/* crypto/bn/bn_add.c */
/*
*
* This package is an SSL implementation written
* by Eric Young ([email protected]).
* 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 ([email protected]).
*
* 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 ([email protected])"
* 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 ([email protected])"
*
* 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);
}
