def readBits(self, address, nbits, endian):
assert endian in (BIG_ENDIAN, LITTLE_ENDIAN)
shift, data, missing = self.read(address, nbits)
if missing:
raise ReadStreamError(nbits, address)
value = str2long(data, endian)
if endian is BIG_ENDIAN:
value >>= len(data) * 8 - shift - nbits
else:
value >>= shift
return value & (1 << nbits) - 1
def readBits(self, address, nbits, endian):
assert endian in (BIG_ENDIAN, LITTLE_ENDIAN, MIDDLE_ENDIAN)
if endian is MIDDLE_ENDIAN:
# read an aligned chunk of words
wordaddr, remainder = divmod(address, 16)
wordnbits = alignValue(remainder+nbits, 16)
_, data, missing = self.read(wordaddr*16, wordnbits)
shift = remainder
else:
shift, data, missing = self.read(address, nbits)
if missing:
raise ReadStreamError(nbits, address)
value = str2long(data, endian)
if endian in (BIG_ENDIAN, MIDDLE_ENDIAN):
value >>= len(data) * 8 - shift - nbits
else:
value >>= shift
return value & (1 << nbits) - 1
def readBits(self, address, nbits, endian):
assert endian in (BIG_ENDIAN, LITTLE_ENDIAN, MIDDLE_ENDIAN)
if endian is MIDDLE_ENDIAN:
# read an aligned chunk of words
wordaddr, remainder = divmod(address, 16)
wordnbits = alignValue(remainder + nbits, 16)
_, data, missing = self.read(wordaddr * 16, wordnbits)
shift = remainder
else:
shift, data, missing = self.read(address, nbits)
if missing:
raise ReadStreamError(nbits, address)
value = str2long(data, endian)
if endian in (BIG_ENDIAN, MIDDLE_ENDIAN):
value >>= len(data) * 8 - shift - nbits
else:
value >>= shift
return value & (1 << nbits) - 1
def fixPNG(data):
# array -> str
data = data.tostring()
origdata = data
datalen = len(data)
data = StringIO(data)
data.seek(0)
data.write("\x89PNG\r\n\x1a\n")
index = 8
while index < (datalen-4):
data.seek(index)
size = str2long(data.read(4), BIG_ENDIAN)
chunksize = size+12
if datalen < (index+chunksize):
info("fixPNG: Skip invalid chunk at %s" % index)
break
crcofs = index+chunksize-4
data.seek(crcofs)
oldcrc = data.read(4)
data.seek(index+4)
o = data.tell()
crcdata = data.read(chunksize-8)
newcrc = long2raw(pngCRC32(crcdata), BIG_ENDIAN, 4)
data.seek(index+chunksize-4)
data.write(newcrc)
index += chunksize
data.seek(0,0)
data = data.read()
assert len(data) == len(origdata)
# str -> array
data = array('B', data)
return data
