bt_overflow.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
 * Mike Olson.
 *
 * 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[] = "@(#)bt_overflow.c 8.5 (Berkeley) 7/16/94";
#endif /* LIBC_SCCS and not lint */

#include <sys/param.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "../include/db.h"
#include "btree.h"

/*
 * Big key/data code.
 *
 * Big key and data entries are stored on linked lists of pages. The initial
 * reference is byte string stored with the key or data and is the page number
 * and size. The actual record is stored in a chain of pages linked by the
 * nextpg field of the PAGE header.
 *
 * The first page of the chain has a special property. If the record is used
 * by an internal page, it cannot be deleted and the P_PRESERVE bit will be set
 * in the header.
 *
 * XXX
 * A single DBT is written to each chain, so a lot of space on the last page
 * is wasted. This is a fairly major bug for some data sets.
 */

/*
 * __OVFL_GET -- Get an overflow key/data item.
 *
 * Parameters:
 * t: tree
 * p: pointer to { pgno_t, u_int32_t }
 * buf: storage address
 * bufsz: storage size
 *
 * Returns:
 * RET_ERROR, RET_SUCCESS
 */
int
__ovfl_get(t, p, ssz, buf, bufsz)
 BTREE *t;
 void *p;
 size_t *ssz;
 void **buf;
 size_t *bufsz;
{
 PAGE *h;
 pgno_t pg;
 size_t nb, plen;
 u_int32_t sz;

 memmove(&pg, p, sizeof(pgno_t));
 memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t));
 *ssz = sz;

#ifdef DEBUG
 if (pg == P_INVALID || sz == 0)
 abort();
#endif
 /* Make the buffer bigger as necessary. */
 if (*bufsz < sz) {
 *buf = (char *)(*buf == NULL ? malloc(sz) : realloc(*buf, sz));
 if (*buf == NULL)
 return (RET_ERROR);
 *bufsz = sz;
 }

 /*
 * Step through the linked list of pages, copying the data on each one
 * into the buffer. Never copy more than the data's length.
 */
 plen = t->bt_psize - BTDATAOFF;
 for (p = *buf;; p = (char *)p + nb, pg = h->nextpg) {
 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 return (RET_ERROR);

 nb = MIN(sz, plen);
 memmove(p, (char *)h + BTDATAOFF, nb);
 mpool_put(t->bt_mp, h, 0);

 if ((sz -= nb) == 0)
 break;
 }
 return (RET_SUCCESS);
}

/*
 * __OVFL_PUT -- Store an overflow key/data item.
 *
 * Parameters:
 * t: tree
 * data: DBT to store
 * pgno: storage page number
 *
 * Returns:
 * RET_ERROR, RET_SUCCESS
 */
int
__ovfl_put(t, dbt, pg)
 BTREE *t;
 const DBT *dbt;
 pgno_t *pg;
{
 PAGE *h, *last;
 void *p;
 pgno_t npg;
 size_t nb, plen;
 u_int32_t sz;

 /*
 * Allocate pages and copy the key/data record into them. Store the
 * number of the first page in the chain.
 */
 plen = t->bt_psize - BTDATAOFF;
 for (last = NULL, p = dbt->data, sz = dbt->size;;
 p = (char *)p + plen, last = h) {
 if ((h = __bt_new(t, &npg)) == NULL)
 return (RET_ERROR);

 h->pgno = npg;
 h->nextpg = h->prevpg = P_INVALID;
 h->flags = P_OVERFLOW;
 h->lower = h->upper = 0;

 nb = MIN(sz, plen);
 memmove((char *)h + BTDATAOFF, p, nb);

 if (last) {
 last->nextpg = h->pgno;
 mpool_put(t->bt_mp, last, MPOOL_DIRTY);
 } else
 *pg = h->pgno;

 if ((sz -= nb) == 0) {
 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 break;
 }
 }
 return (RET_SUCCESS);
}

/*
 * __OVFL_DELETE -- Delete an overflow chain.
 *
 * Parameters:
 * t: tree
 * p: pointer to { pgno_t, u_int32_t }
 *
 * Returns:
 * RET_ERROR, RET_SUCCESS
 */
int
__ovfl_delete(t, p)
 BTREE *t;
 void *p;
{
 PAGE *h;
 pgno_t pg;
 size_t plen;
 u_int32_t sz;

 memmove(&pg, p, sizeof(pgno_t));
 memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t));

#ifdef DEBUG
 if (pg == P_INVALID || sz == 0)
 abort();
#endif
 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 return (RET_ERROR);

 /* Don't delete chains used by internal pages. */
 if (h->flags & P_PRESERVE) {
 mpool_put(t->bt_mp, h, 0);
 return (RET_SUCCESS);
 }

 /* Step through the chain, calling the free routine for each page. */
 for (plen = t->bt_psize - BTDATAOFF;; sz -= plen) {
 pg = h->nextpg;
 __bt_free(t, h);
 if (sz <= plen)
 break;
 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 return (RET_ERROR);
 }
 return (RET_SUCCESS);
}