bn_add.c
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- /* 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);
- }