db.subproj/btree.subproj/bt_page.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  * Redistribution and use in source and binary forms, with or without
  27  * modification, are permitted provided that the following conditions
  28  * are met:
  29  * 1. Redistributions of source code must retain the above copyright
  30  *    notice, this list of conditions and the following disclaimer.
  31  * 2. Redistributions in binary form must reproduce the above copyright
  32  *    notice, this list of conditions and the following disclaimer in the
  33  *    documentation and/or other materials provided with the distribution.
  34  * 3. All advertising materials mentioning features or use of this software
  35  *    must display the following acknowledgement:
  36  *      This product includes software developed by the University of
  37  *      California, Berkeley and its contributors.
  38  * 4. Neither the name of the University nor the names of its contributors
  39  *    may be used to endorse or promote products derived from this software
  40  *    without specific prior written permission.
  41  *
  42  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  43  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  44  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  45  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  46  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  47  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  48  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  49  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  50  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  51  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  52  * SUCH DAMAGE.
  53  */
  54
  55
  56 #include <sys/types.h>
  57
  58 #include <stdio.h>
  59
  60 #include <db.h>
  61 #include "btree.h"
  62
  63 /*
  64  * __BT_FREE -- Put a page on the freelist.
  65  *
  66  * Parameters:
  67  *      t:      tree
  68  *      h:      page to free
  69  *
  70  * Returns:
  71  *      RET_ERROR, RET_SUCCESS
  72  */
  73 int
  74 __bt_free(t, h)
  75         BTREE *t;
  76         PAGE *h;
  77 {
  78         /* Insert the page at the start of the free list. */
  79         h->prevpg = P_INVALID;
  80         h->nextpg = t->bt_free;
  81         t->bt_free = h->pgno;
  82
  83         /* Make sure the page gets written back. */
  84         return (mpool_put(t->bt_mp, h, MPOOL_DIRTY));
  85 }
  86
  87 /*
  88  * __BT_NEW -- Get a new page, preferably from the freelist.
  89  *
  90  * Parameters:
  91  *      t:      tree
  92  *      npg:    storage for page number.
  93  *
  94  * Returns:
  95  *      Pointer to a page, NULL on error.
  96  */
  97 PAGE *
  98 __bt_new(t, npg)
  99         BTREE *t;
 100         pgno_t *npg;
 101 {
 102         PAGE *h;
 103
 104         if (t->bt_free != P_INVALID &&
 105             (h = mpool_get(t->bt_mp, t->bt_free, 0)) != NULL) {
 106                         *npg = t->bt_free;
 107                         t->bt_free = h->nextpg;
 108                         return (h);
 109         }
 110         return (mpool_new(t->bt_mp, npg));
 111 }