prettiness police

[unix-history] / usr / src / lib / libc / db / btree / bt_search.c

/*-
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Mike Olson.
*
* %sccs.include.redist.c%
*/

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)bt_search.c 5.5 (Berkeley) %G%";
#endif /* LIBC_SCCS and not lint */

#include <sys/types.h>

#include <db.h>
#include <stdio.h>

#include "btree.h"

/*
* __BT_SEARCH -- Search a btree for a key.
*
* Parameters:
*      t:      tree to search
*      key:    key to find
*      exactp: pointer to exact match flag
*
* Returns:
*      EPG for matching record, if any, or the EPG for the location of the
*      key, if it were inserted into the tree.
*
* Warnings:
*      The EPG returned is in static memory, and will be overwritten by the
*      next search of any kind in any tree.
*/
EPG *
__bt_search(t, key, exactp)
       BTREE *t;
       const DBT *key;
       int *exactp;
{
       register index_t index;
       register int base, cmp, lim;
       register PAGE *h;
       pgno_t pg;
       static EPG e;

       for (pg = P_ROOT;;) {
               if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
                       return (NULL);

               /* Do a binary search on the current page. */
               e.page = h;
               for (base = 0, lim = NEXTINDEX(h); lim; lim >>= 1) {
                       e.index = index = base + (lim >> 1);
                       if ((cmp = __bt_cmp(t, key, &e)) == 0) {
                               if (h->flags & P_BLEAF) {
                                       *exactp = 1;
                                       return (&e);
                               }
                               goto next;
                       }
                       if (cmp > 0) {
                               base = index + 1;
                               --lim;
                       }
               }

               /*
                * No match found.  Base is the smallest index greater than
                * key but may be an illegal index.  Use base if it's a leaf
                * page, decrement it by one if it's an internal page.  This
                * is safe because internal pages can't be empty.
                */
               index = h->flags & P_BLEAF ? base : base - 1;

               /* If it's a leaf page, we're done. */
               if (h->flags & P_BLEAF) {
                       e.index = index;
                       *exactp = 0;
                       return (&e);
               }

next:           if (__bt_push(t, h->pgno, index) == RET_ERROR)
                       return (NULL);
               pg = GETBINTERNAL(h, index)->pgno;
               mpool_put(t->bt_mp, h, 0);
       }
}