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/*
* Copyright (c) 2012, 2016 Jonas 'Sortie' Termansen.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* stdlib/bsearch.c
* Binary search.
*/
#include <stdint.h>
#include <stdlib.h>
/*
* Semantics of binary search:
*
* bsearch(key, base, 0, size, compare) may return NULL.
*
* If 0 <= i < nmemb
* and ptr = base + size * i
* and compare(key, ptr) = 0 then
* bsearch(key, base, nmemb, size, compare) may return ptr.
*
* If 0 <= i < nmemb
* and ptr = base + size * i
* and compare(key, ptr) < 0 then
* bsearch(key, base, nmemb, size, compare) may return
* bsearch(key, base, i, size, compare).
*
* If 0 <= i < nmemb
* and ptr = base + size * i
* and compare(key, ptr) > 0 then
* bsearch(key, base, nmemb, size, compare) may return
* bsearch(key, base + size * (i + 1), nemb - (i + 1), size, compare).
*/
void* bsearch(const void* key,
const void* base_ptr,
size_t nmemb,
size_t size,
int (*compare)(const void*, const void*))
{
const unsigned char* base = (const unsigned char*) base_ptr;
while ( nmemb )
{
size_t i = nmemb / 2;
const unsigned char* candidate = base + i * size;
int rel = compare(key, candidate);
if ( rel < 0 ) /* key smaller than candidate */
nmemb = i;
else if ( 0 < rel ) /* key greater than candidate */
{
base = candidate + size;
nmemb -= i + 1;
}
else /* key equal to candidate */
return (void*) candidate;
}
return NULL;
}
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