/* crypto/bn/bn_shift.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"

int BN_lshift1(BIGNUM *r, const BIGNUM *a)

{

    register BN_ULONG *ap, *rp, t, c;

    int i;

    bn_check_top(r);

    bn_check_top(a);

    if (r != a) {

        r->neg = a->neg;

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

            return (0);

        r->top = a->top;

    } else {

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

            return (0);

    }

    ap = a->d;

    rp = r->d;

    c = 0;

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

        t = *(ap++);

        *(rp++) = ((t << 1) | c) & BN_MASK2;

        c = (t & BN_TBIT) ? 1 : 0;

    }

    if (c) {

        *rp = 1;

        r->top++;

    }

    bn_check_top(r);

    return (1);

}

int BN_rshift1(BIGNUM *r, const BIGNUM *a)

{

    BN_ULONG *ap, *rp, t, c;

    int i, j;

    bn_check_top(r);

    bn_check_top(a);

    if (BN_is_zero(a)) {

        BN_zero(r);

        return (1);

    }

    i = a->top;

    ap = a->d;

    j = i - (ap[i - 1] == 1);

    if (a != r) {

        if (bn_wexpand(r, j) == NULL)

            return (0);

        r->neg = a->neg;

    }

    rp = r->d;

    t = ap[--i];

    c = (t & 1) ? BN_TBIT : 0;

    if (t >>= 1)

        rp[i] = t;

    while (i > 0) {

        t = ap[--i];

        rp[i] = ((t >> 1) & BN_MASK2) | c;

        c = (t & 1) ? BN_TBIT : 0;

    }

    r->top = j;

    bn_check_top(r);

    return (1);

}

int BN_lshift(BIGNUM *r, const BIGNUM *a, int n)

{

    int i, nw, lb, rb;

    BN_ULONG *t, *f;

    BN_ULONG l;

    bn_check_top(r);

    bn_check_top(a);

    if (n < 0) {

        BNerr(BN_F_BN_LSHIFT, BN_R_INVALID_SHIFT);

        return 0;

    }

    r->neg = a->neg;

    nw = n / BN_BITS2;

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

        return (0);

    lb = n % BN_BITS2;

    rb = BN_BITS2 - lb;

    f = a->d;

    t = r->d;

    t[a->top + nw] = 0;

    if (lb == 0)

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

            t[nw + i] = f[i];

    else

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

            l = f[i];

            t[nw + i + 1] |= (l >> rb) & BN_MASK2;

            t[nw + i] = (l << lb) & BN_MASK2;

        }

    memset(t, 0, nw * sizeof(t[0]));

    /*

     * for (i=0; i<nw; i++) t[i]=0;

     */

    r->top = a->top + nw + 1;

    bn_correct_top(r);

    bn_check_top(r);

    return (1);

}

int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)

{

    int i, j, nw, lb, rb;

    BN_ULONG *t, *f;

    BN_ULONG l, tmp;

    bn_check_top(r);

    bn_check_top(a);

    if (n < 0) {

        BNerr(BN_F_BN_RSHIFT, BN_R_INVALID_SHIFT);

        return 0;

    }

    nw = n / BN_BITS2;

    rb = n % BN_BITS2;

    lb = BN_BITS2 - rb;

    if (nw >= a->top || a->top == 0) {

        BN_zero(r);

        return (1);

    }

    i = (BN_num_bits(a) - n + (BN_BITS2 - 1)) / BN_BITS2;

    if (r != a) {

        r->neg = a->neg;

        if (bn_wexpand(r, i) == NULL)

            return (0);

    } else {

        if (n == 0)

            return 1;           /* or the copying loop will go berserk */

    }

    f = &(a->d[nw]);

    t = r->d;

    j = a->top - nw;

    r->top = i;

    if (rb == 0) {

        for (i = j; i != 0; i--)

            *(t++) = *(f++);

    } else {

        l = *(f++);

        for (i = j - 1; i != 0; i--) {

            tmp = (l >> rb) & BN_MASK2;

            l = *(f++);

            *(t++) = (tmp | (l << lb)) & BN_MASK2;

        }

        if ((l = (l >> rb) & BN_MASK2))

            *(t) = l;

    }

    bn_check_top(r);

    return (1);

}