tmpinvert.c - plan9port - [fork] Plan 9 from user space
  HTML git clone git://src.adamsgaard.dk/plan9port
   DIR Log
   DIR Files
   DIR Refs
   DIR README
   DIR LICENSE
       ---
       tmpinvert.c (403B)
       ---
            1 #include "os.h"
            2 #include <mp.h>
            3 
            4 #define iseven(a)        (((a)->p[0] & 1) == 0)
            5 
            6 /* use extended gcd to find the multiplicative inverse */
            7 /* res = b**-1 mod m */
            8 void
            9 mpinvert(mpint *b, mpint *m, mpint *res)
           10 {
           11         mpint *dc1, *dc2;        /* don't care */
           12 
           13         dc1 = mpnew(0);
           14         dc2 = mpnew(0);
           15         mpextendedgcd(b, m, dc1, res, dc2);
           16         if(mpcmp(dc1, mpone) != 0)
           17                 abort();
           18         mpmod(res, m, res);
           19         mpfree(dc1);
           20         mpfree(dc2);
           21 }