lib/libc/DB/btree/bt_stack.c

   1 /*-
   2  * Copyright (c) 1990 The Regents of the University of California.
   3  * All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Mike Olson.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 static char sccsid[] = "@(#)bt_stack.c  5.4 (Berkeley) 2/11/93";
  39 #endif /* LIBC_SCCS and not lint */
  40
  41 #include <sys/types.h>
  42
  43 #include <errno.h>
  44 #include <stdio.h>
  45 #include <stdlib.h>
  46
  47 #include <db.h>
  48 #include "btree.h"
  49
  50 /*
  51  * When a page splits, a new record has to be inserted into its parent page.
  52  * This page may have to split as well, all the way up to the root.  Since
  53  * parent pointers in each page would be expensive, we maintain a stack of
  54  * parent pages as we descend the tree.
  55  *
  56  * XXX
  57  * This is a concurrency problem -- if user a builds a stack, then user b
  58  * splits the tree, then user a tries to split the tree, there's a new level
  59  * in the tree that user a doesn't know about.
  60  */
  61
  62 /*
  63  * __BT_PUSH -- Push parent page info onto the stack (LIFO).
  64  *
  65  * Parameters:
  66  *      t:      tree
  67  *      pgno:   page
  68  *      index:  page index
  69  *
  70  * Returns:
  71  *      RET_ERROR, RET_SUCCESS
  72  */
  73 int
  74 __bt_push(t, pgno, index)
  75         BTREE *t;
  76         pgno_t pgno;
  77         int index;
  78 {
  79         if (t->bt_sp == t->bt_maxstack) {
  80                 t->bt_maxstack += 50;
  81                 if ((t->bt_stack = realloc(t->bt_stack,
  82                     t->bt_maxstack * sizeof(EPGNO))) == NULL) {
  83                         t->bt_maxstack -= 50;
  84                         return (RET_ERROR);
  85                 }
  86         }
  87
  88         t->bt_stack[t->bt_sp].pgno = pgno;
  89         t->bt_stack[t->bt_sp].index = index;
  90         ++t->bt_sp;
  91         return (RET_SUCCESS);
  92 }