src/soc/decoder/selectable_int.py

   1 import unittest
   2 from copy import copy
   3
   4
   5 class SelectableInt:
   6     def __init__(self, value, bits):
   7         mask = (1 << bits) - 1
   8         self.value = value & mask
   9         self.bits = bits
  10
  11     def __add__(self, b):
  12         assert b.bits == self.bits
  13         return SelectableInt(self.value + b.value, self.bits)
  14
  15     def __sub__(self, b):
  16         assert b.bits == self.bits
  17         return SelectableInt(self.value - b.value, self.bits)
  18
  19     def __mul__(self, b):
  20         assert b.bits == self.bits
  21         return SelectableInt(self.value * b.value, self.bits)
  22
  23     def __or__(self, b):
  24         assert b.bits == self.bits
  25         return SelectableInt(self.value | b.value, self.bits)
  26
  27     def __and__(self, b):
  28         assert b.bits == self.bits
  29         return SelectableInt(self.value & b.value, self.bits)
  30
  31     def __xor__(self, b):
  32         assert b.bits == self.bits
  33         return SelectableInt(self.value ^ b.value, self.bits)
  34
  35     def __invert__(self):
  36         return SelectableInt(~self.value, self.bits)
  37
  38     def __neg__(self):
  39         return SelectableInt(~self.value + 1, self.bits)
  40
  41     def __getitem__(self, key):
  42         if isinstance(key, int):
  43             assert key < self.bits, "key %d accessing %d" % (key, self.bits)
  44             assert key >= 0
  45             key = self.bits - (key + 1)
  46
  47             value = (self.value >> key) & 1
  48             return SelectableInt(value, 1)
  49         elif isinstance(key, slice):
  50             assert key.step is None or key.step == 1
  51             assert key.start < key.stop
  52             assert key.start >= 0
  53             assert key.stop <= self.bits
  54
  55             stop = self.bits - key.start
  56             start = self.bits - key.stop
  57
  58             bits = stop - start + 1
  59             mask = (1 << bits) - 1
  60             value = (self.value >> start) & mask
  61             return SelectableInt(value, bits)
  62
  63     def __setitem__(self, key, value):
  64         if isinstance(key, int):
  65             assert key < self.bits
  66             assert key >= 0
  67             key = self.bits - (key + 1)
  68             if isinstance(value, SelectableInt):
  69                 assert value.bits == 1
  70                 value = value.value
  71
  72             value = value << key
  73             mask = 1 << key
  74             self.value = (self.value & ~mask) | (value & mask)
  75         elif isinstance(key, slice):
  76             assert key.step is None or key.step == 1
  77             assert key.start < key.stop
  78             assert key.start >= 0
  79             assert key.stop <= self.bits
  80
  81             stop = self.bits - key.start
  82             start = self.bits - key.stop
  83
  84             bits = stop - start + 1
  85             if isinstance(value, SelectableInt):
  86                 assert value.bits == bits, "%d into %d" % (value.bits, bits)
  87                 value = value.value
  88             mask = ((1 << bits) - 1) << start
  89             value = value << start
  90             self.value = (self.value & ~mask) | (value & mask)
  91
  92     def __eq__(self, other):
  93         if isinstance(other, SelectableInt):
  94             return other.value == self.value and other.bits == self.bits
  95         if isinstance(other, int):
  96             return other == self.value
  97         assert False
  98
  99     def __repr__(self):
 100         return "SelectableInt(value={:x}, bits={})".format(self.value,
 101                                                            self.bits)
 102
 103 # XXX this probably isn't needed...
 104 def selectassign(lhs, idx, rhs):
 105     if isinstance(idx, tuple):
 106         if len(idx) == 2:
 107             lower, upper = idx
 108             step = None
 109         else:
 110             lower, upper, step = idx
 111         toidx = range(lower, upper, step)
 112         fromidx = range(0, upper-lower, step) # XXX eurgh...
 113     else:
 114         toidx = [idx]
 115         fromidx = [0]
 116     for t, f in zip(toidx, fromidx):
 117         lhs[t] = rhs[f]
 118
 119
 120 def selectconcat(*args):
 121     res = copy(args[0])
 122     for i in args[1:]:
 123         assert isinstance(i, SelectableInt), "can only concat SIs, sorry"
 124         res.bits += i.bits
 125         res.value = (res.value << i.bits) | i.value
 126     return res
 127
 128
 129 class SelectableIntTestCase(unittest.TestCase):
 130     def test_arith(self):
 131         a = SelectableInt(5, 8)
 132         b = SelectableInt(9, 8)
 133         c = a + b
 134         d = a - b
 135         e = a * b
 136         f = -a
 137         self.assertEqual(c.value, a.value + b.value)
 138         self.assertEqual(d.value, (a.value - b.value) & 0xFF)
 139         self.assertEqual(e.value, (a.value * b.value) & 0xFF)
 140         self.assertEqual(f.value, (-a.value) & 0xFF)
 141         self.assertEqual(c.bits, a.bits)
 142         self.assertEqual(d.bits, a.bits)
 143         self.assertEqual(e.bits, a.bits)
 144
 145     def test_logic(self):
 146         a = SelectableInt(0x0F, 8)
 147         b = SelectableInt(0xA5, 8)
 148         c = a & b
 149         d = a | b
 150         e = a ^ b
 151         f = ~a
 152         self.assertEqual(c.value, a.value & b.value)
 153         self.assertEqual(d.value, a.value | b.value)
 154         self.assertEqual(e.value, a.value ^ b.value)
 155         self.assertEqual(f.value, 0xF0)
 156
 157
 158     def test_get(self):
 159         a = SelectableInt(0xa2, 8)
 160         # These should be big endian
 161         self.assertEqual(a[7], 0)
 162         self.assertEqual(a[0:4], 10)
 163         self.assertEqual(a[4:8], 2)
 164
 165     def test_set(self):
 166         a = SelectableInt(0x5, 8)
 167         a[7] = SelectableInt(0, 1)
 168         self.assertEqual(a, 4)
 169         a[4:8] = 9
 170         self.assertEqual(a, 9)
 171         a[0:4] = 3
 172         self.assertEqual(a, 0x39)
 173         a[0:4] = a[4:8]
 174         self.assertEqual(a, 0x199)
 175
 176 if __name__ == "__main__":
 177     unittest.main()