/*
 * Copyright 1995-2020 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
 */

/*
 * RC4 low level APIs are deprecated for public use, but still ok for internal
 * use.
 */
#include "internal/deprecated.h"

#include <openssl/rc4.h>
#include "rc4_local.h"

/*-
 * RC4 as implemented from a posting from
 * Newsgroups: sci.crypt
 * Subject: RC4 Algorithm revealed.
 * Message-ID: <sternCvKL4B.Hyy@netcom.com>
 * Date: Wed, 14 Sep 1994 06:35:31 GMT
 */

void RC4(RC4_KEY *key, size_t len, const unsigned char *indata,
    unsigned char *outdata)
{
    register RC4_INT *d;
    register RC4_INT x, y, tx, ty;
    size_t i;

    x = key->x;
    y = key->y;
    d = key->data;

#define LOOP(in, out)     \
    x = ((x + 1) & 0xff); \
    tx = d[x];            \
    y = (tx + y) & 0xff;  \
    d[x] = ty = d[y];     \
    d[y] = tx;            \
    (out) = d[(tx + ty) & 0xff] ^ (in);

    i = len >> 3;
    if (i) {
        for (;;) {
            LOOP(indata[0], outdata[0]);
            LOOP(indata[1], outdata[1]);
            LOOP(indata[2], outdata[2]);
            LOOP(indata[3], outdata[3]);
            LOOP(indata[4], outdata[4]);
            LOOP(indata[5], outdata[5]);
            LOOP(indata[6], outdata[6]);
            LOOP(indata[7], outdata[7]);
            indata += 8;
            outdata += 8;
            if (--i == 0)
                break;
        }
    }
    i = len & 0x07;
    if (i) {
        for (;;) {
            LOOP(indata[0], outdata[0]);
            if (--i == 0)
                break;
            LOOP(indata[1], outdata[1]);
            if (--i == 0)
                break;
            LOOP(indata[2], outdata[2]);
            if (--i == 0)
                break;
            LOOP(indata[3], outdata[3]);
            if (--i == 0)
                break;
            LOOP(indata[4], outdata[4]);
            if (--i == 0)
                break;
            LOOP(indata[5], outdata[5]);
            if (--i == 0)
                break;
            LOOP(indata[6], outdata[6]);
            break;
        }
    }
    key->x = x;
    key->y = y;
}