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bt_page.c revision 1.3 
      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 = "from: @(#)bt_page.c	8.1 (Berkeley) 6/4/93";*/
     36 static char *rcsid = "$Id: bt_page.c,v 1.3 1993/08/26 00:43:24 jtc Exp $";
     37 #endif /* LIBC_SCCS and not lint */
     38 
     39 #include <sys/types.h>
     40 
     41 #define	__DBINTERFACE_PRIVATE
     42 #include <stdio.h>
     43 
     44 #include <db.h>
     45 #include "btree.h"
     46 
     47 /*
     48  * __BT_FREE -- Put a page on the freelist.
     49  *
     50  * Parameters:
     51  *	t:	tree
     52  *	h:	page to free
     53  *
     54  * Returns:
     55  *	RET_ERROR, RET_SUCCESS
     56  */
     57 int
     58 __bt_free(t, h)
     59 	BTREE *t;
     60 	PAGE *h;
     61 {
     62 	/* Insert the page at the start of the free list. */
     63 	h->prevpg = P_INVALID;
     64 	h->nextpg = t->bt_free;
     65 	t->bt_free = h->pgno;
     66 
     67 	/* Make sure the page gets written back. */
     68 	return (mpool_put(t->bt_mp, h, MPOOL_DIRTY));
     69 }
     70 
     71 /*
     72  * __BT_NEW -- Get a new page, preferably from the freelist.
     73  *
     74  * Parameters:
     75  *	t:	tree
     76  *	npg:	storage for page number.
     77  *
     78  * Returns:
     79  *	Pointer to a page, NULL on error.
     80  */
     81 PAGE *
     82 __bt_new(t, npg)
     83 	BTREE *t;
     84 	pgno_t *npg;
     85 {
     86 	PAGE *h;
     87 
     88 	if (t->bt_free != P_INVALID &&
     89 	    (h = mpool_get(t->bt_mp, t->bt_free, 0)) != NULL) {
     90 			*npg = t->bt_free;
     91 			t->bt_free = h->nextpg;
     92 			return (h);
     93 	}
     94 	return (mpool_new(t->bt_mp, npg));
     95 }
     96