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36 #include "block_abi.h"
37 #define COMPAR(x,y) CALL_BLOCK(compar, x, y)
38 typedef DECLARE_BLOCK(int, compar_block, const void *, const void *);
40 #define COMPAR(x,y) compar(x, y)
44 * Perform a binary search.
46 * The code below is a bit sneaky. After a comparison fails, we
47 * divide the work in half by moving either left or right. If lim
48 * is odd, moving left simply involves halving lim: e.g., when lim
49 * is 5 we look at item 2, so we change lim to 2 so that we will
50 * look at items 0 & 1. If lim is even, the same applies. If lim
51 * is odd, moving right again involves halving lim, this time moving
52 * the base up one item past p: e.g., when lim is 5 we change base
53 * to item 3 and make lim 2 so that we will look at items 3 and 4.
54 * If lim is even, however, we have to shrink it by one before
55 * halving: e.g., when lim is 4, we still looked at item 2, so we
56 * have to make lim 3, then halve, obtaining 1, so that we will only
61 bsearch_b(const void *key, const void *base0, size_t nmemb, size_t size,
65 bsearch(const void *key, const void *base0, size_t nmemb, size_t size,
66 int (*compar)(const void *, const void *))
69 const char *base = base0;
74 for (lim = nmemb; lim != 0; lim >>= 1) {
75 p = base + (lim >> 1) * size;
79 if (cmp > 0) { /* key > p: move right */
80 base = (char *)p + size;
82 } /* else move left */