Package tlslite :: Package utils :: Module codec |
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# Source Code for Module tlslite.utils.codec

     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()
    88