Viewing file:  codec.py (2.71 KB) -rw-r--r--
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"""Classes for reading/writing binary data (such as TLS records)."""
from compat import *
class Writer:
def __init__(self, length=0):
#If length is zero, then this is just a "trial run" to determine length
self.index = 0
self.bytes = createByteArrayZeros(length)
def add(self, x, length):
if self.bytes:
newIndex = self.index+length-1
while newIndex >= self.index:
self.bytes[newIndex] = x & 0xFF
x >>= 8
newIndex -= 1
self.index += length
def addFixSeq(self, seq, length):
if self.bytes:
for e in seq:
self.add(e, length)
else:
self.index += len(seq)*length
def addVarSeq(self, seq, length, lengthLength):
if self.bytes:
self.add(len(seq)*length, lengthLength)
for e in seq:
self.add(e, length)
else:
self.index += lengthLength + (len(seq)*length)
class Parser:
def __init__(self, bytes):
self.bytes = bytes
self.index = 0
def get(self, length):
if self.index + length > len(self.bytes):
raise SyntaxError()
x = 0
for count in range(length):
x <<= 8
x |= self.bytes[self.index]
self.index += 1
return x
def getFixBytes(self, lengthBytes):
bytes = self.bytes[self.index : self.index+lengthBytes]
self.index += lengthBytes
return bytes
def getVarBytes(self, lengthLength):
lengthBytes = self.get(lengthLength)
return self.getFixBytes(lengthBytes)
def getFixList(self, length, lengthList):
l = [0] * lengthList
for x in range(lengthList):
l[x] = self.get(length)
return l
def getVarList(self, length, lengthLength):
lengthList = self.get(lengthLength)
if lengthList % length != 0:
raise SyntaxError()
lengthList = int(lengthList/length)
l = [0] * lengthList
for x in range(lengthList):
l[x] = self.get(length)
return l
def startLengthCheck(self, lengthLength):
self.lengthCheck = self.get(lengthLength)
self.indexCheck = self.index
def setLengthCheck(self, length):
self.lengthCheck = length
self.indexCheck = self.index
def stopLengthCheck(self):
if (self.index - self.indexCheck) != self.lengthCheck:
raise SyntaxError()
def atLengthCheck(self):
if (self.index - self.indexCheck) < self.lengthCheck:
return False
elif (self.index - self.indexCheck) == self.lengthCheck:
return True
else:
raise SyntaxError()
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