src/nmutil/byterev.py

   1 from nmigen import Signal
   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         for i in range(j):
  16             dest = data_r.word_select(i, 8)
  17             src = data.word_select(j-1-i, 8)
  18             comb += dest.eq(src)
  19         return data_r
  20
  21     with m.Switch(length):
  22         for j in [1,2,4,8]:
  23             with m.Case(j):
  24                 for i in range(j):
  25                     dest = data_r.word_select(i, 8)
  26                     src = data.word_select(j-1-i, 8)
  27                     comb += dest.eq(src)
  28     return data_r
  29
  30