/* $OpenBSD: ofb128.c,v 1.4 2015/02/10 09:46:30 miod Exp $ */

/* ====================================================================

 * Copyright (c) 2008 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.

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 * 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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 */

#include <openssl/crypto.h>

#include "modes_lcl.h"

#include <string.h>

#ifndef MODES_DEBUG

# ifndef NDEBUG

#  define NDEBUG

# endif

#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 CRYPTO_ofb128_encrypt(const unsigned char *in, unsigned char *out,

      size_t len, const void *key,

      unsigned char ivec[16], int *num,

      block128_f block)

{

  unsigned int n;

  size_t l=0;

  n = *num;

#if !defined(OPENSSL_SMALL_FOOTPRINT)

  if (16%sizeof(size_t) == 0) do { /* always true actually */

    while (n && len) {

      *(out++) = *(in++) ^ ivec[n];

      --len;

      n = (n+1) % 16;

    }

#ifdef __STRICT_ALIGNMENT

    if (((size_t)in|(size_t)out|(size_t)ivec)%sizeof(size_t) != 0)

      break;

#endif

    while (len>=16) {

      (*block)(ivec, ivec, key);

      for (; n<16; n+=sizeof(size_t))

        *(size_t*)(out+n) =

        *(size_t*)(in+n) ^ *(size_t*)(ivec+n);

      len -= 16;

      out += 16;

      in  += 16;

      n = 0;

    }

    if (len) {

      (*block)(ivec, ivec, key);

      while (len--) {

        out[n] = in[n] ^ ivec[n];

        ++n;

      }

    }

    *num = n;

    return;

  } while(0);

  /* the rest would be commonly eliminated by x86* compiler */

#endif

  while (l<len) {

    if (n==0) {

      (*block)(ivec, ivec, key);

    }

    out[l] = in[l] ^ ivec[n];

    ++l;

    n = (n+1) % 16;

  }

  *num=n;

}