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author | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
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committer | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
commit | 554fd8c5195424bdbcabf5de30fdc183aba391bd (patch) | |
tree | 976dc5ab7fddf506dadce60ae936f43f58787092 /libiberty/bsearch.c | |
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Diffstat (limited to 'libiberty/bsearch.c')
-rw-r--r-- | libiberty/bsearch.c | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/libiberty/bsearch.c b/libiberty/bsearch.c new file mode 100644 index 000000000..35fad1997 --- /dev/null +++ b/libiberty/bsearch.c @@ -0,0 +1,91 @@ +/* + * Copyright (c) 1990 Regents of the University of California. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. [rescinded 22 July 1999] + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +/* + +@deftypefn Supplemental void* bsearch (const void *@var{key}, @ + const void *@var{base}, size_t @var{nmemb}, size_t @var{size}, @ + int (*@var{compar})(const void *, const void *)) + +Performs a search over an array of @var{nmemb} elements pointed to by +@var{base} for a member that matches the object pointed to by @var{key}. +The size of each member is specified by @var{size}. The array contents +should be sorted in ascending order according to the @var{compar} +comparison function. This routine should take two arguments pointing to +the @var{key} and to an array member, in that order, and should return an +integer less than, equal to, or greater than zero if the @var{key} object +is respectively less than, matching, or greater than the array member. + +@end deftypefn + +*/ + +#include "config.h" +#include "ansidecl.h" +#include <sys/types.h> /* size_t */ +#include <stdio.h> + +/* + * Perform a binary search. + * + * The code below is a bit sneaky. After a comparison fails, we + * divide the work in half by moving either left or right. If lim + * is odd, moving left simply involves halving lim: e.g., when lim + * is 5 we look at item 2, so we change lim to 2 so that we will + * look at items 0 & 1. If lim is even, the same applies. If lim + * is odd, moving right again involes halving lim, this time moving + * the base up one item past p: e.g., when lim is 5 we change base + * to item 3 and make lim 2 so that we will look at items 3 and 4. + * If lim is even, however, we have to shrink it by one before + * halving: e.g., when lim is 4, we still looked at item 2, so we + * have to make lim 3, then halve, obtaining 1, so that we will only + * look at item 3. + */ +void * +bsearch (register const void *key, const void *base0, + size_t nmemb, register size_t size, + register int (*compar)(const void *, const void *)) +{ + register const char *base = (const char *) base0; + register int lim, cmp; + register const void *p; + + for (lim = nmemb; lim != 0; lim >>= 1) { + p = base + (lim >> 1) * size; + cmp = (*compar)(key, p); + if (cmp == 0) + return (void *)p; + if (cmp > 0) { /* key > p: move right */ + base = (const char *)p + size; + lim--; + } /* else move left */ + } + return (NULL); +} |