src/nmutil/byterev.py

   1 from nmigen import Signal, Cat
   2
   3 # TODO: turn this into a module
   4 def byte_reverse(m, name, data, length):
   5     """byte_reverse: unlike nmigen word_select this takes a dynamic length
   6
   7     nmigen Signal.word_select may only take a fixed length.  we need
   8     bigendian byte-reverse, half-word reverse, word and dword reverse.
   9     """
  10     comb = m.d.comb
  11     data_r = Signal.like(data, name=name)
  12
  13     if isinstance(length, int):
  14         j = length
  15         rev = []
  16         for i in range(j):
  17             dest = data_r.word_select(i, 8)
  18             res.append(data.word_select(j-1-i, 8))
  19         comb += data_r.eq(Cat(*rev))
  20         return data_r
  21
  22     with m.Switch(length):
  23         for j in [1,2,4,8]:
  24             with m.Case(j):
  25                 rev = []
  26                 for i in range(j):
  27                     rev.append(data.word_select(j-1-i, 8))
  28                 comb += data_r.eq(Cat(*rev))
  29     return data_r
  30
  31