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

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