebit(None) mybitwriter.flush()
def decompress(compressed, uncompressed):
# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
# First, read a Huffman tree from the 'tree_stream' using your
# read_tree function. Then use that tree to decode the rest of the
# stream and write the resulting symbols to the 'uncompressed'
# stream.
# Args:
# compressed: A file stream from which compressed input is read.
# uncompressed: A writable file stream to which the uncompressed
# output is written.
# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
# unpickling the tree from the compressed file stream
unpkltree = read_tree(compressed)
# creating BitReader and BitWriter objects
bitread = bitio.BitReader(compressed)
bitwriter = bitio.BitWriter(uncompressed)
while True:
try:
nextbyte = decode_byte(unpkltree, bitread)
# use bitwriter to write indiviual bits to a file
bitwriter.writebits(nextbyte, 8)
except:
break
# flushing the bit writer object
bitwriter.flush()
pass
def decompress(compressed, uncompressed):
'''First, read a Huffman tree from the 'compressed' stream using your
read_tree function. Then use that tree to decode the rest of the
stream and write the resulting symbols to the 'uncompressed'
stream.
Args:
compressed: A file stream from which compressed input is read.
uncompressed: A writable file stream to which the uncompressed
output is written.
'''
decompTree = read_tree(compressed) # read whole tree
binary = bitio.BitReader(compressed) # convert compressed to binary
writing = bitio.BitWriter(uncompressed) # writing to huff tree to var
end = False
place = 0
while end == False:
try:
place = decode_byte(decompTree,
binary) # compare whole tree with binary
writing.writebits(place, 8)
except:
end = True
writing.flush()
pass
def decompress(compressed, uncompressed):
'''First, read a Huffman tree from the 'compressed' stream using your
read_tree function. Then use that tree to decode the rest of the
stream and write the resulting symbols to the 'uncompressed'
stream.
Args:
compressed: A file stream from which compressed input is read.
uncompressed: A writable file stream to which the uncompressed
output is written.
'''
#set up reader and writer
reader = bitio.BitReader(compressed)
writer = bitio.BitWriter(uncompressed)
#read in and construct tree
tree = read_tree(reader)
while (True):
byte = decode_byte(tree, reader)
#if the byte is the eof char, break you are done
if byte == None:
break
else:
#write bits to uncompressed file
writer.writebits(byte, 8)
def decompress(compressed, uncompressed):
'''First, read a Huffman tree from the 'compressed' stream using your
read_tree function. Then use that tree to decode the rest of the
stream and write the resulting symbols to the 'uncompressed'
stream.
Args:
compressed: A file stream from which compressed input is read.
uncompressed: A writable file stream to which the uncompressed
output is written.
'''
# instances of the BitReader and BitWriter
reader = bitio.BitReader(compressed)
writer = bitio.BitWriter(uncompressed)
# first read the huffman tree off the compressed file
huffman_tree = read_tree(reader)
# continue to read the bytes encoded using tree
while True:
# decode the next byte
byte_read = decode_byte(huffman_tree, reader)
# stop when end-of-message is read
if byte_read == None:
break
# write the byte to the uncompressed file
writer.writebits(byte_read, 8)
def decompress(compressed, uncompressed):
'''First, read a Huffman tree from the 'compressed' stream using your
read_tree function. Then use that tree to decode the rest of the
stream and write the resulting symbols to the 'uncompressed'
stream.
Args:
compressed: A file stream from which compressed input is read.
uncompressed: A writable file stream to which the uncompressed
output is written.
'''
tree = read_tree(compressed)
encoded = bitio.BitReader(compressed)
decoded = bitio.BitWriter(uncompressed)
end_of_file = False
try:
while not end_of_file:
byte = decode_byte(tree, encoded)
if byte is None:
end_of_file = True
else:
decoded.writebits(byte, 8)
except EOFError:
end_of_file = True
def decompress(compressed, uncompressed):
'''First, read a Huffman tree from the 'compressed' stream using your
read_tree function. Then use that tree to decode the rest of the
stream and write the resulting symbols to the 'uncompressed'
stream.
Args:
compressed: A file stream from which compressed input is read.
uncompressed: A writable file stream to which the uncompressed
output is written.
'''
# load the tree
tree = read_tree(compressed)
# Instantiate the Bit Reader and Bit Writer objects
read_bit = bitio.BitReader(compressed)
write_val = bitio.BitWriter(uncompressed)
# Continously decode the bytes from the compressed file until EOF is
# reached
try:
while True:
val = decode_byte(tree, read_bit)
write_val.writebits(val, 8)
except:
pass # EOF
# flush the bitwriter
write_val.flush()
return
def decompress(compressed, uncompressed):
'''First, read a Huffman tree from the 'compressed' stream using your
read_tree function. Then use that tree to decode the rest of the
stream and write the resulting symbols to the 'uncompressed'
stream.
Args:
compressed: A file stream from which compressed input is read.
uncompressed: A writable file stream to which the uncompressed
output is written.
'''
flag = 1
# We get the bits from the compressed stream and use it to obtain our tree
unpickled = read_tree(compressed)
# Bit Reader object is created
in_stream = bitio.BitReader(compressed)
# Bit Writer object is created
out_stream = bitio.BitWriter(uncompressed)
while flag == 1:
# Coded bits will be decoded until we reach the end and None will be returned
decoded = decode_byte(unpickled, in_stream)
if decoded == None:
flag = 0
# Keep writing the bits until we reach the end of the file
elif decoded != None:
out_stream.writebits(decoded, 8)
out_stream.flush()
def decompress(compressed, uncompressed):
'''First, read a Huffman tree from the 'compressed' stream using your
read_tree function. Then use that tree to decode the rest of the
stream and write the resulting symbols to the 'uncompressed'
stream.
Args:
compressed: A file stream from which compressed input is read.
uncompressed: A writable file stream to which the uncompressed
output is written.
'''
bitreader = bitio.BitReader(compressed)
bitwriter = bitio.BitWriter(uncompressed)
# read Huffman tree from beginning of file
tree = read_tree(bitreader)
# while compressed stream has data
while True:
b = decode_byte(tree, bitreader)
# if we reach the end
if b == None:
break
else:
# write decoded bytes
bitwriter.writebits(b, 8)
def compress(tree, uncompressed, compressed):
'''First write the given tree to the stream 'compressed' using the
write_tree function. Then use the same tree to encode the data
from the input stream 'uncompressed' and write it to 'compressed'.
If there are any partially-written bytes remaining at the end,
write 0 bits to form a complete byte.
Flush the bitwriter after writing the entire compressed file.
Args:
tree: A Huffman tree.
uncompressed: A file stream from which you can read the input.
compressed: A file stream that will receive the tree description
and the coded input data.
'''
write_tree(tree, compressed)
decoded = bitio.BitReader(uncompressed)
encoded = bitio.BitWriter(compressed)
table = huffman.make_encoding_table(tree)
end_of_file = False
try:
while not end_of_file:
byte = decoded.readbits(8)
for x in table[byte]:
encoded.writebit(x)
except EOFError:
for x in table[None]:
encoded.writebit(x)
encoded.flush()
def compress(tree, uncompressed, compressed):
'''First write the given tree to the stream 'compressed' using the
write_tree function. Then use the same tree to encode the data
from the input stream 'uncompressed' and write it to 'compressed'.
If there are any partially-written bytes remaining at the end,
write 0 bits to form a complete byte.
Flush the bitwriter after writing the entire compressed file.
Args:
tree: A Huffman tree.
uncompressed: A file stream from which you can read the input.
compressed: A file stream that will receive the tree description
and the coded input data.
'''
write_tree(tree, compressed)
# instantiate classes
bitwriter = bitio.BitWriter(compressed)
bitreader = bitio.BitReader(uncompressed)
# create table with paths to bytes
table = huffman.make_encoding_table(tree)
end_of_file = False
while not end_of_file:
try:
# read in byte
compress = bitreader.readbits(8)
# write byte in compressed form
for el in (table[compress]):
bitwriter.writebit(el)
except EOFError:
# reached end of file
bitwriter.flush()
end_of_file = True
def decompress(compressed, uncompressed): '''First, read a Huffman tree from the 'compressed' stream using your read_tree function. Then use that tree to decode the rest of the stream and write the resulting symbols to the 'uncompressed' stream. Args: compressed: A file stream from which compressed input is read. uncompressed: A writable file stream to which the uncompressed output is written. ''' #let compressed be an instance of bitio.BitReader reading = bitio.BitReader(compressed) #use read_tree to get the huffman tree tree = read_tree(reading) #let uncompressed be an instance of bitio.BitWriter Target = bitio.BitWriter(uncompressed) while True: #get the value of leaf val = decode_byte(tree, reading) #if EOF just break if val is None: break #write the value of leaf to uncompressed file Target.writebits(val,8) Target.flush()
def compress(tree, uncompressed, compressed):
'''First write the given tree to the stream 'compressed' using the
write_tree function. Then use the same tree to encode the data
from the input stream 'uncompressed' and write it to 'compressed'.
If there are any partially-written bytes remaining at the end,
write 0 bits to form a complete byte.
Flush the bitwriter after writing the entire compressed file.
Args:
tree: A Huffman tree.
uncompressed: A file stream from which you can read the input.
compressed: A file stream that will receive the tree description
and the coded input data.
'''
# no try statement given, becuase if file exists, and
try:
write_tree(tree, compressed)
except:
print("File does not contain any bits to compress")
return
encoding_table = huffman.make_encoding_table(tree)
# open using bitio
bitread = bitio.BitReader(uncompressed)
bitwrite = bitio.BitWriter(compressed)
# assume EOF is not reached
eof = False
# read till EOF is reached
while not eof:
try:
# read 8 bits to byte
byte = bitread.readbits(8)
# encode using encoding_table
code = encoding_table[byte]
# write code bitwise
for bit in code:
bitwrite.writebit(bit)
# this is a crucial step to ensure loop stops
# and compressed files are marked with None to indicate EOF
except EOFError:
# stop loop
eof = True
# manually write None to indicate EOF to decompressor
code = encoding_table[None]
for bit in code:
bitwrite.writebit(bit)
bitwrite.flush()
pass
def compress(tree, uncompressed, compressed):
'''
First write the given tree to the stream 'compressed' using the
write_tree function. Then use the same tree to encode the data
from the input stream 'uncompressed' and write it to 'compressed'.
If there are any partially-written bytes remaining at the end,
write 0 bits to form a complete byte.
Flush the bitwriter after writing the entire compressed file.
Args:
tree: A Huffman tree.
uncompressed: A file stream from which you can read the input.
compressed: A file stream that will receive the tree description
and the coded input data.
'''
bitreader = bitio.BitReader(uncompressed)
bitwriter = bitio.BitWriter(compressed)
# write tree to the beginning of the file
write_tree(tree, bitwriter)
# create encoding table for compressed bits of file using our tree
table = huffman.make_encoding_table(tree)
counter = 0
# read from uncompressed stream until done
while True:
try:
# find path description (tuple) from encoding table
path = table[bitreader.readbits(8)]
# if we have reached the end of the file
except EOFError:
bitwriter.writebits(0, 2)
# to have a full byte at the end
counter += 2
break
# write the path to the compressed file
for p in path:
if p:
bitwriter.writebit(1)
counter += 1
else:
bitwriter.writebit(0)
counter += 1
# find how many bits left to make an even byte
counter %= 8
# complete byte with 0s
while counter:
bitwriter.writebit(0)
counter -= 1
def decompress(compressed, uncompressed):
bitreader = bitio.BitReader(compressed)
bitwriter = bitio.BitWriter(uncompressed)
tree = read_tree(bitreader)
# Repeatedly read coded bits from the file, decode them using tree
while True:
decoded = huffman.decode(tree, bitreader)
# As soon as you decode the end-of-message symbol, you should stop reading.
if decoded is None:
break
# write the decoded byte to the uncompressed output
bitwriter.writebits(decoded, 8)
def compress(tree, uncompressed, compressed):
'''First write the given tree to the stream 'compressed' using the
write_tree function. Then use the same tree to encode the data
from the input stream 'uncompressed' and write it to 'compressed'.
If there are any partially-written bytes remaining at the end,
write 0 bits to form a complete byte.
Flush the bitwriter after writing the entire compressed file.
Args:
tree: A Huffman tree.
uncompressed: A file stream from which you can read the input.
compressed: A file stream that will receive the tree description
and the coded input data.
'''
bitwriter = bitio.BitWriter(compressed)
bitreader = bitio.BitReader(uncompressed)
# table maps the byte of a leaf node to a tuple containiing the bit sequence
table = huffman.make_encoding_table(tree)
write_tree(tree, bitwriter)
# holds the bits written to the compressed stream
bit_count = 0
# read bits from the uncompressed stream until there are none left
while True:
try:
symbol = bitreader.readbits(8)
except:
break
# write the bit sequence for the symbol read
encoded = table[symbol]
for bit in encoded:
bit_count += 1
bitwriter.writebit(bit)
# write the end of file message
for bit in table[None]:
bit_count += 1
bitwriter.writebit(bit)
# pad with zeros if there are partial bytes
remaining = bit_count % 8
if remaining != 0:
for i in range(remaining):
bitwriter.writebit(False)
bitwriter.flush()
def compress(tree, uncompressed, compressed):
"""First write the given tree to the stream 'compressed' using the
write_tree function. Then use the same tree to encode the data
from the input stream 'uncompressed' and write it to 'compressed'.
If there are any partially-written bytes remaining at the end,
write 0 bits to form a complete byte.
Flush the BitWriter after writing the entire compressed file.
Args:
tree: A Huffman tree.
uncompressed: A file stream from which you can read the input.
compressed: A file stream that will receive the tree description
and the coded input data.
"""
def read_byte(bit_stream):
"""
Short function to read the file, just to allow for use of iter(), decreasing clutter
:param bit_stream: a BitReader object
:return: None when EOF, the byte read otherwise.
"""
try:
return bit_stream.readbits(8)
except EOFError:
return None
write_tree(tree, compressed)
encoding_table = huffman.make_encoding_table(tree)
# Open a BitReader for uncompressed file
in_stream = bitio.BitReader(uncompressed)
output = []
# Read the uncompressed file until EOF
for uncompressed_byte in iter(lambda: read_byte(in_stream), None):
compressed_byte = encoding_table[uncompressed_byte]
output += list(compressed_byte)
# Add EOF
output += list(encoding_table[None])
# Open BitWriter for compressed file
out_stream = bitio.BitWriter(compressed)
# Write out bits
for bit in output:
out_stream.writebit(bit)
# Flush stream
out_stream.flush()
def compress(tree, uncompressed, compressed):
'''First write the given tree to the stream 'compressed' using the
write_tree function. Then use the same tree to encode the data
from the input stream 'uncompressed' and write it to 'compressed'.
If there are any partially-written bytes remaining at the end,
write 0 bits to form a complete byte.
Flush the bitwriter after writing the entire compressed file.
Args:
tree: A Huffman tree.
uncompressed: A file stream from which you can read the input.
compressed: A file stream that will receive the tree description
and the coded input data.
'''
# instances of the BitReader and BitWriter
reader = bitio.BitReader(uncompressed)
writer = bitio.BitWriter(compressed)
# make the encoding table for the given tree
encode_table = huffman.make_encoding_table(tree)
# call write_tree, to write the tree to the compressed file
write_tree(tree, writer)
# write all the bytes untill EOFError occurs
while True:
try:
# read the byte from uncompressed file
byte_towrite = reader.readbits(8)
# encode the byte using the dictionary
bit_sequence = encode_table[byte_towrite]
# write each bit to the compressed file
for b in bit_sequence:
if b == True:
writer.writebit(1)
elif b == False:
writer.writebit(0)
except EOFError:
bit_sequence = encode_table[None]
# write each bit to the compressed file
for b in bit_sequence:
if b == True:
writer.writebit(1)
elif b == False:
writer.writebit(0)
# stop the loop
break
# Flush the bitwriter
writer.flush()
def decompress(compressed, uncompressed):
#defining reader and writer
bitreader1 = bitio.BitReader(compressed)
bitwriter1 = bitio.BitWriter(uncompressed)
tree = read_tree(compressed)
alphabet = 0
while alphabet!=None:
letter = decode_byte(tree, bitreader1)
bitwriter1.writebits(letter, 8)
bitwriter1.flush()
def compress(tree, uncompressed, compressed):
'''First write the given tree to the stream 'compressed' using the
write_tree function. Then use the same tree to encode the data
from the input stream 'uncompressed' and write it to 'compressed'.
If there are any partially-written bytes remaining at the end,
write 0 bits to form a complete byte.
Args:
tree: A Huffman tree.
uncompressed: A file stream from which you can read the input.
compressed: A file stream that will receive the tree description
and the coded input data.
'''
bitwriter = bitio.BitWriter(compressed)
# encode the tree itself
write_tree(tree, bitwriter)
# create a dictionary for codes where each code takes the form (bool,bool,bool,...)
codes = huffman.make_encoding_table(tree)
buff = bytearray(512) # the buffer in which to read the input
while True:
count = uncompressed.readinto(buff)
for i in range(count):
for node in codes[buff[i]]:
if node == True:
bitwriter.writebit(1)
elif node == False:
bitwriter.writebit(0)
else:
# if the node is for some reason not stored correctly
raise Exception("Nodetype not boolean, found: {}".format(
type(node)))
if count < len(buff): # when there is no more input
break
# encode and send an end of message character to finish the message
for node in codes[None]: # None is the end of message character
if node == True:
bitwriter.writebit(1)
elif node == False:
bitwriter.writebit(0)
else:
# if the node is for some reason not stored correctly
raise Exception("Nodetype not boolean, found: {}".format(
type(node)))
# write extra bits if needed to fill the last byte
bitwriter.writebits(0, 8 - bitwriter.bcount)
bitwriter.flush()
def decompress(compressed, uncompressed):
'''First, read a Huffman tree from the 'compressed' stream using your
read_tree function. Then use that tree to decode the rest of the
stream and write the resulting symbols to the 'uncompressed'
stream.
Args:
compressed: A file stream from which compressed input is read.
uncompressed: A writable file stream to which the uncompressed
output is written.
'''
'''br = BitReader(compressed)
tree = read_tree(br)
print(tree.left.left.left.left.left)
# encoded_table = huffman.make_encoding_table(tree)
# print(encoded_table)
# print(bin(br.readbits(100)))
bw = BitWriter(uncompressed)
while True:
try:
bit = br.readbit()
byte = decode_byte(tree, br)
bw.writebits(byte, 8)
except EOFError:
break
bw.writebit(0b0)
bw.writebit(0b1)
bw.writebit(0b0)
bw.writebit(0b1)
bw.writebit(0b0)
bw.writebit(0b0)
bw.writebit(0b1)
bw.writebit(0b0)'''
# initialize the reading and writing
reader = bitio.BitReader(compressed)
writer = bitio.BitWriter(uncompressed)
tree = read_tree(reader)
while 1:
byte = decode_byte(tree, reader)
if byte == None: # means ending
break
else:
writer.writebits(byte, 8)
def compress(tree, uncompressed, compressed):
'''First write the given tree to the stream 'compressed' using the
write_tree function. Then use the same tree to encode the data
from the input stream 'uncompressed' and write it to 'compressed'.
If there are any partially-written bytes remaining at the end,
write 0 bits to form a complete byte.
Flush the bitwriter after writing the entire compressed file.
Args:
tree: A Huffman tree.
uncompressed: A file stream from which you can read the input.
compressed: A file stream that will receive the tree description
and the coded input data.
'''
# initialise tables and input and output bitstreams
table = huffman.make_encoding_table(tree)
input_stream = bitio.BitReader(uncompressed)
output_stream = bitio.BitWriter(compressed)
write_tree(tree, output_stream)
# set up a counter to find partially filled bytes
counter = 0
while (True):
try:
# tries to read 8 bytes, if end of file found, go to except
byte = input_stream.readbits(8)
path = table[byte] # find the path
counter += len(path)
for i in path:
# output the bits
output_stream.writebit(i)
except:
# for partially filled bytes, pad with 0's to make a byte
path = table[None] # find the path
counter += len(path)
for i in path:
# output the bits
output_stream.writebit(i)
output_stream.writebits(0, counter % 8)
# flush
output_stream.flush()
return
def decompress(compressed, uncompressed):
'''First, read a Huffman tree from the 'compressed' stream using your
read_tree function. Then use that tree to decode the rest of the
stream and write the resulting symbols to the 'uncompressed'
stream.
Args:
compressed: A file stream from which compressed input is read.
uncompressed: A writable file stream to which the uncompressed
output is written.
'''
# create tree using read_tree
try:
tree = read_tree(compressed)
except:
print("Huffman tree description invalid")
return
# open using bitio
bitread = bitio.BitReader(compressed)
bitwrite = bitio.BitWriter(uncompressed)
# attempt to decode file bits after Huffman tree description
try:
decode = decode_byte(tree, bitread)
except EOFError:
decode = None
print("No bits to read after Huffman tree description")
# if bits are successfully decoded, begin writing them, till EOF is reached
while decode != None:
try:
# write decoded symbol with 8 bits and decode the next bits
bitwrite.writebits(decode, 8)
decode = decode_byte(tree, bitread)
# exception in case compressed file does not have None written before EOF
except EOFError:
decode = None
pass
def compress(tree, uncompressed, compressed):
'''First write the given tree to the stream 'compressed' using the
write_tree function. Then use the same tree to encode the data
from the input stream 'uncompressed' and write it to 'compressed'.
If there are any partially-written bytes remaining at the end,
write 0 bits to form a complete byte.
Flush the bitwriter after writing the entire compressed file.
Args:
tree: A Huffman tree.
uncompressed: A file stream from which you can read the input.
compressed: A file stream that will receive the tree description
and the coded input data.
'''
# Same initial setup as decompress
reader = bitio.BitReader(uncompressed)
writer = bitio.BitWriter(compressed)
# This time we are writing the tree instead
write_tree(tree, writer)
# key is a dictionary that is used to find the specific bitsequence for a
# specific byte using the huffman coding
key = huffman.make_encoding_table(tree)
while 1:
try:
# use the key to map the specific byte to the corresponding
# huffman bitsequence. By looping through the whole file, we can
# compress every byte to a huffman compressed bit sequence, thus
# compressing the whole file to a .huff extension
byte = reader.readbits(8)
bitsequence = key[byte]
for bit in bitsequence:
writer.writebit(bit)
# This flag is hear to indicate we have reached the end of the file
# and to thus stop compressing
except EOFError:
break
pass
def compress(tree, uncompressed, compressed): '''First write the given tree to the stream 'compressed' using the write_tree function. Then use the same tree to encode the data from the input stream 'uncompressed' and write it to 'compressed'. If there are any partially-written bytes remaining at the end, write 0 bits to form a complete byte. Flush the bitwriter after writing the entire compressed file. Args: tree: A Huffman tree. uncompressed: A file stream from which you can read the input. compressed: A file stream that will receive the tree description and the coded input data. ''' ##let compressed be an instance of bitio.BitWriter Target = bitio.BitWriter(compressed) #let uncompressed be an instance of bitio.BitReader readingfile = bitio.BitReader(uncompressed) #Write the Huffman tree to compressed file. write_tree(tree, Target) #to get encoding table encode = huffman.make_encoding_table(tree) while True: # try EOFError try: # can read a byte ? reading = readingfile.readbits(8) except EOFError: # reach EOF encode eof,then get out of loop Target.writebit(0) Target.writebit(0) break #if no EOFError, get the sequence from tree using encoding table value = encode[reading] for v in value: # write v as a bit Target.writebit(v) Target.flush()
def compress(tree, uncompressed, compressed):
'''First write the given tree to the stream 'compressed' using the
write_tree function. Then use the same tree to encode the data
from the input stream 'uncompressed' and write it to 'compressed'.
If there are any partially-written bytes remaining at the end,
write 0 bits to form a complete byte.
Args:
tree: A Huffman tree.
uncompressed: A file stream from which you can read the input.
compressed: A file stream that will receive the tree description
and the coded input data.
'''
bitstream = bitio.BitWriter(compressed)
write_tree(tree, bitstream)
enc_table = huffman.make_encoding_table(tree) # Create encoding table
end_char = enc_table[None] # Get end char
input_stream = uncompressed.read(1) # Read inn one byte
while input_stream:
input_char = ord(input_stream) # Convert to binary
compressed_char = enc_table[input_char] # Get compressed byte
for bit in compressed_char: # Print the compressed byte
if bit:
bitstream.writebit(1)
else:
bitstream.writebit(0)
input_stream = uncompressed.read(1) # Read the next byte
# Print end bit
for bit in end_char:
if bit:
bitstream.writebit(1)
else:
bitstream.writebit(0)
bitstream.flush()
def compress(tree, uncompressed, compressed):
'''
First write the given tree to the stream 'compressed' using the
write_tree function. Then use the same tree to encode the data
from the input stream 'uncompressed' and write it to 'compressed'.
If there are any partially-written bytes remaining at the end,
write 0 bits to form a complete byte.
Flush the bitwriter after writing the entire compressed file.
Args:
tree: A Huffman tree.
uncompressed: A file stream from which you can read the input.
compressed: A file stream that will receive the tree description
and the coded input data.
'''
# The given tree is written to the compressed
write_tree(tree, compressed)
# The bit writer object is created
compressed_ = bitio.BitWriter(compressed)
# The bit reader object is created
uncompressed_ = bitio.BitReader(uncompressed)
# Encoding table is made here
encoding_table = huffman.make_encoding_table(tree)
flag1 = 1
while flag1 == 1:
# To catch the End of File error
try:
# Reading 8 bits (byte)
current_bits = uncompressed_.readbits(8)
# These are stored in an encoding table
compressed1 = encoding_table[current_bits]
for bits in compressed1:
compressed_.writebit(bits)
except EOFError:
for bits in encoding_table[None]:
compressed_.writebit(bits)
# Where the while loop will end
flag1 = 0
compressed_.flush()
