Zerocode

zero encoding and decoding functions and a couple of useful functions from http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/510399

<python># From http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/510399

1. From http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/510399

def ByteToHex( byteStr ):

   """
   Convert a byte string to it's hex string representation e.g. for output.
   """
   
   # Uses list comprehension which is a fractionally faster implementation than
   # the alternative, more readable, implementation below
   #   
   #    hex = []
   #    for aChar in byteStr:
   #        hex.append( "%02X " % ord( aChar ) )
   #
   #    return .join( hex ).strip()        

   return .join( [ "%02X " % ord( x ) for x in byteStr ] ).strip()

def HexToByte( hexStr ):

   """
   Convert a string hex byte values into a byte string. The Hex Byte values may
   or may not be space separated.
   """
   # The list comprehension implementation is fractionally slower in this case    
   #
   #    hexStr = .join( hexStr.split(" ") )
   #    return .join( ["%c" % chr( int ( hexStr[i:i+2],16 ) ) \
   #                                   for i in range(0, len( hexStr ), 2) ] )

   bytes = []

   hexStr = .join( hexStr.split(" ") )

   for i in range(0, len(hexStr), 2):
       bytes.append( chr( int (hexStr[i:i+2], 16 ) ) )

   return .join( bytes )

def zero_encode(inputbuf):

   newstring =""
   zero = False
   zero_count = 0            
   for c in inputbuf:
       if c != '\0':
           if zero_count != 0:
               newstring = newstring + chr(zero_count)
               zero_count = 0
               zero = False

           newstring = newstring + c
           
       else:
           if zero == False:
               newstring = newstring + c
               zero = True
               
           zero_count = zero_count + 1
   if zero_count != 0:
       newstring = newstring + chr(zero_count)

   return newstring

def zero_decode(inputbuf):

   newstring =""
   in_zero = False
   for c in inputbuf:
       if c != '\0':
           if in_zero == True:
               zero_count = ord(c)
               zero_count = zero_count -1
               while zero_count>0:

                   newstring = newstring + '\0'
                   zero_count = zero_count -1
               in_zero = False
           else:
               newstring = newstring + c
       else:
           newstring = newstring + c
           in_zero = True
   return newstring

def zero_decode_ID(inputbuf):

   newstring =""
   in_zero = False
   #print "in encode, input is", ByteToHex(inputbuf)
   for c in inputbuf:
       if c != '\0':
           if in_zero == True:
               zero_count = ord(c)
               zero_count = zero_count -1
               while zero_count>0:

                   newstring = newstring + '\0'
                   zero_count = zero_count -1
               in_zero = False
           else:
               newstring = newstring + c
       else:
           newstring = newstring + c
           in_zero = True
   return newstring[:4]
               

</python>