string/stpncpy.c

   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 }