/*

 * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the OpenSSL license (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 "des_local.h"

/*

 * The input and output are loaded in multiples of 8 bits. What this means is

 * that if you have 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(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;

}