from array import array
'''
Description:
This library provide array of bit-stream.
Naming Rules:
Inner function/class start with _
Author:
Lanser
License:
GPL v1
'''
class BitArray(object):
'''
Bit array in which big-endian bytes stored.
*** Promise ***
This array start from index 1 instead of 0 for convenience.
'''
def __init__(self, initializer=None):
if initializer:
self.bytearray = array('B', initializer)
else:
self.bytearray = array('B')
self.remainder = 0
@staticmethod
def _getbit(byte, index):
return ((byte >> (7-index)) & 0x1)
@staticmethod
def _setbit(byte, index, bit):
if bit == 0:
byte &= ~(1 << index)
else:
byte |= 1 << index
return byte
@staticmethod
def _key(len, key):
if not isinstance(key, int):
raise TypeError
if key == 0:
raise IndexError
if key > 0 and len < key:
raise IndexError
else:
key -= 1
return key
if key < 0 and len < -key:
raise IndexError
else:
key = len + key
return key
@staticmethod
def MakeByte(bits):
''' reform sliced bits as byte, i.e PID '''
result = 0
offset = 0
for i in reversed(bits):
result |= (i << offset)
offset += 1
return result
def __str__(self):
print ('%02X ' * len(self.bytearray)) % tuple(self.bytearray)
def __len__(self):
if self.remainder == 0:
return len(self.bytearray)*8 + self.remainder
else:
return (len(self.bytearray)-1)*8 + self.remainder
def __getitem__(self, key):
key = self._key(self.__len__(), key)
remainder = key % 8
index = key / 8
return self._getbit(self.bytearray[index], remainder)
def __setitem__(self, key, value):
assert value == 0 or value == 1, 'bit value should be 0 or 1'
key = self._key(self.__len__(), key)
remainder = key % 8
index = key / 8
self.bytearray[index] = \
self._setbit(self.bytearray[index], 7-remainder, value)
def __delitem__(self, key):
assert False, 'NOT support del method yet'
def __getslice__(self, start, stop):
''' it should be optimize as byte + bits '''
result = []
index = range(start, stop)
for i in index:
result.append(self[i])
return result
def __setslice__(self, start, stop, value):
''' it should be optimize as byte + bits '''
if len(value) == 1:
index = range(start, stop)
for i in index:
self[i] = value
else:
assert len(value) == stop-start, 'value must map to index'
if isinstance(value, str):
value = map(lambda x:int(x), value)
for i in range(0, stop-start):
self[start+i] = value[i]
class _Iterator(object):
def __init__(self, sequence, index=0):
self.seq = sequence
self.index = index
def __iter__(self):
return self
def next(self):
if self.index > len(self.seq):
raise StopIteration
else:
result = self.seq[self.index]
self.index += 1
return result
def __iter__(self):
return self._Iterator(self, 1)
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