2 * SPDX-License-Identifier: BSD-3-Clause
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32 #if defined(LIBC_SCCS) && !defined(lint)
33 static char sccsid[] = "@(#)bsearch.c 8.1 (Berkeley) 6/4/93";
34 #endif /* LIBC_SCCS and not lint */
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD$");
42 #include "block_abi.h"
43 #define COMPAR(x,y) CALL_BLOCK(compar, x, y)
45 #define COMPAR(x,y) compar(x, y)
49 * Perform a binary search.
51 * The code below is a bit sneaky. After a comparison fails, we
52 * divide the work in half by moving either left or right. If lim
53 * is odd, moving left simply involves halving lim: e.g., when lim
54 * is 5 we look at item 2, so we change lim to 2 so that we will
55 * look at items 0 & 1. If lim is even, the same applies. If lim
56 * is odd, moving right again involves halving lim, this time moving
57 * the base up one item past p: e.g., when lim is 5 we change base
58 * to item 3 and make lim 2 so that we will look at items 3 and 4.
59 * If lim is even, however, we have to shrink it by one before
60 * halving: e.g., when lim is 4, we still looked at item 2, so we
61 * have to make lim 3, then halve, obtaining 1, so that we will only
66 bsearch_b(const void *key, const void *base0, size_t nmemb, size_t size,
67 DECLARE_BLOCK(int, compar, const void *, const void *))
70 bsearch(const void *key, const void *base0, size_t nmemb, size_t size,
71 int (*compar)(const void *, const void *))
74 const char *base = base0;
79 for (lim = nmemb; lim != 0; lim >>= 1) {
80 p = base + (lim >> 1) * size;
84 if (cmp > 0) { /* key > p: move right */
85 base = (char *)p + size;
87 } /* else move left */