usr/src/lib/libc/port/gen/strlcat.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 #pragma ident   "%Z%%M% %I%     %E% SMI"
  28
  29 #include "lint.h"
  30 #include <string.h>
  31 #include <sys/types.h>
  32
  33 /*
  34  * Appends src to the dstsize buffer at dst. The append will never
  35  * overflow the destination buffer and the buffer will always be null
  36  * terminated. Never reference beyond &dst[dstsize-1] when computing
  37  * the length of the pre-existing string.
  38  */
  39
  40 size_t
  41 strlcat(char *dst, const char *src, size_t dstsize)
  42 {
  43         char *df = dst;
  44         size_t left = dstsize;
  45         size_t l1;
  46         size_t l2 = strlen(src);
  47         size_t copied;
  48
  49         while (left-- != 0 && *df != '\0')
  50                 df++;
  51         l1 = df - dst;
  52         if (dstsize == l1)
  53                 return (l1 + l2);
  54
  55         copied = l1 + l2 >= dstsize ? dstsize - l1 - 1 : l2;
  56         (void) memcpy(dst + l1, src, copied);
  57         dst[l1+copied] = '\0';
  58         return (l1 + l2);
  59 }