1 "Collection of tools for displaying bit representation of numbers.""" 2 3 import StringIO 4 5 def binary(n, width=None): 6 """ 7 Return a list of (0|1)'s for the binary representation of n where n >= 0. 8 If you specify a width, it must be > 0, otherwise it is ignored. The list 9 could be padded with 0 bits if width is specified. 10 """ 11 l = [] 12 if width and width <= 0: 13 width = None 14 while n > 0: 15 l.append(1 if n&1 else 0) 16 n = n >> 1 17 18 if width: 19 for i in range(width - len(l)): 20 l.append(0) 21 22 l.reverse() 23 return l 24 25 def twos_complement(n, width): 26 """ 27 Return a list of (0|1)'s for the binary representation of a width-bit two's 28 complement numeral system of an integer n which may be negative. 29 """ 30 val = 2**(width-1) 31 if n >= 0: 32 if n > (val-1): 33 return None 34 # It is safe to represent n with width-bits. 35 return binary(n, width) 36 37 if n < 0: 38 if abs(n) > val: 39 return None 40 # It is safe to represent n (a negative int) with width-bits. 41 return binary(val*2 - abs(n)) 42 43 # print binary(0xABCD) 44 # [1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1] 45 # print binary(0x1F, 8) 46 # [0, 0, 0, 1, 1, 1, 1, 1] 47 # print twos_complement(-5, 4) 48 # [1, 0, 1, 1] 49 # print twos_complement(7, 4) 50 # [0, 1, 1, 1] 51 # print binary(7) 52 # [1, 1, 1] 53 # print twos_complement(-5, 64) 54 # [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1] 55 56 def positions(width): 57 """Helper function returning a list describing the bit positions. 58 Bit positions greater than 99 are truncated to 2 digits, for example, 59 100 -> 00 and 127 -> 27.""" 60 return ['{0:2}'.format(i)[-2:] for i in reversed(range(width))] 61 62 63 def utob(debugger, command_line, result, dict): 64 """Convert the unsigned integer to print its binary representation. 65 args[0] (mandatory) is the unsigned integer to be converted 66 args[1] (optional) is the bit width of the binary representation 67 args[2] (optional) if specified, turns on verbose printing""" 68 args = command_line.split() 69 try: 70 n = int(args[0], 0) 71 width = None 72 if len(args) > 1: 73 width = int(args[1], 0) 74 if width < 0: 75 width = 0 76 except: 77 print utob.__doc__ 78 return 79 80 if len(args) > 2: 81 verbose = True 82 else: 83 verbose = False 84 85 bits = binary(n, width) 86 if not bits: 87 print "insufficient width value: %d" % width 88 return 89 if verbose and width > 0: 90 pos = positions(width) 91 print ' '+' '.join(pos) 92 print ' %s' % str(bits) 93 94 def itob(debugger, command_line, result, dict): 95 """Convert the integer to print its two's complement representation. 96 args[0] (mandatory) is the integer to be converted 97 args[1] (mandatory) is the bit width of the two's complement representation 98 args[2] (optional) if specified, turns on verbose printing""" 99 args = command_line.split() 100 try: 101 n = int(args[0], 0) 102 width = int(args[1], 0) 103 if width < 0: 104 width = 0 105 except: 106 print itob.__doc__ 107 return 108 109 if len(args) > 2: 110 verbose = True 111 else: 112 verbose = False 113 114 bits = twos_complement(n, width) 115 if not bits: 116 print "insufficient width value: %d" % width 117 return 118 if verbose and width > 0: 119 pos = positions(width) 120 print ' '+' '.join(pos) 121 print ' %s' % str(bits) 122 123
