Hello Derfel,
I have a file of binary data. I want to read this file and parse the data in
it. The format of the file is:
8 bits number of data pakets
6 bits offset
20 bits time
8 states
How can I read this fields in binary? I see the struct module and the
binascii, but I can't split the diferent fiels.
--- bitter.py ---
# Testing
'''
b = BitStream(chr(i nt("10111010", 2)))
b.get_bits(3)
5 b.get_bits(2)
3 b.get_bits(3)
2 b.get_bits(0)
0 b.get_bits(1)
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "/tmp/bitter.py", line 27, in get_bits
raise EOFError
EOFError
'''
from array import array
class BitStream:
'''Bit stream implementation' ''
def __init__(self, data):
self.arr = array("c", data)
self.bit = 0 # Current output bit
def get_bits(self, count):
'''Get `count' bits from stream'''
if count == 0: # Nothing to get
return 0
if not self.arr: # EOF
raise EOFError
value = 0
for c in range(count):
if not self.arr: # EOF
raise EOFError
value <<= 1
shifted = ord(self.arr[0]) >> (8 - self.bit - 1)
value |= (shifted & 1)
self.bit += 1
if self.bit == 8: # Get new byte
self.arr.pop(0)
self.bit = 0
return value
def _test():
from doctest import testmod
import bitter
testmod(bitter)
if __name__ == "__main__":
_test()
--- bitter.py ---
HTH.
Miki
