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bt_page.c revision 1.4 
      1 /*-
      2  * Copyright (c) 1990, 1993
      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	8.2 (Berkeley) 2/21/94";
     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 -- Put a page on the freelist.
     47  *
     48  * Parameters:
     49  *	t:	tree
     50  *	h:	page to free
     51  *
     52  * Returns:
     53  *	RET_ERROR, RET_SUCCESS
     54  */
     55 int
     56 __bt_free(t, h)
     57 	BTREE *t;
     58 	PAGE *h;
     59 {
     60 	/* Insert the page at the start of the free list. */
     61 	h->prevpg = P_INVALID;
     62 	h->nextpg = t->bt_free;
     63 	t->bt_free = h->pgno;
     64 
     65 	/* Make sure the page gets written back. */
     66 	return (mpool_put(t->bt_mp, h, MPOOL_DIRTY));
     67 }
     68 
     69 /*
     70  * __BT_NEW -- Get a new page, preferably from the freelist.
     71  *
     72  * Parameters:
     73  *	t:	tree
     74  *	npg:	storage for page number.
     75  *
     76  * Returns:
     77  *	Pointer to a page, NULL on error.
     78  */
     79 PAGE *
     80 __bt_new(t, npg)
     81 	BTREE *t;
     82 	pgno_t *npg;
     83 {
     84 	PAGE *h;
     85 
     86 	if (t->bt_free != P_INVALID &&
     87 	    (h = mpool_get(t->bt_mp, t->bt_free, 0)) != NULL) {
     88 			*npg = t->bt_free;
     89 			t->bt_free = h->nextpg;
     90 			return (h);
     91 	}
     92 	return (mpool_new(t->bt_mp, npg));
     93 }
     94