mpow.cpp

   1 // Bignum power
   2
   3 #include "stdafx.h"
   4 #include "defs.h"
   5
   6 unsigned int *
   7 mpow(unsigned int *a, unsigned int n)
   8 {
   9         unsigned int *aa, *t;
  10
  11         a = mcopy(a);
  12
  13         aa = mint(1);
  14
  15         for (;;) {
  16
  17                 if (n & 1) {
  18                         t = mmul(aa, a);
  19                         mfree(aa);
  20                         aa = t;
  21                 }
  22
  23                 n >>= 1;
  24
  25                 if (n == 0)
  26                         break;
  27
  28                 t = mmul(a, a);
  29                 mfree(a);
  30                 a = t;
  31         }
  32
  33         mfree(a);
  34
  35         return aa;
  36 }