Safer version of strcpy/strncpy/strlcpy

srtlncpy.c

#include "strlncpy.h"

size_t strlncpy(char *dst, const char *src, size_t dbytes, size_t sbytes)
{
    char *d = dst;
    const char *s = src;
    size_t n = (dbytes > sbytes) ? sbytes : dbytes;

    /* Copy as many bytes as will fit */
    while(n-- > 0) {
        if('\0' == (*d++ = *s++))
            break;
    }   

    /* Not enough room in dst */
    if(0 == n && dbytes != 0)
        *d = '\0'; /* NUL-terminate dst */

    return d - dst - 1; /* count does not include NUL */
}

strlncpy.h

/*
 * Copyright (c) 2019 Daniel L. Heater
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
 * WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE
 * LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY
 * DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
 * IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
 * ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#ifndef __STRLNCPY_H__
#define __STRLNCPY_H__

#include <stddef.h>

/**
 * Safer version of str[nl]cpy()
 * Always NUL terminates (unless dbytes== 0).
 * @param dst Destination string to copy to.
 * @param src Source string to copy from.
 * @param dbytes Length of the destination buffer.
 * @param sbytes Length of the sourcebuffer.
 * @retrun The number of bytes copied.
 */
size_t strlncpy(char *dst, const char *src, size_t dbytes, size_t sbytes);

#endif /* __STRLNCPY_H__ */