Age         Owner                  TLA  Line data    Source code

                                  1                 : /*
                                  2                 :  * bsearch_arg.c: bsearch variant with a user-supplied pointer
                                  3                 :  *
                                  4                 :  * Copyright (c) 2021-2023, PostgreSQL Global Development Group
                                  5                 :  * Copyright (c) 1990 Regents of the University of California.
                                  6                 :  * All rights reserved.
                                  7                 :  *
                                  8                 :  * Redistribution and use in source and binary forms, with or without
                                  9                 :  * modification, are permitted provided that the following conditions
                                 10                 :  * are met:
                                 11                 :  * 1. Redistributions of source code must retain the above copyright
                                 12                 :  *    notice, this list of conditions and the following disclaimer.
                                 13                 :  * 2. Redistributions in binary form must reproduce the above copyright
                                 14                 :  *    notice, this list of conditions and the following disclaimer in the
                                 15                 :  *    documentation and/or other materials provided with the distribution.
                                 16                 :  * 3. [rescinded 22 July 1999]
                                 17                 :  * 4. Neither the name of the University nor the names of its contributors
                                 18                 :  *    may be used to endorse or promote products derived from this software
                                 19                 :  *    without specific prior written permission.
                                 20                 :  *
                                 21                 :  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
                                 22                 :  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                                 23                 :  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                                 24                 :  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
                                 25                 :  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                                 26                 :  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                                 27                 :  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                                 28                 :  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                                 29                 :  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                                 30                 :  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                                 31                 :  * SUCH DAMAGE.
                                 32                 :  *
                                 33                 :  * src/port/bsearch_arg.c
                                 34                 :  */
                                 35                 : 
                                 36                 : #include "c.h"
                                 37                 : 
                                 38                 : /*
                                 39                 :  * Perform a binary search.
                                 40                 :  *
                                 41                 :  * The code below is a bit sneaky.  After a comparison fails, we
                                 42                 :  * divide the work in half by moving either left or right. If lim
                                 43                 :  * is odd, moving left simply involves halving lim: e.g., when lim
                                 44                 :  * is 5 we look at item 2, so we change lim to 2 so that we will
                                 45                 :  * look at items 0 & 1.  If lim is even, the same applies.  If lim
                                 46                 :  * is odd, moving right again involves halving lim, this time moving
                                 47                 :  * the base up one item past p: e.g., when lim is 5 we change base
                                 48                 :  * to item 3 and make lim 2 so that we will look at items 3 and 4.
                                 49                 :  * If lim is even, however, we have to shrink it by one before
                                 50                 :  * halving: e.g., when lim is 4, we still looked at item 2, so we
                                 51                 :  * have to make lim 3, then halve, obtaining 1, so that we will only
                                 52                 :  * look at item 3.
                                 53                 :  */
                                 54                 : void *
  747 tomas.vondra               55 CBC     7943733 : bsearch_arg(const void *key, const void *base0,
                                 56                 :             size_t nmemb, size_t size,
                                 57                 :             int (*compar) (const void *, const void *, void *),
                                 58                 :             void *arg)
                                 59                 : {
                                 60         7943733 :     const char *base = (const char *) base0;
                                 61                 :     int         lim,
                                 62                 :                 cmp;
                                 63                 :     const void *p;
                                 64                 : 
                                 65        50875074 :     for (lim = nmemb; lim != 0; lim >>= 1)
                                 66                 :     {
                                 67        42955566 :         p = base + (lim >> 1) * size;
                                 68        42955566 :         cmp = (*compar) (key, p, arg);
                                 69        42955566 :         if (cmp == 0)
                                 70           24225 :             return (void *) p;
                                 71        42931341 :         if (cmp > 0)
                                 72                 :         {                       /* key > p: move right */
                                 73        42486237 :             base = (const char *) p + size;
                                 74        42486237 :             lim--;
                                 75                 :         }                       /* else move left */
                                 76                 :     }
                                 77         7919508 :     return (NULL);
                                 78                 : }