src/port/memcmp.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * memcmp.c
   4  *        compares memory bytes
   5  *
   6  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
   7  *
   8  *
   9  * IDENTIFICATION
  10  *        $PostgreSQL$
  11  *
  12  * This file was taken from NetBSD and is used by SunOS because memcmp
  13  * on that platform does not properly compare negative bytes. The
  14  * NetBSD copyright terms follow.
  15  */
  16
  17 /*-
  18  * Copyright (c) 1990, 1993
  19  *      The Regents of the University of California.  All rights reserved.
  20  *
  21  * This code is derived from software contributed to Berkeley by
  22  * Chris Torek.
  23  *
  24  * Redistribution and use in source and binary forms, with or without
  25  * modification, are permitted provided that the following conditions
  26  * are met:
  27  * 1. Redistributions of source code must retain the above copyright
  28  *        notice, this list of conditions and the following disclaimer.
  29  * 2. Redistributions in binary form must reproduce the above copyright
  30  *        notice, this list of conditions and the following disclaimer in the
  31  *        documentation and/or other materials provided with the distribution.
  32  * 3. Neither the name of the University nor the names of its contributors
  33  *        may be used to endorse or promote products derived from this software
  34  *        without specific prior written permission.
  35  *
  36  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  37  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  38  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  39  * ARE DISCLAIMED.      IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  40  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  41  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  42  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  43  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  44  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  45  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  46  * SUCH DAMAGE.
  47  */
  48
  49 #include "c.h"
  50
  51
  52 /*
  53  * Compare memory regions.
  54  */
  55 int
  56 memcmp(const void *s1, const void *s2, size_t n)
  57 {
  58         if (n != 0)
  59         {
  60                 const unsigned char *p1 = s1,
  61                                    *p2 = s2;
  62
  63                 do
  64                 {
  65                         if (*p1++ != *p2++)
  66                                 return (*--p1 - *--p2);
  67                 } while (--n != 0);
  68         }
  69         return 0;
  70 }