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-rw-r--r--db/hash/hash_buf.c355
1 files changed, 355 insertions, 0 deletions
diff --git a/db/hash/hash_buf.c b/db/hash/hash_buf.c
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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. 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.
+ */
+
+#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
+ */
+
+#include <sys/param.h>
+
+#include <errno.h>
+#include <stddef.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_int32_t, 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_int32_t addr;
+ BUFHEAD *prev_bp;
+ int newpage; /* If prev_bp set, indicates a new overflow page. */
+{
+ register BUFHEAD *bp;
+ register u_int32_t 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 *)((ptrdiff_t)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_int32_t 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_int16_t 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);
+#ifdef PURIFY
+ memset(bp, 0xff, sizeof(BUFHEAD));
+#endif
+ if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) {
+ free(bp);
+ return (NULL);
+ }
+#ifdef PURIFY
+ memset(bp->page, 0xff, hashp->BSIZE);
+#endif
+ 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_int16_t *)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_int16_t *)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);
+}
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