314 lines
6.7 KiB
C
314 lines
6.7 KiB
C
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/* crypto/bn/bn_add.c */
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/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
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* All rights reserved.
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*
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* This package is an SSL implementation written
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* by Eric Young (eay@cryptsoft.com).
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* The implementation was written so as to conform with Netscapes SSL.
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*
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* This library is free for commercial and non-commercial use as long as
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* the following conditions are aheared to. The following conditions
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* apply to all code found in this distribution, be it the RC4, RSA,
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* lhash, DES, etc., code; not just the SSL code. The SSL documentation
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* included with this distribution is covered by the same copyright terms
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* except that the holder is Tim Hudson (tjh@cryptsoft.com).
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*
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* Copyright remains Eric Young's, and as such any Copyright notices in
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* the code are not to be removed.
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* If this package is used in a product, Eric Young should be given attribution
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* as the author of the parts of the library used.
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* This can be in the form of a textual message at program startup or
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* in documentation (online or textual) provided with the package.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* "This product includes cryptographic software written by
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* Eric Young (eay@cryptsoft.com)"
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* The word 'cryptographic' can be left out if the rouines from the library
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* being used are not cryptographic related :-).
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* 4. If you include any Windows specific code (or a derivative thereof) from
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* the apps directory (application code) you must include an acknowledgement:
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* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
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*
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* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* The licence and distribution terms for any publically available version or
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* derivative of this code cannot be changed. i.e. this code cannot simply be
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* copied and put under another distribution licence
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* [including the GNU Public Licence.]
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*/
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#include <stdio.h>
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#include "cryptlib.h"
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#include "bn_lcl.h"
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/* r can == a or b */
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int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
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{
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const BIGNUM *tmp;
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int a_neg = a->neg, ret;
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bn_check_top(a);
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bn_check_top(b);
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/* a + b a+b
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* a + -b a-b
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* -a + b b-a
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* -a + -b -(a+b)
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*/
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if (a_neg ^ b->neg)
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{
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/* only one is negative */
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if (a_neg)
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{ tmp=a; a=b; b=tmp; }
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/* we are now a - b */
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if (BN_ucmp(a,b) < 0)
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{
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if (!BN_usub(r,b,a)) return(0);
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r->neg=1;
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}
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else
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{
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if (!BN_usub(r,a,b)) return(0);
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r->neg=0;
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}
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return(1);
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}
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ret = BN_uadd(r,a,b);
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r->neg = a_neg;
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bn_check_top(r);
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return ret;
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}
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/* unsigned add of b to a */
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int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
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{
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int max,min,dif;
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BN_ULONG *ap,*bp,*rp,carry,t1,t2;
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const BIGNUM *tmp;
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bn_check_top(a);
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bn_check_top(b);
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if (a->top < b->top)
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{ tmp=a; a=b; b=tmp; }
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max = a->top;
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min = b->top;
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dif = max - min;
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if (bn_wexpand(r,max+1) == NULL)
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return 0;
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r->top=max;
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ap=a->d;
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bp=b->d;
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rp=r->d;
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carry=bn_add_words(rp,ap,bp,min);
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rp+=min;
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ap+=min;
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bp+=min;
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if (carry)
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{
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while (dif)
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{
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dif--;
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t1 = *(ap++);
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t2 = (t1+1) & BN_MASK2;
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*(rp++) = t2;
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if (t2)
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{
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carry=0;
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break;
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}
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}
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if (carry)
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{
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/* carry != 0 => dif == 0 */
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*rp = 1;
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r->top++;
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}
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}
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if (dif && rp != ap)
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while (dif--)
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/* copy remaining words if ap != rp */
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*(rp++) = *(ap++);
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r->neg = 0;
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bn_check_top(r);
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return 1;
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}
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/* unsigned subtraction of b from a, a must be larger than b. */
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int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
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{
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int max,min,dif;
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register BN_ULONG t1,t2,*ap,*bp,*rp;
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int i,carry;
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#if defined(IRIX_CC_BUG) && !defined(LINT)
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int dummy;
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#endif
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bn_check_top(a);
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bn_check_top(b);
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max = a->top;
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min = b->top;
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dif = max - min;
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if (dif < 0) /* hmm... should not be happening */
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{
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BNerr(BN_F_BN_USUB,BN_R_ARG2_LT_ARG3);
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return(0);
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}
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if (bn_wexpand(r,max) == NULL) return(0);
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ap=a->d;
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bp=b->d;
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rp=r->d;
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#if 1
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carry=0;
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for (i = min; i != 0; i--)
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{
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t1= *(ap++);
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t2= *(bp++);
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if (carry)
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{
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carry=(t1 <= t2);
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t1=(t1-t2-1)&BN_MASK2;
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}
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else
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{
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carry=(t1 < t2);
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t1=(t1-t2)&BN_MASK2;
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}
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#if defined(IRIX_CC_BUG) && !defined(LINT)
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dummy=t1;
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#endif
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*(rp++)=t1&BN_MASK2;
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}
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#else
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carry=bn_sub_words(rp,ap,bp,min);
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ap+=min;
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bp+=min;
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rp+=min;
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#endif
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if (carry) /* subtracted */
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{
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if (!dif)
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/* error: a < b */
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return 0;
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while (dif)
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{
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dif--;
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t1 = *(ap++);
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t2 = (t1-1)&BN_MASK2;
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*(rp++) = t2;
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if (t1)
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break;
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}
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}
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#if 0
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memcpy(rp,ap,sizeof(*rp)*(max-i));
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#else
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if (rp != ap)
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{
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for (;;)
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{
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if (!dif--) break;
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rp[0]=ap[0];
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if (!dif--) break;
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rp[1]=ap[1];
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if (!dif--) break;
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rp[2]=ap[2];
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if (!dif--) break;
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rp[3]=ap[3];
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rp+=4;
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ap+=4;
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}
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}
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#endif
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r->top=max;
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r->neg=0;
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bn_correct_top(r);
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return(1);
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}
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int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
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{
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int max;
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int add=0,neg=0;
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const BIGNUM *tmp;
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bn_check_top(a);
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bn_check_top(b);
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/* a - b a-b
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* a - -b a+b
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* -a - b -(a+b)
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* -a - -b b-a
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*/
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if (a->neg)
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{
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if (b->neg)
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{ tmp=a; a=b; b=tmp; }
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else
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{ add=1; neg=1; }
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}
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else
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{
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if (b->neg) { add=1; neg=0; }
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}
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if (add)
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{
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if (!BN_uadd(r,a,b)) return(0);
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r->neg=neg;
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return(1);
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}
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/* We are actually doing a - b :-) */
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max=(a->top > b->top)?a->top:b->top;
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if (bn_wexpand(r,max) == NULL) return(0);
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if (BN_ucmp(a,b) < 0)
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{
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if (!BN_usub(r,b,a)) return(0);
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r->neg=1;
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}
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else
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{
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if (!BN_usub(r,a,b)) return(0);
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r->neg=0;
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}
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bn_check_top(r);
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return(1);
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}
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