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);
}