bn_shift.c

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/* crypto/bn/bn_shift.c */
/* Copyright (C) 1995-1998 Eric Young ([email protected])
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young ([email protected]).
 * 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 ([email protected]).
 * 
 * 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 ([email protected])"
 *    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 ([email protected])"
 * 
 * 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);

    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);

    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);
    }