rec_search.c

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/*-
 * Copyright (c) 1990, 1993
 *  The 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *  This product includes software developed by the University of
 *  California, Berkeley and its contributors.
 * 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.
 */
 
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)rec_search.c    8.4 (Berkeley) 7/14/94";
#endif /* LIBC_SCCS and not lint */
 
#include <sys/types.h>
 
#include <errno.h>
#include <stdio.h>
 
#include "../include/db.h"
#include "recno.h"
 
/*
 * __REC_SEARCH -- Search a btree for a key.
 *
 * Parameters:
 *  t:  tree to search
 *  recno:  key to find
 *  op:     search operation
 *
 * Returns:
 *  EPG for matching record, if any, or the EPG for the location of the
 *  key, if it were inserted into the tree.
 *
 * Returns:
 *  The EPG for matching record, if any, or the EPG for the location
 *  of the key, if it were inserted into the tree, is entered into
 *  the bt_cur field of the tree.  A pointer to the field is returned.
 */
EPG *
__rec_search(t, recno, op)
    BTREE *t;
    recno_t recno;
    enum SRCHOP op;
{
    register indx_t index;
    register PAGE *h;
    EPGNO *parent;
    RINTERNAL *r;
    pgno_t pg;
    indx_t top;
    recno_t total;
    int sverrno;
 
    BT_CLR(t);
    for (pg = P_ROOT, total = 0;;) {
        if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
            goto err;
        if (h->flags & P_RLEAF) {
            t->bt_cur.page = h;
            t->bt_cur.index = recno - total;
            return (&t->bt_cur);
        }
        for (index = 0, top = NEXTINDEX(h);;) {
            r = GETRINTERNAL(h, index);
            if (++index == top || total + r->nrecs > recno)
                break;
            total += r->nrecs;
        }
 
        BT_PUSH(t, pg, index - 1);
 
        pg = r->pgno;
        switch (op) {
        case SDELETE:
            --GETRINTERNAL(h, (index - 1))->nrecs;
            mpool_put(t->bt_mp, h, MPOOL_DIRTY);
            break;
        case SINSERT:
            ++GETRINTERNAL(h, (index - 1))->nrecs;
            mpool_put(t->bt_mp, h, MPOOL_DIRTY);
            break;
        case SEARCH:
            mpool_put(t->bt_mp, h, 0);
            break;
        }
 
    }
    /* Try and recover the tree. */
err:    sverrno = errno;
    if (op != SEARCH)
        while  ((parent = BT_POP(t)) != NULL) {
            if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
                break;
            if (op == SINSERT)
                --GETRINTERNAL(h, parent->index)->nrecs;
            else
                ++GETRINTERNAL(h, parent->index)->nrecs;
                        mpool_put(t->bt_mp, h, MPOOL_DIRTY);
                }
    errno = sverrno;
    return (NULL);
}