/*-
 * SPDX-License-Identifier: BSD-2-Clause
 * Copyright (c) 2024 rilysh <nightquick@proton.me>
 */

#include <string.h>
#include <unistd.h>
#include <sys/endian.h>

void
swab(const void * __restrict from, void * __restrict to, ssize_t len)
{
        const char *f = from;
        char *t = to;
        uint16_t tmp;

        /*
         * POSIX says overlapping copy behavior is undefined, however many
         * applications assume the old FreeBSD and current GNU libc behavior
         * that will swap the bytes correctly when from == to. Reading both bytes
         * and swapping them before writing them back accomplishes this.
         */
        while (len > 1) {
                memcpy(&tmp, f, 2);
                tmp = bswap16(tmp);
                memcpy(t, &tmp, 2);

                f += 2;
                t += 2;
                len -= 2;
        }
}