1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1987, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include <sys/libkern.h> 36 #include <machine/endian.h> 37 38 typedef const void *cvp; 39 typedef const unsigned char *ustring; 40 typedef unsigned long ul; 41 typedef const unsigned long *culp; 42 43 /* 44 * bcmp -- vax cmpc3 instruction 45 */ 46 int 47 (bcmp)(const void *b1, const void *b2, size_t length) 48 { 49 #if BYTE_ORDER == LITTLE_ENDIAN 50 /* 51 * The following code is endian specific. Changing it from 52 * little-endian to big-endian is fairly trivial, but making 53 * it do both is more difficult. 54 * 55 * Note that this code will reference the entire longword which 56 * includes the final byte to compare. I don't believe this is 57 * a problem since AFAIK, objects are not protected at smaller 58 * than longword boundaries. 59 */ 60 int shl, shr, len = length; 61 ustring p1 = b1, p2 = b2; 62 ul va, vb; 63 64 if (len == 0) 65 return (0); 66 67 /* 68 * align p1 to a longword boundary 69 */ 70 while ((long)p1 & (sizeof(long) - 1)) { 71 if (*p1++ != *p2++) 72 return (1); 73 if (--len <= 0) 74 return (0); 75 } 76 77 /* 78 * align p2 to longword boundary and calculate the shift required to 79 * align p1 and p2 80 */ 81 shr = (long)p2 & (sizeof(long) - 1); 82 if (shr != 0) { 83 p2 -= shr; /* p2 now longword aligned */ 84 shr <<= 3; /* offset in bits */ 85 shl = (sizeof(long) << 3) - shr; 86 87 va = *(culp)p2; 88 p2 += sizeof(long); 89 90 while ((len -= sizeof(long)) >= 0) { 91 vb = *(culp)p2; 92 p2 += sizeof(long); 93 if (*(culp)p1 != (va >> shr | vb << shl)) 94 return (1); 95 p1 += sizeof(long); 96 va = vb; 97 } 98 /* 99 * At this point, len is between -sizeof(long) and -1, 100 * representing 0 .. sizeof(long)-1 bytes remaining. 101 */ 102 if (!(len += sizeof(long))) 103 return (0); 104 105 len <<= 3; /* remaining length in bits */ 106 /* 107 * The following is similar to the `if' condition 108 * inside the above while loop. The ?: is necessary 109 * to avoid accessing the longword after the longword 110 * containing the last byte to be compared. 111 */ 112 return ((((va >> shr | ((shl < len) ? *(culp)p2 << shl : 0)) ^ 113 *(culp)p1) & ((1L << len) - 1)) != 0); 114 } else { 115 /* p1 and p2 have common alignment so no shifting needed */ 116 while ((len -= sizeof(long)) >= 0) { 117 if (*(culp)p1 != *(culp)p2) 118 return (1); 119 p1 += sizeof(long); 120 p2 += sizeof(long); 121 } 122 123 /* 124 * At this point, len is between -sizeof(long) and -1, 125 * representing 0 .. sizeof(long)-1 bytes remaining. 126 */ 127 if (!(len += sizeof(long))) 128 return (0); 129 130 return (((*(culp)p1 ^ *(culp)p2) 131 & ((1L << (len << 3)) - 1)) != 0); 132 } 133 #else 134 const char *p1, *p2; 135 136 if (length == 0) 137 return(0); 138 p1 = b1; 139 p2 = b2; 140 do 141 if (*p1++ != *p2++) 142 break; 143 while (--length); 144 return(length); 145 #endif 146 } 147