GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: lib/libc/db/hash/hash_buf.c Lines: 0 107 0.0 %
Date: 2017-11-13 Branches: 0 90 0.0 %

Line Branch Exec Source
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/*	$OpenBSD: hash_buf.c,v 1.19 2015/01/16 16:48:51 deraadt Exp $	*/
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/*-
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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. 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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/*
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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 <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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#include <string.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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#define MAXIMUM(a, b)	(((a) > (b)) ? (a) : (b))
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static BUFHEAD *newbuf(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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BUFHEAD *
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__get_buf(HTAB *hashp, u_int32_t addr,
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    BUFHEAD *prev_bp,	/* If prev_bp set, indicates a new overflow page. */
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    int newpage)
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{
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	BUFHEAD *bp;
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	u_int32_t is_disk_mask;
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	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(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp)
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{
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	BUFHEAD *bp;		/* The buffer we're going to use */
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	BUFHEAD *xbp;		/* Temp pointer */
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	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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        /* It is bad to overwrite the page under the cursor. */
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        if (bp == hashp->cpage) {
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                BUF_REMOVE(bp);
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                MRU_INSERT(bp);
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                bp = LRU;
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        }
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	/* If prev_bp is part of bp overflow, create a new buffer. */
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	if (hashp->nbufs == 0 && prev_bp && bp->ovfl) {
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		BUFHEAD *ovfl;
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		for (ovfl = bp->ovfl; ovfl ; ovfl = ovfl->ovfl) {
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			if (ovfl == prev_bp) {
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				hashp->nbufs++;
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				break;
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			}
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		}
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	}
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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) || bp == hashp->cpage) {
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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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		memset(bp, 0xff, sizeof(BUFHEAD));
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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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		memset(bp->page, 0xff, hashp->BSIZE);
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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 ? prev_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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void
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__buf_init(HTAB *hashp, 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 = MAXIMUM(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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int
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__buf_free(HTAB *hashp, int do_free, int 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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				(void)memset(bp->page, 0, hashp->BSIZE);
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				free(bp->page);
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			}
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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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void
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__reclaim_buf(HTAB *hashp, 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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}