1 /* 2 * Copyright (c) 1987, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * $FreeBSD: src/sys/libkern/bcmp.c,v 1.6 1999/08/28 00:46:31 peter Exp $ 30 * $DragonFly: src/sys/libkern/bcmp.c,v 1.4 2005/01/04 05:27:47 cpressey Exp $ 31 */ 32 33 #include <string.h> 34 #include <machine/endian.h> 35 36 typedef const void *cvp; 37 typedef const unsigned char *ustring; 38 typedef unsigned long ul; 39 typedef const unsigned long *culp; 40 41 /* 42 * bcmp -- vax cmpc3 instruction 43 */ 44 int 45 bcmp(const void *b1, const void *b2, size_t length) 46 { 47 #if BYTE_ORDER == LITTLE_ENDIAN 48 /* 49 * The following code is endian specific. Changing it from 50 * little-endian to big-endian is fairly trivial, but making 51 * it do both is more difficult. 52 * 53 * Note that this code will reference the entire longword which 54 * includes the final byte to compare. I don't believe this is 55 * a problem since AFAIK, objects are not protected at smaller 56 * than longword boundaries. 57 */ 58 int shl, shr, len = length; 59 ustring p1 = b1, p2 = b2; 60 ul va, vb; 61 62 if (len == 0) 63 return (0); 64 65 /* 66 * align p1 to a longword boundary 67 */ 68 while ((long)p1 & (sizeof(long) - 1)) { 69 if (*p1++ != *p2++) 70 return (1); 71 if (--len <= 0) 72 return (0); 73 } 74 75 /* 76 * align p2 to longword boundary and calculate the shift required to 77 * align p1 and p2 78 */ 79 shr = (long)p2 & (sizeof(long) - 1); 80 if (shr != 0) { 81 p2 -= shr; /* p2 now longword aligned */ 82 shr <<= 3; /* offset in bits */ 83 shl = (sizeof(long) << 3) - shr; 84 85 va = *(culp)p2; 86 p2 += sizeof(long); 87 88 while ((len -= sizeof(long)) >= 0) { 89 vb = *(culp)p2; 90 p2 += sizeof(long); 91 if (*(culp)p1 != (va >> shr | vb << shl)) 92 return (1); 93 p1 += sizeof(long); 94 va = vb; 95 } 96 /* 97 * At this point, len is between -sizeof(long) and -1, 98 * representing 0 .. sizeof(long)-1 bytes remaining. 99 */ 100 if (!(len += sizeof(long))) 101 return (0); 102 103 len <<= 3; /* remaining length in bits */ 104 /* 105 * The following is similar to the `if' condition 106 * inside the above while loop. The ?: is necessary 107 * to avoid accessing the longword after the longword 108 * containing the last byte to be compared. 109 */ 110 return ((((va >> shr | ((shl < len) ? *(culp)p2 << shl : 0)) ^ 111 *(culp)p1) & ((1L << len) - 1)) != 0); 112 } else { 113 /* p1 and p2 have common alignment so no shifting needed */ 114 while ((len -= sizeof(long)) >= 0) { 115 if (*(culp)p1 != *(culp)p2) 116 return (1); 117 p1 += sizeof(long); 118 p2 += sizeof(long); 119 } 120 121 /* 122 * At this point, len is between -sizeof(long) and -1, 123 * representing 0 .. sizeof(long)-1 bytes remaining. 124 */ 125 if (!(len += sizeof(long))) 126 return (0); 127 128 return (((*(culp)p1 ^ *(culp)p2) 129 & ((1L << (len << 3)) - 1)) != 0); 130 } 131 #else 132 char *p1, *p2; 133 134 if (length == 0) 135 return(0); 136 p1 = (char *)b1; 137 p2 = (char *)b2; 138 do 139 if (*p1++ != *p2++) 140 break; 141 while (--length); 142 return(length); 143 #endif 144 } 145