[thirdparty/openssl.git] / crypto / bn / bn_add.c

/* 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 "internal/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;
    const BN_ULONG *ap, *bp;
    BN_ULONG *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, *rp;
    register const BN_ULONG *ap, *bp;
    int i, carry;

    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;
        }
        *(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;
        }
    }
    memcpy(rp, ap, sizeof(*rp) * dif);

    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);
}
Commit	Line	Data
d02b48c6	1	/* crypto/bn/bn_add.c */
58964a49	2	/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
d02b48c6 RE	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.
0f113f3e	8	*
d02b48c6 RE	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).
0f113f3e	15	*
d02b48c6 RE	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.
0f113f3e	22	*
d02b48c6 RE	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 :-).
0f113f3e	37	* 4. If you include any Windows specific code (or a derivative thereof) from
d02b48c6 RE	38	* the apps directory (application code) you must include an acknowledgement:
d02b48c6 RE	39	* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
0f113f3e	40	*
d02b48c6 RE	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.
0f113f3e	52	*
d02b48c6 RE	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
b39fc560	59	#include "internal/cryptlib.h"
d02b48c6 RE	60	#include "bn_lcl.h"
	61
	62	/* r can == a or b */
dd8dec69	63	int BN_add(BIGNUM r, const BIGNUM a, const BIGNUM *b)
0f113f3e MC	64	{
	65	const BIGNUM *tmp;
	66	int a_neg = a->neg, ret;
	67
	68	bn_check_top(a);
	69	bn_check_top(b);
	70
50e735f9 MC	71	/*-
	72	* a + b a+b
	73	* a + -b a-b
	74	* -a + b b-a
	75	* -a + -b -(a+b)
	76	*/
0f113f3e MC	77	if (a_neg ^ b->neg) {
	78	/* only one is negative */
	79	if (a_neg) {
	80	tmp = a;
	81	a = b;
	82	b = tmp;
	83	}
	84
	85	/* we are now a - b */
	86
	87	if (BN_ucmp(a, b) < 0) {
	88	if (!BN_usub(r, b, a))
	89	return (0);
	90	r->neg = 1;
	91	} else {
	92	if (!BN_usub(r, a, b))
	93	return (0);
	94	r->neg = 0;
	95	}
	96	return (1);
	97	}
	98
	99	ret = BN_uadd(r, a, b);
	100	r->neg = a_neg;
	101	bn_check_top(r);
	102	return ret;
	103	}
d02b48c6	104
380e145d	105	/* unsigned add of b to a */
84c15db5	106	int BN_uadd(BIGNUM r, const BIGNUM a, const BIGNUM *b)
0f113f3e MC	107	{
	108	int max, min, dif;
	109	const BN_ULONG ap, bp;
	110	BN_ULONG *rp, carry, t1, t2;
	111	const BIGNUM *tmp;
	112
	113	bn_check_top(a);
	114	bn_check_top(b);
	115
	116	if (a->top < b->top) {
	117	tmp = a;
	118	a = b;
	119	b = tmp;
	120	}
	121	max = a->top;
	122	min = b->top;
	123	dif = max - min;
	124
	125	if (bn_wexpand(r, max + 1) == NULL)
	126	return 0;
	127
	128	r->top = max;
	129
	130	ap = a->d;
	131	bp = b->d;
	132	rp = r->d;
	133
	134	carry = bn_add_words(rp, ap, bp, min);
	135	rp += min;
	136	ap += min;
	137	bp += min;
	138
	139	if (carry) {
	140	while (dif) {
	141	dif--;
	142	t1 = *(ap++);
	143	t2 = (t1 + 1) & BN_MASK2;
	144	*(rp++) = t2;
	145	if (t2) {
	146	carry = 0;
	147	break;
	148	}
	149	}
	150	if (carry) {
	151	/* carry != 0 => dif == 0 */
	152	*rp = 1;
	153	r->top++;
	154	}
	155	}
	156	if (dif && rp != ap)
	157	while (dif--)
	158	/* copy remaining words if ap != rp */
	159	(rp++) = (ap++);
	160	r->neg = 0;
	161	bn_check_top(r);
	162	return 1;
	163	}
dfeab068 RE	164
dfeab068 RE	165	/* unsigned subtraction of b from a, a must be larger than b. */
84c15db5	166	int BN_usub(BIGNUM r, const BIGNUM a, const BIGNUM *b)
0f113f3e MC	167	{
	168	int max, min, dif;
	169	register BN_ULONG t1, t2, *rp;
	170	register const BN_ULONG ap, bp;
	171	int i, carry;
dfeab068	172
0f113f3e MC	173	bn_check_top(a);
0f113f3e MC	174	bn_check_top(b);
dfeab068	175
0f113f3e MC	176	max = a->top;
	177	min = b->top;
	178	dif = max - min;
380e145d	179
0f113f3e MC	180	if (dif < 0) { /* hmm... should not be happening */
	181	BNerr(BN_F_BN_USUB, BN_R_ARG2_LT_ARG3);
	182	return (0);
	183	}
dfeab068	184
0f113f3e MC	185	if (bn_wexpand(r, max) == NULL)
0f113f3e MC	186	return (0);
dfeab068	187
0f113f3e MC	188	ap = a->d;
	189	bp = b->d;
	190	rp = r->d;
dfeab068 RE	191
dfeab068 RE	192	#if 1
0f113f3e MC	193	carry = 0;
	194	for (i = min; i != 0; i--) {
	195	t1 = *(ap++);
	196	t2 = *(bp++);
	197	if (carry) {
	198	carry = (t1 <= t2);
	199	t1 = (t1 - t2 - 1) & BN_MASK2;
	200	} else {
	201	carry = (t1 < t2);
	202	t1 = (t1 - t2) & BN_MASK2;
	203	}
	204	*(rp++) = t1 & BN_MASK2;
	205	}
dfeab068	206	#else
0f113f3e MC	207	carry = bn_sub_words(rp, ap, bp, min);
	208	ap += min;
	209	bp += min;
	210	rp += min;
dfeab068	211	#endif
0f113f3e MC	212	if (carry) { /* subtracted */
	213	if (!dif)
	214	/* error: a < b */
	215	return 0;
	216	while (dif) {
	217	dif--;
	218	t1 = *(ap++);
	219	t2 = (t1 - 1) & BN_MASK2;
	220	*(rp++) = t2;
	221	if (t1)
	222	break;
	223	}
	224	}
c2cfc956	225	memcpy(rp, ap, sizeof(rp) dif);
dfeab068	226
0f113f3e MC	227	r->top = max;
	228	r->neg = 0;
	229	bn_correct_top(r);
	230	return (1);
	231	}
dfeab068	232
84c15db5	233	int BN_sub(BIGNUM r, const BIGNUM a, const BIGNUM *b)
0f113f3e MC	234	{
	235	int max;
	236	int add = 0, neg = 0;
	237	const BIGNUM *tmp;
	238
	239	bn_check_top(a);
	240	bn_check_top(b);
	241
50e735f9 MC	242	/*-
	243	* a - b a-b
	244	* a - -b a+b
	245	* -a - b -(a+b)
	246	* -a - -b b-a
	247	*/
0f113f3e MC	248	if (a->neg) {
	249	if (b->neg) {
	250	tmp = a;
	251	a = b;
	252	b = tmp;
	253	} else {
	254	add = 1;
	255	neg = 1;
	256	}
	257	} else {
	258	if (b->neg) {
	259	add = 1;
	260	neg = 0;
	261	}
	262	}
	263
	264	if (add) {
	265	if (!BN_uadd(r, a, b))
	266	return (0);
	267	r->neg = neg;
	268	return (1);
	269	}
	270
	271	/* We are actually doing a - b :-) */
	272
	273	max = (a->top > b->top) ? a->top : b->top;
	274	if (bn_wexpand(r, max) == NULL)
	275	return (0);
	276	if (BN_ucmp(a, b) < 0) {
	277	if (!BN_usub(r, b, a))
	278	return (0);
	279	r->neg = 1;
	280	} else {
	281	if (!BN_usub(r, a, b))
	282	return (0);
	283	r->neg = 0;
	284	}
	285	bn_check_top(r);
	286	return (1);
	287	}