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bt_page.c revision 1.5 
      1 /*	$NetBSD: bt_page.c,v 1.5 1995/02/27 13:20:36 cgd Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1990, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *	This product includes software developed by the University of
     18  *	California, Berkeley and its contributors.
     19  * 4. Neither the name of the University nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  */
     35 
     36 #if defined(LIBC_SCCS) && !defined(lint)
     37 #if 0
     38 static char sccsid[] = "@(#)bt_page.c	8.2 (Berkeley) 2/21/94";
     39 #else
     40 static char rcsid[] = "$NetBSD: bt_page.c,v 1.5 1995/02/27 13:20:36 cgd Exp $";
     41 #endif
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 #include <sys/types.h>
     45 
     46 #include <stdio.h>
     47 
     48 #include <db.h>
     49 #include "btree.h"
     50 
     51 /*
     52  * __BT_FREE -- Put a page on the freelist.
     53  *
     54  * Parameters:
     55  *	t:	tree
     56  *	h:	page to free
     57  *
     58  * Returns:
     59  *	RET_ERROR, RET_SUCCESS
     60  */
     61 int
     62 __bt_free(t, h)
     63 	BTREE *t;
     64 	PAGE *h;
     65 {
     66 	/* Insert the page at the start of the free list. */
     67 	h->prevpg = P_INVALID;
     68 	h->nextpg = t->bt_free;
     69 	t->bt_free = h->pgno;
     70 
     71 	/* Make sure the page gets written back. */
     72 	return (mpool_put(t->bt_mp, h, MPOOL_DIRTY));
     73 }
     74 
     75 /*
     76  * __BT_NEW -- Get a new page, preferably from the freelist.
     77  *
     78  * Parameters:
     79  *	t:	tree
     80  *	npg:	storage for page number.
     81  *
     82  * Returns:
     83  *	Pointer to a page, NULL on error.
     84  */
     85 PAGE *
     86 __bt_new(t, npg)
     87 	BTREE *t;
     88 	pgno_t *npg;
     89 {
     90 	PAGE *h;
     91 
     92 	if (t->bt_free != P_INVALID &&
     93 	    (h = mpool_get(t->bt_mp, t->bt_free, 0)) != NULL) {
     94 			*npg = t->bt_free;
     95 			t->bt_free = h->nextpg;
     96 			return (h);
     97 	}
     98 	return (mpool_new(t->bt_mp, npg));
     99 }
    100