356 lines
9.0 KiB
C
356 lines
9.0 KiB
C
/*-
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* Copyright (c) 1990, 1993, 1994
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Margo Seltzer.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "@(#)hash_buf.c 8.5 (Berkeley) 7/15/94";
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#endif /* LIBC_SCCS and not lint */
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/*
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* PACKAGE: hash
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*
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* DESCRIPTION:
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* Contains buffer management
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*
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* ROUTINES:
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* External
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* __buf_init
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* __get_buf
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* __buf_free
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* __reclaim_buf
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* Internal
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* newbuf
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*/
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#include <sys/param.h>
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#include <errno.h>
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#include <stddef.h>
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#include <stdio.h>
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#include <stdlib.h>
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#ifdef DEBUG
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#include <assert.h>
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#endif
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#include <db.h>
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#include "hash.h"
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#include "page.h"
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#include "extern.h"
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static BUFHEAD *newbuf __P((HTAB *, u_int32_t, BUFHEAD *));
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/* Unlink B from its place in the lru */
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#define BUF_REMOVE(B) { \
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(B)->prev->next = (B)->next; \
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(B)->next->prev = (B)->prev; \
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}
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/* Insert B after P */
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#define BUF_INSERT(B, P) { \
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(B)->next = (P)->next; \
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(B)->prev = (P); \
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(P)->next = (B); \
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(B)->next->prev = (B); \
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}
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#define MRU hashp->bufhead.next
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#define LRU hashp->bufhead.prev
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#define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead)
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#define LRU_INSERT(B) BUF_INSERT((B), LRU)
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/*
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* We are looking for a buffer with address "addr". If prev_bp is NULL, then
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* address is a bucket index. If prev_bp is not NULL, then it points to the
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* page previous to an overflow page that we are trying to find.
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*
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* CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer
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* be valid. Therefore, you must always verify that its address matches the
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* address you are seeking.
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*/
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extern BUFHEAD *
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__get_buf(hashp, addr, prev_bp, newpage)
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HTAB *hashp;
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u_int32_t addr;
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BUFHEAD *prev_bp;
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int newpage; /* If prev_bp set, indicates a new overflow page. */
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{
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register BUFHEAD *bp;
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register u_int32_t is_disk_mask;
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register int is_disk, segment_ndx;
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SEGMENT segp;
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is_disk = 0;
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is_disk_mask = 0;
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if (prev_bp) {
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bp = prev_bp->ovfl;
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if (!bp || (bp->addr != addr))
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bp = NULL;
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if (!newpage)
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is_disk = BUF_DISK;
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} else {
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/* Grab buffer out of directory */
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segment_ndx = addr & (hashp->SGSIZE - 1);
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/* valid segment ensured by __call_hash() */
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segp = hashp->dir[addr >> hashp->SSHIFT];
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#ifdef DEBUG
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assert(segp != NULL);
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#endif
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bp = PTROF(segp[segment_ndx]);
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is_disk_mask = ISDISK(segp[segment_ndx]);
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is_disk = is_disk_mask || !hashp->new_file;
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}
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if (!bp) {
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bp = newbuf(hashp, addr, prev_bp);
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if (!bp ||
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__get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))
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return (NULL);
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if (!prev_bp)
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segp[segment_ndx] =
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(BUFHEAD *)((ptrdiff_t)bp | is_disk_mask);
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} else {
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BUF_REMOVE(bp);
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MRU_INSERT(bp);
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}
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return (bp);
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}
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/*
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* We need a buffer for this page. Either allocate one, or evict a resident
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* one (if we have as many buffers as we're allowed) and put this one in.
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*
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* If newbuf finds an error (returning NULL), it also sets errno.
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*/
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static BUFHEAD *
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newbuf(hashp, addr, prev_bp)
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HTAB *hashp;
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u_int32_t addr;
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BUFHEAD *prev_bp;
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{
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register BUFHEAD *bp; /* The buffer we're going to use */
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register BUFHEAD *xbp; /* Temp pointer */
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register BUFHEAD *next_xbp;
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SEGMENT segp;
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int segment_ndx;
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u_int16_t oaddr, *shortp;
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oaddr = 0;
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bp = LRU;
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/*
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* If LRU buffer is pinned, the buffer pool is too small. We need to
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* allocate more buffers.
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*/
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if (hashp->nbufs || (bp->flags & BUF_PIN)) {
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/* Allocate a new one */
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if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL)
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return (NULL);
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#ifdef PURIFY
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memset(bp, 0xff, sizeof(BUFHEAD));
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#endif
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if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) {
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free(bp);
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return (NULL);
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}
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#ifdef PURIFY
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memset(bp->page, 0xff, hashp->BSIZE);
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#endif
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if (hashp->nbufs)
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hashp->nbufs--;
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} else {
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/* Kick someone out */
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BUF_REMOVE(bp);
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/*
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* If this is an overflow page with addr 0, it's already been
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* flushed back in an overflow chain and initialized.
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*/
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if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) {
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/*
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* Set oaddr before __put_page so that you get it
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* before bytes are swapped.
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*/
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shortp = (u_int16_t *)bp->page;
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if (shortp[0])
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oaddr = shortp[shortp[0] - 1];
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if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
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bp->addr, (int)IS_BUCKET(bp->flags), 0))
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return (NULL);
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/*
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* Update the pointer to this page (i.e. invalidate it).
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*
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* If this is a new file (i.e. we created it at open
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* time), make sure that we mark pages which have been
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* written to disk so we retrieve them from disk later,
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* rather than allocating new pages.
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*/
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if (IS_BUCKET(bp->flags)) {
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segment_ndx = bp->addr & (hashp->SGSIZE - 1);
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segp = hashp->dir[bp->addr >> hashp->SSHIFT];
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#ifdef DEBUG
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assert(segp != NULL);
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#endif
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if (hashp->new_file &&
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((bp->flags & BUF_MOD) ||
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ISDISK(segp[segment_ndx])))
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segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
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else
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segp[segment_ndx] = NULL;
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}
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/*
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* Since overflow pages can only be access by means of
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* their bucket, free overflow pages associated with
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* this bucket.
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*/
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for (xbp = bp; xbp->ovfl;) {
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next_xbp = xbp->ovfl;
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xbp->ovfl = 0;
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xbp = next_xbp;
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/* Check that ovfl pointer is up date. */
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if (IS_BUCKET(xbp->flags) ||
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(oaddr != xbp->addr))
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break;
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shortp = (u_int16_t *)xbp->page;
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if (shortp[0])
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/* set before __put_page */
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oaddr = shortp[shortp[0] - 1];
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if ((xbp->flags & BUF_MOD) && __put_page(hashp,
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xbp->page, xbp->addr, 0, 0))
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return (NULL);
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xbp->addr = 0;
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xbp->flags = 0;
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BUF_REMOVE(xbp);
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LRU_INSERT(xbp);
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}
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}
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}
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/* Now assign this buffer */
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bp->addr = addr;
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#ifdef DEBUG1
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(void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
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bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
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#endif
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bp->ovfl = NULL;
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if (prev_bp) {
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/*
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* If prev_bp is set, this is an overflow page, hook it in to
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* the buffer overflow links.
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*/
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#ifdef DEBUG1
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(void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
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prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0),
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(bp ? bp->addr : 0));
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#endif
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prev_bp->ovfl = bp;
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bp->flags = 0;
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} else
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bp->flags = BUF_BUCKET;
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MRU_INSERT(bp);
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return (bp);
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}
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extern void
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__buf_init(hashp, nbytes)
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HTAB *hashp;
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int nbytes;
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{
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BUFHEAD *bfp;
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int npages;
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bfp = &(hashp->bufhead);
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npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
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npages = MAX(npages, MIN_BUFFERS);
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hashp->nbufs = npages;
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bfp->next = bfp;
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bfp->prev = bfp;
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/*
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* This space is calloc'd so these are already null.
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*
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* bfp->ovfl = NULL;
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* bfp->flags = 0;
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* bfp->page = NULL;
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* bfp->addr = 0;
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*/
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}
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extern int
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__buf_free(hashp, do_free, to_disk)
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HTAB *hashp;
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int do_free, to_disk;
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{
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BUFHEAD *bp;
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/* Need to make sure that buffer manager has been initialized */
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if (!LRU)
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return (0);
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for (bp = LRU; bp != &hashp->bufhead;) {
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/* Check that the buffer is valid */
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if (bp->addr || IS_BUCKET(bp->flags)) {
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if (to_disk && (bp->flags & BUF_MOD) &&
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__put_page(hashp, bp->page,
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bp->addr, IS_BUCKET(bp->flags), 0))
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return (-1);
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}
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/* Check if we are freeing stuff */
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if (do_free) {
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if (bp->page)
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free(bp->page);
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BUF_REMOVE(bp);
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free(bp);
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bp = LRU;
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} else
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bp = bp->prev;
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}
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return (0);
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}
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extern void
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__reclaim_buf(hashp, bp)
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HTAB *hashp;
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BUFHEAD *bp;
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{
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bp->ovfl = 0;
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bp->addr = 0;
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bp->flags = 0;
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BUF_REMOVE(bp);
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LRU_INSERT(bp);
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}
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