nmigen/utils.py

   1 __all__ = ["log2_int", "bits_for"]
   2
   3
   4 def log2_int(n, need_pow2=True):
   5     if n == 0:
   6         return 0
   7     r = (n - 1).bit_length()
   8     if need_pow2 and (1 << r) != n:
   9         raise ValueError("{} is not a power of 2".format(n))
  10     return r
  11
  12
  13 def bits_for(n, require_sign_bit=False):
  14     if n > 0:
  15         r = log2_int(n + 1, False)
  16     else:
  17         require_sign_bit = True
  18         r = log2_int(-n, False)
  19     if require_sign_bit:
  20         r += 1
  21     return r