src/soc/decoder/selectable_int.py

   1 import unittest
   2
   3
   4 class SelectableInt:
   5     def __init__(self, value, bits):
   6         mask = (1 << bits) - 1
   7         self.value = value & mask
   8         self.bits = bits
   9
  10     def __add__(self, b):
  11         assert b.bits == self.bits
  12         return SelectableInt(self.value + b.value, self.bits)
  13
  14     def __sub__(self, b):
  15         assert b.bits == self.bits
  16         return SelectableInt(self.value - b.value, self.bits)
  17
  18     def __mul__(self, b):
  19         assert b.bits == self.bits
  20         return SelectableInt(self.value * b.value, self.bits)
  21
  22     def __or__(self, b):
  23         assert b.bits == self.bits
  24         return SelectableInt(self.value | b.value, self.bits)
  25
  26     def __and__(self, b):
  27         assert b.bits == self.bits
  28         return SelectableInt(self.value & b.value, self.bits)
  29
  30     def __xor__(self, b):
  31         assert b.bits == self.bits
  32         return SelectableInt(self.value ^ b.value, self.bits)
  33
  34     def __invert__(self):
  35         return SelectableInt(~self.value, self.bits)
  36
  37     def __neg__(self):
  38         return SelectableInt(~self.value + 1, self.bits)
  39
  40     def __getitem__(self, key):
  41         if isinstance(key, int):
  42             assert key < self.bits, "key %d accessing %d" % (key, self.bits)
  43             assert key >= 0
  44             key = self.bits - (key + 1)
  45
  46             value = (self.value >> key) & 1
  47             return SelectableInt(value, 1)
  48         elif isinstance(key, slice):
  49             assert key.step is None or key.step == 1
  50             assert key.start < key.stop
  51             assert key.start >= 0
  52             assert key.stop <= self.bits
  53
  54             stop = self.bits - key.start
  55             start = self.bits - key.stop
  56
  57             bits = stop - start
  58             mask = (1 << bits) - 1
  59             value = (self.value >> start) & mask
  60             return SelectableInt(value, bits)
  61
  62     def __setitem__(self, key, value):
  63         if isinstance(key, int):
  64             assert key < self.bits
  65             assert key >= 0
  66             key = self.bits - (key + 1)
  67             if isinstance(value, SelectableInt):
  68                 assert value.bits == 1
  69                 value = value.value
  70
  71             value = value << key
  72             mask = 1 << key
  73             self.value = (self.value & ~mask) | (value & mask)
  74         elif isinstance(key, slice):
  75             assert key.step is None or key.step == 1
  76             assert key.start < key.stop
  77             assert key.start >= 0
  78             assert key.stop <= self.bits
  79
  80             stop = self.bits - key.start
  81             start = self.bits - key.stop
  82
  83             bits = stop - start
  84             if isinstance(value, SelectableInt):
  85                 assert value.bits == bits
  86                 value = value.value
  87             mask = ((1 << bits) - 1) << start
  88             value = value << start
  89             self.value = (self.value & ~mask) | (value & mask)
  90
  91     def __eq__(self, other):
  92         if isinstance(other, SelectableInt):
  93             return other.value == self.value and other.bits == self.bits
  94         if isinstance(other, int):
  95             return other == self.value
  96         assert False
  97
  98     def __repr__(self):
  99         return "SelectableInt(value={:x}, bits={})".format(self.value,
 100                                                            self.bits)
 101
 102
 103 class SelectableIntTestCase(unittest.TestCase):
 104     def test_arith(self):
 105         a = SelectableInt(5, 8)
 106         b = SelectableInt(9, 8)
 107         c = a + b
 108         d = a - b
 109         e = a * b
 110         f = -a
 111         self.assertEqual(c.value, a.value + b.value)
 112         self.assertEqual(d.value, (a.value - b.value) & 0xFF)
 113         self.assertEqual(e.value, (a.value * b.value) & 0xFF)
 114         self.assertEqual(f.value, (-a.value) & 0xFF)
 115         self.assertEqual(c.bits, a.bits)
 116         self.assertEqual(d.bits, a.bits)
 117         self.assertEqual(e.bits, a.bits)
 118
 119     def test_logic(self):
 120         a = SelectableInt(0x0F, 8)
 121         b = SelectableInt(0xA5, 8)
 122         c = a & b
 123         d = a | b
 124         e = a ^ b
 125         f = ~a
 126         self.assertEqual(c.value, a.value & b.value)
 127         self.assertEqual(d.value, a.value | b.value)
 128         self.assertEqual(e.value, a.value ^ b.value)
 129         self.assertEqual(f.value, 0xF0)
 130
 131
 132     def test_get(self):
 133         a = SelectableInt(0xa2, 8)
 134         # These should be big endian
 135         self.assertEqual(a[7], 0)
 136         self.assertEqual(a[0:4], 10)
 137         self.assertEqual(a[4:8], 2)
 138
 139     def test_set(self):
 140         a = SelectableInt(0x5, 8)
 141         a[7] = SelectableInt(0, 1)
 142         self.assertEqual(a, 4)
 143         a[4:8] = 9
 144         self.assertEqual(a, 9)
 145         a[0:4] = 3
 146         self.assertEqual(a, 0x39)
 147         a[0:4] = a[4:8]
 148         self.assertEqual(a, 0x99)
 149
 150
 151 if __name__ == "__main__":
 152     unittest.main()