lib/libc/DB/recno/rec_search.c

   1 /*-
   2  * Copyright (c) 1990 The Regents of the University of California.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  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
  34 #if defined(LIBC_SCCS) && !defined(lint)
  35 static char sccsid[] = "@(#)rec_search.c        5.8 (Berkeley) 2/14/93";
  36 #endif /* LIBC_SCCS and not lint */
  37
  38 #include <sys/types.h>
  39
  40 #include <errno.h>
  41 #include <stdio.h>
  42
  43 #include <db.h>
  44 #include "recno.h"
  45
  46 /*
  47  * __REC_SEARCH -- Search a btree for a key.
  48  *
  49  * Parameters:
  50  *      t:      tree to search
  51  *      recno:  key to find
  52  *      op:     search operation
  53  *
  54  * Returns:
  55  *      EPG for matching record, if any, or the EPG for the location of the
  56  *      key, if it were inserted into the tree.
  57  *
  58  * Warnings:
  59  *      The EPG returned is in static memory, and will be overwritten by the
  60  *      next search of any kind in any tree.
  61  */
  62 EPG *
  63 __rec_search(t, recno, op)
  64         BTREE *t;
  65         recno_t recno;
  66         enum SRCHOP op;
  67 {
  68         static EPG e;
  69         register indx_t index;
  70         register PAGE *h;
  71         EPGNO *parent;
  72         RINTERNAL *r;
  73         pgno_t pg;
  74         indx_t top;
  75         recno_t total;
  76         int serrno;
  77
  78         BT_CLR(t);
  79         for (pg = P_ROOT, total = 0;;) {
  80                 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
  81                         goto err;
  82                 if (h->flags & P_RLEAF) {
  83                         e.page = h;
  84                         e.index = recno - total;
  85                         return (&e);
  86                 }
  87                 for (index = 0, top = NEXTINDEX(h);;) {
  88                         r = GETRINTERNAL(h, index);
  89                         if (++index == top || total + r->nrecs > recno)
  90                                 break;
  91                         total += r->nrecs;
  92                 }
  93
  94                 if (__bt_push(t, pg, index - 1) == RET_ERROR)
  95                         return (NULL);
  96
  97                 pg = r->pgno;
  98                 switch (op) {
  99                 case SDELETE:
 100                         --GETRINTERNAL(h, (index - 1))->nrecs;
 101                         mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 102                         break;
 103                 case SINSERT:
 104                         ++GETRINTERNAL(h, (index - 1))->nrecs;
 105                         mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 106                         break;
 107                 case SEARCH:
 108                         mpool_put(t->bt_mp, h, 0);
 109                         break;
 110                 }
 111
 112         }
 113         /* Try and recover the tree. */
 114 err:    serrno = errno;
 115         if (op != SEARCH)
 116                 while  ((parent = BT_POP(t)) != NULL) {
 117                         if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
 118                                 break;
 119                         if (op == SINSERT)
 120                                 --GETRINTERNAL(h, parent->index)->nrecs;
 121                         else
 122                                 ++GETRINTERNAL(h, parent->index)->nrecs;
 123                         mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 124                 }
 125         errno = serrno;
 126         return (NULL);
 127 }