def decode(self):
if len(self) == 0:
return ''
# get the string buffer and reverse its bytes
buf = ''.join([c for c in reversed(self())])
buflen = len(buf)*8
# use shtr to shift the string buffer
buf = shtr(buf)
# count number of chars and remove padding bits
chars_num = buflen//7
buf = buf << buflen - (7*chars_num)
# consume 7 bit by 7 bit
chars = []
for i in range(chars_num):
chars.append(buf.left_val(7))
buf = buf << 7
# revert back the list of decoded character and return it
chars.reverse()
return ''.join(map(chr, chars))
def map(self, string='', byte_offset=0):
# pop each member of the initial csn1List
# and see what we have
# 1) CSN1FIELD -> map it directly
# 2) dict -> conditions -> CSN1FIELD | dict | tuple
# 3) tuple -> CSN1FIELD | dict
# consume the string buffer bit per bit depending of the
# csn1List member poped
#
# as a CSN1 field does not always start on a byte limit,
# we need to keep track of the byte offset,
# for solving padding (L | H) adequately
#
# in case CSN1 list is empty
if len(self.csn1List) == 0:
return
# initialize the string buffer to be mapped
self.BUF, self._buflen = shtr(string), len(string)*8
self._consumed, self._offset, self._map_exit = 0, byte_offset, False
self.elementList = []
#
# MAIN loop
# go over the string, bit per bit
index = 0
while (self._consumed + self._offset) < self._buflen:
if self._map_exit:
break
# get csn1 fields 1 by 1
self._eval_csn1(self.csn1List[index])
index += 1
# when csn1List is empty, finish with padding
if index >= len(self.csn1List):
break
#
# TODO: the padding should only be done when instructed so in CSN1
remaining = self._buflen - (self._consumed + self._offset)
if remaining:
if self.dbg >= DBG:
log(DBG, '(CSN1._eval_csn1_dict) bits are remaining unmapped')
# clean temporary data
del self.BUF, self._buflen, self._consumed, \
self._offset, self._map_exit
