/* $Id$ */
/*
 * Copyright (C) 1998-2002 RSA Security Inc. All rights reserved.
 *
 * This work contains proprietary information of RSA Security.
 * Distribution is limited to authorized licensees of RSA
 * Security. Any unauthorized reproduction, distribution or
 * modification of this work is strictly prohibited.
 *
 */

#include "bn_lcl.h"

#if !(defined(NO_SPLIT) && defined(SPLIT_FILE))
 
#ifdef NO_SPLIT
#define SPLIT_BN_RSHIFT1
#define SPLIT_BN_RSHIFT
#endif /* NO_SPLIT */

#ifdef SPLIT_BN_RSHIFT1
#ifdef SMALL_CODE_SIZE
int BN_rshift1(r, a)
BIGNUM *r;
BIGNUM *a;
    {
    return(BN_rshift(r,a,1));
    }

#else

int BN_rshift1(r, a)
BIGNUM *r;
BIGNUM *a;
    {
    BN_ULONG *ap,*rp,t,c;
    int i;

    bn_check_top(a);

    if (BN_is_zero(a))
        {
        BN_zero(r);
        return(1);
        }
    if (a != r)
        {
        if (bn_wexpand(r,a->top) == NULL) return(0);
        r->top=a->top;
        r->neg=a->neg;
        }
    ap=a->d;
    rp=r->d;
    c=0;
    for (i=a->top-1; i>=0; i--)
        {
        t=ap[i];
        rp[i]=((t>>1)&BN_MASK2)|c;
        c=(t&1)?BN_TBIT:0;
        }
    bn_fix_top(r);
    return(1);
    }
#endif
#endif

#ifdef SPLIT_BN_RSHIFT
int BN_rshift(r, a, n)
BIGNUM *r;
BIGNUM *a;
int n;
    {
    int i,j,nw,lb,rb;
    BN_ULONG *t,*f;
    BN_ULONG l,tmp;

    bn_check_top(a);

#ifndef SMALL_CODE_SIZE
    if (n == 1) return(BN_rshift1(r,a));
#endif
    nw=n/BN_BITS2;
    rb=n%BN_BITS2;
    lb=BN_BITS2-rb;
    if (nw > a->top)
        {
        (void)BN_zero(r);
        return(1);
        }
    if (r != a)
        {
        if (bn_wexpand(r,a->top-nw+1+1/*???*/) == NULL) return(0);
        r->neg=a->neg;
        }

    f= &(a->d[nw]);
    t=r->d;
    j=a->top-nw;
    r->top=j;

    if (rb == 0)
        {
        for (i=j+1; i > 0; i--)
            *(t++)= *(f++);
        }
    else
        {
        l= *(f++);
        for (i=1; i<j; i++)
            {
            tmp =(l>>rb)&BN_MASK2;
            l= *(f++);
            *(t++) =(tmp|(l<<lb))&BN_MASK2;
            }
        *(t++) =(l>>rb)&BN_MASK2;
        *t=0;
        }
    bn_fix_top(r);
    return(1);
    }
#endif

#endif