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 */ 35 36 #include <string.h> 37 #include <machine/endian.h> 38 39 typedef const void *cvp; 40 typedef const unsigned char *ustring; 41 typedef unsigned long ul; 42 typedef const unsigned long *culp; 43 44 /* 45 * bcmp -- vax cmpc3 instruction 46 */ 47 int 48 bcmp(b1, b2, length) 49 const void *b1, *b2; 50 register size_t length; 51 { 52 #if BYTE_ORDER == LITTLE_ENDIAN 53 /* 54 * The following code is endian specific. Changing it from 55 * little-endian to big-endian is fairly trivial, but making 56 * it do both is more difficult. 57 * 58 * Note that this code will reference the entire longword which 59 * includes the final byte to compare. I don't believe this is 60 * a problem since AFAIK, objects are not protected at smaller 61 * than longword boundaries. 62 */ 63 int shl, shr, len = length; 64 ustring p1 = b1, p2 = b2; 65 ul va, vb; 66 67 if (len == 0) 68 return (0); 69 70 /* 71 * align p1 to a longword boundary 72 */ 73 while ((long)p1 & (sizeof(long) - 1)) { 74 if (*p1++ != *p2++) 75 return (1); 76 if (--len <= 0) 77 return (0); 78 } 79 80 /* 81 * align p2 to longword boundary and calculate the shift required to 82 * align p1 and p2 83 */ 84 shr = (long)p2 & (sizeof(long) - 1); 85 if (shr != 0) { 86 p2 -= shr; /* p2 now longword aligned */ 87 shr <<= 3; /* offset in bits */ 88 shl = (sizeof(long) << 3) - shr; 89 90 va = *(culp)p2; 91 p2 += sizeof(long); 92 93 while ((len -= sizeof(long)) >= 0) { 94 vb = *(culp)p2; 95 p2 += sizeof(long); 96 if (*(culp)p1 != (va >> shr | vb << shl)) 97 return (1); 98 p1 += sizeof(long); 99 va = vb; 100 } 101 /* 102 * At this point, len is between -sizeof(long) and -1, 103 * representing 0 .. sizeof(long)-1 bytes remaining. 104 */ 105 if (!(len += sizeof(long))) 106 return (0); 107 108 len <<= 3; /* remaining length in bits */ 109 /* 110 * The following is similar to the `if' condition 111 * inside the above while loop. The ?: is necessary 112 * to avoid accessing the longword after the longword 113 * containing the last byte to be compared. 114 */ 115 return ((((va >> shr | ((shl < len) ? *(culp)p2 << shl : 0)) ^ 116 *(culp)p1) & ((1L << len) - 1)) != 0); 117 } else { 118 /* p1 and p2 have common alignment so no shifting needed */ 119 while ((len -= sizeof(long)) >= 0) { 120 if (*(culp)p1 != *(culp)p2) 121 return (1); 122 p1 += sizeof(long); 123 p2 += sizeof(long); 124 } 125 126 /* 127 * At this point, len is between -sizeof(long) and -1, 128 * representing 0 .. sizeof(long)-1 bytes remaining. 129 */ 130 if (!(len += sizeof(long))) 131 return (0); 132 133 return (((*(culp)p1 ^ *(culp)p2) 134 & ((1L << (len << 3)) - 1)) != 0); 135 } 136 #else 137 register char *p1, *p2; 138 139 if (length == 0) 140 return(0); 141 p1 = (char *)b1; 142 p2 = (char *)b2; 143 do 144 if (*p1++ != *p2++) 145 break; 146 while (--length); 147 return(length); 148 #endif 149 } 150