db/btree/bt_stack.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23 /*
  24  * Copyright (c) 1990, 1993
  25  *      The Regents of the University of California.  All rights reserved.
  26  *
  27  * This code is derived from software contributed to Berkeley by
  28  * Mike Olson.
  29  *
  30  * Redistribution and use in source and binary forms, with or without
  31  * modification, are permitted provided that the following conditions
  32  * are met:
  33  * 1. Redistributions of source code must retain the above copyright
  34  *    notice, this list of conditions and the following disclaimer.
  35  * 2. Redistributions in binary form must reproduce the above copyright
  36  *    notice, this list of conditions and the following disclaimer in the
  37  *    documentation and/or other materials provided with the distribution.
  38  * 3. All advertising materials mentioning features or use of this software
  39  *    must display the following acknowledgement:
  40  *      This product includes software developed by the University of
  41  *      California, Berkeley and its contributors.
  42  * 4. Neither the name of the University nor the names of its contributors
  43  *    may be used to endorse or promote products derived from this software
  44  *    without specific prior written permission.
  45  *
  46  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  47  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  48  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  49  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  50  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  51  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  52  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  53  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  54  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  55  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  56  * SUCH DAMAGE.
  57  */
  58
  59
  60 #include <sys/types.h>
  61
  62 #include <errno.h>
  63 #include <stdio.h>
  64 #include <stdlib.h>
  65
  66 #include <db.h>
  67 #include "btree.h"
  68
  69 /*
  70  * When a page splits, a new record has to be inserted into its parent page.
  71  * This page may have to split as well, all the way up to the root.  Since
  72  * parent pointers in each page would be expensive, we maintain a stack of
  73  * parent pages as we descend the tree.
  74  *
  75  * XXX
  76  * This is a concurrency problem -- if user a builds a stack, then user b
  77  * splits the tree, then user a tries to split the tree, there's a new level
  78  * in the tree that user a doesn't know about.
  79  */
  80
  81 /*
  82  * __BT_PUSH -- Push parent page info onto the stack (LIFO).
  83  *
  84  * Parameters:
  85  *      t:      tree
  86  *      pgno:   page
  87  *      index:  page index
  88  *
  89  * Returns:
  90  *      RET_ERROR, RET_SUCCESS
  91  */
  92 int
  93 __bt_push(t, pgno, index)
  94         BTREE *t;
  95         pgno_t pgno;
  96         indx_t index;
  97 {
  98         if (t->bt_sp == t->bt_maxstack) {
  99                 t->bt_maxstack += 50;
 100                 if ((t->bt_stack = (EPGNO *)realloc(t->bt_stack,
 101                     t->bt_maxstack * sizeof(EPGNO))) == NULL) {
 102                         t->bt_maxstack -= 50;
 103                         return (RET_ERROR);
 104                 }
 105         }
 106
 107         t->bt_stack[t->bt_sp].pgno = pgno;
 108         t->bt_stack[t->bt_sp].index = index;
 109         ++t->bt_sp;
 110         return (RET_SUCCESS);
 111 }