db.1.85/btree/bt_page.c

   1 /*-
   2  * Copyright (c) 1990, 1993, 1994
   3  *      The Regents of the University of California.  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[] = "@(#)bt_page.c   8.3 (Berkeley) 7/14/94";
  36 #endif /* LIBC_SCCS and not lint */
  37
  38 #include <sys/types.h>
  39
  40 #include <stdio.h>
  41
  42 #include <db.h>
  43 #include "btree.h"
  44
  45 /*
  46  * __bt_free --
  47  *      Put a page on the freelist.
  48  *
  49  * Parameters:
  50  *      t:      tree
  51  *      h:      page to free
  52  *
  53  * Returns:
  54  *      RET_ERROR, RET_SUCCESS
  55  *
  56  * Side-effect:
  57  *      mpool_put's the page.
  58  */
  59 int
  60 __bt_free(t, h)
  61         BTREE *t;
  62         PAGE *h;
  63 {
  64         /* Insert the page at the head of the free list. */
  65         h->prevpg = P_INVALID;
  66         h->nextpg = t->bt_free;
  67         t->bt_free = h->pgno;
  68
  69         /* Make sure the page gets written back. */
  70         return (mpool_put(t->bt_mp, h, MPOOL_DIRTY));
  71 }
  72
  73 /*
  74  * __bt_new --
  75  *      Get a new page, preferably from the freelist.
  76  *
  77  * Parameters:
  78  *      t:      tree
  79  *      npg:    storage for page number.
  80  *
  81  * Returns:
  82  *      Pointer to a page, NULL on error.
  83  */
  84 PAGE *
  85 __bt_new(t, npg)
  86         BTREE *t;
  87         pgno_t *npg;
  88 {
  89         PAGE *h;
  90
  91         if (t->bt_free != P_INVALID &&
  92             (h = mpool_get(t->bt_mp, t->bt_free, 0)) != NULL) {
  93                 *npg = t->bt_free;
  94                 t->bt_free = h->nextpg;
  95                 return (h);
  96         }
  97         return (mpool_new(t->bt_mp, npg));
  98 }