/* crypto/des/ofb_enc.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 "des_locl.h"

/* The input and output are loaded in multiples of 8 bits.

 * What this means is that if you hame numbits=12 and length=2

 * the first 12 bits will be retrieved from the first byte and half

 * the second.  The second 12 bits will come from the 3rd and half the 4th

 * byte.

 */

EXPORT_C void DES_ofb_encrypt(const unsigned char *in, unsigned char *out, int numbits,

		     long length, DES_key_schedule *schedule,

		     DES_cblock *ivec)

	{

	register DES_LONG d0,d1,vv0,vv1,v0,v1,n=(numbits+7)/8;

	register DES_LONG mask0,mask1;

	register long l=length;

	register int num=numbits;

	DES_LONG ti[2];

	unsigned char *iv;

	if (num > 64) return;

	if (num > 32)

		{

		mask0=0xffffffffL;

		if (num >= 64)

			mask1=mask0;

		else

			mask1=(1L<<(num-32))-1;

		}

	else

		{

		if (num == 32)

			mask0=0xffffffffL;

		else

			mask0=(1L<<num)-1;

		mask1=0x00000000L;

		}

	iv = &(*ivec)[0];

	c2l(iv,v0);

	c2l(iv,v1);

	ti[0]=v0;

	ti[1]=v1;

	while (l-- > 0)

		{

		ti[0]=v0;

		ti[1]=v1;

		DES_encrypt1((DES_LONG *)ti,schedule,DES_ENCRYPT);

		vv0=ti[0];

		vv1=ti[1];

		c2ln(in,d0,d1,n);

		in+=n;

		d0=(d0^vv0)&mask0;

		d1=(d1^vv1)&mask1;

		l2cn(d0,d1,out,n);

		out+=n;

		if (num == 32)

			{ v0=v1; v1=vv0; }

		else if (num == 64)

				{ v0=vv0; v1=vv1; }

		else if (num > 32) /* && num != 64 */

			{

			v0=((v1>>(num-32))|(vv0<<(64-num)))&0xffffffffL;

			v1=((vv0>>(num-32))|(vv1<<(64-num)))&0xffffffffL;

			}

		else /* num < 32 */

			{

			v0=((v0>>num)|(v1<<(32-num)))&0xffffffffL;

			v1=((v1>>num)|(vv0<<(32-num)))&0xffffffffL;

			}

		}

	iv = &(*ivec)[0];

	l2c(v0,iv);

	l2c(v1,iv);

	v0=v1=d0=d1=ti[0]=ti[1]=vv0=vv1=0;

	}