Commit 7d628405 authored by Andy Polyakov's avatar Andy Polyakov
Browse files

bn/bn_add.c: favour counted loops over ifs and breaks. 



Reviewed-by: default avatarRich Salz <rsalz@openssl.org>
parent 2ac68bd6

crypto/bn/bn_add.c

+38 −72
Original line number Diff line number Diff line
@@ -13,7 +13,6 @@ 
/* r can == a or b */

int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)

{

    const BIGNUM *tmp;

    int a_neg = a->neg, ret;



    bn_check_top(a);
@@ -28,6 +27,8 @@ int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 
    if (a_neg ^ b->neg) {

        /* only one is negative */

        if (a_neg) {

            const BIGNUM *tmp;



            tmp = a;

            a = b;

            b = tmp;
@@ -37,14 +38,14 @@ int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 


        if (BN_ucmp(a, b) < 0) {

            if (!BN_usub(r, b, a))

                return (0);

                return 0;

            r->neg = 1;

        } else {

            if (!BN_usub(r, a, b))

                return (0);

                return 0;

            r->neg = 0;

        }

        return (1);

        return 1;

    }



    ret = BN_uadd(r, a, b);
@@ -59,12 +60,13 @@ int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 
    int max, min, dif;

    const BN_ULONG *ap, *bp;

    BN_ULONG *rp, carry, t1, t2;

    const BIGNUM *tmp;



    bn_check_top(a);

    bn_check_top(b);



    if (a->top < b->top) {

        const BIGNUM *tmp;



        tmp = a;

        a = b;

        b = tmp;
@@ -85,29 +87,17 @@ int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 
    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;

        t2 = (t1 + carry) & BN_MASK2;

        *(rp++) = t2;

            if (t2) {

                carry = 0;

                break;

        carry &= (t2 == 0);

    }

        }

        if (carry) {

            /* carry != 0 => dif == 0 */

            *rp = 1;

            r->top++;

        }

    }

    if (dif && rp != ap)

        while (dif--)

            /* copy remaining words if ap != rp */

            *(rp++) = *(ap++);

    *rp = carry;

    r->top += carry;



    r->neg = 0;

    bn_check_top(r);

    return 1;
@@ -117,9 +107,8 @@ int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 
int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)

{

    int max, min, dif;

    register BN_ULONG t1, t2, *rp;

    register const BN_ULONG *ap, *bp;

    int i, carry;

    BN_ULONG t1, t2, borrow, *rp;

    const BN_ULONG *ap, *bp;



    bn_check_top(a);

    bn_check_top(b);
@@ -130,63 +119,38 @@ int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 


    if (dif < 0) {              /* hmm... should not be happening */

        BNerr(BN_F_BN_USUB, BN_R_ARG2_LT_ARG3);

        return (0);

        return 0;

    }



    if (bn_wexpand(r, max) == NULL)

        return (0);

        return 0;



    ap = a->d;

    bp = b->d;

    rp = r->d;



#if 1

    carry = 0;

    for (i = min; i != 0; i--) {

        t1 = *(ap++);

        t2 = *(bp++);

        if (carry) {

            carry = (t1 <= t2);

            t1 = (t1 - t2 - 1) & BN_MASK2;

        } else {

            carry = (t1 < t2);

            t1 = (t1 - t2) & BN_MASK2;

        }

        *(rp++) = t1 & BN_MASK2;

    }

#else

    carry = bn_sub_words(rp, ap, bp, min);

    borrow = bn_sub_words(rp, ap, bp, min);

    ap += min;

    bp += min;

    rp += min;

#endif

    if (carry) {                /* subtracted */

        if (!dif)

            /* error: a < b */

            return 0;



    while (dif) {

        dif--;

        t1 = *(ap++);

            t2 = (t1 - 1) & BN_MASK2;

        t2 = (t1 - borrow) & BN_MASK2;

        *(rp++) = t2;

            if (t1)

                break;

        }

        borrow &= (t1 == 0);

    }

    if (dif && ap != rp)

        memcpy(rp, ap, sizeof(*rp) * dif);



    r->top = max;

    r->neg = 0;

    bn_correct_top(r);

    return (1);

    return 1;

}



int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)

{

    int max;

    int add = 0, neg = 0;

    const BIGNUM *tmp;



    bn_check_top(a);

    bn_check_top(b);
@@ -199,6 +163,8 @@ int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 
     */

    if (a->neg) {

        if (b->neg) {

            const BIGNUM *tmp;



            tmp = a;

            a = b;

            b = tmp;
@@ -215,25 +181,25 @@ int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 


    if (add) {

        if (!BN_uadd(r, a, b))

            return (0);

            return 0;

        r->neg = neg;

        return (1);

        return 1;

    }



    /* We are actually doing a - b :-) */



    max = (a->top > b->top) ? a->top : b->top;

    if (bn_wexpand(r, max) == NULL)

        return (0);

        return 0;

    if (BN_ucmp(a, b) < 0) {

        if (!BN_usub(r, b, a))

            return (0);

            return 0;

        r->neg = 1;

    } else {

        if (!BN_usub(r, a, b))

            return (0);

            return 0;

        r->neg = 0;

    }

    bn_check_top(r);

    return (1);

    return 1;

}