cosmopolitan/libc/str/strlcpy.c

/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8   -*-│
│vi: set et ft=c ts=8 tw=8 fenc=utf-8                                       :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright (c) 1998, 2015 Todd C. Miller <millert@openbsd.org>                │
│                                                                              │
│ Permission to use, copy, modify, and/or 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.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/str/str.h"
// clang-format off
// $OpenBSD: strlcpy.c,v 1.16 2019/01/25 00:19:25 millert Exp $

asm(".ident\t\"\\n\\n\
OpenBSD Strings (ISC)\\n\
Copyright (c) 1998, 2015 Todd C. Miller <millert@openbsd.org>\"");
asm(".include \"libc/disclaimer.inc\"");

/**
 * Copies string, the BSD way.
 *
 * Copy string src to buffer `dst` of size `dsize`. At most `dsize-1`
 * chars will be copied. Always NUL terminates (unless `dsize == 0`).
 * Returns `strlen(src)`; if `retval >= dsize`, truncation occurred.
 */
size_t
strlcpy(char *dst, const char *src, size_t dsize)
{
	const char *osrc = src;
	size_t nleft = dsize;

	/* Copy as many bytes as will fit. */
	if (nleft != 0) {
		while (--nleft != 0) {
			if ((*dst++ = *src++) == '\0')
				break;
		}
	}

	/* Not enough room in dst, add NUL and traverse rest of src. */
	if (nleft == 0) {
		if (dsize != 0)
			*dst = '\0';		/* NUL-terminate dst */
		while (*src++)
			;
	}

	return(src - osrc - 1);	/* count does not include NUL */
}