ref: 29e8ea26f2f9af2b9924e16dffd784bc5ae5685e
dir: /sys/src/libmp/port/mpinvert.c/
#include "os.h" #include <mp.h> // use extended gcd to find the multiplicative inverse // res = b**-1 mod m void mpinvert(mpint *b, mpint *m, mpint *res) { mpint *v; v = mpnew(0); mpextendedgcd(b, m, v, res, nil); if(mpcmp(v, mpone) != 0) abort(); mpfree(v); mpmod(res, m, res); }