source: rtems-libbsd/freebsd-userspace/lib/libc/db/btree/bt_overflow.c @ e4e1746

#include "port_before.h"

/*-
 * 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.
 * 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/cdefs.h>
__FBSDID("$FreeBSD$");

#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;

        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 = reallocf(*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(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);
}