ofb_enc.c

基于DSP的用C语言实现语音编码解码

/* lib/des/ofb_enc.c */
/* Copyright (C) 1995 Eric Young ([e-mail])
 * All rights reserved.
 * 
 * This file is part of an SSL implementation written
 * by Eric Young ([e-mail]).
 * The implementation was written so as to conform with Netscapes SSL
 * specification.  This library and applications are
 * FREE FOR COMMERCIAL AND NON-COMMERCIAL USE
 * as long as the following conditions are aheared to.
 * 
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.	If this code is used in a product,
 * Eric Young should be given attribution as the author of the parts 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 software developed by Eric Young ([e-mail])
 * 
 * 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.
 */
void des_ofb_encrypt(in, out, numbits, length, schedule, ivec)
unsigned char *in;
unsigned char *out;
int numbits;
long length;
des_key_schedule schedule;
des_cblock (*ivec);
		{
		register unsigned long d0,d1,v0,v1,n=(numbits+7)/8;
		register unsigned long mask0,mask1;
		register long l=length;
		register int num=numbits;
		unsigned 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=0x00000000;
				}

		iv=(unsigned char *)ivec;
		c2l(iv,v0);
		c2l(iv,v1);
		ti[0]=v0;
		ti[1]=v1;
		while (l-- > 0)
				{
				des_encrypt((unsigned long *)ti,schedule,DES_ENCRYPT);
				c2ln(in,d0,d1,n);
				in+=n;
				d0=(d0^ti[0])&mask0;
				d1=(d1^ti[1])&mask1;
				l2cn(d0,d1,out,n);
				out+=n;
				}
		v0=ti[0];
		v1=ti[1];
		iv=(unsigned char *)ivec;
		l2c(v0,iv);
		l2c(v1,iv);
		v0=v1=d0=d1=ti[0]=ti[1]=0;
		}