+
+ ap=a->d;
+ bp=b->d;
+ rp=r->d;
+
+ carry=bn_add_words(rp,ap,bp,min);
+ rp+=min;
+ ap+=min;
+ bp+=min;
+
+ if (carry)
+ {
+ while (dif)
+ {
+ dif--;
+ t1 = *(ap++);
+ t2 = (t1+1) & BN_MASK2;
+ *(rp++) = t2;
+ if (t2)
+ {
+ carry=0;
+ break;
+ }
+ }
+ if (carry)
+ {
+ /* carry != 0 => dif == 0 */
+ *rp = 1;
+ r->top++;
+ }
+ }
+ if (dif && rp != ap)
+ while (dif--)
+ /* copy remaining words if ap != rp */
+ *(rp++) = *(ap++);
+ r->neg = 0;
+ bn_check_top(r);
+ return 1;
+ }
+
+/* unsigned subtraction of b from a, a must be larger than b. */
+int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
+ {
+ int max,min,dif;
+ register BN_ULONG t1,t2,*ap,*bp,*rp;
+ int i,carry;
+#if defined(IRIX_CC_BUG) && !defined(LINT)
+ int dummy;
+#endif
+
+ bn_check_top(a);
+ bn_check_top(b);
+
+ max = a->top;
+ min = b->top;
+ dif = max - min;
+
+ if (dif < 0) /* hmm... should not be happening */
+ {
+ BNerr(BN_F_BN_USUB,BN_R_ARG2_LT_ARG3);
+ return(0);
+ }
+
+ if (bn_wexpand(r,max) == NULL) return(0);
+