1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1990, 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 <stddef.h> 33 #include <stdlib.h> 34 35 #ifdef I_AM_BSEARCH_S 36 #include <errno.h> 37 #include <stdint.h> 38 #include "libc_private.h" 39 #endif 40 41 #ifdef I_AM_BSEARCH_B 42 #include "block_abi.h" 43 #define COMPAR(x,y) CALL_BLOCK(compar, x, y) 44 typedef DECLARE_BLOCK(int, compar_block, const void *, const void *); 45 #elif defined(I_AM_BSEARCH_S) 46 #define COMPAR(x,y) compar((x), (y), context) 47 #else 48 #define COMPAR(x,y) compar(x, y) 49 #endif 50 51 /* 52 * Perform a binary search. 53 * 54 * The code below is a bit sneaky. After a comparison fails, we 55 * divide the work in half by moving either left or right. If lim 56 * is odd, moving left simply involves halving lim: e.g., when lim 57 * is 5 we look at item 2, so we change lim to 2 so that we will 58 * look at items 0 & 1. If lim is even, the same applies. If lim 59 * is odd, moving right again involves halving lim, this time moving 60 * the base up one item past p: e.g., when lim is 5 we change base 61 * to item 3 and make lim 2 so that we will look at items 3 and 4. 62 * If lim is even, however, we have to shrink it by one before 63 * halving: e.g., when lim is 4, we still looked at item 2, so we 64 * have to make lim 3, then halve, obtaining 1, so that we will only 65 * look at item 3. 66 */ 67 #ifdef I_AM_BSEARCH_B 68 void * 69 bsearch_b(const void *key, const void *base0, size_t nmemb, size_t size, 70 compar_block compar) 71 #elif defined(I_AM_BSEARCH_S) 72 void * 73 bsearch_s(const void *key, const void *base0, rsize_t nmemb, rsize_t size, 74 int (*compar)(const void *, const void *, void *), void *context) 75 #else 76 void * 77 bsearch(const void *key, const void *base0, size_t nmemb, size_t size, 78 int (*compar)(const void *, const void *)) 79 #endif 80 { 81 const char *base = base0; 82 size_t lim; 83 int cmp; 84 const void *p; 85 86 #ifdef I_AM_BSEARCH_S 87 if (nmemb > RSIZE_MAX) { 88 __throw_constraint_handler_s("bsearch_s : nmemb > RSIZE_MAX", 89 EINVAL); 90 return (NULL); 91 } else if (size > RSIZE_MAX) { 92 __throw_constraint_handler_s("bsearch_s : size > RSIZE_MAX", 93 EINVAL); 94 return (NULL); 95 } else if (nmemb != 0) { 96 if (key == NULL) { 97 __throw_constraint_handler_s("bsearch_s : key == NULL", 98 EINVAL); 99 return (NULL); 100 } else if (base0 == NULL) { 101 __throw_constraint_handler_s("bsearch_s : base == NULL", 102 EINVAL); 103 return (NULL); 104 } else if (compar == NULL) { 105 __throw_constraint_handler_s("bsearch_s : compar == NULL", 106 EINVAL); 107 return (NULL); 108 } 109 } 110 #endif 111 112 for (lim = nmemb; lim != 0; lim >>= 1) { 113 p = base + (lim >> 1) * size; 114 cmp = COMPAR(key, p); 115 if (cmp == 0) 116 return ((void *)p); 117 if (cmp > 0) { /* key > p: move right */ 118 base = (char *)p + size; 119 lim--; 120 } /* else move left */ 121 } 122 return (NULL); 123 } 124