Add "dif" variable to clean up the loop implementations.

Submitted by: Nils Larsch

diff --git a/crypto/bn/bn_add.c b/crypto/bn/bn_add.c
index a13b8a11cb85e33f3fc8c29e95d212a4b2de1a80..9405163706aae5dc8064780a2ce879fece80ccdf 100644 (file)
--- a/crypto/bn/bn_add.c
+++ b/crypto/bn/bn_add.c
@@ -64,7 +64,7 @@
 int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
        {
        const BIGNUM *tmp;
-       int a_neg = a->neg;
+       int a_neg = a->neg, ret;
 
        bn_check_top(a);
        bn_check_top(b);
@@ -95,21 +95,17 @@ int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
                return(1);
                }
 
-       if (!BN_uadd(r,a,b)) return(0);
-       if (a_neg) /* both are neg */
-               r->neg=1;
-       else
-               r->neg=0;
+       ret = BN_uadd(r,a,b);
+       r->neg = a_neg;
        bn_check_top(r);
-       return(1);
+       return ret;
        }
 
-/* unsigned add of b to a, r must be large enough */
+/* unsigned add of b to a */
 int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
        {
-       register int i;
-       int max,min;
-       BN_ULONG *ap,*bp,*rp,carry,t1;
+       int max,min,dif;
+       BN_ULONG *ap,*bp,*rp,carry,t1,t2;
        const BIGNUM *tmp;
 
        bn_check_top(a);
@@ -117,11 +113,12 @@ int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
 
        if (a->top < b->top)
                { tmp=a; a=b; b=tmp; }
-       max=a->top;
-       min=b->top;
+       max = a->top;
+       min = b->top;
+       dif = max - min;
 
        if (bn_wexpand(r,max+1) == NULL)
-               return(0);
+               return 0;
 
        r->top=max;
 
@@ -129,47 +126,46 @@ int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
        ap=a->d;
        bp=b->d;
        rp=r->d;
-       carry=0;
 
        carry=bn_add_words(rp,ap,bp,min);
        rp+=min;
        ap+=min;
        bp+=min;
-       i=min;
 
        if (carry)
                {
-               while (i < max)
+               while (dif)
                        {
-                       i++;
-                       t1= *(ap++);
-                       if ((*(rp++)=(t1+1)&BN_MASK2) >= t1)
+                       dif--;
+                       t1 = *(ap++);
+                       t2 = (t1+1) & BN_MASK2;
+                       *(rp++) = t2;
+                       if (t2)
                                {
                                carry=0;
                                break;
                                }
                        }
-               if ((i >= max) && carry)
+               if (carry)
                        {
-                       *(rp++)=1;
+                       /* carry != 0 => dif == 0 */
+                       *rp = 1;
                        r->top++;
                        }
                }
-       if (rp != ap)
-               {
-               for (; i<max; i++)
-                       *(rp++)= *(ap++);
-               }
-       /* memcpy(rp,ap,sizeof(*ap)*(max-i));*/
+       if (dif && rp != ap)
+               while (dif--)
+                       /* copy remaining words if ap != rp */
+                       *(rp++) = *(ap++);
        r->neg = 0;
        bn_check_top(r);
-       return(1);
+       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;
+       int max,min,dif;
        register BN_ULONG t1,t2,*ap,*bp,*rp;
        int i,carry;
 #if defined(IRIX_CC_BUG) && !defined(LINT)
@@ -179,14 +175,16 @@ int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
        bn_check_top(a);
        bn_check_top(b);
 
-       if (a->top < b->top) /* hmm... should not be happening */
+       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);
                }
 
-       max=a->top;
-       min=b->top;
        if (bn_wexpand(r,max) == NULL) return(0);
 
        ap=a->d;
@@ -195,7 +193,7 @@ int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
 
 #if 1
        carry=0;
-       for (i=0; i<min; i++)
+       for (i = min; i != 0; i--)
                {
                t1= *(ap++);
                t2= *(bp++);
@@ -219,17 +217,20 @@ int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
        ap+=min;
        bp+=min;
        rp+=min;
-       i=min;
 #endif
        if (carry) /* subtracted */
                {
-               while (i < max)
+               if (!dif)
+                       /* error: a < b */
+                       return 0;
+               while (dif)
                        {
-                       i++;
-                       t1= *(ap++);
-                       t2=(t1-1)&BN_MASK2;
-                       *(rp++)=t2;
-                       if (t1 > t2) break;
+                       dif--;
+                       t1 = *(ap++);
+                       t2 = (t1-1)&BN_MASK2;
+                       *(rp++) = t2;
+                       if (t1)
+                               break;
                        }
                }
 #if 0
@@ -239,13 +240,13 @@ int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
                {
                for (;;)
                        {
-                       if (i++ >= max) break;
+                       if (!dif--) break;
                        rp[0]=ap[0];
-                       if (i++ >= max) break;
+                       if (!dif--) break;
                        rp[1]=ap[1];
-                       if (i++ >= max) break;
+                       if (!dif--) break;
                        rp[2]=ap[2];
-                       if (i++ >= max) break;
+                       if (!dif--) break;
                        rp[3]=ap[3];
                        rp+=4;
                        ap+=4;