/* crypto/bn/bn_word.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"

BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w)

{

#ifndef BN_LLONG

    BN_ULONG ret = 0;

#else

    BN_ULLONG ret = 0;

#endif

    int i;

    if (w == 0)

        return (BN_ULONG)-1;

#ifndef BN_LLONG

    /*

     * If |w| is too long and we don't have BN_ULLONG then we need to fall

     * back to using BN_div_word

     */

    if (w > ((BN_ULONG)1 << BN_BITS4)) {

        BIGNUM *tmp = BN_dup(a);

        if (tmp == NULL)

            return (BN_ULONG)-1;

        ret = BN_div_word(tmp, w);

        BN_free(tmp);

        return ret;

    }

#endif

    bn_check_top(a);

    w &= BN_MASK2;

    for (i = a->top - 1; i >= 0; i--) {

#ifndef BN_LLONG

        /*

         * We can assume here that | w <= ((BN_ULONG)1 << BN_BITS4) | and so

         * | ret < ((BN_ULONG)1 << BN_BITS4) | and therefore the shifts here are

         * safe and will not overflow

         */

        ret = ((ret << BN_BITS4) | ((a->d[i] >> BN_BITS4) & BN_MASK2l)) % w;

        ret = ((ret << BN_BITS4) | (a->d[i] & BN_MASK2l)) % w;

#else

        ret = (BN_ULLONG) (((ret << (BN_ULLONG) BN_BITS2) | a->d[i]) %

                           (BN_ULLONG) w);

#endif

    }

    return ((BN_ULONG)ret);

}

BN_ULONG BN_div_word(BIGNUM *a, BN_ULONG w)

{

    BN_ULONG ret = 0;

    int i, j;

    bn_check_top(a);

    w &= BN_MASK2;

    if (!w)

        /* actually this an error (division by zero) */

        return (BN_ULONG)-1;

    if (a->top == 0)

        return 0;

    /* normalize input (so bn_div_words doesn't complain) */

    j = BN_BITS2 - BN_num_bits_word(w);

    w <<= j;

    if (!BN_lshift(a, a, j))

        return (BN_ULONG)-1;

    for (i = a->top - 1; i >= 0; i--) {

        BN_ULONG l, d;

        l = a->d[i];

        d = bn_div_words(ret, l, w);

        ret = (l - ((d * w) & BN_MASK2)) & BN_MASK2;

        a->d[i] = d;

    }

    if ((a->top > 0) && (a->d[a->top - 1] == 0))

        a->top--;

    ret >>= j;

    bn_check_top(a);

    return (ret);

}

int BN_add_word(BIGNUM *a, BN_ULONG w)

{

    BN_ULONG l;

    int i;

    bn_check_top(a);

    w &= BN_MASK2;

    /* degenerate case: w is zero */

    if (!w)

        return 1;

    /* degenerate case: a is zero */

    if (BN_is_zero(a))

        return BN_set_word(a, w);

    /* handle 'a' when negative */

    if (a->neg) {

        a->neg = 0;

        i = BN_sub_word(a, w);

        if (!BN_is_zero(a))

            a->neg = !(a->neg);

        return (i);

    }

    for (i = 0; w != 0 && i < a->top; i++) {

        a->d[i] = l = (a->d[i] + w) & BN_MASK2;

        w = (w > l) ? 1 : 0;

    }

    if (w && i == a->top) {

        if (bn_wexpand(a, a->top + 1) == NULL)

            return 0;

        a->top++;

        a->d[i] = w;

    }

    bn_check_top(a);

    return (1);

}

int BN_sub_word(BIGNUM *a, BN_ULONG w)

{

    int i;

    bn_check_top(a);

    w &= BN_MASK2;

    /* degenerate case: w is zero */

    if (!w)

        return 1;

    /* degenerate case: a is zero */

    if (BN_is_zero(a)) {

        i = BN_set_word(a, w);

        if (i != 0)

            BN_set_negative(a, 1);

        return i;

    }

    /* handle 'a' when negative */

    if (a->neg) {

        a->neg = 0;

        i = BN_add_word(a, w);

        a->neg = 1;

        return (i);

    }

    if ((a->top == 1) && (a->d[0] < w)) {

        a->d[0] = w - a->d[0];

        a->neg = 1;

        return (1);

    }

    i = 0;

    for (;;) {

        if (a->d[i] >= w) {

            a->d[i] -= w;

            break;

        } else {

            a->d[i] = (a->d[i] - w) & BN_MASK2;

            i++;

            w = 1;

        }

    }

    if ((a->d[i] == 0) && (i == (a->top - 1)))

        a->top--;

    bn_check_top(a);

    return (1);

}

int BN_mul_word(BIGNUM *a, BN_ULONG w)

{

    BN_ULONG ll;

    bn_check_top(a);

    w &= BN_MASK2;

    if (a->top) {

        if (w == 0)

            BN_zero(a);

        else {

            ll = bn_mul_words(a->d, a->d, a->top, w);

            if (ll) {

                if (bn_wexpand(a, a->top + 1) == NULL)

                    return (0);

                a->d[a->top++] = ll;

            }

        }

    }

    bn_check_top(a);

    return (1);

}