src/nmutil/divmod.py

   1 """
   2     This work is funded through NLnet under Grant 2019-02-012
   3
   4     License: LGPLv3+
   5
   6
   7 """
   8
   9 from copy import copy
  10 # this is a POWER ISA 3.0B compatible *signed* div function
  11 # however it is also the c, c++, rust, java *and* x86 way of doing things
  12
  13
  14 def trunc_divs(n, d):
  15     abs_n = abs(n.to_signed_int())
  16     abs_d = abs(d.to_signed_int())
  17     print("trunc_div n", abs_n, n.to_signed_int())
  18     print("trunc_div d", abs_d, d.to_signed_int())
  19     abs_q = abs_n // abs_d
  20     sign_n = n.value & (1 << (n.bits - 1)) != 0
  21     sign_d = d.value & (1 << (d.bits - 1)) != 0
  22     print("trunc_div", hex(n.value), hex(d.value),
  23           hex(abs_n), hex(abs_d), hex(abs_q),
  24           sign_n, sign_d)
  25     res = copy(n)
  26     if (sign_n == sign_d):
  27         res.value = abs_q
  28         if res.value & (1 << (res.bits - 1)) != 0:
  29             # result should be positive but is negative
  30             raise OverflowError()
  31         return res
  32     mask = (1 << res.bits) - 1
  33     res.value = (-abs_q) & mask
  34
  35     return res
  36
  37
  38 # this is a POWER ISA 3.0B compatible *signed* mod / remainder function
  39 # however it is also the c, c++, rust, java *and* x86 way of doing things
  40 def trunc_rems(n, d):
  41     m = d * trunc_divs(n, d)
  42
  43     # cheat - really shouldn't do this. mul returns full length
  44     m.bits = n.bits
  45     return n - m