/*
* Copyright (c) 1987, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD: src/sys/libkern/bcmp.c,v 1.6 1999/08/28 00:46:31 peter Exp $
* $DragonFly: src/sys/libkern/bcmp.c,v 1.4 2005/01/04 05:27:47 cpressey Exp $
*/
#include
#include
typedef const void *cvp;
typedef const unsigned char *ustring;
typedef unsigned long ul;
typedef const unsigned long *culp;
/*
* bcmp -- vax cmpc3 instruction
*/
int
bcmp(const void *b1, const void *b2, size_t length)
{
#if BYTE_ORDER == LITTLE_ENDIAN
/*
* The following code is endian specific. Changing it from
* little-endian to big-endian is fairly trivial, but making
* it do both is more difficult.
*
* Note that this code will reference the entire longword which
* includes the final byte to compare. I don't believe this is
* a problem since AFAIK, objects are not protected at smaller
* than longword boundaries.
*/
int shl, shr, len = length;
ustring p1 = b1, p2 = b2;
ul va, vb;
if (len == 0)
return (0);
/*
* align p1 to a longword boundary
*/
while ((long)p1 & (sizeof(long) - 1)) {
if (*p1++ != *p2++)
return (1);
if (--len <= 0)
return (0);
}
/*
* align p2 to longword boundary and calculate the shift required to
* align p1 and p2
*/
shr = (long)p2 & (sizeof(long) - 1);
if (shr != 0) {
p2 -= shr; /* p2 now longword aligned */
shr <<= 3; /* offset in bits */
shl = (sizeof(long) << 3) - shr;
va = *(culp)p2;
p2 += sizeof(long);
while ((len -= sizeof(long)) >= 0) {
vb = *(culp)p2;
p2 += sizeof(long);
if (*(culp)p1 != (va >> shr | vb << shl))
return (1);
p1 += sizeof(long);
va = vb;
}
/*
* At this point, len is between -sizeof(long) and -1,
* representing 0 .. sizeof(long)-1 bytes remaining.
*/
if (!(len += sizeof(long)))
return (0);
len <<= 3; /* remaining length in bits */
/*
* The following is similar to the `if' condition
* inside the above while loop. The ?: is necessary
* to avoid accessing the longword after the longword
* containing the last byte to be compared.
*/
return ((((va >> shr | ((shl < len) ? *(culp)p2 << shl : 0)) ^
*(culp)p1) & ((1L << len) - 1)) != 0);
} else {
/* p1 and p2 have common alignment so no shifting needed */
while ((len -= sizeof(long)) >= 0) {
if (*(culp)p1 != *(culp)p2)
return (1);
p1 += sizeof(long);
p2 += sizeof(long);
}
/*
* At this point, len is between -sizeof(long) and -1,
* representing 0 .. sizeof(long)-1 bytes remaining.
*/
if (!(len += sizeof(long)))
return (0);
return (((*(culp)p1 ^ *(culp)p2)
& ((1L << (len << 3)) - 1)) != 0);
}
#else
char *p1, *p2;
if (length == 0)
return(0);
p1 = (char *)b1;
p2 = (char *)b2;
do
if (*p1++ != *p2++)
break;
while (--length);
return(length);
#endif
}