diff options
author | Andy Polyakov <appro@openssl.org> | 2016-06-12 12:34:46 +0200 |
---|---|---|
committer | Andy Polyakov <appro@openssl.org> | 2016-06-13 12:35:39 +0200 |
commit | 7d6284057b66458f6c99bd65ba67377d63411090 (patch) | |
tree | d9f5f99cdba25944f93497c188d074c0f13add9b /crypto/bn | |
parent | 2ac68bd6f14f27504cf9ae86e714030083de732b (diff) |
bn/bn_add.c: favour counted loops over ifs and breaks.
Reviewed-by: Rich Salz <rsalz@openssl.org>
Diffstat (limited to 'crypto/bn')
-rw-r--r-- | crypto/bn/bn_add.c | 110 |
1 files changed, 38 insertions, 72 deletions
diff --git a/crypto/bn/bn_add.c b/crypto/bn/bn_add.c index d44e8f7d89..6479650afb 100644 --- a/crypto/bn/bn_add.c +++ b/crypto/bn/bn_add.c @@ -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; - *(rp++) = t2; - if (t2) { - carry = 0; - break; - } - } - if (carry) { - /* carry != 0 => dif == 0 */ - *rp = 1; - r->top++; - } + + while (dif) { + dif--; + t1 = *(ap++); + t2 = (t1 + carry) & BN_MASK2; + *(rp++) = t2; + carry &= (t2 == 0); } - 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; - *(rp++) = t2; - if (t1) - break; - } + + while (dif) { + dif--; + t1 = *(ap++); + t2 = (t1 - borrow) & BN_MASK2; + *(rp++) = t2; + 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; } |