/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998
 *      Sleepycat Software.  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_dup.c    10.27 (Sleepycat) 12/6/98";
#endif /* not lint */

/*
 * PACKAGE:  hashing
 *
 * DESCRIPTION:
 *      Manipulation of duplicates for the hash package.
 *
 * ROUTINES:
 *
 * External
 *      __add_dup
 * Internal
 */

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

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

#include "db_int.h"
#include "db_page.h"
#include "hash.h"
#include "btree.h"

static int __ham_check_move __P((DBC *, int32_t));
static int __ham_dup_convert __P((DBC *));
static int __ham_make_dup __P((const DBT *, DBT *d, void **, u_int32_t *));

/*
 * Called from hash_access to add a duplicate key. nval is the new
 * value that we want to add.  The flags correspond to the flag values
 * to cursor_put indicating where to add the new element.
 * There are 4 cases.
 * Case 1: The existing duplicate set already resides on a separate page.
 *         We can use common code for this.
 * Case 2: The element is small enough to just be added to the existing set.
 * Case 3: The element is large enough to be a big item, so we're going to
 *         have to push the set onto a new page.
 * Case 4: The element is large enough to push the duplicate set onto a
 *         separate page.
 *
 * PUBLIC: int __ham_add_dup __P((DBC *, DBT *, u_int32_t));
 */
int
__ham_add_dup(dbc, nval, flags)
        DBC *dbc;
        DBT *nval;
        u_int32_t flags;
{
        DB *dbp;
        HASH_CURSOR *hcp;
        DBT dbt, pval, tmp_val;
        u_int32_t del_len, new_size;
        int cmp, ret;
        u_int8_t *hk;

        dbp = dbc->dbp;
        hcp = (HASH_CURSOR *)dbc->internal;
        if (flags == DB_CURRENT && hcp->dpgno == PGNO_INVALID)
                del_len = hcp->dup_len;
        else
                del_len = 0;

        if ((ret = __ham_check_move(dbc,
            (int32_t)DUP_SIZE(nval->size) - (int32_t)del_len)) != 0)
                return (ret);

        /*
         * Check if resulting duplicate set is going to need to go
         * onto a separate duplicate page.  If so, convert the
         * duplicate set and add the new one.  After conversion,
         * hcp->dndx is the first free ndx or the index of the
         * current pointer into the duplicate set.
         */
        hk = H_PAIRDATA(hcp->pagep, hcp->bndx);
        new_size = DUP_SIZE(nval->size) - del_len + LEN_HKEYDATA(hcp->pagep,
            hcp->hdr->pagesize, H_DATAINDEX(hcp->bndx));

        /*
         * We convert to off-page duplicates if the item is a big item,
         * the addition of the new item will make the set large, or
         * if there isn't enough room on this page to add the next item.
         */
        if (HPAGE_PTYPE(hk) != H_OFFDUP &&
            (HPAGE_PTYPE(hk) == H_OFFPAGE || ISBIG(hcp, new_size) ||
            DUP_SIZE(nval->size) - del_len > P_FREESPACE(hcp->pagep))) {

                if ((ret = __ham_dup_convert(dbc)) != 0)
                        return (ret);
                else
                        hk = H_PAIRDATA(hcp->pagep, hcp->bndx);
        }

        /* There are two separate cases here: on page and off page. */
        if (HPAGE_PTYPE(hk) != H_OFFDUP) {
                if (HPAGE_PTYPE(hk) != H_DUPLICATE) {
                        HPAGE_PTYPE(hk) = H_DUPLICATE;
                        pval.flags = 0;
                        pval.data = HKEYDATA_DATA(hk);
                        pval.size = LEN_HDATA(hcp->pagep, dbp->pgsize,
                            hcp->bndx);
                        if ((ret =
                            __ham_make_dup(&pval, &tmp_val, &dbc->rdata.data,
                            &dbc->rdata.size)) != 0 || (ret =
                            __ham_replpair(dbc, &tmp_val, 1)) != 0)
                                return (ret);
                }

                /* Now make the new entry a duplicate. */
                if ((ret = __ham_make_dup(nval,
                    &tmp_val, &dbc->rdata.data, &dbc->rdata.size)) != 0)
                        return (ret);

                tmp_val.dlen = 0;
                switch (flags) {                        /* On page. */
                case DB_KEYFIRST:
                case DB_KEYLAST:
                        if (dbp->dup_compare != NULL)
                                __ham_dsearch(dbc, nval, &tmp_val.doff, &cmp);
                        else if (flags == DB_KEYFIRST)
                                tmp_val.doff = 0;
                        else
                                tmp_val.doff = LEN_HDATA(hcp->pagep,
                                    hcp->hdr->pagesize, hcp->bndx);
                        break;
                case DB_CURRENT:
                        /*
                         * If we have a sort function, we need to verify that
                         * the new item sorts identically to the old item.
                         */
                        if (dbp->dup_compare != NULL) {
                                dbt.data = HKEYDATA_DATA(H_PAIRDATA(hcp->pagep,
                                    hcp->bndx)) + hcp->dup_off;
                                dbt.size = DUP_SIZE(hcp->dup_len);
                                if (dbp->dup_compare(nval, &dbt) != 0)
                                        return (EINVAL);
                        }
                        tmp_val.doff = hcp->dup_off;
                        tmp_val.dlen = DUP_SIZE(hcp->dup_len);
                        break;
                case DB_BEFORE:
                        tmp_val.doff = hcp->dup_off;
                        break;
                case DB_AFTER:
                        tmp_val.doff = hcp->dup_off + DUP_SIZE(hcp->dup_len);
                        break;
                }
                /* Add the duplicate. */
                ret = __ham_replpair(dbc, &tmp_val, 0);
                if (ret == 0)
                        ret = __ham_dirty_page(dbp, hcp->pagep);
                __ham_c_update(hcp, hcp->pgno, tmp_val.size, 1, 1);
                return (ret);
        }

        /* If we get here, then we're on duplicate pages. */
        if (hcp->dpgno == PGNO_INVALID) {
                memcpy(&hcp->dpgno, HOFFDUP_PGNO(hk), sizeof(db_pgno_t));
                hcp->dndx = 0;
        }

        switch (flags) {
        case DB_KEYFIRST:
                if (dbp->dup_compare != NULL)
                        goto sorted_dups;
                /*
                 * The only way that we are already on a dup page is
                 * if we just converted the on-page representation.
                 * In that case, we've only got one page of duplicates.
                 */
                if (hcp->dpagep == NULL && (ret =
                    __db_dend(dbc, hcp->dpgno, &hcp->dpagep)) != 0)
                        return (ret);
                hcp->dndx = 0;
                break;
        case DB_KEYLAST:
                if (dbp->dup_compare != NULL) {
sorted_dups:            if ((ret = __db_dsearch(dbc, 1, nval,
                            hcp->dpgno, &hcp->dndx, &hcp->dpagep, &cmp)) != 0)
                                return (ret);
                        if (cmp == 0)
                                hcp->dpgno = PGNO(hcp->dpagep);
                } else {
                        if (hcp->dpagep == NULL && (ret =
                            __db_dend(dbc, hcp->dpgno, &hcp->dpagep)) != 0)
                                return (ret);
                        hcp->dpgno = PGNO(hcp->dpagep);
                        hcp->dndx = NUM_ENT(hcp->dpagep);
                }
                break;
        case DB_CURRENT:
                if (dbp->dup_compare != NULL && __bam_cmp(dbp,
                    nval, hcp->dpagep, hcp->dndx, dbp->dup_compare) != 0)
                        return (EINVAL);
                switch (GET_BKEYDATA(hcp->dpagep, hcp->dndx)->type) {
                case B_KEYDATA:
                        del_len = BKEYDATA_SIZE(GET_BKEYDATA(hcp->dpagep,
                            hcp->dndx)->len);
                        break;
                case B_OVERFLOW:
                        del_len = BOVERFLOW_SIZE;
                        break;
                }
                if ((ret =
                    __db_ditem(dbc, hcp->dpagep, hcp->dndx, del_len)) != 0)
                        return (ret);
                break;
        case DB_BEFORE: /* The default behavior is correct. */
                break;
        case DB_AFTER:
                hcp->dndx++;
                break;
        }

        ret = __db_dput(dbc,
            nval, &hcp->dpagep, &hcp->dndx, __ham_overflow_page);
        hcp->pgno = PGNO(hcp->pagep);
        __ham_c_update(hcp, hcp->pgno, nval->size, 1, 1);
        return (ret);
}

/*
 * Convert an on-page set of duplicates to an offpage set of duplicates.
 */
static int
__ham_dup_convert(dbc)
        DBC *dbc;
{
        DB *dbp;
        HASH_CURSOR *hcp;
        BOVERFLOW bo;
        DBT dbt;
        HOFFPAGE ho;
        db_indx_t dndx, i, len, off;
        int ret;
        u_int8_t *p, *pend;

        /*
         * Create a new page for the duplicates.
         */
        dbp = dbc->dbp;
        hcp = (HASH_CURSOR *)dbc->internal;
        if ((ret =
            __ham_overflow_page(dbc, P_DUPLICATE, &hcp->dpagep)) != 0)
                return (ret);
        hcp->dpagep->type = P_DUPLICATE;
        hcp->dpgno = PGNO(hcp->dpagep);

        /*
         * Now put the duplicates onto the new page.
         */
        dndx = 0;
        dbt.flags = 0;
        switch (HPAGE_PTYPE(H_PAIRDATA(hcp->pagep, hcp->bndx))) {
        case H_KEYDATA:
                /* Simple case, one key on page; move it to dup page. */
                dbt.size =
                    LEN_HDATA(hcp->pagep, hcp->hdr->pagesize, hcp->bndx);
                dbt.data = HKEYDATA_DATA(H_PAIRDATA(hcp->pagep, hcp->bndx));
                ret = __db_pitem(dbc, hcp->dpagep,
                    (u_int32_t)dndx, BKEYDATA_SIZE(dbt.size), NULL, &dbt);
                if (ret == 0)
                        __ham_dirty_page(dbp, hcp->dpagep);
                break;
        case H_OFFPAGE:
                /* Simple case, one key on page; move it to dup page. */
                memcpy(&ho,
                    P_ENTRY(hcp->pagep, H_DATAINDEX(hcp->bndx)), HOFFPAGE_SIZE);
                UMRW(bo.unused1);
                B_TSET(bo.type, ho.type, 0);
                UMRW(bo.unused2);
                bo.pgno = ho.pgno;
                bo.tlen = ho.tlen;
                dbt.size = BOVERFLOW_SIZE;
                dbt.data = &bo;

                ret = __db_pitem(dbc, hcp->dpagep,
                   (u_int32_t)dndx, dbt.size, &dbt, NULL);
                if (ret == 0)
                        __ham_dirty_page(dbp, hcp->dpagep);
                break;
        case H_DUPLICATE:
                p = HKEYDATA_DATA(H_PAIRDATA(hcp->pagep, hcp->bndx));
                pend = p +
                    LEN_HDATA(hcp->pagep, hcp->hdr->pagesize, hcp->bndx);

                /*
                 * We need to maintain the duplicate cursor position.
                 * Keep track of where we are in the duplicate set via
                 * the offset, and when it matches the one in the cursor,
                 * set the off-page duplicate cursor index to the current
                 * index.
                 */
                for (off = 0, i = 0; p < pend; i++) {
                        if (off == hcp->dup_off)
                                dndx = i;
                        memcpy(&len, p, sizeof(db_indx_t));
                        dbt.size = len;
                        p += sizeof(db_indx_t);
                        dbt.data = p;
                        p += len + sizeof(db_indx_t);
                        off += len + 2 * sizeof(db_indx_t);
                        ret = __db_dput(dbc, &dbt,
                            &hcp->dpagep, &i, __ham_overflow_page);
                        if (ret != 0)
                                break;
                }
                break;
        default:
                ret = __db_pgfmt(dbp, (u_long)hcp->pgno);
                break;
        }
        if (ret == 0) {
                /*
                 * Now attach this to the source page in place of
                 * the old duplicate item.
                 */
                __ham_move_offpage(dbc, hcp->pagep,
                    (u_int32_t)H_DATAINDEX(hcp->bndx), hcp->dpgno);

                /* Can probably just do a "put" here. */
                ret = __ham_dirty_page(dbp, hcp->pagep);
                hcp->dndx = dndx;
        } else {
                (void)__ham_del_page(dbc, hcp->dpagep);
                hcp->dpagep = NULL;
        }
        return (ret);
}

static int
__ham_make_dup(notdup, duplicate, bufp, sizep)
        const DBT *notdup;
        DBT *duplicate;
        void **bufp;
        u_int32_t *sizep;
{
        db_indx_t tsize, item_size;
        int ret;
        u_int8_t *p;

        item_size = (db_indx_t)notdup->size;
        tsize = DUP_SIZE(item_size);
        if ((ret = __ham_init_dbt(duplicate, tsize, bufp, sizep)) != 0)
                return (ret);

        duplicate->dlen = 0;
        duplicate->flags = notdup->flags;
        F_SET(duplicate, DB_DBT_PARTIAL);

        p = duplicate->data;
        memcpy(p, &item_size, sizeof(db_indx_t));
        p += sizeof(db_indx_t);
        memcpy(p, notdup->data, notdup->size);
        p += notdup->size;
        memcpy(p, &item_size, sizeof(db_indx_t));

        duplicate->doff = 0;
        duplicate->dlen = notdup->size;

        return (0);
}

static int
__ham_check_move(dbc, add_len)
        DBC *dbc;
        int32_t add_len;
{
        DB *dbp;
        HASH_CURSOR *hcp;
        DBT k, d;
        DB_LSN new_lsn;
        PAGE *next_pagep;
        db_pgno_t next_pgno;
        u_int32_t new_datalen, old_len, rectype;
        u_int8_t *hk;
        int ret;

        dbp = dbc->dbp;
        hcp = (HASH_CURSOR *)dbc->internal;
        /*
         * Check if we can do whatever we need to on this page.  If not,
         * then we'll have to move the current element to a new page.
         */
        hk = H_PAIRDATA(hcp->pagep, hcp->bndx);

        /*
         * If the item is already off page duplicates or an offpage item,
         * then we know we can do whatever we need to do in-place
         */
        if (HPAGE_PTYPE(hk) == H_OFFDUP || HPAGE_PTYPE(hk) == H_OFFPAGE)
                return (0);

        old_len =
            LEN_HITEM(hcp->pagep, hcp->hdr->pagesize, H_DATAINDEX(hcp->bndx));
        new_datalen = old_len - HKEYDATA_SIZE(0) + add_len;

        /*
         * We need to add a new page under two conditions:
         * 1. The addition makes the total data length cross the BIG
         *    threshold and the OFFDUP structure won't fit on this page.
         * 2. The addition does not make the total data cross the
         *    threshold, but the new data won't fit on the page.
         * If neither of these is true, then we can return.
         */
        if (ISBIG(hcp, new_datalen) && (old_len > HOFFDUP_SIZE ||
            HOFFDUP_SIZE - old_len <= P_FREESPACE(hcp->pagep)))
                return (0);

        if (!ISBIG(hcp, new_datalen) &&
            add_len <= (int32_t)P_FREESPACE(hcp->pagep))
                return (0);

        /*
         * If we get here, then we need to move the item to a new page.
         * Check if there are more pages in the chain.
         */

        new_datalen = ISBIG(hcp, new_datalen) ?
            HOFFDUP_SIZE : HKEYDATA_SIZE(new_datalen);

        next_pagep = NULL;
        for (next_pgno = NEXT_PGNO(hcp->pagep); next_pgno != PGNO_INVALID;
            next_pgno = NEXT_PGNO(next_pagep)) {
                if (next_pagep != NULL &&
                    (ret = __ham_put_page(dbp, next_pagep, 0)) != 0)
                        return (ret);

                if ((ret =
                    __ham_get_page(dbp, next_pgno, &next_pagep)) != 0)
                        return (ret);

                if (P_FREESPACE(next_pagep) >= new_datalen)
                        break;
        }

        /* No more pages, add one. */
        if (next_pagep == NULL && (ret = __ham_add_ovflpage(dbc,
            hcp->pagep, 0, &next_pagep)) != 0)
                return (ret);

        /* Add new page at the end of the chain. */
        if (P_FREESPACE(next_pagep) < new_datalen && (ret =
            __ham_add_ovflpage(dbc, next_pagep, 1, &next_pagep)) != 0)
                return (ret);

        /* Copy the item to the new page. */
        if (DB_LOGGING(hcp->dbc)) {
                rectype = PUTPAIR;
                k.flags = 0;
                d.flags = 0;
                if (HPAGE_PTYPE(
                    H_PAIRKEY(hcp->pagep, hcp->bndx)) == H_OFFPAGE) {
                        rectype |= PAIR_KEYMASK;
                        k.data = H_PAIRKEY(hcp->pagep, hcp->bndx);
                        k.size = HOFFPAGE_SIZE;
                } else {
                        k.data =
                            HKEYDATA_DATA(H_PAIRKEY(hcp->pagep, hcp->bndx));
                        k.size = LEN_HKEY(hcp->pagep,
                            hcp->hdr->pagesize, hcp->bndx);
                }

                if (HPAGE_PTYPE(hk) == H_OFFPAGE) {
                        rectype |= PAIR_DATAMASK;
                        d.data = H_PAIRDATA(hcp->pagep, hcp->bndx);
                        d.size = HOFFPAGE_SIZE;
                } else {
                        d.data =
                            HKEYDATA_DATA(H_PAIRDATA(hcp->pagep, hcp->bndx));
                        d.size = LEN_HDATA(hcp->pagep,
                            hcp->hdr->pagesize, hcp->bndx);
                }


                if ((ret = __ham_insdel_log(dbp->dbenv->lg_info,
                    dbc->txn, &new_lsn, 0, rectype,
                    dbp->log_fileid, PGNO(next_pagep),
                    (u_int32_t)H_NUMPAIRS(next_pagep), &LSN(next_pagep),
                    &k, &d)) != 0)
                        return (ret);

                /* Move lsn onto page. */
                LSN(next_pagep) = new_lsn;      /* Structure assignment. */
        }

        __ham_copy_item(dbp->pgsize,
            hcp->pagep, H_KEYINDEX(hcp->bndx), next_pagep);
        __ham_copy_item(dbp->pgsize,
            hcp->pagep, H_DATAINDEX(hcp->bndx), next_pagep);

        /* Now delete the pair from the current page. */
        ret = __ham_del_pair(dbc, 0);

        (void)__ham_put_page(dbp, hcp->pagep, 1);
        hcp->pagep = next_pagep;
        hcp->pgno = PGNO(hcp->pagep);
        hcp->bndx = H_NUMPAIRS(hcp->pagep) - 1;
        F_SET(hcp, H_EXPAND);
        return (ret);
}

/*
 * __ham_move_offpage --
 *      Replace an onpage set of duplicates with the OFFDUP structure
 *      that references the duplicate page.
 *
 * XXX
 * This is really just a special case of __onpage_replace; we should
 * probably combine them.
 *
 * PUBLIC: void __ham_move_offpage __P((DBC *, PAGE *, u_int32_t, db_pgno_t));
 */
void
__ham_move_offpage(dbc, pagep, ndx, pgno)
        DBC *dbc;
        PAGE *pagep;
        u_int32_t ndx;
        db_pgno_t pgno;
{
        DB *dbp;
        HASH_CURSOR *hcp;
        DBT new_dbt;
        DBT old_dbt;
        HOFFDUP od;
        db_indx_t i;
        int32_t shrink;
        u_int8_t *src;

        dbp = dbc->dbp;
        hcp = (HASH_CURSOR *)dbc->internal;
        od.type = H_OFFDUP;
        UMRW(od.unused[0]);
        UMRW(od.unused[1]);
        UMRW(od.unused[2]);
        od.pgno = pgno;

        if (DB_LOGGING(dbc)) {
                new_dbt.data = &od;
                new_dbt.size = HOFFDUP_SIZE;
                old_dbt.data = P_ENTRY(pagep, ndx);
                old_dbt.size = LEN_HITEM(pagep, hcp->hdr->pagesize, ndx);
                (void)__ham_replace_log(dbp->dbenv->lg_info,
                    dbc->txn, &LSN(pagep), 0, dbp->log_fileid,
                    PGNO(pagep), (u_int32_t)ndx, &LSN(pagep), -1,
                    &old_dbt, &new_dbt, 0);
        }

        shrink =
            LEN_HITEM(pagep, hcp->hdr->pagesize, ndx) - HOFFDUP_SIZE;

        if (shrink != 0) {
                /* Copy data. */
                src = (u_int8_t *)(pagep) + HOFFSET(pagep);
                memmove(src + shrink, src, pagep->inp[ndx] - HOFFSET(pagep));
                HOFFSET(pagep) += shrink;

                /* Update index table. */
                for (i = ndx; i < NUM_ENT(pagep); i++)
                        pagep->inp[i] += shrink;
        }

        /* Now copy the offdup entry onto the page. */
        memcpy(P_ENTRY(pagep, ndx), &od, HOFFDUP_SIZE);
}

/*
 * __ham_dsearch:
 *      Locate a particular duplicate in a duplicate set.
 *
 * PUBLIC: void __ham_dsearch __P((DBC *, DBT *, u_int32_t *, int *));
 */
void
__ham_dsearch(dbc, dbt, offp, cmpp)
        DBC *dbc;
        DBT *dbt;
        u_int32_t *offp;
        int *cmpp;
{
        DB *dbp;
        HASH_CURSOR *hcp;
        DBT cur;
        db_indx_t i, len;
        int (*func) __P((const DBT *, const DBT *));
        u_int8_t *data;

        dbp = dbc->dbp;
        hcp = (HASH_CURSOR *)dbc->internal;
        if (dbp->dup_compare == NULL)
                func = __bam_defcmp;
        else
                func = dbp->dup_compare;

        i = F_ISSET(dbc, DBC_CONTINUE) ? hcp->dup_off: 0;
        data = HKEYDATA_DATA(H_PAIRDATA(hcp->pagep, hcp->bndx)) + i;
        while (i < LEN_HDATA(hcp->pagep, hcp->hdr->pagesize, hcp->bndx)) {
                memcpy(&len, data, sizeof(db_indx_t));
                data += sizeof(db_indx_t);
                cur.data = data;
                cur.size = (u_int32_t)len;
                *cmpp = func(dbt, &cur);
                if (*cmpp == 0 || (*cmpp < 0 && dbp->dup_compare != NULL))
                        break;
                i += len + 2 * sizeof(db_indx_t);
                data += len + sizeof(db_indx_t);
        }
        *offp = i;
}