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/* $OpenBSD: bt_overflow.c,v 1.9 2005/08/05 13:02:59 espie Exp $ */
/*-
* 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. 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.
*/
#include <sys/param.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#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(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;
void *tp;
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) {
tp = (char *)(*buf == NULL ? malloc(sz) : realloc(*buf, sz));
if (tp == NULL)
return (RET_ERROR);
*buf = tp;
*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(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(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);
}
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