Update.

[glibc.git] / db2 / hash / hash.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998
 *      Sleepycat Software.  All rights reserved.
 */
/*
 * Copyright (c) 1990, 1993, 1994
 *      Margo Seltzer.  All rights reserved.
 */
/*
 * 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.
 */

#include "config.h"

#ifndef lint
static const char sccsid[] = "@(#)hash.c        10.45 (Sleepycat) 5/11/98";
#endif /* not lint */

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>

#include <errno.h>
#include <stdlib.h>
#include <string.h>
#endif

#include "db_int.h"
#include "shqueue.h"
#include "db_page.h"
#include "db_am.h"
#include "db_ext.h"
#include "hash.h"
#include "log.h"

static int  __ham_c_close __P((DBC *));
static int  __ham_c_del __P((DBC *, u_int32_t));
static int  __ham_c_get __P((DBC *, DBT *, DBT *, u_int32_t));
static int  __ham_c_put __P((DBC *, DBT *, DBT *, u_int32_t));
static int  __ham_c_init __P((DB *, DB_TXN *, DBC **));
static int  __ham_cursor __P((DB *, DB_TXN *, DBC **));
static int  __ham_delete __P((DB *, DB_TXN *, DBT *, u_int32_t));
static int  __ham_dup_return __P((HTAB *, HASH_CURSOR *, DBT *, u_int32_t));
static int  __ham_get __P((DB *, DB_TXN *, DBT *, DBT *, u_int32_t));
static void __ham_init_htab __P((HTAB *, u_int32_t, u_int32_t));
static int  __ham_lookup __P((HTAB *,
                HASH_CURSOR *, const DBT *, u_int32_t, db_lockmode_t));
static int  __ham_overwrite __P((HTAB *, HASH_CURSOR *, DBT *));
static int  __ham_put __P((DB *, DB_TXN *, DBT *, DBT *, u_int32_t));
static int  __ham_sync __P((DB *, u_int32_t));

/************************** INTERFACE ROUTINES ***************************/
/* OPEN/CLOSE */

/*
 * __ham_open --
 *
 * PUBLIC: int __ham_open __P((DB *, DB_INFO *));
 */
int
__ham_open(dbp, dbinfo)
        DB *dbp;
        DB_INFO *dbinfo;
{
        DB_ENV *dbenv;
        DBC *curs;
        HTAB *hashp;
        int file_existed, ret;

        dbenv = dbp->dbenv;

        if ((hashp = (HTAB *)__db_calloc(1, sizeof(HTAB))) == NULL)
                return (ENOMEM);
        hashp->dbp = dbp;

        /* Set the hash function if specified by the user. */
        if (dbinfo != NULL && dbinfo->h_hash != NULL)
                hashp->hash = dbinfo->h_hash;

        /*
         * Initialize the remaining fields of the dbp.  The type, close and
         * fd functions are all set in db_open.
         */
        dbp->internal = hashp;
        dbp->cursor = __ham_cursor;
        dbp->del = __ham_delete;
        dbp->get = __ham_get;
        dbp->put = __ham_put;
        dbp->sync = __ham_sync;

        /* If locking is turned on, lock the meta data page. */
        if (F_ISSET(dbp, DB_AM_LOCKING)) {
                dbp->lock.pgno = BUCKET_INVALID;
                if ((ret = lock_get(dbenv->lk_info, dbp->locker,
                    0, &dbp->lock_dbt, DB_LOCK_READ, &hashp->hlock)) != 0) {
                        if (ret < 0)
                                ret = EAGAIN;
                        goto out;
                }
        }

        /*
         * Now, we can try to read the meta-data page and figure out
         * if we set up locking and get the meta-data page properly.
         * If this is a new file, initialize it, and put it back dirty.
         */
        if ((ret = __ham_get_page(hashp->dbp, 0, (PAGE **)&hashp->hdr)) != 0)
                goto out;

        /* Initialize the hashp structure */
        if (hashp->hdr->magic == DB_HASHMAGIC) {
                file_existed = 1;
                /* File exists, verify the data in the header. */
                if (hashp->hash == NULL)
                        hashp->hash =
                            hashp->hdr->version < 5 ? __ham_func4 : __ham_func5;
                if (hashp->hash(CHARKEY, sizeof(CHARKEY)) !=
                    hashp->hdr->h_charkey) {
                        __db_err(hashp->dbp->dbenv,
                            "hash: incompatible hash function");
                        ret = EINVAL;
                        goto out;
                }
                if (F_ISSET(hashp->hdr, DB_HASH_DUP))
                        F_SET(dbp, DB_AM_DUP);
        } else {
                /*
                 * File does not exist, we must initialize the header.  If
                 * locking is enabled that means getting a write lock first.
                 */
                file_existed = 0;
                if (F_ISSET(dbp, DB_AM_LOCKING) &&
                    ((ret = lock_put(dbenv->lk_info, hashp->hlock)) != 0 ||
                    (ret = lock_get(dbenv->lk_info, dbp->locker, 0,
                        &dbp->lock_dbt, DB_LOCK_WRITE, &hashp->hlock)) != 0)) {
                        if (ret < 0)
                                ret = EAGAIN;
                        goto out;
                }

                __ham_init_htab(hashp,
                    dbinfo != NULL ? dbinfo->h_nelem : 0,
                    dbinfo != NULL ? dbinfo->h_ffactor : 0);
                if (F_ISSET(dbp, DB_AM_DUP))
                        F_SET(hashp->hdr, DB_HASH_DUP);
                if ((ret = __ham_dirty_page(hashp, (PAGE *)hashp->hdr)) != 0)
                        goto out;
        }

        /* Initialize the default cursor. */
        __ham_c_init(dbp, NULL, &curs);
        TAILQ_INSERT_TAIL(&dbp->curs_queue, curs, links);

        /* Allocate memory for our split buffer. */
        if ((hashp->split_buf = (PAGE *)__db_malloc(dbp->pgsize)) == NULL) {
                ret = ENOMEM;
                goto out;
        }

#ifdef NO_STATISTICS_FOR_DB_ERR
        __db_err(dbp->dbenv,
            "%s%lx\n%s%ld\n%s%ld\n%s%ld\n%s%ld\n%s0x%lx\n%s0x%lx\n%s%ld\n%s%ld\n%s0x%lx",
            "TABLE POINTER   ", (long)hashp,
            "BUCKET SIZE     ", (long)hashp->hdr->pagesize,
            "FILL FACTOR     ", (long)hashp->hdr->ffactor,
            "MAX BUCKET      ", (long)hashp->hdr->max_bucket,
            "OVFL POINT      ", (long)hashp->hdr->ovfl_point,
            "LAST FREED      ", (long)hashp->hdr->last_freed,
            "HIGH MASK       ", (long)hashp->hdr->high_mask,
            "LOW  MASK       ", (long)hashp->hdr->low_mask,
            "NELEM           ", (long)hashp->hdr->nelem,
            "FLAGS           ", (long)hashp->hdr->flags);
#endif

        /* Release the meta data page */
        (void)__ham_put_page(hashp->dbp, (PAGE *)hashp->hdr, 0);
        if (F_ISSET(dbp, DB_AM_LOCKING) &&
            (ret = lock_put(dbenv->lk_info, hashp->hlock)) != 0) {
                if (ret < 0)
                        ret = EAGAIN;
                goto out;
        }

        hashp->hlock = 0;
        hashp->hdr = NULL;
        /* Sync the file so that we know that the meta data goes to disk. */
        if (!file_existed && (ret = dbp->sync(dbp, 0)) != 0)
                goto out;
        return (0);

out:    (void)__ham_close(dbp);
        return (ret);
}

/*
 * PUBLIC: int __ham_close __P((DB *));
 */
int
__ham_close(dbp)
        DB *dbp;
{
        HTAB *hashp;
        int ret, t_ret;

        DEBUG_LWRITE(dbp, NULL, "ham_close", NULL, NULL, 0);
        hashp = (HTAB *)dbp->internal;
        ret = 0;

        /* Free the split page. */
        if (hashp->split_buf)
                FREE(hashp->split_buf, dbp->pgsize);

        if (hashp->hdr && (t_ret = __ham_put_page(hashp->dbp,
            (PAGE *)hashp->hdr, 0)) != 0 && ret == 0)
                ret = t_ret;
        if (hashp->hlock && (t_ret = lock_put(hashp->dbp->dbenv->lk_info,
            hashp->hlock)) != 0 && ret == 0)
                ret = t_ret;

        FREE(hashp, sizeof(HTAB));
        dbp->internal = NULL;
        return (ret);
}

/************************** LOCAL CREATION ROUTINES **********************/
/*
 * Returns 0 on No Error
 */
static void
__ham_init_htab(hashp, nelem, ffactor)
        HTAB *hashp;
        u_int32_t nelem, ffactor;
{
        int32_t l2, nbuckets;

        memset(hashp->hdr, 0, sizeof(HASHHDR));
        hashp->hdr->ffactor = ffactor;
        hashp->hdr->pagesize = hashp->dbp->pgsize;
        ZERO_LSN(hashp->hdr->lsn);
        hashp->hdr->magic = DB_HASHMAGIC;
        hashp->hdr->version = DB_HASHVERSION;
        if (hashp->hash == NULL)
                hashp->hash =
                    hashp->hdr->version < 5 ? __ham_func4 : __ham_func5;
        hashp->hdr->h_charkey = hashp->hash(CHARKEY, sizeof(CHARKEY));
        if (nelem != 0 && hashp->hdr->ffactor != 0) {
                nelem = (nelem - 1) / hashp->hdr->ffactor + 1;
                l2 = __db_log2(nelem > 2 ? nelem : 2);
        } else
                l2 = 2;

        nbuckets = 1 << l2;

        hashp->hdr->ovfl_point = l2;
        hashp->hdr->last_freed = PGNO_INVALID;

        hashp->hdr->max_bucket = hashp->hdr->high_mask = nbuckets - 1;
        hashp->hdr->low_mask = (nbuckets >> 1) - 1;
        memcpy(hashp->hdr->uid, hashp->dbp->lock.fileid, DB_FILE_ID_LEN);
}

/********************** DESTROY/CLOSE ROUTINES ************************/


/*
 * Write modified pages to disk
 *
 * Returns:
 *       0 == OK
 *      -1 ERROR
 */
static int
__ham_sync(dbp, flags)
        DB *dbp;
        u_int32_t flags;
{
        int ret;

        DEBUG_LWRITE(dbp, NULL, "ham_sync", NULL, NULL, flags);
        if ((ret = __db_syncchk(dbp, flags)) != 0)
                return (ret);
        if (F_ISSET(dbp, DB_AM_RDONLY))
                return (0);

        if ((ret = memp_fsync(dbp->mpf)) == DB_INCOMPLETE)
                ret = 0;

        return (ret);
}

/*******************************SEARCH ROUTINES *****************************/
/*
 * All the access routines return
 *
 * Returns:
 *       0 on SUCCESS
 *       1 to indicate an external ERROR (i.e. key not found, etc)
 *      -1 to indicate an internal ERROR (i.e. out of memory, etc)
 */

static int
__ham_get(dbp, txn, key, data, flags)
        DB *dbp;
        DB_TXN *txn;
        DBT *key;
        DBT *data;
        u_int32_t flags;
{
        DB *ldbp;
        HTAB *hashp;
        HASH_CURSOR *hcp;
        int ret, t_ret;

        DEBUG_LREAD(dbp, txn, "ham_get", key, NULL, flags);
        if ((ret = __db_getchk(dbp, key, data, flags)) != 0)
                return (ret);

        ldbp = dbp;
        if (F_ISSET(dbp, DB_AM_THREAD) &&
            (ret = __db_gethandle(dbp, __ham_hdup, &ldbp)) != 0)
                return (ret);

        hashp = (HTAB *)ldbp->internal;
        SET_LOCKER(ldbp, txn);
        GET_META(ldbp, hashp);

        hashp->hash_accesses++;
        hcp = (HASH_CURSOR *)TAILQ_FIRST(&ldbp->curs_queue)->internal;
        if ((ret = __ham_lookup(hashp, hcp, key, 0, DB_LOCK_READ)) == 0)
                if (F_ISSET(hcp, H_OK))
                        ret = __ham_dup_return(hashp, hcp, data, DB_FIRST);
                else /* Key was not found */
                        ret = DB_NOTFOUND;

        if ((t_ret = __ham_item_done(hashp, hcp, 0)) != 0 && ret == 0)
                ret = t_ret;
        RELEASE_META(ldbp, hashp);
        if (F_ISSET(dbp, DB_AM_THREAD))
                __db_puthandle(ldbp);
        return (ret);
}

static int
__ham_put(dbp, txn, key, data, flags)
        DB *dbp;
        DB_TXN *txn;
        DBT *key;
        DBT *data;
        u_int32_t flags;
{
        DB *ldbp;
        DBT tmp_val, *myval;
        HASH_CURSOR *hcp;
        HTAB *hashp;
        u_int32_t nbytes;
        int ret, t_ret;

        DEBUG_LWRITE(dbp, txn, "ham_put", key, data, flags);
        if ((ret = __db_putchk(dbp, key, data,
            flags, F_ISSET(dbp, DB_AM_RDONLY), F_ISSET(dbp, DB_AM_DUP))) != 0)
                return (ret);

        ldbp = dbp;
        if (F_ISSET(dbp, DB_AM_THREAD) &&
            (ret = __db_gethandle(dbp, __ham_hdup, &ldbp)) != 0)
                return (ret);

        hashp = (HTAB *)ldbp->internal;
        SET_LOCKER(ldbp, txn);
        GET_META(ldbp, hashp);
        hcp = TAILQ_FIRST(&ldbp->curs_queue)->internal;

        nbytes = (ISBIG(hashp, key->size) ? HOFFPAGE_PSIZE :
            HKEYDATA_PSIZE(key->size)) +
            (ISBIG(hashp, data->size) ? HOFFPAGE_PSIZE :
            HKEYDATA_PSIZE(data->size));

        hashp->hash_accesses++;
        ret = __ham_lookup(hashp, hcp, key, nbytes, DB_LOCK_WRITE);

        if (ret == DB_NOTFOUND) {
                ret = 0;
                if (hcp->seek_found_page != PGNO_INVALID &&
                    hcp->seek_found_page != hcp->pgno) {
                        if ((ret = __ham_item_done(hashp, hcp, 0)) != 0)
                                goto out;
                        hcp->pgno = hcp->seek_found_page;
                        hcp->bndx = NDX_INVALID;
                }

                if (F_ISSET(data, DB_DBT_PARTIAL) && data->doff != 0) {
                        /*
                         * Doing a partial put, but the key does not exist
                         * and we are not beginning the write at 0.  We
                         * must create a data item padded up to doff and
                         * then write the new bytes represented by val.
                         */
                        ret = __ham_init_dbt(&tmp_val, data->size + data->doff,
                            &hcp->big_data, &hcp->big_datalen);
                        if (ret == 0) {
                                memset(tmp_val.data, 0, data->doff);
                                memcpy((u_int8_t *)tmp_val.data + data->doff,
                                    data->data, data->size);
                                myval = &tmp_val;
                        }
                } else
                        myval = (DBT *)data;

                if (ret == 0)
                        ret = __ham_add_el(hashp, hcp, key, myval, H_KEYDATA);
        } else if (ret == 0 && F_ISSET(hcp, H_OK)) {
                if (flags == DB_NOOVERWRITE)
                        ret = DB_KEYEXIST;
                else if (F_ISSET(ldbp, DB_AM_DUP))
                        ret = __ham_add_dup(hashp, hcp, data, DB_KEYLAST);
                else
                        ret = __ham_overwrite(hashp, hcp, data);
        }

        /* Free up all the cursor pages. */
        if ((t_ret = __ham_item_done(hashp, hcp, ret == 0)) != 0 && ret == 0)
                ret = t_ret;
        /* Now check if we have to grow. */
out:    if (ret == 0 && F_ISSET(hcp, H_EXPAND)) {
                ret = __ham_expand_table(hashp);
                F_CLR(hcp, H_EXPAND);
        }

        if ((t_ret = __ham_item_done(hashp, hcp, ret == 0)) != 0 && ret == 0)
                ret = t_ret;
        RELEASE_META(ldbp, hashp);
        if (F_ISSET(dbp, DB_AM_THREAD))
                __db_puthandle(ldbp);
        return (ret);
}

static int
__ham_cursor(dbp, txnid, dbcp)
        DB *dbp;
        DB_TXN *txnid;
        DBC **dbcp;
{
        int ret;

        DEBUG_LWRITE(dbp, txnid, "ham_cursor", NULL, NULL, 0);
        if ((ret = __ham_c_init(dbp, txnid, dbcp)) != 0)
                return (ret);

        DB_THREAD_LOCK(dbp);
        TAILQ_INSERT_TAIL(&dbp->curs_queue, *dbcp, links);
        DB_THREAD_UNLOCK(dbp);
        return (ret);
}

static int
__ham_c_init(dbp, txnid, dbcp)
        DB *dbp;
        DB_TXN *txnid;
        DBC **dbcp;
{
        DBC *db_curs;
        HASH_CURSOR *new_curs;

        if ((db_curs = (DBC *)__db_calloc(sizeof(DBC), 1)) == NULL)
                return (ENOMEM);

        if ((new_curs =
            (HASH_CURSOR *)__db_calloc(sizeof(struct cursor_t), 1)) == NULL) {
                FREE(db_curs, sizeof(DBC));
                return (ENOMEM);
        }

        db_curs->internal = new_curs;
        db_curs->c_close = __ham_c_close;
        db_curs->c_del = __ham_c_del;
        db_curs->c_get = __ham_c_get;
        db_curs->c_put = __ham_c_put;
        db_curs->txn = txnid;
        db_curs->dbp = dbp;

        new_curs->db_cursor = db_curs;
        __ham_item_init(new_curs);

        if (dbcp != NULL)
                *dbcp = db_curs;
        return (0);
}

static int
__ham_delete(dbp, txn, key, flags)
        DB *dbp;
        DB_TXN *txn;
        DBT *key;
        u_int32_t flags;
{
        DB *ldbp;
        HTAB *hashp;
        HASH_CURSOR *hcp;
        int ret, t_ret;

        DEBUG_LWRITE(dbp, txn, "ham_delete", key, NULL, flags);
        if ((ret =
            __db_delchk(dbp, key, flags, F_ISSET(dbp, DB_AM_RDONLY))) != 0)
                return (ret);

        ldbp = dbp;
        if (F_ISSET(dbp, DB_AM_THREAD) &&
            (ret = __db_gethandle(dbp, __ham_hdup, &ldbp)) != 0)
                return (ret);
        hashp = (HTAB *)ldbp->internal;
        SET_LOCKER(ldbp, txn);
        GET_META(ldbp, hashp);
        hcp = TAILQ_FIRST(&ldbp->curs_queue)->internal;

        hashp->hash_accesses++;
        if ((ret = __ham_lookup(hashp, hcp, key, 0, DB_LOCK_WRITE)) == 0)
                if (F_ISSET(hcp, H_OK))
                        ret = __ham_del_pair(hashp, hcp, 1);
                else
                        ret = DB_NOTFOUND;

        if ((t_ret = __ham_item_done(hashp, hcp, ret == 0)) != 0 && ret == 0)
                ret = t_ret;
        RELEASE_META(ldbp, hashp);
        if (F_ISSET(dbp, DB_AM_THREAD))
                __db_puthandle(ldbp);
        return (ret);
}

/* ****************** CURSORS ********************************** */
static int
__ham_c_close(cursor)
        DBC *cursor;
{
        DB  *ldbp;
        int ret;

        DEBUG_LWRITE(cursor->dbp, cursor->txn, "ham_c_close", NULL, NULL, 0);
        /*
         * If the pagep, dpagep, and lock fields of the cursor are all NULL,
         * then there really isn't a need to get a handle here.  However,
         * the normal case is that at least one of those fields is non-NULL,
         * and putting those checks in here would couple the ham_item_done
         * functionality with cursor close which would be pretty disgusting.
         * Instead, we pay the overhead here of always getting the handle.
         */
        ldbp = cursor->dbp;
        if (F_ISSET(cursor->dbp, DB_AM_THREAD) &&
            (ret = __db_gethandle(cursor->dbp, __ham_hdup, &ldbp)) != 0)
                return (ret);

        ret = __ham_c_iclose(ldbp, cursor);

        if (F_ISSET(ldbp, DB_AM_THREAD))
                __db_puthandle(ldbp);
        return (ret);
}
/*
 * __ham_c_iclose --
 *
 * Internal cursor close routine; assumes it is being passed the correct
 * handle, rather than getting and putting a handle.
 *
 * PUBLIC: int __ham_c_iclose __P((DB *, DBC *));
 */
int
__ham_c_iclose(dbp, dbc)
        DB *dbp;
        DBC *dbc;
{
        HASH_CURSOR *hcp;
        HTAB *hashp;
        int ret;

        hashp = (HTAB *)dbp->internal;
        hcp = (HASH_CURSOR *)dbc->internal;
        ret = __ham_item_done(hashp, hcp, 0);

        if (hcp->big_key)
                FREE(hcp->big_key, hcp->big_keylen);
        if (hcp->big_data)
                FREE(hcp->big_data, hcp->big_datalen);

        /*
         * All cursors (except the default ones) are linked off the master.
         * Therefore, when we close the cursor, we have to remove it from
         * the master, not the local one.
         * XXX I am always removing from the master; what about local cursors?
         */
        DB_THREAD_LOCK(dbc->dbp);
        TAILQ_REMOVE(&dbc->dbp->curs_queue, dbc, links);
        DB_THREAD_UNLOCK(dbc->dbp);

        FREE(hcp, sizeof(HASH_CURSOR));
        FREE(dbc, sizeof(DBC));

        return (ret);
}

static int
__ham_c_del(cursor, flags)
        DBC *cursor;
        u_int32_t flags;
{
        DB *ldbp;
        HASH_CURSOR *hcp;
        HASH_CURSOR save_curs;
        HTAB *hashp;
        db_pgno_t ppgno, chg_pgno;
        int ret, t_ret;

        DEBUG_LWRITE(cursor->dbp, cursor->txn, "ham_c_del", NULL, NULL, flags);
        ldbp = cursor->dbp;
        if (F_ISSET(cursor->dbp, DB_AM_THREAD) &&
            (ret = __db_gethandle(cursor->dbp, __ham_hdup, &ldbp)) != 0)
                return (ret);
        hashp = (HTAB *)ldbp->internal;
        hcp = (HASH_CURSOR *)cursor->internal;
        save_curs = *hcp;
        if ((ret = __db_cdelchk(ldbp, flags,
            F_ISSET(ldbp, DB_AM_RDONLY), IS_VALID(hcp))) != 0)
                return (ret);
        if (F_ISSET(hcp, H_DELETED))
                return (DB_NOTFOUND);

        SET_LOCKER(hashp->dbp, cursor->txn);
        GET_META(hashp->dbp, hashp);
        hashp->hash_accesses++;
        if ((ret = __ham_get_cpage(hashp, hcp, DB_LOCK_WRITE)) != 0)
                goto out;
        if (F_ISSET(hcp, H_ISDUP) && hcp->dpgno != PGNO_INVALID) {
                /*
                 * We are about to remove a duplicate from offpage.
                 *
                 * There are 4 cases.
                 * 1. We will remove an item on a page, but there are more
                 *    items on that page.
                 * 2. We will remove the last item on a page, but there is a
                 *    following page of duplicates.
                 * 3. We will remove the last item on a page, this page was the
                 *    last page in a duplicate set, but there were dups before
                 *    it.
                 * 4. We will remove the last item on a page, removing the last
                 *    duplicate.
                 * In case 1 hcp->dpagep is unchanged.
                 * In case 2 hcp->dpagep comes back pointing to the next dup
                 *     page.
                 * In case 3 hcp->dpagep comes back NULL.
                 * In case 4 hcp->dpagep comes back NULL.
                 *
                 * Case 4 results in deleting the pair off the master page.
                 * The normal code for doing this knows how to delete the
                 * duplicates, so we will handle this case in the normal code.
                 */
                ppgno = PREV_PGNO(hcp->dpagep);
                if (ppgno == PGNO_INVALID &&
                    NEXT_PGNO(hcp->dpagep) == PGNO_INVALID &&
                    NUM_ENT(hcp->dpagep) == 1)
                        goto normal;

                /* Remove item from duplicate page. */
                chg_pgno = hcp->dpgno;
                if ((ret = __db_drem(hashp->dbp,
                    &hcp->dpagep, hcp->dndx, __ham_del_page)) != 0)
                        goto out;

                if (hcp->dpagep == NULL) {
                        if (ppgno != PGNO_INVALID) {            /* Case 3 */
                                hcp->dpgno = ppgno;
                                if ((ret = __ham_get_cpage(hashp, hcp,
                                    DB_LOCK_READ)) != 0)
                                        goto out;
                                hcp->dndx = NUM_ENT(hcp->dpagep);
                                F_SET(hcp, H_DELETED);
                        } else {                                /* Case 4 */
                                ret = __ham_del_pair(hashp, hcp, 1);
                                hcp->dpgno = PGNO_INVALID;
                                /*
                                 * Delpair updated the cursor queue, so we
                                 * don't have to do that here.
                                 */
                                chg_pgno = PGNO_INVALID;
                        }
                } else if (PGNO(hcp->dpagep) != hcp->dpgno) {
                        hcp->dndx = 0;                          /* Case 2 */
                        hcp->dpgno = PGNO(hcp->dpagep);
                        if (ppgno == PGNO_INVALID)
                                memcpy(HOFFDUP_PGNO(P_ENTRY(hcp->pagep,
                                    H_DATAINDEX(hcp->bndx))),
                                    &hcp->dpgno, sizeof(db_pgno_t));
                        F_SET(hcp, H_DELETED);
                } else                                          /* Case 1 */
                        F_SET(hcp, H_DELETED);
                if (chg_pgno != PGNO_INVALID)
                        __ham_c_update(hcp, chg_pgno, 0, 0, 1);
        } else if (F_ISSET(hcp, H_ISDUP)) {                     /* on page */
                if (hcp->dup_off == 0 && DUP_SIZE(hcp->dup_len) ==
                    LEN_HDATA(hcp->pagep, hashp->hdr->pagesize, hcp->bndx))
                        ret = __ham_del_pair(hashp, hcp, 1);
                else {
                        DBT repldbt;

                        repldbt.flags = 0;
                        F_SET(&repldbt, DB_DBT_PARTIAL);
                        repldbt.doff = hcp->dup_off;
                        repldbt.dlen = DUP_SIZE(hcp->dup_len);
                        repldbt.size = 0;
                        ret = __ham_replpair(hashp, hcp, &repldbt, 0);
                        hcp->dup_tlen -= DUP_SIZE(hcp->dup_len);
                        F_SET(hcp, H_DELETED);
                        __ham_c_update(hcp, hcp->pgno,
                            DUP_SIZE(hcp->dup_len), 0, 1);
                }

        } else
                /* Not a duplicate */
normal:         ret = __ham_del_pair(hashp, hcp, 1);

out:    if ((t_ret = __ham_item_done(hashp, hcp, ret == 0)) != 0 && ret == 0)
                ret = t_ret;
        if (ret != 0)
                *hcp = save_curs;
        RELEASE_META(hashp->dbp, hashp);
        if (F_ISSET(cursor->dbp, DB_AM_THREAD))
                __db_puthandle(ldbp);
        return (ret);
}

static int
__ham_c_get(cursor, key, data, flags)
        DBC *cursor;
        DBT *key;
        DBT *data;
        u_int32_t flags;
{
        DB *ldbp;
        HTAB *hashp;
        HASH_CURSOR *hcp, save_curs;
        int get_key, ret, t_ret;

        DEBUG_LREAD(cursor->dbp, cursor->txn, "ham_c_get",
            flags == DB_SET || flags == DB_SET_RANGE ? key : NULL,
            NULL, flags);
        ldbp = cursor->dbp;
        if (F_ISSET(cursor->dbp, DB_AM_THREAD) &&
            (ret = __db_gethandle(cursor->dbp, __ham_hdup, &ldbp)) != 0)
                return (ret);
        hashp = (HTAB *)(ldbp->internal);
        hcp = (HASH_CURSOR *)cursor->internal;
        save_curs = *hcp;
        if ((ret =
            __db_cgetchk(hashp->dbp, key, data, flags, IS_VALID(hcp))) != 0)
                return (ret);

        SET_LOCKER(hashp->dbp, cursor->txn);
        GET_META(hashp->dbp, hashp);
        hashp->hash_accesses++;

        hcp->seek_size = 0;

        ret = 0;
        get_key = 1;
        switch (flags) {
        case DB_PREV:
                if (hcp->bucket != BUCKET_INVALID) {
                        ret = __ham_item_prev(hashp, hcp, DB_LOCK_READ);
                        break;
                }
                /* FALLTHROUGH */
        case DB_LAST:
                ret = __ham_item_last(hashp, hcp, DB_LOCK_READ);
                break;
        case DB_FIRST:
                ret = __ham_item_first(hashp, hcp, DB_LOCK_READ);
                break;
        case DB_NEXT:
                if (hcp->bucket == BUCKET_INVALID)
                        hcp->bucket = 0;
                ret = __ham_item_next(hashp, hcp, DB_LOCK_READ);
                break;
        case DB_SET:
        case DB_SET_RANGE:
                ret = __ham_lookup(hashp, hcp, key, 0, DB_LOCK_READ);
                get_key = 0;
                break;
        case DB_CURRENT:
                if (F_ISSET(hcp, H_DELETED)) {
                        ret = DB_KEYEMPTY;
                        goto out;
                }

                ret = __ham_item(hashp, hcp, DB_LOCK_READ);
                break;
        }

        /*
         * Must always enter this loop to do error handling and
         * check for big key/data pair.
         */
        while (1) {
                if (ret != 0 && ret != DB_NOTFOUND)
                        goto out1;
                else if (F_ISSET(hcp, H_OK)) {
                        /* Get the key. */
                        if (get_key && (ret = __db_ret(hashp->dbp, hcp->pagep,
                            H_KEYINDEX(hcp->bndx), key, &hcp->big_key,
                            &hcp->big_keylen)) != 0)
                                goto out1;

                        ret = __ham_dup_return(hashp, hcp, data, flags);
                        break;
                } else if (!F_ISSET(hcp, H_NOMORE)) {
                        abort();
                        break;
                }

                /*
                 * Ran out of entries in a bucket; change buckets.
                 */
                switch (flags) {
                        case DB_LAST:
                        case DB_PREV:
                                ret = __ham_item_done(hashp, hcp, 0);
                                if (hcp->bucket == 0) {
                                        ret = DB_NOTFOUND;
                                        goto out1;
                                }
                                hcp->bucket--;
                                hcp->bndx = NDX_INVALID;
                                if (ret == 0)
                                        ret = __ham_item_prev(hashp,
                                            hcp, DB_LOCK_READ);
                                break;
                        case DB_FIRST:
                        case DB_NEXT:
                                ret = __ham_item_done(hashp, hcp, 0);
                                hcp->bndx = NDX_INVALID;
                                hcp->bucket++;
                                hcp->pgno = PGNO_INVALID;
                                hcp->pagep = NULL;
                                if (hcp->bucket > hashp->hdr->max_bucket) {
                                        ret = DB_NOTFOUND;
                                        goto out1;
                                }
                                if (ret == 0)
                                        ret = __ham_item_next(hashp,
                                            hcp, DB_LOCK_READ);
                                break;
                        case DB_SET:
                        case DB_SET_RANGE:
                                /* Key not found. */
                                ret = DB_NOTFOUND;
                                goto out1;
                }
        }
out1:   if ((t_ret = __ham_item_done(hashp, hcp, 0)) != 0 && ret == 0)
                ret = t_ret;
out:    if (ret)
                *hcp = save_curs;
        RELEASE_META(hashp->dbp, hashp);
        if (F_ISSET(cursor->dbp, DB_AM_THREAD))
                __db_puthandle(ldbp);
        return (ret);
}

static int
__ham_c_put(cursor, key, data, flags)
        DBC *cursor;
        DBT *key;
        DBT *data;
        u_int32_t flags;
{
        DB *ldbp;
        HASH_CURSOR *hcp, save_curs;
        HTAB *hashp;
        u_int32_t nbytes;
        int ret, t_ret;

        DEBUG_LWRITE(cursor->dbp, cursor->txn, "ham_c_put",
            flags == DB_KEYFIRST || flags == DB_KEYLAST ? key : NULL,
            data, flags);
        ldbp = cursor->dbp;
        if (F_ISSET(cursor->dbp, DB_AM_THREAD) &&
            (ret = __db_gethandle(cursor->dbp, __ham_hdup, &ldbp)) != 0)
                return (ret);
        hashp = (HTAB *)(ldbp->internal);
        hcp = (HASH_CURSOR *)cursor->internal;
        save_curs = *hcp;

        if ((ret = __db_cputchk(hashp->dbp, key, data, flags,
            F_ISSET(ldbp, DB_AM_RDONLY), IS_VALID(hcp))) != 0)
                return (ret);
        if (F_ISSET(hcp, H_DELETED))
                return (DB_NOTFOUND);

        SET_LOCKER(hashp->dbp, cursor->txn);
        GET_META(hashp->dbp, hashp);
        ret = 0;

        switch (flags) {
        case DB_KEYLAST:
        case DB_KEYFIRST:
                nbytes = (ISBIG(hashp, key->size) ? HOFFPAGE_PSIZE :
                    HKEYDATA_PSIZE(key->size)) +
                    (ISBIG(hashp, data->size) ? HOFFPAGE_PSIZE :
                    HKEYDATA_PSIZE(data->size));
                ret = __ham_lookup(hashp, hcp, key, nbytes, DB_LOCK_WRITE);
                break;
        case DB_BEFORE:
        case DB_AFTER:
        case DB_CURRENT:
                ret = __ham_item(hashp, hcp, DB_LOCK_WRITE);
                break;
        }

        if (ret == 0) {
                if (flags == DB_CURRENT && !F_ISSET(ldbp, DB_AM_DUP))
                        ret = __ham_overwrite(hashp, hcp, data);
                else
                        ret = __ham_add_dup(hashp, hcp, data, flags);
        }

        if (ret == 0 && F_ISSET(hcp, H_EXPAND)) {
                ret = __ham_expand_table(hashp);
                F_CLR(hcp, H_EXPAND);
        }

        if ((t_ret = __ham_item_done(hashp, hcp, ret == 0)) != 0 && ret == 0)
                ret = t_ret;
        if (ret != 0)
                *hcp = save_curs;
        RELEASE_META(hashp->dbp, hashp);
        if (F_ISSET(cursor->dbp, DB_AM_THREAD))
                __db_puthandle(ldbp);
        return (ret);
}

/********************************* UTILITIES ************************/

/*
 * __ham_expand_table --
 *
 * PUBLIC: int __ham_expand_table __P((HTAB *));
 */
int
__ham_expand_table(hashp)
        HTAB *hashp;
{
        DB_LSN new_lsn;
        u_int32_t old_bucket, new_bucket, spare_ndx;
        int ret;

        ret = 0;
        DIRTY_META(hashp, ret);
        if (ret)
                return (ret);

        /*
         * If the split point is about to increase, make sure that we
         * have enough extra pages.  The calculation here is weird.
         * We'd like to do this after we've upped max_bucket, but it's
         * too late then because we've logged the meta-data split.  What
         * we'll do between then and now is increment max bucket and then
         * see what the log of one greater than that is; here we have to
         * look at the log of max + 2.  VERY NASTY STUFF.
         */
        if (__db_log2(hashp->hdr->max_bucket + 2) > hashp->hdr->ovfl_point) {
                /*
                 * We are about to shift the split point.  Make sure that
                 * if the next doubling is going to be big (more than 8
                 * pages), we have some extra pages around.
                 */
                if (hashp->hdr->max_bucket + 1 >= 8 &&
                    hashp->hdr->spares[hashp->hdr->ovfl_point] <
                    hashp->hdr->spares[hashp->hdr->ovfl_point - 1] +
                    hashp->hdr->ovfl_point + 1)
                        __ham_init_ovflpages(hashp);
        }

        /* Now we can log the meta-data split. */
        if (DB_LOGGING(hashp->dbp)) {
                if ((ret = __ham_splitmeta_log(hashp->dbp->dbenv->lg_info,
                    (DB_TXN *)hashp->dbp->txn, &new_lsn, 0,
                    hashp->dbp->log_fileid,
                    hashp->hdr->max_bucket, hashp->hdr->ovfl_point,
                    hashp->hdr->spares[hashp->hdr->ovfl_point],
                    &hashp->hdr->lsn)) != 0)
                        return (ret);

                hashp->hdr->lsn = new_lsn;
        }

        hashp->hash_expansions++;
        new_bucket = ++hashp->hdr->max_bucket;
        old_bucket = (hashp->hdr->max_bucket & hashp->hdr->low_mask);

        /*
         * If the split point is increasing, copy the current contents
         * of the spare split bucket to the next bucket.
         */
        spare_ndx = __db_log2(hashp->hdr->max_bucket + 1);
        if (spare_ndx > hashp->hdr->ovfl_point) {
                hashp->hdr->spares[spare_ndx] =
                    hashp->hdr->spares[hashp->hdr->ovfl_point];
                hashp->hdr->ovfl_point = spare_ndx;
        }

        if (new_bucket > hashp->hdr->high_mask) {
                /* Starting a new doubling */
                hashp->hdr->low_mask = hashp->hdr->high_mask;
                hashp->hdr->high_mask = new_bucket | hashp->hdr->low_mask;
        }

        if (BUCKET_TO_PAGE(hashp, new_bucket) > MAX_PAGES(hashp)) {
                __db_err(hashp->dbp->dbenv,
                    "hash: Cannot allocate new bucket.  Pages exhausted.");
                return (ENOSPC);
        }

        /* Relocate records to the new bucket */
        return (__ham_split_page(hashp, old_bucket, new_bucket));
}

/*
 * PUBLIC: u_int32_t __ham_call_hash __P((HTAB *, u_int8_t *, int32_t));
 */
u_int32_t
__ham_call_hash(hashp, k, len)
        HTAB *hashp;
        u_int8_t *k;
        int32_t len;
{
        u_int32_t n, bucket;

        n = (u_int32_t)hashp->hash(k, len);
        bucket = n & hashp->hdr->high_mask;
        if (bucket > hashp->hdr->max_bucket)
                bucket = bucket & hashp->hdr->low_mask;
        return (bucket);
}

/*
 * Check for duplicates, and call __db_ret appropriately.  Release
 * everything held by the cursor.
 */
static int
__ham_dup_return(hashp, hcp, val, flags)
        HTAB *hashp;
        HASH_CURSOR *hcp;
        DBT *val;
        u_int32_t flags;
{
        PAGE *pp;
        DBT *myval, tmp_val;
        db_indx_t ndx;
        db_pgno_t pgno;
        u_int8_t *hk, type;
        int ret;
        db_indx_t len;

        /* Check for duplicate and return the first one. */
        ndx = H_DATAINDEX(hcp->bndx);
        type = HPAGE_TYPE(hcp->pagep, ndx);
        pp = hcp->pagep;
        myval = val;

        /*
         * There are 3 cases:
         * 1. We are not in duplicate, simply call db_ret.
         * 2. We are looking at keys and stumbled onto a duplicate.
         * 3. We are in the middle of a duplicate set. (ISDUP set)
         */

        /*
         * Here we check for the case where we just stumbled onto a
         * duplicate.  In this case, we do initialization and then
         * let the normal duplicate code handle it.
         */
        if (!F_ISSET(hcp, H_ISDUP))
                if (type == H_DUPLICATE) {
                        F_SET(hcp, H_ISDUP);
                        hcp->dup_tlen = LEN_HDATA(hcp->pagep,
                            hashp->hdr->pagesize, hcp->bndx);
                        hk = H_PAIRDATA(hcp->pagep, hcp->bndx);
                        if (flags == DB_LAST || flags == DB_PREV) {
                                hcp->dndx = 0;
                                hcp->dup_off = 0;
                                do {
                                        memcpy(&len,
                                            HKEYDATA_DATA(hk) + hcp->dup_off,
                                            sizeof(db_indx_t));
                                        hcp->dup_off += DUP_SIZE(len);
                                        hcp->dndx++;
                                } while (hcp->dup_off < hcp->dup_tlen);
                                hcp->dup_off -= DUP_SIZE(len);
                                hcp->dndx--;
                        } else {
                                memcpy(&len,
                                    HKEYDATA_DATA(hk), sizeof(db_indx_t));
                                hcp->dup_off = 0;
                                hcp->dndx = 0;
                        }
                        hcp->dup_len = len;
                } else if (type == H_OFFDUP) {
                        F_SET(hcp, H_ISDUP);
                        memcpy(&pgno, HOFFDUP_PGNO(P_ENTRY(hcp->pagep, ndx)),
                            sizeof(db_pgno_t));
                        if (flags == DB_LAST || flags == DB_PREV) {
                                if ((ret = __db_dend(hashp->dbp,
                                    pgno, &hcp->dpagep)) != 0)
                                        return (ret);
                                hcp->dpgno = PGNO(hcp->dpagep);
                                hcp->dndx = NUM_ENT(hcp->dpagep) - 1;
                        } else if ((ret = __ham_next_cpage(hashp,
                            hcp, pgno, 0, H_ISDUP)) != 0)
                                return (ret);
                }


        /*
         * Now, everything is initialized, grab a duplicate if
         * necessary.
         */
        if (F_ISSET(hcp, H_ISDUP))
                if (hcp->dpgno != PGNO_INVALID) {
                        pp = hcp->dpagep;
                        ndx = hcp->dndx;
                } else {
                        /*
                         * Copy the DBT in case we are retrieving into
                         * user memory and we need the parameters for
                         * it.
                         */
                        memcpy(&tmp_val, val, sizeof(*val));
                        F_SET(&tmp_val, DB_DBT_PARTIAL);
                        tmp_val.dlen = hcp->dup_len;
                        tmp_val.doff = hcp->dup_off + sizeof(db_indx_t);
                        myval = &tmp_val;
                }


        /*
         * Finally, if we had a duplicate, pp, ndx, and myval should be
         * set appropriately.
         */
        if ((ret = __db_ret(hashp->dbp, pp, ndx, myval, &hcp->big_data,
            &hcp->big_datalen)) != 0)
                return (ret);

        /*
         * In case we sent a temporary off to db_ret, set the real
         * return values.
         */
        val->data = myval->data;
        val->size = myval->size;

        return (0);
}

static int
__ham_overwrite(hashp, hcp, nval)
        HTAB *hashp;
        HASH_CURSOR *hcp;
        DBT *nval;
{
        DBT *myval, tmp_val;
        u_int8_t *hk;

        if (F_ISSET(hashp->dbp, DB_AM_DUP))
                return (__ham_add_dup(hashp, hcp, nval, DB_KEYLAST));
        else if (!F_ISSET(nval, DB_DBT_PARTIAL)) {
                /* Put/overwrite */
                memcpy(&tmp_val, nval, sizeof(*nval));
                F_SET(&tmp_val, DB_DBT_PARTIAL);
                tmp_val.doff = 0;
                hk = H_PAIRDATA(hcp->pagep, hcp->bndx);
                if (HPAGE_PTYPE(hk) == H_OFFPAGE)
                        memcpy(&tmp_val.dlen,
                            HOFFPAGE_TLEN(hk), sizeof(u_int32_t));
                else
                        tmp_val.dlen = LEN_HDATA(hcp->pagep,
                            hashp->hdr->pagesize,hcp->bndx);
                myval = &tmp_val;
        } else /* Regular partial put */
                myval = nval;

        return (__ham_replpair(hashp, hcp, myval, 0));
}

/*
 * Given a key and a cursor, sets the cursor to the page/ndx on which
 * the key resides.  If the key is found, the cursor H_OK flag is set
 * and the pagep, bndx, pgno (dpagep, dndx, dpgno) fields are set.
 * If the key is not found, the H_OK flag is not set.  If the sought
 * field is non-0, the pagep, bndx, pgno (dpagep, dndx, dpgno) fields
 * are set indicating where an add might take place.  If it is 0,
 * non of the cursor pointer field are valid.
 */
static int
__ham_lookup(hashp, hcp, key, sought, mode)
        HTAB *hashp;
        HASH_CURSOR *hcp;
        const DBT *key;
        u_int32_t sought;
        db_lockmode_t mode;
{
        db_pgno_t pgno;
        u_int32_t tlen;
        int match, ret, t_ret;
        u_int8_t *hk;

        /*
         * Set up cursor so that we're looking for space to add an item
         * as we cycle through the pages looking for the key.
         */
        if ((ret = __ham_item_reset(hashp, hcp)) != 0)
                return (ret);
        hcp->seek_size = sought;

        hcp->bucket = __ham_call_hash(hashp, (u_int8_t *)key->data, key->size);
        while (1) {
                if ((ret = __ham_item_next(hashp, hcp, mode)) != 0)
                        return (ret);

                if (F_ISSET(hcp, H_NOMORE))
                        break;

                hk = H_PAIRKEY(hcp->pagep, hcp->bndx);
                switch (HPAGE_PTYPE(hk)) {
                case H_OFFPAGE:
                        memcpy(&tlen, HOFFPAGE_TLEN(hk), sizeof(u_int32_t));
                        if (tlen == key->size) {
                                memcpy(&pgno,
                                    HOFFPAGE_PGNO(hk), sizeof(db_pgno_t));
                                match = __db_moff(hashp->dbp, key, pgno);
                                if (match == 0) {
                                        F_SET(hcp, H_OK);
                                        return (0);
                                }
                        }
                        break;
                case H_KEYDATA:
                        if (key->size == LEN_HKEY(hcp->pagep,
                            hashp->hdr->pagesize, hcp->bndx) &&
                            memcmp(key->data,
                            HKEYDATA_DATA(hk), key->size) == 0) {
                                F_SET(hcp, H_OK);
                                return (0);
                        }
                        break;
                case H_DUPLICATE:
                case H_OFFDUP:
                        /*
                         * These are errors because keys are never
                         * duplicated, only data items are.
                         */
                        return (__db_pgfmt(hashp->dbp, PGNO(hcp->pagep)));
                }
                hashp->hash_collisions++;
        }

        /*
         * Item was not found, adjust cursor properly.
         */

        if (sought != 0)
                return (ret);

        if ((t_ret = __ham_item_done(hashp, hcp, 0)) != 0 && ret == 0)
                ret = t_ret;
        return (ret);
}

/*
 * Initialize a dbt using some possibly already allocated storage
 * for items.
 * PUBLIC: int __ham_init_dbt __P((DBT *, u_int32_t, void **, u_int32_t *));
 */
int
__ham_init_dbt(dbt, size, bufp, sizep)
        DBT *dbt;
        u_int32_t size;
        void **bufp;
        u_int32_t *sizep;
{
        memset(dbt, 0, sizeof(*dbt));
        if (*sizep < size) {
                if ((*bufp = (void *)(*bufp == NULL ?
                    __db_malloc(size) : __db_realloc(*bufp, size))) == NULL) {
                        *sizep = 0;
                        return (ENOMEM);
                }
                *sizep = size;
        }
        dbt->data = *bufp;
        dbt->size = size;
        return (0);
}

/*
 * Adjust the cursor after an insert or delete.  The cursor passed is
 * the one that was operated upon; we just need to check any of the
 * others.
 *
 * len indicates the length of the item added/deleted
 * add indicates if the item indicated by the cursor has just been
 * added (add == 1) or deleted (add == 0).
 * dup indicates if the addition occurred into a duplicate set.
 *
 * PUBLIC: void __ham_c_update
 * PUBLIC:    __P((HASH_CURSOR *, db_pgno_t, u_int32_t, int, int));
 */
void
__ham_c_update(hcp, chg_pgno, len, add, is_dup)
        HASH_CURSOR *hcp;
        db_pgno_t chg_pgno;
        u_int32_t len;
        int add, is_dup;
{
        DBC *cp;
        HTAB *hp;
        HASH_CURSOR *lcp;
        int page_deleted;

        /*
         * Regular adds are always at the end of a given page, so we never
         * have to adjust anyone's cursor after a regular add.
         */
        if (!is_dup && add)
                return;

        /*
         * Determine if a page was deleted.    If this is a regular update
         * (i.e., not is_dup) then the deleted page's number will be that in
         * chg_pgno, and the pgno in the cursor will be different.  If this
         * was an onpage-duplicate, then the same conditions apply.  If this
         * was an off-page duplicate, then we need to verify if hcp->dpgno
         * is the same (no delete) or different (delete) than chg_pgno.
         */
        if (!is_dup || hcp->dpgno == PGNO_INVALID)
                page_deleted =
                    chg_pgno != PGNO_INVALID && chg_pgno != hcp->pgno;
        else
                page_deleted =
                    chg_pgno != PGNO_INVALID && chg_pgno != hcp->dpgno;

        hp = hcp->db_cursor->dbp->master->internal;
        DB_THREAD_LOCK(hp->dbp);

        for (cp = TAILQ_FIRST(&hp->dbp->curs_queue); cp != NULL;
            cp = TAILQ_NEXT(cp, links)) {
                if (cp->internal == hcp)
                        continue;

                lcp = (HASH_CURSOR *)cp->internal;

                if (!is_dup && lcp->pgno != chg_pgno)
                        continue;

                if (is_dup) {
                        if (F_ISSET(hcp, H_DELETED) && lcp->pgno != chg_pgno)
                                continue;
                        if (!F_ISSET(hcp, H_DELETED) && lcp->dpgno != chg_pgno)
                                continue;
                }

                if (page_deleted) {
                        if (is_dup) {
                                lcp->dpgno = hcp->dpgno;
                                lcp->dndx = hcp->dndx;
                        } else {
                                lcp->pgno = hcp->pgno;
                                lcp->bndx = hcp->bndx;
                                lcp->bucket = hcp->bucket;
                        }
                        F_CLR(lcp, H_ISDUP);
                        continue;
                }

                if (!is_dup && lcp->bndx > hcp->bndx)
                        lcp->bndx--;
                else if (!is_dup && lcp->bndx == hcp->bndx)
                        F_SET(lcp, H_DELETED);
                else if (is_dup && lcp->bndx == hcp->bndx) {
                        /* Assign dpgno in case there was page conversion. */
                        lcp->dpgno = hcp->dpgno;
                        if (add && lcp->dndx >= hcp->dndx )
                                lcp->dndx++;
                        else if (!add && lcp->dndx > hcp->dndx)
                                lcp->dndx--;
                        else if (!add && lcp->dndx == hcp->dndx)
                                F_SET(lcp, H_DELETED);

                        /* Now adjust on-page information. */
                        if (lcp->dpgno == PGNO_INVALID)
                                if (add) {
                                        lcp->dup_tlen += len;
                                        if (lcp->dndx > hcp->dndx)
                                                lcp->dup_off += len;
                                } else {
                                        lcp->dup_tlen -= len;
                                        if (lcp->dndx > hcp->dndx)
                                                lcp->dup_off -= len;
                                }
                }
        }
        DB_THREAD_UNLOCK(hp->dbp);
}

/*
 * __ham_hdup --
 *      This function gets called when we create a duplicate handle for a
 *      threaded DB.  It should create the private part of the DB structure.
 *
 * PUBLIC: int  __ham_hdup __P((DB *, DB *));
 */
int
__ham_hdup(orig, new)
        DB *orig, *new;
{
        DBC *curs;
        HTAB *hashp;
        int ret;

        if ((hashp = (HTAB *)__db_malloc(sizeof(HTAB))) == NULL)
                return (ENOMEM);

        new->internal = hashp;

        hashp->dbp = new;
        hashp->hlock = 0;
        hashp->hdr = NULL;
        hashp->hash = ((HTAB *)orig->internal)->hash;
        if ((hashp->split_buf = (PAGE *)__db_malloc(orig->pgsize)) == NULL)
                return (ENOMEM);
        hashp->local_errno = 0;
        hashp->hash_accesses = 0;
        hashp->hash_collisions = 0;
        hashp->hash_expansions = 0;
        hashp->hash_overflows = 0;
        hashp->hash_bigpages = 0;
        /* Initialize the cursor queue. */
        ret = __ham_c_init(new, NULL, &curs);
        TAILQ_INSERT_TAIL(&new->curs_queue, curs, links);
        return (ret);
}