db.subproj/btree.subproj/bt_stack.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * Copyright (c) 1990, 1993
  24  *      The Regents of the University of California.  All rights reserved.
  25  *
  26  * This code is derived from software contributed to Berkeley by
  27  * Mike Olson.
  28  *
  29  * Redistribution and use in source and binary forms, with or without
  30  * modification, are permitted provided that the following conditions
  31  * are met:
  32  * 1. Redistributions of source code must retain the above copyright
  33  *    notice, this list of conditions and the following disclaimer.
  34  * 2. Redistributions in binary form must reproduce the above copyright
  35  *    notice, this list of conditions and the following disclaimer in the
  36  *    documentation and/or other materials provided with the distribution.
  37  * 3. All advertising materials mentioning features or use of this software
  38  *    must display the following acknowledgement:
  39  *      This product includes software developed by the University of
  40  *      California, Berkeley and its contributors.
  41  * 4. Neither the name of the University nor the names of its contributors
  42  *    may be used to endorse or promote products derived from this software
  43  *    without specific prior written permission.
  44  *
  45  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  46  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  47  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  48  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  49  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  50  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  51  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  52  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  53  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  54  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  55  * SUCH DAMAGE.
  56  */
  57
  58
  59 #include <sys/types.h>
  60
  61 #include <errno.h>
  62 #include <stdio.h>
  63 #include <stdlib.h>
  64
  65 #include <db.h>
  66 #include "btree.h"
  67
  68 /*
  69  * When a page splits, a new record has to be inserted into its parent page.
  70  * This page may have to split as well, all the way up to the root.  Since
  71  * parent pointers in each page would be expensive, we maintain a stack of
  72  * parent pages as we descend the tree.
  73  *
  74  * XXX
  75  * This is a concurrency problem -- if user a builds a stack, then user b
  76  * splits the tree, then user a tries to split the tree, there's a new level
  77  * in the tree that user a doesn't know about.
  78  */
  79
  80 /*
  81  * __BT_PUSH -- Push parent page info onto the stack (LIFO).
  82  *
  83  * Parameters:
  84  *      t:      tree
  85  *      pgno:   page
  86  *      index:  page index
  87  *
  88  * Returns:
  89  *      RET_ERROR, RET_SUCCESS
  90  */
  91 int
  92 __bt_push(t, pgno, index)
  93         BTREE *t;
  94         pgno_t pgno;
  95         indx_t index;
  96 {
  97         if (t->bt_sp == t->bt_maxstack) {
  98                 t->bt_maxstack += 50;
  99                 if ((t->bt_stack = (EPGNO *)realloc(t->bt_stack,
 100                     t->bt_maxstack * sizeof(EPGNO))) == NULL) {
 101                         t->bt_maxstack -= 50;
 102                         return (RET_ERROR);
 103                 }
 104         }
 105
 106         t->bt_stack[t->bt_sp].pgno = pgno;
 107         t->bt_stack[t->bt_sp].index = index;
 108         ++t->bt_sp;
 109         return (RET_SUCCESS);
 110 }