src/third_party/tlslite/tlslite/utils/codec.py

   1 # Author: Trevor Perrin
   2 # See the LICENSE file for legal information regarding use of this file.
   3
   4 """Classes for reading/writing binary data (such as TLS records)."""
   5
   6 from .compat import *
   7
   8 class Writer(object):
   9     def __init__(self):
  10         self.bytes = bytearray(0)
  11
  12     def add(self, x, length):
  13         self.bytes += bytearray(length)
  14         newIndex = len(self.bytes) - 1
  15         for count in range(length):
  16             self.bytes[newIndex] = x & 0xFF
  17             x >>= 8
  18             newIndex -= 1
  19
  20     def addFixSeq(self, seq, length):
  21         for e in seq:
  22             self.add(e, length)
  23
  24     def addVarSeq(self, seq, length, lengthLength):
  25         self.add(len(seq)*length, lengthLength)
  26         for e in seq:
  27             self.add(e, length)
  28
  29 class Parser(object):
  30     def __init__(self, bytes):
  31         self.bytes = bytes
  32         self.index = 0
  33
  34     def get(self, length):
  35         if self.index + length > len(self.bytes):
  36             raise SyntaxError()
  37         x = 0
  38         for count in range(length):
  39             x <<= 8
  40             x |= self.bytes[self.index]
  41             self.index += 1
  42         return x
  43
  44     def getFixBytes(self, lengthBytes):
  45         bytes = self.bytes[self.index : self.index+lengthBytes]
  46         self.index += lengthBytes
  47         return bytes
  48
  49     def getVarBytes(self, lengthLength):
  50         lengthBytes = self.get(lengthLength)
  51         return self.getFixBytes(lengthBytes)
  52
  53     def getFixList(self, length, lengthList):
  54         l = [0] * lengthList
  55         for x in range(lengthList):
  56             l[x] = self.get(length)
  57         return l
  58
  59     def getVarList(self, length, lengthLength):
  60         lengthList = self.get(lengthLength)
  61         if lengthList % length != 0:
  62             raise SyntaxError()
  63         lengthList = lengthList // length
  64         l = [0] * lengthList
  65         for x in range(lengthList):
  66             l[x] = self.get(length)
  67         return l
  68
  69     def startLengthCheck(self, lengthLength):
  70         self.lengthCheck = self.get(lengthLength)
  71         self.indexCheck = self.index
  72
  73     def setLengthCheck(self, length):
  74         self.lengthCheck = length
  75         self.indexCheck = self.index
  76
  77     def stopLengthCheck(self):
  78         if (self.index - self.indexCheck) != self.lengthCheck:
  79             raise SyntaxError()
  80
  81     def atLengthCheck(self):
  82         if (self.index - self.indexCheck) < self.lengthCheck:
  83             return False
  84         elif (self.index - self.indexCheck) == self.lengthCheck:
  85             return True
  86         else:
  87             raise SyntaxError()