1  /*
 2   * Copyright (c) 2011 Apple, Inc. All rights reserved.
 3   *
 4   * @APPLE_LICENSE_HEADER_START@
 5   * 
 6   * This file contains Original Code and/or Modifications of Original Code
 7   * as defined in and that are subject to the Apple Public Source License
 8   * Version 2.0 (the 'License'). You may not use this file except in
 9   * compliance with the License. Please obtain a copy of the License at
10   * http://www.opensource.apple.com/apsl/ and read it before using this
11   * file.
12   * 
13   * The Original Code and all software distributed under the License are
14   * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
15   * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
16   * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
17   * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
18   * Please see the License for the specific language governing rights and
19   * limitations under the License.
20   * 
21   * @APPLE_LICENSE_HEADER_END@
22   */
23  
24  #include <string.h>
25  
26  char *
27  strncat(char *restrict dst, const char *restrict src, size_t maxlen) {
28  	const size_t dstlen = strlen(dst);
29  	const size_t srclen = strnlen(src, maxlen);
30      //  The strcat() and strncat() functions append a copy of the null-
31      //  terminated string src to the end of the null-terminated string dst,
32      //  then add a terminating '\0'.  The string dst must have sufficient
33      //  space to hold the result.
34      //
35      //  The strncat() function appends not more than maxlen characters
36      //  from src, and then adds a terminating '\0'.
37      const size_t cpylen = srclen < maxlen ? srclen : maxlen;
38      memcpy(dst+dstlen, src, cpylen);
39      dst[dstlen+cpylen] = '\0';
40      //  The strcat() and strncat() functions return dst.
41      return dst;
42  }