[apple/libc.git] / db / hash / hash_buf.c

/*
 * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Margo Seltzer.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */


/*
 * PACKAGE: hash
 *
 * DESCRIPTION:
 *	Contains buffer management
 *
 * ROUTINES:
 * External
 *	__buf_init
 *	__get_buf
 *	__buf_free
 *	__reclaim_buf
 * Internal
 *	newbuf
 */

#include <sys/param.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#ifdef DEBUG
#include <assert.h>
#endif

#include <db.h>
#include "hash.h"
#include "page.h"
#include "extern.h"

static BUFHEAD *newbuf __P((HTAB *, u_int, BUFHEAD *));

/* Unlink B from its place in the lru */
#define BUF_REMOVE(B) { \
	(B)->prev->next = (B)->next; \
	(B)->next->prev = (B)->prev; \
}

/* Insert B after P */
#define BUF_INSERT(B, P) { \
	(B)->next = (P)->next; \
	(B)->prev = (P); \
	(P)->next = (B); \
	(B)->next->prev = (B); \
}

#define	MRU	hashp->bufhead.next
#define	LRU	hashp->bufhead.prev

#define MRU_INSERT(B)	BUF_INSERT((B), &hashp->bufhead)
#define LRU_INSERT(B)	BUF_INSERT((B), LRU)

/*
 * We are looking for a buffer with address "addr".  If prev_bp is NULL, then
 * address is a bucket index.  If prev_bp is not NULL, then it points to the
 * page previous to an overflow page that we are trying to find.
 *
 * CAVEAT:  The buffer header accessed via prev_bp's ovfl field may no longer
 * be valid.  Therefore, you must always verify that its address matches the
 * address you are seeking.
 */
extern BUFHEAD *
__get_buf(hashp, addr, prev_bp, newpage)
	HTAB *hashp;
	u_int addr;
	BUFHEAD *prev_bp;
	int newpage;	/* If prev_bp set, indicates a new overflow page. */
{
	register BUFHEAD *bp;
	register u_int is_disk_mask;
	register int is_disk, segment_ndx;
	SEGMENT segp;

	is_disk = 0;
	is_disk_mask = 0;
	if (prev_bp) {
		bp = prev_bp->ovfl;
		if (!bp || (bp->addr != addr))
			bp = NULL;
		if (!newpage)
			is_disk = BUF_DISK;
	} else {
		/* Grab buffer out of directory */
		segment_ndx = addr & (hashp->SGSIZE - 1);

		/* valid segment ensured by __call_hash() */
		segp = hashp->dir[addr >> hashp->SSHIFT];
#ifdef DEBUG
		assert(segp != NULL);
#endif
		bp = PTROF(segp[segment_ndx]);
		is_disk_mask = ISDISK(segp[segment_ndx]);
		is_disk = is_disk_mask || !hashp->new_file;
	}

	if (!bp) {
		bp = newbuf(hashp, addr, prev_bp);
		if (!bp ||
		    __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))
			return (NULL);
		if (!prev_bp)
			segp[segment_ndx] =
			    (BUFHEAD *)((u_int)bp | is_disk_mask);
	} else {
		BUF_REMOVE(bp);
		MRU_INSERT(bp);
	}
	return (bp);
}

/*
 * We need a buffer for this page. Either allocate one, or evict a resident
 * one (if we have as many buffers as we're allowed) and put this one in.
 *
 * If newbuf finds an error (returning NULL), it also sets errno.
 */
static BUFHEAD *
newbuf(hashp, addr, prev_bp)
	HTAB *hashp;
	u_int addr;
	BUFHEAD *prev_bp;
{
	register BUFHEAD *bp;		/* The buffer we're going to use */
	register BUFHEAD *xbp;		/* Temp pointer */
	register BUFHEAD *next_xbp;
	SEGMENT segp;
	int segment_ndx;
	u_short oaddr, *shortp;

	oaddr = 0;
	bp = LRU;
	/*
	 * If LRU buffer is pinned, the buffer pool is too small. We need to
	 * allocate more buffers.
	 */
	if (hashp->nbufs || (bp->flags & BUF_PIN)) {
		/* Allocate a new one */
		if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL)
			return (NULL);
		if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) {
			free(bp);
			return (NULL);
		}
		if (hashp->nbufs)
			hashp->nbufs--;
	} else {
		/* Kick someone out */
		BUF_REMOVE(bp);
		/*
		 * If this is an overflow page with addr 0, it's already been
		 * flushed back in an overflow chain and initialized.
		 */
		if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) {
			/*
			 * Set oaddr before __put_page so that you get it
			 * before bytes are swapped.
			 */
			shortp = (u_short *)bp->page;
			if (shortp[0])
				oaddr = shortp[shortp[0] - 1];
			if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
			    bp->addr, (int)IS_BUCKET(bp->flags), 0))
				return (NULL);
			/*
			 * Update the pointer to this page (i.e. invalidate it).
			 *
			 * If this is a new file (i.e. we created it at open
			 * time), make sure that we mark pages which have been
			 * written to disk so we retrieve them from disk later,
			 * rather than allocating new pages.
			 */
			if (IS_BUCKET(bp->flags)) {
				segment_ndx = bp->addr & (hashp->SGSIZE - 1);
				segp = hashp->dir[bp->addr >> hashp->SSHIFT];
#ifdef DEBUG
				assert(segp != NULL);
#endif

				if (hashp->new_file &&
				    ((bp->flags & BUF_MOD) ||
				    ISDISK(segp[segment_ndx])))
					segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
				else
					segp[segment_ndx] = NULL;
			}
			/*
			 * Since overflow pages can only be access by means of
			 * their bucket, free overflow pages associated with
			 * this bucket.
			 */
			for (xbp = bp; xbp->ovfl;) {
				next_xbp = xbp->ovfl;
				xbp->ovfl = 0;
				xbp = next_xbp;

				/* Check that ovfl pointer is up date. */
				if (IS_BUCKET(xbp->flags) ||
				    (oaddr != xbp->addr))
					break;

				shortp = (u_short *)xbp->page;
				if (shortp[0])
					/* set before __put_page */
					oaddr = shortp[shortp[0] - 1];
				if ((xbp->flags & BUF_MOD) && __put_page(hashp,
				    xbp->page, xbp->addr, 0, 0))
					return (NULL);
				xbp->addr = 0;
				xbp->flags = 0;
				BUF_REMOVE(xbp);
				LRU_INSERT(xbp);
			}
		}
	}

	/* Now assign this buffer */
	bp->addr = addr;
#ifdef DEBUG1
	(void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
	    bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
#endif
	bp->ovfl = NULL;
	if (prev_bp) {
		/*
		 * If prev_bp is set, this is an overflow page, hook it in to
		 * the buffer overflow links.
		 */
#ifdef DEBUG1
		(void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
		    prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0),
		    (bp ? bp->addr : 0));
#endif
		prev_bp->ovfl = bp;
		bp->flags = 0;
	} else
		bp->flags = BUF_BUCKET;
	MRU_INSERT(bp);
	return (bp);
}

extern void
__buf_init(hashp, nbytes)
	HTAB *hashp;
	int nbytes;
{
	BUFHEAD *bfp;
	int npages;

	bfp = &(hashp->bufhead);
	npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
	npages = MAX(npages, MIN_BUFFERS);

	hashp->nbufs = npages;
	bfp->next = bfp;
	bfp->prev = bfp;
	/*
	 * This space is calloc'd so these are already null.
	 *
	 * bfp->ovfl = NULL;
	 * bfp->flags = 0;
	 * bfp->page = NULL;
	 * bfp->addr = 0;
	 */
}

extern int
__buf_free(hashp, do_free, to_disk)
	HTAB *hashp;
	int do_free, to_disk;
{
	BUFHEAD *bp;

	/* Need to make sure that buffer manager has been initialized */
	if (!LRU)
		return (0);
	for (bp = LRU; bp != &hashp->bufhead;) {
		/* Check that the buffer is valid */
		if (bp->addr || IS_BUCKET(bp->flags)) {
			if (to_disk && (bp->flags & BUF_MOD) &&
			    __put_page(hashp, bp->page,
			    bp->addr, IS_BUCKET(bp->flags), 0))
				return (-1);
		}
		/* Check if we are freeing stuff */
		if (do_free) {
			if (bp->page)
				free(bp->page);
			BUF_REMOVE(bp);
			free(bp);
			bp = LRU;
		} else
			bp = bp->prev;
	}
	return (0);
}

extern void
__reclaim_buf(hashp, bp)
	HTAB *hashp;
	BUFHEAD *bp;
{
	bp->ovfl = 0;
	bp->addr = 0;
	bp->flags = 0;
	BUF_REMOVE(bp);
	LRU_INSERT(bp);
}
Commit	Line	Data
e9ce8d39 A	1	/*
	2	* Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
	3	*
	4	* @APPLE_LICENSE_HEADER_START@
	5	*
734aad71	6	* Copyright (c) 1999-2003 Apple Computer, Inc. All Rights Reserved.
e9ce8d39	7	*
734aad71 A	8	* This file contains Original Code and/or Modifications of Original Code
	9	* as defined in and that are subject to the Apple Public Source License
	10	* Version 2.0 (the 'License'). You may not use this file except in
	11	* compliance with the License. Please obtain a copy of the License at
	12	* http://www.opensource.apple.com/apsl/ and read it before using this
	13	* file.
	14	*
	15	* The Original Code and all software distributed under the License are
	16	* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
e9ce8d39 A	17	* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
e9ce8d39 A	18	* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
734aad71 A	19	* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
	20	* Please see the License for the specific language governing rights and
	21	* limitations under the License.
e9ce8d39 A	22	*
	23	* @APPLE_LICENSE_HEADER_END@
	24	*/
	25	/*
	26	* Copyright (c) 1990, 1993
	27	* The Regents of the University of California. All rights reserved.
	28	*
	29	* This code is derived from software contributed to Berkeley by
	30	* Margo Seltzer.
	31	*
	32	* Redistribution and use in source and binary forms, with or without
	33	* modification, are permitted provided that the following conditions
	34	* are met:
	35	* 1. Redistributions of source code must retain the above copyright
	36	* notice, this list of conditions and the following disclaimer.
	37	* 2. Redistributions in binary form must reproduce the above copyright
	38	* notice, this list of conditions and the following disclaimer in the
	39	* documentation and/or other materials provided with the distribution.
	40	* 3. All advertising materials mentioning features or use of this software
	41	* must display the following acknowledgement:
	42	* This product includes software developed by the University of
	43	* California, Berkeley and its contributors.
	44	* 4. Neither the name of the University nor the names of its contributors
	45	* may be used to endorse or promote products derived from this software
	46	* without specific prior written permission.
	47	*
	48	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	49	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	50	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	51	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	52	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	53	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	54	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	55	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	56	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	57	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	58	* SUCH DAMAGE.
	59	*/
	60
	61
	62	/*
	63	* PACKAGE: hash
	64	*
	65	* DESCRIPTION:
	66	* Contains buffer management
	67	*
	68	* ROUTINES:
	69	* External
	70	* __buf_init
	71	* __get_buf
	72	* __buf_free
	73	* __reclaim_buf
	74	* Internal
	75	* newbuf
	76	*/
	77
	78	#include <sys/param.h>
	79
	80	#include <errno.h>
	81	#include <stdio.h>
	82	#include <stdlib.h>
	83	#ifdef DEBUG
	84	#include <assert.h>
	85	#endif
86
87	#include <db.h>
88	#include "hash.h"
89	#include "page.h"
90	#include "extern.h"
91
92	static BUFHEAD newbuf __P((HTAB , u_int, BUFHEAD *));
93
94	/* Unlink B from its place in the lru */
95	#define BUF_REMOVE(B) { \
96	(B)->prev->next = (B)->next; \
97	(B)->next->prev = (B)->prev; \
98	}
99
100	/* Insert B after P */
101	#define BUF_INSERT(B, P) { \
102	(B)->next = (P)->next; \
103	(B)->prev = (P); \
104	(P)->next = (B); \
105	(B)->next->prev = (B); \
106	}
107
108	#define MRU hashp->bufhead.next
109	#define LRU hashp->bufhead.prev
110
111	#define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead)
112	#define LRU_INSERT(B) BUF_INSERT((B), LRU)
113
114	/*
115	* We are looking for a buffer with address "addr". If prev_bp is NULL, then
116	* address is a bucket index. If prev_bp is not NULL, then it points to the
117	* page previous to an overflow page that we are trying to find.
118	*
119	* CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer
120	* be valid. Therefore, you must always verify that its address matches the
121	* address you are seeking.
122	*/
123	extern BUFHEAD *
124	__get_buf(hashp, addr, prev_bp, newpage)
125	HTAB *hashp;
126	u_int addr;
127	BUFHEAD *prev_bp;
128	int newpage; /* If prev_bp set, indicates a new overflow page. */
129	{
130	register BUFHEAD *bp;
131	register u_int is_disk_mask;
132	register int is_disk, segment_ndx;
133	SEGMENT segp;
134
135	is_disk = 0;
136	is_disk_mask = 0;
137	if (prev_bp) {
138	bp = prev_bp->ovfl;
139	if (!bp \|\| (bp->addr != addr))
140	bp = NULL;
141	if (!newpage)
142	is_disk = BUF_DISK;
143	} else {
144	/* Grab buffer out of directory */
145	segment_ndx = addr & (hashp->SGSIZE - 1);
146
147	/* valid segment ensured by __call_hash() */
148	segp = hashp->dir[addr >> hashp->SSHIFT];
149	#ifdef DEBUG
150	assert(segp != NULL);
151	#endif
152	bp = PTROF(segp[segment_ndx]);
153	is_disk_mask = ISDISK(segp[segment_ndx]);
154	is_disk = is_disk_mask \|\| !hashp->new_file;
155	}
156
157	if (!bp) {
158	bp = newbuf(hashp, addr, prev_bp);
159	if (!bp \|\|
160	__get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))
161	return (NULL);
162	if (!prev_bp)
163	segp[segment_ndx] =
164	(BUFHEAD *)((u_int)bp \| is_disk_mask);
165	} else {
166	BUF_REMOVE(bp);
167	MRU_INSERT(bp);
168	}
169	return (bp);
170	}
171
172	/*
173	* We need a buffer for this page. Either allocate one, or evict a resident
174	* one (if we have as many buffers as we're allowed) and put this one in.
175	*
176	* If newbuf finds an error (returning NULL), it also sets errno.
177	*/
178	static BUFHEAD *
179	newbuf(hashp, addr, prev_bp)
180	HTAB *hashp;
181	u_int addr;
182	BUFHEAD *prev_bp;
183	{
184	register BUFHEAD bp; / The buffer we're going to use */
185	register BUFHEAD xbp; / Temp pointer */
186	register BUFHEAD *next_xbp;
187	SEGMENT segp;
188	int segment_ndx;
189	u_short oaddr, *shortp;
190
191	oaddr = 0;
192	bp = LRU;
193	/*
194	* If LRU buffer is pinned, the buffer pool is too small. We need to
195	* allocate more buffers.
196	*/
197	if (hashp->nbufs \|\| (bp->flags & BUF_PIN)) {
198	/* Allocate a new one */
199	if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL)
200	return (NULL);
201	if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) {
202	free(bp);
203	return (NULL);
204	}
205	if (hashp->nbufs)
206	hashp->nbufs--;
207	} else {
208	/* Kick someone out */
209	BUF_REMOVE(bp);
210	/*
211	* If this is an overflow page with addr 0, it's already been
212	* flushed back in an overflow chain and initialized.
213	*/
214	if ((bp->addr != 0) \|\| (bp->flags & BUF_BUCKET)) {
215	/*
216	* Set oaddr before __put_page so that you get it
217	* before bytes are swapped.
218	*/
219	shortp = (u_short *)bp->page;
220	if (shortp[0])
221	oaddr = shortp[shortp[0] - 1];
222	if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
223	bp->addr, (int)IS_BUCKET(bp->flags), 0))
224	return (NULL);
225	/*
226	* Update the pointer to this page (i.e. invalidate it).
227	*
228	* If this is a new file (i.e. we created it at open
229	* time), make sure that we mark pages which have been
230	* written to disk so we retrieve them from disk later,
231	* rather than allocating new pages.
232	*/
233	if (IS_BUCKET(bp->flags)) {
234	segment_ndx = bp->addr & (hashp->SGSIZE - 1);
235	segp = hashp->dir[bp->addr >> hashp->SSHIFT];
236	#ifdef DEBUG
237	assert(segp != NULL);
238	#endif
239
240	if (hashp->new_file &&
241	((bp->flags & BUF_MOD) \|\|
242	ISDISK(segp[segment_ndx])))
243	segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
244	else
245	segp[segment_ndx] = NULL;
246	}
247	/*
248	* Since overflow pages can only be access by means of
249	* their bucket, free overflow pages associated with
250	* this bucket.
251	*/
252	for (xbp = bp; xbp->ovfl;) {
253	next_xbp = xbp->ovfl;
254	xbp->ovfl = 0;
255	xbp = next_xbp;
256
257	/* Check that ovfl pointer is up date. */
258	if (IS_BUCKET(xbp->flags) \|\|
259	(oaddr != xbp->addr))
260	break;
261
262	shortp = (u_short *)xbp->page;
263	if (shortp[0])
264	/* set before __put_page */
265	oaddr = shortp[shortp[0] - 1];
266	if ((xbp->flags & BUF_MOD) && __put_page(hashp,
267	xbp->page, xbp->addr, 0, 0))
268	return (NULL);
269	xbp->addr = 0;
270	xbp->flags = 0;
271	BUF_REMOVE(xbp);
272	LRU_INSERT(xbp);
273	}
274	}
275	}
276
277	/* Now assign this buffer */
278	bp->addr = addr;
279	#ifdef DEBUG1
280	(void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
281	bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
282	#endif
283	bp->ovfl = NULL;
284	if (prev_bp) {
285	/*
286	* If prev_bp is set, this is an overflow page, hook it in to
287	* the buffer overflow links.
288	*/
289	#ifdef DEBUG1
290	(void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
291	prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0),
292	(bp ? bp->addr : 0));
293	#endif
294	prev_bp->ovfl = bp;
295	bp->flags = 0;
296	} else
297	bp->flags = BUF_BUCKET;
298	MRU_INSERT(bp);
299	return (bp);
300	}
301
302	extern void
303	__buf_init(hashp, nbytes)
304	HTAB *hashp;
305	int nbytes;
306	{
307	BUFHEAD *bfp;
308	int npages;
309
310	bfp = &(hashp->bufhead);
311	npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
312	npages = MAX(npages, MIN_BUFFERS);
313
314	hashp->nbufs = npages;
315	bfp->next = bfp;
316	bfp->prev = bfp;
317	/*
318	* This space is calloc'd so these are already null.
319	*
320	* bfp->ovfl = NULL;
321	* bfp->flags = 0;
322	* bfp->page = NULL;
323	* bfp->addr = 0;
324	*/
325	}
326
327	extern int
328	__buf_free(hashp, do_free, to_disk)
329	HTAB *hashp;
330	int do_free, to_disk;
331	{
332	BUFHEAD *bp;
333
334	/* Need to make sure that buffer manager has been initialized */
335	if (!LRU)
336	return (0);
337	for (bp = LRU; bp != &hashp->bufhead;) {
338	/* Check that the buffer is valid */
339	if (bp->addr \|\| IS_BUCKET(bp->flags)) {
340	if (to_disk && (bp->flags & BUF_MOD) &&
341	__put_page(hashp, bp->page,
342	bp->addr, IS_BUCKET(bp->flags), 0))
343	return (-1);
344	}
345	/* Check if we are freeing stuff */
346	if (do_free) {
347	if (bp->page)
348	free(bp->page);
349	BUF_REMOVE(bp);
350	free(bp);
351	bp = LRU;
352	} else
353	bp = bp->prev;
354	}
355	return (0);
356	}
357
358	extern void
359	__reclaim_buf(hashp, bp)
360	HTAB *hashp;
361	BUFHEAD *bp;
362	{
363	bp->ovfl = 0;
364	bp->addr = 0;
365	bp->flags = 0;
366	BUF_REMOVE(bp);
367	LRU_INSERT(bp);
368	}