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. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * $FreeBSD: src/sys/libkern/bcmp.c,v 1.6 1999/08/28 00:46:31 peter Exp $ 34 * $DragonFly: src/sys/libkern/bcmp.c,v 1.4 2005/01/04 05:27:47 cpressey Exp $ 35 */ 36 37 #include <string.h> 38 #include <machine/endian.h> 39 40 typedef const void *cvp; 41 typedef const unsigned char *ustring; 42 typedef unsigned long ul; 43 typedef const unsigned long *culp; 44 45 /* 46 * bcmp -- vax cmpc3 instruction 47 */ 48 int 49 bcmp(const void *b1, const void *b2, size_t length) 50 { 51 #if BYTE_ORDER == LITTLE_ENDIAN 52 /* 53 * The following code is endian specific. Changing it from 54 * little-endian to big-endian is fairly trivial, but making 55 * it do both is more difficult. 56 * 57 * Note that this code will reference the entire longword which 58 * includes the final byte to compare. I don't believe this is 59 * a problem since AFAIK, objects are not protected at smaller 60 * than longword boundaries. 61 */ 62 int shl, shr, len = length; 63 ustring p1 = b1, p2 = b2; 64 ul va, vb; 65 66 if (len == 0) 67 return (0); 68 69 /* 70 * align p1 to a longword boundary 71 */ 72 while ((long)p1 & (sizeof(long) - 1)) { 73 if (*p1++ != *p2++) 74 return (1); 75 if (--len <= 0) 76 return (0); 77 } 78 79 /* 80 * align p2 to longword boundary and calculate the shift required to 81 * align p1 and p2 82 */ 83 shr = (long)p2 & (sizeof(long) - 1); 84 if (shr != 0) { 85 p2 -= shr; /* p2 now longword aligned */ 86 shr <<= 3; /* offset in bits */ 87 shl = (sizeof(long) << 3) - shr; 88 89 va = *(culp)p2; 90 p2 += sizeof(long); 91 92 while ((len -= sizeof(long)) >= 0) { 93 vb = *(culp)p2; 94 p2 += sizeof(long); 95 if (*(culp)p1 != (va >> shr | vb << shl)) 96 return (1); 97 p1 += sizeof(long); 98 va = vb; 99 } 100 /* 101 * At this point, len is between -sizeof(long) and -1, 102 * representing 0 .. sizeof(long)-1 bytes remaining. 103 */ 104 if (!(len += sizeof(long))) 105 return (0); 106 107 len <<= 3; /* remaining length in bits */ 108 /* 109 * The following is similar to the `if' condition 110 * inside the above while loop. The ?: is necessary 111 * to avoid accessing the longword after the longword 112 * containing the last byte to be compared. 113 */ 114 return ((((va >> shr | ((shl < len) ? *(culp)p2 << shl : 0)) ^ 115 *(culp)p1) & ((1L << len) - 1)) != 0); 116 } else { 117 /* p1 and p2 have common alignment so no shifting needed */ 118 while ((len -= sizeof(long)) >= 0) { 119 if (*(culp)p1 != *(culp)p2) 120 return (1); 121 p1 += sizeof(long); 122 p2 += sizeof(long); 123 } 124 125 /* 126 * At this point, len is between -sizeof(long) and -1, 127 * representing 0 .. sizeof(long)-1 bytes remaining. 128 */ 129 if (!(len += sizeof(long))) 130 return (0); 131 132 return (((*(culp)p1 ^ *(culp)p2) 133 & ((1L << (len << 3)) - 1)) != 0); 134 } 135 #else 136 char *p1, *p2; 137 138 if (length == 0) 139 return(0); 140 p1 = (char *)b1; 141 p2 = (char *)b2; 142 do 143 if (*p1++ != *p2++) 144 break; 145 while (--length); 146 return(length); 147 #endif 148 } 149