bn_add.c revision 1.1 
1/* crypto/bn/bn_add.c */
2/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
3 * All rights reserved.
4 *
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
8 *
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to.  The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
15 *
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
26 * 1. Redistributions of source code must retain the copyright
27 *    notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 *    notice, this list of conditions and the following disclaimer in the
30 *    documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 *    must display the following acknowledgement:
33 *    "This product includes cryptographic software written by
34 *     Eric Young (eay@cryptsoft.com)"
35 *    The word 'cryptographic' can be left out if the rouines from the library
36 *    being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 *    the apps directory (application code) you must include an acknowledgement:
39 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
40 *
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
51 * SUCH DAMAGE.
52 *
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed.  i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
57 */
58
59#include <stdio.h>
60#include "cryptlib.h"
61#include "bn_lcl.h"
62
63/* r can == a or b */
64int BN_add(r, a, b)
65BIGNUM *r;
66BIGNUM *a;
67BIGNUM *b;
68	{
69	int i;
70	BIGNUM *tmp;
71
72	/*  a +  b	a+b
73	 *  a + -b	a-b
74	 * -a +  b	b-a
75	 * -a + -b	-(a+b)
76	 */
77	if (a->neg ^ b->neg)
78		{
79		/* only one is negative */
80		if (a->neg)
81			{ tmp=a; a=b; b=tmp; }
82
83		/* we are now a - b */
84
85		if (BN_ucmp(a,b) < 0)
86			{
87			if (bn_wexpand(r,b->top) == NULL) return(0);
88			bn_qsub(r,b,a);
89			r->neg=1;
90			}
91		else
92			{
93			if (bn_wexpand(r,a->top) == NULL) return(0);
94			bn_qsub(r,a,b);
95			r->neg=0;
96			}
97		return(1);
98		}
99
100	if (a->neg) /* both are neg */
101		r->neg=1;
102	else
103		r->neg=0;
104
105	i=(a->top > b->top);
106
107	if (i)
108		{
109		if (bn_wexpand(r,a->top+1) == NULL) return(0);
110		bn_qadd(r,a,b);
111		}
112	else
113		{
114		if (bn_wexpand(r,b->top+1) == NULL) return(0);
115		bn_qadd(r,b,a);
116		}
117	return(1);
118	}
119
120/* unsigned add of b to a, r must be large enough */
121void bn_qadd(r,a,b)
122BIGNUM *r;
123BIGNUM *a;
124BIGNUM *b;
125	{
126	register int i;
127	int max,min;
128	BN_ULONG *ap,*bp,*rp,carry,t1;
129
130	max=a->top;
131	min=b->top;
132	r->top=max;
133
134	ap=a->d;
135	bp=b->d;
136	rp=r->d;
137	carry=0;
138
139	carry=bn_add_words(rp,ap,bp,min);
140	rp+=min;
141	ap+=min;
142	bp+=min;
143	i=min;
144
145	if (carry)
146		{
147		while (i < max)
148			{
149			i++;
150			t1= *(ap++);
151			if ((*(rp++)=(t1+1)&BN_MASK2) >= t1)
152				{
153				carry=0;
154				break;
155				}
156			}
157		if ((i >= max) && carry)
158			{
159			*(rp++)=1;
160			r->top++;
161			}
162		}
163	for (; i<max; i++)
164		*(rp++)= *(ap++);
165	/* memcpy(rp,ap,sizeof(*ap)*(max-i));*/
166	}
167
168