| /* crypto/bn/bn_add.c */ |
| /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) |
| * All rights reserved. |
| * |
| * This package is an SSL implementation written |
| * by Eric Young (eay@cryptsoft.com). |
| * The implementation was written so as to conform with Netscapes SSL. |
| * |
| * This library is free for commercial and non-commercial use as long as |
| * the following conditions are aheared to. The following conditions |
| * apply to all code found in this distribution, be it the RC4, RSA, |
| * lhash, DES, etc., code; not just the SSL code. The SSL documentation |
| * included with this distribution is covered by the same copyright terms |
| * except that the holder is Tim Hudson (tjh@cryptsoft.com). |
| * |
| * Copyright remains Eric Young's, and as such any Copyright notices in |
| * the code are not to be removed. |
| * If this package is used in a product, Eric Young should be given attribution |
| * as the author of the parts of the library used. |
| * This can be in the form of a textual message at program startup or |
| * in documentation (online or textual) provided with the package. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. All advertising materials mentioning features or use of this software |
| * must display the following acknowledgement: |
| * "This product includes cryptographic software written by |
| * Eric Young (eay@cryptsoft.com)" |
| * The word 'cryptographic' can be left out if the rouines from the library |
| * being used are not cryptographic related :-). |
| * 4. If you include any Windows specific code (or a derivative thereof) from |
| * the apps directory (application code) you must include an acknowledgement: |
| * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" |
| * |
| * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND |
| * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| * |
| * The licence and distribution terms for any publically available version or |
| * derivative of this code cannot be changed. i.e. this code cannot simply be |
| * copied and put under another distribution licence |
| * [including the GNU Public Licence.] |
| */ |
| |
| #include <stdio.h> |
| #include "cryptlib.h" |
| #include "bn_lcl.h" |
| |
| /* 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); |
| bn_check_top(b); |
| |
| /*- |
| * a + b a+b |
| * a + -b a-b |
| * -a + b b-a |
| * -a + -b -(a+b) |
| */ |
| if (a_neg ^ b->neg) { |
| /* only one is negative */ |
| if (a_neg) { |
| tmp = a; |
| a = b; |
| b = tmp; |
| } |
| |
| /* we are now a - b */ |
| |
| if (BN_ucmp(a, b) < 0) { |
| if (!BN_usub(r, b, a)) |
| return (0); |
| r->neg = 1; |
| } else { |
| if (!BN_usub(r, a, b)) |
| return (0); |
| r->neg = 0; |
| } |
| return (1); |
| } |
| |
| ret = BN_uadd(r, a, b); |
| r->neg = a_neg; |
| bn_check_top(r); |
| return ret; |
| } |
| |
| /* unsigned add of b to a */ |
| int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) |
| { |
| int max, min, dif; |
| BN_ULONG *ap, *bp, *rp, carry, t1, t2; |
| const BIGNUM *tmp; |
| |
| bn_check_top(a); |
| bn_check_top(b); |
| |
| if (a->top < b->top) { |
| tmp = a; |
| a = b; |
| b = tmp; |
| } |
| max = a->top; |
| min = b->top; |
| dif = max - min; |
| |
| if (bn_wexpand(r, max + 1) == NULL) |
| return 0; |
| |
| r->top = max; |
| |
| 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); |
| |
| 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; |
| } |
| # if defined(IRIX_CC_BUG) && !defined(LINT) |
| dummy = t1; |
| # endif |
| *(rp++) = t1 & BN_MASK2; |
| } |
| #else |
| carry = 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; |
| } |
| } |
| #if 0 |
| memcpy(rp, ap, sizeof(*rp) * (max - i)); |
| #else |
| if (rp != ap) { |
| for (;;) { |
| if (!dif--) |
| break; |
| rp[0] = ap[0]; |
| if (!dif--) |
| break; |
| rp[1] = ap[1]; |
| if (!dif--) |
| break; |
| rp[2] = ap[2]; |
| if (!dif--) |
| break; |
| rp[3] = ap[3]; |
| rp += 4; |
| ap += 4; |
| } |
| } |
| #endif |
| |
| r->top = max; |
| r->neg = 0; |
| bn_correct_top(r); |
| 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); |
| |
| /*- |
| * a - b a-b |
| * a - -b a+b |
| * -a - b -(a+b) |
| * -a - -b b-a |
| */ |
| if (a->neg) { |
| if (b->neg) { |
| tmp = a; |
| a = b; |
| b = tmp; |
| } else { |
| add = 1; |
| neg = 1; |
| } |
| } else { |
| if (b->neg) { |
| add = 1; |
| neg = 0; |
| } |
| } |
| |
| if (add) { |
| if (!BN_uadd(r, a, b)) |
| return (0); |
| r->neg = neg; |
| 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); |
| if (BN_ucmp(a, b) < 0) { |
| if (!BN_usub(r, b, a)) |
| return (0); |
| r->neg = 1; |
| } else { |
| if (!BN_usub(r, a, b)) |
| return (0); |
| r->neg = 0; |
| } |
| bn_check_top(r); |
| return (1); |
| } |
