/* crypto/aes/aes_ofb.c -*- mode:C; c-file-style: "eay" -*- */
/* ====================================================================
 * Copyright (c) 2002-2006 The OpenSSL Project.  All rights reserved.
 *
 * 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 above 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 acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    openssl-core@openssl.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED 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 OpenSSL PROJECT OR
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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 */

#ifndef AES_DEBUG
# ifndef NDEBUG
#  define NDEBUG
# endif
#endif
#include <assert.h>

#include <openssl/aes.h>
#include "aes_locl.h"

#define STRICT_ALIGNMENT
#if defined(__i386) || defined(__i386__) || \
    defined(__x86_64) || defined(__x86_64__) || \
    defined(_M_IX86) || defined(_M_AMD64) || defined(_M_X64)
#  undef STRICT_ALIGNMENT
#endif

/* The input and output encrypted as though 128bit ofb mode is being
 * used.  The extra state information to record how much of the
 * 128bit block we have used is contained in *num;
 */
void AES_ofb128_encrypt(const unsigned char *in, unsigned char *out,
	unsigned long length, const AES_KEY *key,
	unsigned char *ivec, int *num) {

	unsigned int n;
	unsigned long l=0;

	assert(in && out && key && ivec && num);

	n = *num;

#if !defined(OPENSSL_SMALL_FOOTPRINT)
	if (AES_BLOCK_SIZE%sizeof(size_t) == 0) do { /* always true actually */
		if (n) {
			while (length) {
				*(out++) = ivec[n] ^ *(in++);
				length--;
				if(!(n = (n + 1) % AES_BLOCK_SIZE))
					break;
			}
		}
#if defined(STRICT_ALIGNMENT)
		if (((size_t)in|(size_t)out|(size_t)ivec)%sizeof(size_t) != 0)
			break;
#endif
		while ((l + AES_BLOCK_SIZE) <= length) {
			unsigned int i;
			AES_encrypt(ivec, ivec, key);
			for (i=0;i<AES_BLOCK_SIZE;i+=sizeof(size_t)) {
				*(size_t*)(out+l+i) =
				*(size_t*)(ivec+i) ^ *(size_t*)(in+l+i);
			}
			l += AES_BLOCK_SIZE;
		}

		if (l < length) {
			AES_encrypt(ivec, ivec, key);
			do {	out[l] = ivec[n] ^ in[l];
				l++; n++;
			} while (l < length);
		}
		*num = n;
		return;
	} while(0);
#endif

	/* this code would be commonly eliminated by x86* compiler */
	while (l<length) {
		if (n == 0) {
			AES_encrypt(ivec, ivec, key);
		}
		out[l] = ivec[n] ^ in[l];
		l++;
		n = (n+1) % AES_BLOCK_SIZE;
	}

	*num=n;
}
