/*

 * Copyright 2008-2021 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy

 * in the file LICENSE in the source distribution or at

 * https://www.openssl.org/source/license.html

 */

#include <string.h>

#include <openssl/crypto.h>

#include "crypto/modes.h"

#if defined(__GNUC__) && !defined(STRICT_ALIGNMENT)

typedef size_t size_t_aX __attribute((__aligned__(1)));

#else

typedef size_t size_t_aX;

#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;

    if (*num < 0) {

        /* There is no good way to signal an error return from here */

        *num = -1;

        return;

    }

    n = *num;

#if !defined(OPENSSL_SMALL_FOOTPRINT)

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

        do {

            while (n && len) {

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

                --len;

                n = (n + 1) % 16;

            }

#if defined(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_aX *)(out + n) = *(size_t_aX *)(in + n)

                        ^ *(size_t_aX *)(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;

}