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  stpncpy(char * restrict dst, const char * restrict src, size_t maxlen) {
28      const size_t srclen = strnlen(src, maxlen);
29      if (srclen < maxlen) {
30          //  The stpncpy() and strncpy() functions copy at most maxlen
31          //  characters from src into dst.
32          memcpy(dst, src, srclen);
33          //  If src is less than maxlen characters long, the remainder
34          //  of dst is filled with '\0' characters.
35          memset(dst+srclen, 0, maxlen-srclen);
36          //  The stpcpy() and stpncpy() functions return a pointer to the
37          //  terminating '\0' character of dst.
38          return dst+srclen;
39      } else {
40          //  The stpncpy() and strncpy() functions copy at most maxlen
41          //  characters from src into dst.
42          memcpy(dst, src, maxlen);
43          //  If stpncpy() does not terminate dst with a NUL character, it
44          //  instead returns a pointer to src[maxlen] (which does not
45          //  necessarily refer to a valid memory location.)
46          return dst+maxlen;
47      }
48  }