/* 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"

EXPORT_C 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);

	}

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

	{

	BN_ULONG *ap,*rp,t,c;

	int i;

	bn_check_top(r);

	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_correct_top(r);

	bn_check_top(r);

	return(1);

	}

EXPORT_C 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);

	}

EXPORT_C 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);

		}

	if (r != a)

		{

		r->neg=a->neg;

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

	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;

			}

		*(t++) =(l>>rb)&BN_MASK2;

		}

	bn_correct_top(r);

	bn_check_top(r);

	return(1);

	}