def flip_bit(good, which):
"""Flip the low-order bit of good[which]."""
if which == -1:
pieces = good[:which], good[-1:], b""
else:
pieces = good[:which], good[which:which + 1], good[which + 1:]
return pieces[0] + bchr(ord(pieces[1]) ^ 0x01) + pieces[2]
def flip_one_bit(s, offset=0, size=None):
""" flip one random bit of the string s, in a byte greater than or equal to offset and less
than offset+size. """
precondition(isinstance(s, binary_type))
if size is None:
size=len(s)-offset
i = randrange(offset, offset+size)
result = s[:i] + bchr(bord(s[i])^(0x01<<randrange(0, 8))) + s[i+1:]
assert result != s, "Internal error -- flip_one_bit() produced the same string as its input: %s == %s" % (result, s)
return result
def flip_bit(start, end):
offset = random.randrange(start, end)
bit = random.randrange(0, 8)
print("[%d..%d): %d.b%d" % (start, end, offset, bit), file=out)
f = open(fn, "rb+")
f.seek(offset)
d = f.read(1)
d = bchr(ord(d) ^ 0x01)
f.seek(offset)
f.write(d)
f.close()
def serialize(obj):
def serialize_int(i):
# make sure i is non negative
i = abs(i)
def int_bytes(i):
rest = True
while rest:
lower = i & 0x7f
rest = i >> 7
yield lower | (0x80 if rest else 0)
i = rest
return ibytes(int_bytes(i))
if obj is None:
return bchr(SerialConstants.SO_NULL)
if isinstance(obj, unicode):
return b''.join([
bchr(SerialConstants.SO_STRING),
serialize_int(len(obj)),
bytes(obj, 'utf-8')
])
if isinstance(obj, int):
return b''.join([
bchr(SerialConstants.SO_POS_INTEGER)
if obj >= 0 else bchr(SerialConstants.SO_NEG_INTEGER),
serialize_int(obj)
])
try:
# Byte vector
if obj.typecode == b'b':
return b''.join([
bchr(SerialConstants.SO_BYTEVECTOR),
serialize_int(len(obj)),
obj.tostring()
])
except:
pass
try:
iobj = iter(obj)
return b''.join([
bchr(SerialConstants.SO_VECTOR),
serialize_int(len(obj)),
b''.join([serialize(elem) for elem in iobj])
])
except:
pass
raise TypeError("cannot serialize object of type %s" % type(obj))
def serialize(obj):
def serialize_int(i):
# make sure i is non negative
i = abs(i)
def int_bytes(i):
rest = True
while rest:
lower = i & 0x7f
rest = i >> 7
yield lower | (0x80 if rest else 0)
i = rest
return ibytes(int_bytes(i))
if obj is None:
return bchr(SerialConstants.SO_NULL)
if isinstance(obj, unicode):
return b''.join([bchr(SerialConstants.SO_STRING), serialize_int(len(obj)),
bytes(obj, 'utf-8')])
if isinstance(obj, int):
return b''.join([bchr(SerialConstants.SO_POS_INTEGER) if obj >= 0 else
bchr(SerialConstants.SO_NEG_INTEGER), serialize_int(obj)])
try:
# Byte vector
if obj.typecode == b'b':
return b''.join([bchr(SerialConstants.SO_BYTEVECTOR),
serialize_int(len(obj)), obj.tostring()])
except:
pass
try:
iobj = iter(obj)
return b''.join([bchr(SerialConstants.SO_VECTOR),
serialize_int(len(obj)),
b''.join([serialize(elem) for elem in iobj])])
except:
pass
raise TypeError("cannot serialize object of type %s" % type(obj))
def add_two(original, byte_offset):
# It isn't enough to simply flip the bit for the version number,
# because 1 is a valid version number. So we add two instead.
return (original[:byte_offset] +
bchr(ord(original[byte_offset:byte_offset + 1]) ^ 0x02) +
original[byte_offset + 1:])
def flip_bit(original, byte_offset):
return (original[:byte_offset] +
bchr(ord(original[byte_offset:byte_offset + 1]) ^ 0x01) +
original[byte_offset + 1:])
def _randbytes(length):
# type: (int) -> bytes
"""Return random bytes string of given length."""
return b"".join([bchr(_RANDOM.randrange(0, 256)) for _ in range(length)])
