sys/libkern/strncpy.c

   1 /*-
   2  * Copyright (c) 1990, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Chris Torek.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * $FreeBSD: src/sys/libkern/strncpy.c,v 1.8 2003/02/10 00:36:27 hsu Exp $
  33  * $DragonFly: src/sys/libkern/strncpy.c,v 1.5 2004/05/05 00:17:44 hsu Exp $
  34  */
  35
  36 #include <sys/libkern.h>
  37
  38 /*
  39  * Copy src to dst, truncating or null-padding to always copy n bytes.
  40  * Return dst.
  41  */
  42 char *
  43 strncpy(char * __restrict dst, const char * __restrict src, size_t n)
  44 {
  45         if (n != 0) {
  46                 char *d = dst;
  47                 const char *s = src;
  48
  49                 do {
  50                         if ((*d++ = *s++) == 0) {
  51                                 /* NUL pad the remaining n-1 bytes */
  52                                 while (--n != 0)
  53                                         *d++ = 0;
  54                                 break;
  55                         }
  56                 } while (--n != 0);
  57         }
  58         return (dst);
  59 }