/* LibTomPoly, Polynomial Basis Math -- Tom St Denis  *  * LibTomPoly is a public domain library that provides * polynomial basis arithmetic support.  It relies on * LibTomMath for large integer support. * * This library is free for all purposes without any * express guarantee that it works. * * Tom St Denis, tomstdenis@iahu.ca, http://poly.libtomcrypt.org */#include <tompoly.h>/* returns the monic GCD only for GF(p^k)[x] */int pb_gcd(pb_poly *a, pb_poly *b, pb_poly *c){   pb_poly A, B, tmp;   int err;   if (mp_iszero(&(c->characteristic)) == MP_YES) {      return MP_VAL;   }   /* special cases (one or both are zero) */   if (a->used == 0 && b->used == 0) {      /* both zero, set to 1 */      pb_zero(c);      c->used = 1;      mp_set(&(c->terms[0]), 1);      return MP_OKAY;   } else if (a->used == 0) {      return pb_copy(b, c);   } else if (b->used == 0) {      return pb_copy(a, c);   }   if ((err = pb_init(&tmp, &(c->characteristic))) != MP_OKAY) {      return err;   }   if ((err = pb_init_copy(&A, a)) != MP_OKAY) {      goto __TMP;   }   if ((err = pb_init_copy(&B, b)) != MP_OKAY) {      goto __A;   }   while (B.used > 0) {       if ((err = pb_mod(&A, &B, &tmp)) != MP_OKAY) {          goto __B;       }       /* A = B, B = tmp */       if ((err = pb_copy(&B, &A)) != MP_OKAY) {          goto __B;       }       if ((err = pb_copy(&tmp, &B)) != MP_OKAY) {          goto __B;       }   }   /* ensure it's monic */   err = pb_monic(&A, c);__B  : pb_clear(&B);__A  : pb_clear(&A);__TMP: pb_clear(&tmp);   return err;}