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- /*-
- * SPDX-License-Identifier: BSD-3-Clause
- *
- * 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.
- */
- #include <sys/cdefs.h>
- __FBSDID("$FreeBSD$");
- #include <sys/libkern.h>
- #include <machine/endian.h>
- 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
- const char *p1, *p2;
- if (length == 0)
- return(0);
- p1 = b1;
- p2 = b2;
- do
- if (*p1++ != *p2++)
- break;
- while (--length);
- return(length);
- #endif
- }
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