/*

 * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the OpenSSL license (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy

 * in the file LICENSE in the source distribution or at

 * https://www.openssl.org/source/license.html

 */

#include "internal/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;

    if (!r->top)

        r->neg = 0; /* don't allow negative zero */

    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;

    }

    nw = n / BN_BITS2;

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

        return 0;

    r->neg = a->neg;

    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, sizeof(*t) * nw);

    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) {

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

            return 0;

        r->neg = a->neg;

    } 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;

    }

    if (!r->top)

        r->neg = 0; /* don't allow negative zero */

    bn_check_top(r);

    return 1;

}