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 /*-

  * Copyright (c) 1990, 1993, 1994

  *	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. ***REMOVED*** - see 

  *    ftp://ftp.cs.berkeley.edu/pub/4bsd/README.Impt.License.Change

  * 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.

  */

 #if defined(LIBC_SCCS) && !defined(lint)

 static char sccsid[] = "@(#)hash_buf.c	8.5 (Berkeley) 7/15/94";

 #endif /* LIBC_SCCS and not lint */

 /*

  * PACKAGE: hash

  *

  * DESCRIPTION:

  *	Contains buffer management

  *

  * ROUTINES:

  * External

  *	__buf_init

  *	__get_buf

  *	__buf_free

  *	__reclaim_buf

  * Internal

  *	newbuf

  */

 #if !defined(_WIN32) && !defined(_WINDOWS) && !defined(macintosh)

 #include <sys/param.h>

 #endif

 #include <errno.h>

 #include <stddef.h>

 #include <stdio.h>

 #include <stdlib.h>

 #include <string.h>

 #ifdef DEBUG

 #include <assert.h>

 #endif

 #include "mcom_db.h"

 #include "hash.h"

 #include "page.h"

 /* #include "extern.h" */

 static BUFHEAD *newbuf __P((HTAB *, uint32, 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(HTAB *hashp, uint32 addr, BUFHEAD *prev_bp, int newpage)

 /* If prev_bp set, indicates a new overflow page. */

 {

 	register BUFHEAD *bp;

 	register uint32 is_disk_mask;

 	register int is_disk, segment_ndx = 0;

 	SEGMENT segp = 0;

 	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)

 			return(NULL);

 		if(__get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))

 		  {

 			/* free bp and its page */

 			if(prev_bp)

 			  {

 				/* if prev_bp is set then the new page that

 				 * failed is hooked onto prev_bp as an overflow page.

 				 * if we don't remove the pointer to the bad page

 				 * we may try and access it later and we will die

 				 * horribly because it will have already been

 				 * free'd and overwritten with bogus data.

 				 */

 				prev_bp->ovfl = NULL;

 			  }

 			BUF_REMOVE(bp);

 			free(bp->page);

 			free(bp);

 			return (NULL);

 		  }

 		if (!prev_bp)			

 		  {

 #if 0

 			/* 16 bit windows and mac can't handle the

 			 * oring of the is disk flag.

 		 	 */			

 			segp[segment_ndx] =

 			    (BUFHEAD *)((ptrdiff_t)bp | is_disk_mask);

 #else   

 			/* set the is_disk thing inside the structure

 			 */

 			bp->is_disk = is_disk_mask;

 			segp[segment_ndx] = bp;

 #endif

 		  }

 	} 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(HTAB *hashp, uint32 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;

 	uint16 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);

 		/* this memset is supposedly unnecessary but lets add

 		 * it anyways.

 		 */

 		memset(bp, 0xff, sizeof(BUFHEAD));

 		if ((bp->page = (char *)malloc((size_t)hashp->BSIZE)) == NULL) {

 			free(bp);

 			return (NULL);

 		}

 		/* this memset is supposedly unnecessary but lets add

 		 * it anyways.

 		 */

 		memset(bp->page, 0xff, (size_t)hashp->BSIZE);

 		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 = (uint16 *)bp->page;

 			if (shortp[0])

 			  {

 				if(shortp[0] > (hashp->BSIZE / sizeof(uint16)))

 				  {

 					return(NULL);

 				  }

 				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;

 				/* leave pinned pages alone, we are still using

 				 * them. */

 				if (xbp->flags & BUF_PIN) {

 					continue;

 				}

 				/* Check that ovfl pointer is up date. */

 				if (IS_BUCKET(xbp->flags) ||

 				    (oaddr != xbp->addr))

 					break;

 				shortp = (uint16 *)xbp->page;

 				if (shortp[0])

 				  {

 					/* LJM is the number of reported

 					 * pages way too much?

 					 */

 					if(shortp[0] > hashp->BSIZE/sizeof(uint16))

 						return NULL;

 					/* 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(HTAB *hashp, int32 nbytes)

 {

 	BUFHEAD *bfp;

 	int npages;

 	bfp = &(hashp->bufhead);

 	npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;

 	npages = PR_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(HTAB *hashp, int do_free, int to_disk)

 {

 	BUFHEAD *bp;

 	int status = -1;

 	/* 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) &&

 			    (status = __put_page(hashp, bp->page,

 			    bp->addr, IS_BUCKET(bp->flags), 0))) {

 				if (do_free) {

 					if (bp->page)

 						free(bp->page);

 					BUF_REMOVE(bp);

 					free(bp);

 				}

 				return (status);

 			}

 		}

 		/* 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(HTAB *hashp, BUFHEAD *bp)

 {

 	bp->ovfl = 0;

 	bp->addr = 0;

 	bp->flags = 0;

 	BUF_REMOVE(bp);

 	LRU_INSERT(bp);

 }