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