cosmopolitan/libc/str/strlcat.c

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ 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/bits/safemacros.internal.h"
#include "libc/str/str.h"

/**
 * Appends string SRC to DEST, the BSD way.
 *
 * @param dest is a buffer holding a NUL-terminated string
 * @param src is a NUL-terminated string
 * @param size is byte capacity of dest
 * @return strlen(dest) + strlen(src)
 * @note dest and src can't overlap
 * @see strncat()
 */
size_t strlcat(char *dest, const char *src, size_t size) {
  size_t destlen = strnlen(dest, size);
  size_t srclen = strlen(src);
  if (size) {
    memcpy(&dest[destlen], src, min(srclen, size - destlen));
    dest[min(destlen + srclen, size - 1)] = '\0';
  }
  return destlen + srclen;
}