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

#include "config.h"

#ifndef lint
static const char sccsid[] = "@(#)bt_cursor.c   10.81 (Sleepycat) 12/16/98";
#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 "db_page.h"
#include "btree.h"
#include "shqueue.h"
#include "db_shash.h"
#include "lock.h"
#include "lock_ext.h"

static int __bam_c_close __P((DBC *));
static int __bam_c_del __P((DBC *, u_int32_t));
static int __bam_c_destroy __P((DBC *));
static int __bam_c_first __P((DBC *, CURSOR *));
static int __bam_c_get __P((DBC *, DBT *, DBT *, u_int32_t));
static int __bam_c_getstack __P((DBC *, CURSOR *));
static int __bam_c_last __P((DBC *, CURSOR *));
static int __bam_c_next __P((DBC *, CURSOR *, int));
static int __bam_c_physdel __P((DBC *, CURSOR *, PAGE *));
static int __bam_c_prev __P((DBC *, CURSOR *));
static int __bam_c_put __P((DBC *, DBT *, DBT *, u_int32_t));
static void __bam_c_reset __P((CURSOR *));
static int __bam_c_rget __P((DBC *, DBT *, u_int32_t));
static int __bam_c_search __P((DBC *, CURSOR *, const DBT *, u_int32_t, int *));
static int __bam_dsearch __P((DBC *, CURSOR *,  DBT *, u_int32_t *));

/* Discard the current page/lock held by a cursor. */
#undef  DISCARD
#define DISCARD(dbc, cp) {                                              \
        if ((cp)->page != NULL) {                                       \
                (void)memp_fput((dbc)->dbp->mpf, (cp)->page, 0);        \
                (cp)->page = NULL;                                      \
        }                                                               \
        if ((cp)->lock != LOCK_INVALID) {                               \
                (void)__BT_TLPUT((dbc), (cp)->lock);                    \
                (cp)->lock = LOCK_INVALID;                              \
        }                                                               \
}

/* If the cursor references a deleted record. */
#undef  IS_CUR_DELETED
#define IS_CUR_DELETED(cp)                                              \
        (((cp)->dpgno == PGNO_INVALID &&                                \
        B_DISSET(GET_BKEYDATA((cp)->page,                               \
        (cp)->indx + O_INDX)->type)) ||                                 \
        ((cp)->dpgno != PGNO_INVALID &&                                 \
        B_DISSET(GET_BKEYDATA((cp)->page, (cp)->dindx)->type)))

/* If the cursor and index combination references a deleted record. */
#undef  IS_DELETED
#define IS_DELETED(cp, indx)                                            \
        (((cp)->dpgno == PGNO_INVALID &&                                \
        B_DISSET(GET_BKEYDATA((cp)->page, (indx) + O_INDX)->type)) ||   \
        ((cp)->dpgno != PGNO_INVALID &&                                 \
        B_DISSET(GET_BKEYDATA((cp)->page, (indx))->type)))

/*
 * Test to see if two cursors could point to duplicates of the same key,
 * whether on-page or off-page.  The leaf page numbers must be the same
 * in both cases.  In the case of off-page duplicates, the key indices
 * on the leaf page will be the same.  In the case of on-page duplicates,
 * the duplicate page number must not be set, and the key index offsets
 * must be the same.  For the last test, as the saved copy of the cursor
 * will not have a valid page pointer, we use the cursor's.
 */
#undef  POSSIBLE_DUPLICATE
#define POSSIBLE_DUPLICATE(cursor, saved_copy)                          \
        ((cursor)->pgno == (saved_copy).pgno &&                         \
        ((cursor)->indx == (saved_copy).indx ||                         \
        ((cursor)->dpgno == PGNO_INVALID &&                             \
            (saved_copy).dpgno == PGNO_INVALID &&                       \
            (cursor)->page->inp[(cursor)->indx] ==                      \
            (cursor)->page->inp[(saved_copy).indx])))

/*
 * __bam_c_reset --
 *      Initialize internal cursor structure.
 */
static void
__bam_c_reset(cp)
        CURSOR *cp;
{
        cp->sp = cp->csp = cp->stack;
        cp->esp = cp->stack + sizeof(cp->stack) / sizeof(cp->stack[0]);
        cp->page = NULL;
        cp->pgno = PGNO_INVALID;
        cp->indx = 0;
        cp->dpgno = PGNO_INVALID;
        cp->dindx = 0;
        cp->lock = LOCK_INVALID;
        cp->mode = DB_LOCK_NG;
        cp->recno = RECNO_OOB;
        cp->flags = 0;
}

/*
 * __bam_c_init --
 *      Initialize the access private portion of a cursor
 *
 * PUBLIC: int __bam_c_init __P((DBC *));
 */
int
__bam_c_init(dbc)
        DBC *dbc;
{
        DB *dbp;
        CURSOR *cp;
        int ret;

        if ((ret = __os_calloc(1, sizeof(CURSOR), &cp)) != 0)
                return (ret);

        dbp = dbc->dbp;
        cp->dbc = dbc;

        /*
         * Logical record numbers are always the same size, and we don't want
         * to have to check for space every time we return one.  Allocate it
         * in advance.
         */
        if (dbp->type == DB_RECNO || F_ISSET(dbp, DB_BT_RECNUM)) {
                if ((ret = __os_malloc(sizeof(db_recno_t),
                    NULL, &dbc->rkey.data)) != 0) {
                        __os_free(cp, sizeof(CURSOR));
                        return (ret);
                }
                dbc->rkey.ulen = sizeof(db_recno_t);
        }

        /* Initialize methods. */
        dbc->internal = cp;
        if (dbp->type == DB_BTREE) {
                dbc->c_am_close = __bam_c_close;
                dbc->c_am_destroy = __bam_c_destroy;
                dbc->c_del = __bam_c_del;
                dbc->c_get = __bam_c_get;
                dbc->c_put = __bam_c_put;
        } else {
                dbc->c_am_close = __bam_c_close;
                dbc->c_am_destroy = __bam_c_destroy;
                dbc->c_del = __ram_c_del;
                dbc->c_get = __ram_c_get;
                dbc->c_put = __ram_c_put;
        }

        /* Initialize dynamic information. */
        __bam_c_reset(cp);

        return (0);
}

/*
 * __bam_c_close --
 *      Close down the cursor from a single use.
 */
static int
__bam_c_close(dbc)
        DBC *dbc;
{
        CURSOR *cp;
        DB *dbp;
        int ret;

        dbp = dbc->dbp;
        cp = dbc->internal;
        ret = 0;

        /*
         * If a cursor deleted a btree key, perform the actual deletion.
         * (Recno keys are either deleted immediately or never deleted.)
         */
        if (dbp->type == DB_BTREE && F_ISSET(cp, C_DELETED))
                ret = __bam_c_physdel(dbc, cp, NULL);

        /* Discard any locks not acquired inside of a transaction. */
        if (cp->lock != LOCK_INVALID) {
                (void)__BT_TLPUT(dbc, cp->lock);
                cp->lock = LOCK_INVALID;
        }

        /* Sanity checks. */
#ifdef DIAGNOSTIC
        if (cp->csp != cp->stack)
                __db_err(dbp->dbenv, "btree cursor close: stack not empty");
#endif

        /* Initialize dynamic information. */
        __bam_c_reset(cp);

        return (ret);
}

/*
 * __bam_c_destroy --
 *      Close a single cursor -- internal version.
 */
static int
__bam_c_destroy(dbc)
        DBC *dbc;
{
        /* Discard the structures. */
        __os_free(dbc->internal, sizeof(CURSOR));

        return (0);
}

/*
 * __bam_c_del --
 *      Delete using a cursor.
 */
static int
__bam_c_del(dbc, flags)
        DBC *dbc;
        u_int32_t flags;
{
        CURSOR *cp;
        DB *dbp;
        DB_LOCK lock;
        PAGE *h;
        db_pgno_t pgno;
        db_indx_t indx;
        int ret;

        dbp = dbc->dbp;
        cp = dbc->internal;
        h = NULL;

        DB_PANIC_CHECK(dbp);

        /* Check for invalid flags. */
        if ((ret = __db_cdelchk(dbp, flags,
            F_ISSET(dbp, DB_AM_RDONLY), cp->pgno != PGNO_INVALID)) != 0)
                return (ret);

        /*
         * If we are running CDB, this had better be either a write
         * cursor or an immediate writer.
         */
        if (F_ISSET(dbp, DB_AM_CDB))
                if (!F_ISSET(dbc, DBC_RMW | DBC_WRITER))
                        return (EINVAL);

        DEBUG_LWRITE(dbc, dbc->txn, "bam_c_del", NULL, NULL, flags);

        /* If already deleted, return failure. */
        if (F_ISSET(cp, C_DELETED))
                return (DB_KEYEMPTY);

        /*
         * We don't physically delete the record until the cursor moves,
         * so we have to have a long-lived write lock on the page instead
         * of a long-lived read lock.  Note, we have to have a read lock
         * to even get here, so we simply discard it.
         */
        if (F_ISSET(dbp, DB_AM_LOCKING) && cp->mode != DB_LOCK_WRITE) {
                if ((ret = __bam_lget(dbc,
                    0, cp->pgno, DB_LOCK_WRITE, &lock)) != 0)
                        goto err;
                (void)__BT_TLPUT(dbc, cp->lock);
                cp->lock = lock;
                cp->mode = DB_LOCK_WRITE;
        }

        /*
         * Acquire the underlying page (which may be different from the above
         * page because it may be a duplicate page), and set the on-page and
         * in-cursor delete flags.  We don't need to lock it as we've already
         * write-locked the page leading to it.
         */
        if (cp->dpgno == PGNO_INVALID) {
                pgno = cp->pgno;
                indx = cp->indx;
        } else {
                pgno = cp->dpgno;
                indx = cp->dindx;
        }

        if ((ret = memp_fget(dbp->mpf, &pgno, 0, &h)) != 0)
                goto err;

        /* Log the change. */
        if (DB_LOGGING(dbc) &&
            (ret = __bam_cdel_log(dbp->dbenv->lg_info, dbc->txn, &LSN(h),
            0, dbp->log_fileid, PGNO(h), &LSN(h), indx)) != 0) {
                (void)memp_fput(dbp->mpf, h, 0);
                goto err;
        }

        /*
         * Set the intent-to-delete flag on the page and update all cursors. */
        if (cp->dpgno == PGNO_INVALID)
                B_DSET(GET_BKEYDATA(h, indx + O_INDX)->type);
        else
                B_DSET(GET_BKEYDATA(h, indx)->type);
        (void)__bam_ca_delete(dbp, pgno, indx, 1);

        ret = memp_fput(dbp->mpf, h, DB_MPOOL_DIRTY);
        h = NULL;

        /*
         * If the tree has record numbers, we have to adjust the counts.
         *
         * !!!
         * This test is right -- we don't yet support duplicates and record
         * numbers in the same tree, so ignore duplicates if DB_BT_RECNUM
         * set.
         */
        if (F_ISSET(dbp, DB_BT_RECNUM)) {
                if ((ret = __bam_c_getstack(dbc, cp)) != 0)
                        goto err;
                if ((ret = __bam_adjust(dbc, -1)) != 0)
                        goto err;
                (void)__bam_stkrel(dbc, 0);
        }

err:    if (h != NULL)
                (void)memp_fput(dbp->mpf, h, 0);
        return (ret);
}

/*
 * __bam_c_get --
 *      Get using a cursor (btree).
 */
static int
__bam_c_get(dbc, key, data, flags)
        DBC *dbc;
        DBT *key, *data;
        u_int32_t flags;
{
        CURSOR *cp, copy, start;
        DB *dbp;
        PAGE *h;
        int exact, ret, tmp_rmw;

        dbp = dbc->dbp;
        cp = dbc->internal;

        DB_PANIC_CHECK(dbp);

        /* Check for invalid flags. */
        if ((ret = __db_cgetchk(dbp,
            key, data, flags, cp->pgno != PGNO_INVALID)) != 0)
                return (ret);

        /* Clear OR'd in additional bits so we can check for flag equality. */
        tmp_rmw = 0;
        if (LF_ISSET(DB_RMW)) {
                if (!F_ISSET(dbp, DB_AM_CDB)) {
                        tmp_rmw = 1;
                        F_SET(dbc, DBC_RMW);
                }
                LF_CLR(DB_RMW);
        }

        DEBUG_LREAD(dbc, dbc->txn, "bam_c_get",
            flags == DB_SET || flags == DB_SET_RANGE ? key : NULL, NULL, flags);

        /*
         * Return a cursor's record number.  It has nothing to do with the
         * cursor get code except that it's been rammed into the interface.
         */
        if (flags == DB_GET_RECNO) {
                ret = __bam_c_rget(dbc, data, flags);
                if (tmp_rmw)
                        F_CLR(dbc, DBC_RMW);
                return (ret);
        }

        /*
         * Initialize the cursor for a new retrieval.  Clear the cursor's
         * page pointer, it was set before this operation, and no longer
         * has any meaning.
         */
        cp->page = NULL;
        copy = *cp;
        cp->lock = LOCK_INVALID;

        switch (flags) {
        case DB_CURRENT:
                /* It's not possible to return a deleted record. */
                if (F_ISSET(cp, C_DELETED)) {
                        ret = DB_KEYEMPTY;
                        goto err;
                }

                /* Acquire the current page. */
                if ((ret = __bam_lget(dbc,
                    0, cp->pgno, DB_LOCK_READ, &cp->lock)) == 0)
                        ret = memp_fget(dbp->mpf,
                            cp->dpgno == PGNO_INVALID ? &cp->pgno : &cp->dpgno,
                            0, &cp->page);
                if (ret != 0)
                        goto err;
                break;
        case DB_NEXT_DUP:
                if (cp->pgno == PGNO_INVALID) {
                        ret = EINVAL;
                        goto err;
                }
                if ((ret = __bam_c_next(dbc, cp, 1)) != 0)
                        goto err;

                /* Make sure we didn't go past the end of the duplicates. */
                if (!POSSIBLE_DUPLICATE(cp, copy)) {
                        ret = DB_NOTFOUND;
                        goto err;
                }
                break;
        case DB_NEXT:
                if (cp->pgno != PGNO_INVALID) {
                        if ((ret = __bam_c_next(dbc, cp, 1)) != 0)
                                goto err;
                        break;
                }
                /* FALLTHROUGH */
        case DB_FIRST:
                if ((ret = __bam_c_first(dbc, cp)) != 0)
                        goto err;
                break;
        case DB_PREV:
                if (cp->pgno != PGNO_INVALID) {
                        if ((ret = __bam_c_prev(dbc, cp)) != 0)
                                goto err;
                        break;
                }
                /* FALLTHROUGH */
        case DB_LAST:
                if ((ret = __bam_c_last(dbc, cp)) != 0)
                        goto err;
                break;
        case DB_SET:
                if ((ret = __bam_c_search(dbc, cp, key, flags, &exact)) != 0)
                        goto err;

                /*
                 * We cannot currently be referencing a deleted record, but we
                 * may be referencing off-page duplicates.
                 *
                 * If we're referencing off-page duplicates, move off-page.
                 * If we moved off-page, move to the next non-deleted record.
                 * If we moved to the next non-deleted record, check to make
                 * sure we didn't switch records because our current record
                 * had no non-deleted data items.
                 */
                start = *cp;
                if ((ret = __bam_dup(dbc, cp, cp->indx, 0)) != 0)
                        goto err;
                if (cp->dpgno != PGNO_INVALID && IS_CUR_DELETED(cp)) {
                        if ((ret = __bam_c_next(dbc, cp, 0)) != 0)
                                goto err;
                        if (!POSSIBLE_DUPLICATE(cp, start)) {
                                ret = DB_NOTFOUND;
                                goto err;
                        }
                }
                break;
        case DB_SET_RECNO:
                if ((ret = __bam_c_search(dbc, cp, key, flags, &exact)) != 0)
                        goto err;
                break;
        case DB_GET_BOTH:
                if (F_ISSET(dbc, DBC_CONTINUE | DBC_KEYSET)) {
                        /* Acquire the current page. */
                        if ((ret = memp_fget(dbp->mpf,
                            cp->dpgno == PGNO_INVALID ? &cp->pgno : &cp->dpgno,
                            0, &cp->page)) != 0)
                                goto err;

                        /* If DBC_CONTINUE, move to the next item. */
                        if (F_ISSET(dbc, DBC_CONTINUE) &&
                            (ret = __bam_c_next(dbc, cp, 1)) != 0)
                                goto err;
                } else {
                        if ((ret =
                            __bam_c_search(dbc, cp, key, flags, &exact)) != 0)
                                goto err;

                        /*
                         * We may be referencing a duplicates page.  Move to
                         * the first duplicate.
                         */
                        if ((ret = __bam_dup(dbc, cp, cp->indx, 0)) != 0)
                                goto err;
                }

                /* Search for a matching entry. */
                if ((ret = __bam_dsearch(dbc, cp, data, NULL)) != 0)
                        goto err;

                /* Ignore deleted entries. */
                if (IS_CUR_DELETED(cp)) {
                        ret = DB_NOTFOUND;
                        goto err;
                }
                break;
        case DB_SET_RANGE:
                if ((ret = __bam_c_search(dbc, cp, key, flags, &exact)) != 0)
                        goto err;

                /*
                 * As we didn't require an exact match, the search function
                 * may have returned an entry past the end of the page.  If
                 * so, move to the next entry.
                 */
                if (cp->indx == NUM_ENT(cp->page) &&
                    (ret = __bam_c_next(dbc, cp, 0)) != 0)
                        goto err;

                /*
                 * We may be referencing off-page duplicates, if so, move
                 * off-page.
                 */
                if ((ret = __bam_dup(dbc, cp, cp->indx, 0)) != 0)
                        goto err;

                /*
                 * We may be referencing a deleted record, if so, move to
                 * the next non-deleted record.
                 */
                if (IS_CUR_DELETED(cp) && (ret = __bam_c_next(dbc, cp, 0)) != 0)
                        goto err;
                break;
        }

        /*
         * Return the key if the user didn't give us one.  If we've moved to
         * a duplicate page, we may no longer have a pointer to the main page,
         * so we have to go get it.  We know that it's already read-locked,
         * however, so we don't have to acquire a new lock.
         */
        if (flags != DB_SET) {
                if (cp->dpgno != PGNO_INVALID) {
                        if ((ret = memp_fget(dbp->mpf, &cp->pgno, 0, &h)) != 0)
                                goto err;
                } else
                        h = cp->page;
                ret = __db_ret(dbp,
                    h, cp->indx, key, &dbc->rkey.data, &dbc->rkey.ulen);
                if (cp->dpgno != PGNO_INVALID)
                        (void)memp_fput(dbp->mpf, h, 0);
                if (ret)
                        goto err;
        }

        /* Return the data. */
        if ((ret = __db_ret(dbp, cp->page,
            cp->dpgno == PGNO_INVALID ? cp->indx + O_INDX : cp->dindx,
            data, &dbc->rdata.data, &dbc->rdata.ulen)) != 0)
                goto err;

        /*
         * If the previous cursor record has been deleted, physically delete
         * the entry from the page.  We clear the deleted flag before we call
         * the underlying delete routine so that, if an error occurs, and we
         * restore the cursor, the deleted flag is cleared.  This is because,
         * if we manage to physically modify the page, and then restore the
         * cursor, we might try to repeat the page modification when closing
         * the cursor.
         */
        if (F_ISSET(&copy, C_DELETED)) {
                F_CLR(&copy, C_DELETED);
                if ((ret = __bam_c_physdel(dbc, &copy, cp->page)) != 0)
                        goto err;
        }
        F_CLR(cp, C_DELETED);

        /* Release the previous lock, if any; the current lock is retained. */
        if (copy.lock != LOCK_INVALID)
                (void)__BT_TLPUT(dbc, copy.lock);

        /* Release the current page. */
        if ((ret = memp_fput(dbp->mpf, cp->page, 0)) != 0)
                goto err;

        if (0) {
err:            if (cp->page != NULL)
                        (void)memp_fput(dbp->mpf, cp->page, 0);
                if (cp->lock != LOCK_INVALID)
                        (void)__BT_TLPUT(dbc, cp->lock);
                *cp = copy;
        }

        /* Release temporary lock upgrade. */
        if (tmp_rmw)
                F_CLR(dbc, DBC_RMW);

        return (ret);
}

/*
 * __bam_dsearch --
 *      Search for a matching data item (or the first data item that's
 *      equal to or greater than the one we're searching for).
 */
static int
__bam_dsearch(dbc, cp, data, iflagp)
        DBC *dbc;
        CURSOR *cp;
        DBT *data;
        u_int32_t *iflagp;
{
        DB *dbp;
        CURSOR copy, last;
        int cmp, ret;

        dbp = dbc->dbp;

        /*
         * If iflagp is non-NULL, we're doing an insert.
         *
         * If the duplicates are off-page, use the duplicate search routine.
         */
        if (cp->dpgno != PGNO_INVALID) {
                if ((ret = __db_dsearch(dbc, iflagp != NULL,
                    data, cp->dpgno, &cp->dindx, &cp->page, &cmp)) != 0)
                        return (ret);
                cp->dpgno = cp->page->pgno;

                if (iflagp == NULL) {
                        if (cmp != 0)
                                return (DB_NOTFOUND);
                        return (0);
                }
                *iflagp = DB_BEFORE;
                return (0);
        }

        /* Otherwise, do the search ourselves. */
        copy = *cp;
        for (;;) {
                /* Save the last interesting cursor position. */
                last = *cp;

                /* See if the data item matches the one we're looking for. */
                if ((cmp = __bam_cmp(dbp, data, cp->page, cp->indx + O_INDX,
                    dbp->dup_compare == NULL ?
                    __bam_defcmp : dbp->dup_compare)) == 0) {
                        if (iflagp != NULL)
                                *iflagp = DB_AFTER;
                        return (0);
                }

                /*
                 * If duplicate entries are sorted, we're done if we find a
                 * page entry that sorts greater than the application item.
                 * If doing an insert, return success, otherwise DB_NOTFOUND.
                 */
                if (dbp->dup_compare != NULL && cmp < 0) {
                        if (iflagp == NULL)
                                return (DB_NOTFOUND);
                        *iflagp = DB_BEFORE;
                        return (0);
                }

                /*
                 * Move to the next item.  If we reach the end of the page and
                 * we're doing an insert, set the cursor to the last item and
                 * set the referenced memory location so callers know to insert
                 * after the item, instead of before it.  If not inserting, we
                 * return DB_NOTFOUND.
                 */
                if ((cp->indx += P_INDX) >= NUM_ENT(cp->page)) {
                        if (iflagp == NULL)
                                return (DB_NOTFOUND);
                        goto use_last;
                }

                /*
                 * Make sure we didn't go past the end of the duplicates.  The
                 * error conditions are the same as above.
                 */
                if (!POSSIBLE_DUPLICATE(cp, copy)) {
                        if (iflagp == NULL)
                                 return (DB_NOTFOUND);
use_last:               *cp = last;
                        *iflagp = DB_AFTER;
                        return (0);
                }
        }
        /* NOTREACHED */
}

/*
 * __bam_c_rget --
 *      Return the record number for a cursor.
 */
static int
__bam_c_rget(dbc, data, flags)
        DBC *dbc;
        DBT *data;
        u_int32_t flags;
{
        CURSOR *cp;
        DB *dbp;
        DBT dbt;
        db_recno_t recno;
        int exact, ret;

        COMPQUIET(flags, 0);
        dbp = dbc->dbp;
        cp = dbc->internal;

        /* Get the page with the current item on it. */
        if ((ret = memp_fget(dbp->mpf, &cp->pgno, 0, &cp->page)) != 0)
                return (ret);

        /* Get a copy of the key. */
        memset(&dbt, 0, sizeof(DBT));
        dbt.flags = DB_DBT_MALLOC | DB_DBT_INTERNAL;
        if ((ret = __db_ret(dbp, cp->page, cp->indx, &dbt, NULL, NULL)) != 0)
                goto err;

        exact = 1;
        if ((ret = __bam_search(dbc, &dbt,
            F_ISSET(dbc, DBC_RMW) ? S_FIND_WR : S_FIND,
            1, &recno, &exact)) != 0)
                goto err;

        ret = __db_retcopy(data, &recno, sizeof(recno),
            &dbc->rdata.data, &dbc->rdata.ulen, dbp->db_malloc);

        /* Release the stack. */
        __bam_stkrel(dbc, 0);

err:    (void)memp_fput(dbp->mpf, cp->page, 0);
        __os_free(dbt.data, dbt.size);
        return (ret);
}

/*
 * __bam_c_put --
 *      Put using a cursor.
 */
static int
__bam_c_put(dbc, key, data, flags)
        DBC *dbc;
        DBT *key, *data;
        u_int32_t flags;
{
        CURSOR *cp, copy;
        DB *dbp;
        DBT dbt;
        db_indx_t indx;
        db_pgno_t pgno;
        u_int32_t iiflags, iiop;
        int exact, needkey, ret, stack;
        void *arg;

        dbp = dbc->dbp;
        cp = dbc->internal;

        DB_PANIC_CHECK(dbp);

        DEBUG_LWRITE(dbc, dbc->txn, "bam_c_put",
            flags == DB_KEYFIRST || flags == DB_KEYLAST ? key : NULL,
            data, flags);

        if ((ret = __db_cputchk(dbp, key, data, flags,
            F_ISSET(dbp, DB_AM_RDONLY), cp->pgno != PGNO_INVALID)) != 0)
                return (ret);

        /*
         * If we are running CDB, this had better be either a write
         * cursor or an immediate writer.  If it's a regular writer,
         * that means we have an IWRITE lock and we need to upgrade
         * it to a write lock.
         */
        if (F_ISSET(dbp, DB_AM_CDB)) {
                if (!F_ISSET(dbc, DBC_RMW | DBC_WRITER))
                        return (EINVAL);

                if (F_ISSET(dbc, DBC_RMW) &&
                    (ret = lock_get(dbp->dbenv->lk_info, dbc->locker,
                    DB_LOCK_UPGRADE, &dbc->lock_dbt, DB_LOCK_WRITE,
                    &dbc->mylock)) != 0)
                        return (EAGAIN);
        }

        if (0) {
split:          /*
                 * To split, we need a valid key for the page.  Since it's a
                 * cursor, we have to build one.
                 *
                 * Acquire a copy of a key from the page.
                 */
                if (needkey) {
                        memset(&dbt, 0, sizeof(DBT));
                        if ((ret = __db_ret(dbp, cp->page, indx,
                            &dbt, &dbc->rkey.data, &dbc->rkey.ulen)) != 0)
                                goto err;
                        arg = &dbt;
                } else
                        arg = key;

                /*
                 * Discard any locks and pinned pages (the locks are discarded
                 * even if we're running with transactions, as they lock pages
                 * that we're sorry we ever acquired).  If stack is set and the
                 * cursor entries are valid, they point to the same entries as
                 * the stack, don't free them twice.
                 */
                if (stack) {
                        (void)__bam_stkrel(dbc, 1);
                        stack = 0;
                } else
                        DISCARD(dbc, cp);

                /*
                 * Restore the cursor to its original value.  This is necessary
                 * for two reasons.  First, we are about to copy it in case of
                 * error, again.  Second, we adjust cursors during the split,
                 * and we have to ensure this cursor is adjusted appropriately,
                 * along with all the other cursors.
                 */
                *cp = copy;

                if ((ret = __bam_split(dbc, arg)) != 0)
                        goto err;
        }

        /*
         * Initialize the cursor for a new retrieval.  Clear the cursor's
         * page pointer, it was set before this operation, and no longer
         * has any meaning.
         */
        cp->page = NULL;
        copy = *cp;
        cp->lock = LOCK_INVALID;

        iiflags = needkey = ret = stack = 0;
        switch (flags) {
        case DB_AFTER:
        case DB_BEFORE:
        case DB_CURRENT:
                needkey = 1;
                if (cp->dpgno == PGNO_INVALID) {
                        pgno = cp->pgno;
                        indx = cp->indx;
                } else {
                        pgno = cp->dpgno;
                        indx = cp->dindx;
                }

                /*
                 * !!!
                 * This test is right -- we don't yet support duplicates and
                 * record numbers in the same tree, so ignore duplicates if
                 * DB_BT_RECNUM set.
                 */
                if (F_ISSET(dbp, DB_BT_RECNUM) &&
                    (flags != DB_CURRENT || F_ISSET(cp, C_DELETED))) {
                        /* Acquire a complete stack. */
                        if ((ret = __bam_c_getstack(dbc, cp)) != 0)
                                goto err;
                        cp->page = cp->csp->page;

                        stack = 1;
                        iiflags = BI_DOINCR;
                } else {
                        /* Acquire the current page. */
                        if ((ret = __bam_lget(dbc,
                            0, cp->pgno, DB_LOCK_WRITE, &cp->lock)) == 0)
                                ret = memp_fget(dbp->mpf, &pgno, 0, &cp->page);
                        if (ret != 0)
                                goto err;

                        iiflags = 0;
                }

                /*
                 * If the user has specified a duplicate comparison function,
                 * we return an error if DB_CURRENT was specified and the
                 * replacement data doesn't compare equal to the current data.
                 * This stops apps from screwing up the duplicate sort order.
                 */
                if (flags == DB_CURRENT && dbp->dup_compare != NULL)
                        if (__bam_cmp(dbp, data,
                            cp->page, indx, dbp->dup_compare) != 0) {
                                ret = EINVAL;
                                goto err;
                        }

                iiop = flags;
                break;
        case DB_KEYFIRST:
        case DB_KEYLAST:
                /*
                 * If we have a duplicate comparison function, we position to
                 * the first of any on-page duplicates, and use __bam_dsearch
                 * to search for the right slot.  Otherwise, we position to
                 * the first/last of any on-page duplicates based on the flag
                 * value.
                 */
                if ((ret = __bam_c_search(dbc, cp, key,
                    flags == DB_KEYFIRST || dbp->dup_compare != NULL ?
                    DB_KEYFIRST : DB_KEYLAST, &exact)) != 0)
                        goto err;
                stack = 1;

                /*
                 * If an exact match:
                 *      If duplicates aren't supported, replace the current
                 *      item.  (When implementing the DB->put function, our
                 *      caller has already checked the DB_NOOVERWRITE flag.)
                 *
                 *      If there's a duplicate comparison function, find the
                 *      correct slot for this duplicate item.
                 *
                 *      If there's no duplicate comparison function, set the
                 *      insert flag based on the argument flags.
                 *
                 * If there's no match, the search function returned the
                 * smallest slot greater than the key, use it.
                 */
                if (exact) {
                        if (F_ISSET(dbp, DB_AM_DUP)) {
                                /*
                                 * If at off-page duplicate page, move to the
                                 * first or last entry -- if a comparison
                                 * function was specified, start searching at
                                 * the first entry.  Otherwise, move based on
                                 * the DB_KEYFIRST/DB_KEYLAST flags.
                                 */
                                if ((ret = __bam_dup(dbc, cp, cp->indx,
                                    dbp->dup_compare == NULL &&
                                    flags != DB_KEYFIRST)) != 0)
                                        goto err;

                                /*
                                 * If there's a comparison function, search for
                                 * the correct slot.  Otherwise, set the insert
                                 * flag based on the argment flag.
                                 */
                                if (dbp->dup_compare == NULL)
                                        iiop = flags == DB_KEYFIRST ?
                                            DB_BEFORE : DB_AFTER;
                                else
                                        if ((ret = __bam_dsearch(dbc,
                                            cp, data, &iiop)) != 0)
                                                goto err;
                        } else
                                iiop = DB_CURRENT;
                        iiflags = 0;
                } else {
                        iiop = DB_BEFORE;
                        iiflags = BI_NEWKEY;
                }

                if (cp->dpgno == PGNO_INVALID) {
                        pgno = cp->pgno;
                        indx = cp->indx;
                } else {
                        pgno = cp->dpgno;
                        indx = cp->dindx;
                }
                break;
        }

        ret = __bam_iitem(dbc, &cp->page, &indx, key, data, iiop, iiflags);

        if (ret == DB_NEEDSPLIT)
                goto split;
        if (ret != 0)
                goto err;

        /*
         * Reset any cursors referencing this item that might have the item
         * marked for deletion.
         */
        if (iiop == DB_CURRENT) {
                (void)__bam_ca_delete(dbp, pgno, indx, 0);

                /*
                 * It's also possible that we are the cursor that had the
                 * item marked for deletion, in which case we want to make
                 * sure that we don't delete it because we had the delete
                 * flag set already.
                 */
                if (cp->pgno == copy.pgno && cp->indx == copy.indx &&
                    cp->dpgno == copy.dpgno && cp->dindx == copy.dindx)
                        F_CLR(&copy, C_DELETED);
        }

        /*
         * Update the cursor to point to the new entry.  The new entry was
         * stored on the current page, because we split pages until it was
         * possible.
         */
        if (cp->dpgno == PGNO_INVALID)
                cp->indx = indx;
        else
                cp->dindx = indx;

        /*
         * If the previous cursor record has been deleted, physically delete
         * the entry from the page.  We clear the deleted flag before we call
         * the underlying delete routine so that, if an error occurs, and we
         * restore the cursor, the deleted flag is cleared.  This is because,
         * if we manage to physically modify the page, and then restore the
         * cursor, we might try to repeat the page modification when closing
         * the cursor.
         */
        if (F_ISSET(&copy, C_DELETED)) {
                F_CLR(&copy, C_DELETED);
                if ((ret = __bam_c_physdel(dbc, &copy, cp->page)) != 0)
                        goto err;
        }
        F_CLR(cp, C_DELETED);

        /* Release the previous lock, if any; the current lock is retained. */
        if (copy.lock != LOCK_INVALID)
                (void)__BT_TLPUT(dbc, copy.lock);

        /*
         * Discard any pages pinned in the tree and their locks, except for
         * the leaf page, for which we only discard the pin, not the lock.
         *
         * Note, the leaf page participated in the stack we acquired, and so
         * we have to adjust the stack as necessary.  If there was only a
         * single page on the stack, we don't have to free further stack pages.
         */
        if (stack && BT_STK_POP(cp) != NULL)
                (void)__bam_stkrel(dbc, 0);

        /* Release the current page. */
        if ((ret = memp_fput(dbp->mpf, cp->page, 0)) != 0)
                goto err;

        if (0) {
err:            /* Discard any pinned pages. */
                if (stack)
                        (void)__bam_stkrel(dbc, 0);
                else
                        DISCARD(dbc, cp);
                *cp = copy;
        }

        if (F_ISSET(dbp, DB_AM_CDB) && F_ISSET(dbc, DBC_RMW))
                (void)__lock_downgrade(dbp->dbenv->lk_info, dbc->mylock,
                    DB_LOCK_IWRITE, 0);

        return (ret);
}

/*
 * __bam_c_first --
 *      Return the first record.
 */
static int
__bam_c_first(dbc, cp)
        DBC *dbc;
        CURSOR *cp;
{
        DB *dbp;
        db_pgno_t pgno;
        int ret;

        dbp = dbc->dbp;

        /* Walk down the left-hand side of the tree. */
        for (pgno = PGNO_ROOT;;) {
                if ((ret =
                    __bam_lget(dbc, 0, pgno, DB_LOCK_READ, &cp->lock)) != 0)
                        return (ret);
                if ((ret = memp_fget(dbp->mpf, &pgno, 0, &cp->page)) != 0)
                        return (ret);

                /* If we find a leaf page, we're done. */
                if (ISLEAF(cp->page))
                        break;

                pgno = GET_BINTERNAL(cp->page, 0)->pgno;
                DISCARD(dbc, cp);
        }

        cp->pgno = cp->page->pgno;
        cp->indx = 0;
        cp->dpgno = PGNO_INVALID;

        /* Check for duplicates. */
        if ((ret = __bam_dup(dbc, cp, cp->indx, 0)) != 0)
                return (ret);

        /* If on an empty page or a deleted record, move to the next one. */
        if (NUM_ENT(cp->page) == 0 || IS_CUR_DELETED(cp))
                if ((ret = __bam_c_next(dbc, cp, 0)) != 0)
                        return (ret);

        return (0);
}

/*
 * __bam_c_last --
 *      Return the last record.
 */
static int
__bam_c_last(dbc, cp)
        DBC *dbc;
        CURSOR *cp;
{
        DB *dbp;
        db_pgno_t pgno;
        int ret;

        dbp = dbc->dbp;

        /* Walk down the right-hand side of the tree. */
        for (pgno = PGNO_ROOT;;) {
                if ((ret =
                    __bam_lget(dbc, 0, pgno, DB_LOCK_READ, &cp->lock)) != 0)
                        return (ret);
                if ((ret = memp_fget(dbp->mpf, &pgno, 0, &cp->page)) != 0)
                        return (ret);

                /* If we find a leaf page, we're done. */
                if (ISLEAF(cp->page))
                        break;

                pgno =
                    GET_BINTERNAL(cp->page, NUM_ENT(cp->page) - O_INDX)->pgno;
                DISCARD(dbc, cp);
        }

        cp->pgno = cp->page->pgno;
        cp->indx = NUM_ENT(cp->page) == 0 ? 0 : NUM_ENT(cp->page) - P_INDX;
        cp->dpgno = PGNO_INVALID;

        /* Check for duplicates. */
        if ((ret = __bam_dup(dbc, cp, cp->indx, 1)) != 0)
                return (ret);

        /* If on an empty page or a deleted record, move to the next one. */
        if (NUM_ENT(cp->page) == 0 || IS_CUR_DELETED(cp))
                if ((ret = __bam_c_prev(dbc, cp)) != 0)
                        return (ret);

        return (0);
}

/*
 * __bam_c_next --
 *      Move to the next record.
 */
static int
__bam_c_next(dbc, cp, initial_move)
        DBC *dbc;
        CURSOR *cp;
        int initial_move;
{
        DB *dbp;
        db_indx_t adjust, indx;
        db_pgno_t pgno;
        int ret;

        dbp = dbc->dbp;

        /*
         * We're either moving through a page of duplicates or a btree leaf
         * page.
         */
        if (cp->dpgno == PGNO_INVALID) {
                adjust = dbp->type == DB_BTREE ? P_INDX : O_INDX;
                pgno = cp->pgno;
                indx = cp->indx;
        } else {
                adjust = O_INDX;
                pgno = cp->dpgno;
                indx = cp->dindx;
        }
        if (cp->page == NULL) {
                if ((ret =
                    __bam_lget(dbc, 0, pgno, DB_LOCK_READ, &cp->lock)) != 0)
                        return (ret);
                if ((ret = memp_fget(dbp->mpf, &pgno, 0, &cp->page)) != 0)
                        return (ret);
        }

        /*
         * If at the end of the page, move to a subsequent page.
         *
         * !!!
         * Check for >= NUM_ENT.  If we're here as the result of a search that
         * landed us on NUM_ENT, we'll increment indx before we test.
         *
         * !!!
         * This code handles empty pages and pages with only deleted entries.
         */
        if (initial_move)
                indx += adjust;
        for (;;) {
                if (indx >= NUM_ENT(cp->page)) {
                        /*
                         * If we're in a btree leaf page, we've reached the end
                         * of the tree.  If we've reached the end of a page of
                         * duplicates, continue from the btree leaf page where
                         * we found this page of duplicates.
                         */
                        pgno = cp->page->next_pgno;
                        if (pgno == PGNO_INVALID) {
                                /* If in a btree leaf page, it's EOF. */
                                if (cp->dpgno == PGNO_INVALID)
                                        return (DB_NOTFOUND);

                                /* Continue from the last btree leaf page. */
                                cp->dpgno = PGNO_INVALID;

                                adjust = P_INDX;
                                pgno = cp->pgno;
                                indx = cp->indx + P_INDX;
                        } else
                                indx = 0;

                        DISCARD(dbc, cp);
                        if ((ret = __bam_lget(dbc,
                            0, pgno, DB_LOCK_READ, &cp->lock)) != 0)
                                return (ret);
                        if ((ret =
                            memp_fget(dbp->mpf, &pgno, 0, &cp->page)) != 0)
                                return (ret);
                        continue;
                }

                /* Ignore deleted records. */
                if (IS_DELETED(cp, indx)) {
                        indx += adjust;
                        continue;
                }

                /*
                 * If we're not in a duplicates page, check to see if we've
                 * found a page of duplicates, in which case we move to the
                 * first entry.
                 */
                if (cp->dpgno == PGNO_INVALID) {
                        cp->pgno = cp->page->pgno;
                        cp->indx = indx;

                        if ((ret = __bam_dup(dbc, cp, indx, 0)) != 0)
                                return (ret);
                        if (cp->dpgno != PGNO_INVALID) {
                                indx = cp->dindx;
                                adjust = O_INDX;
                                continue;
                        }
                } else {
                        cp->dpgno = cp->page->pgno;
                        cp->dindx = indx;
                }
                break;
        }
        return (0);
}

/*
 * __bam_c_prev --
 *      Move to the previous record.
 */
static int
__bam_c_prev(dbc, cp)
        DBC *dbc;
        CURSOR *cp;
{
        DB *dbp;
        db_indx_t indx, adjust;
        db_pgno_t pgno;
        int ret, set_indx;

        dbp = dbc->dbp;

        /*
         * We're either moving through a page of duplicates or a btree leaf
         * page.
         */
        if (cp->dpgno == PGNO_INVALID) {
                adjust = dbp->type == DB_BTREE ? P_INDX : O_INDX;
                pgno = cp->pgno;
                indx = cp->indx;
        } else {
                adjust = O_INDX;
                pgno = cp->dpgno;
                indx = cp->dindx;
        }
        if (cp->page == NULL) {
                if ((ret =
                    __bam_lget(dbc, 0, pgno, DB_LOCK_READ, &cp->lock)) != 0)
                        return (ret);
                if ((ret = memp_fget(dbp->mpf, &pgno, 0, &cp->page)) != 0)
                        return (ret);
        }

        /*
         * If at the beginning of the page, move to any previous one.
         *
         * !!!
         * This code handles empty pages and pages with only deleted entries.
         */
        for (;;) {
                if (indx == 0) {
                        /*
                         * If we're in a btree leaf page, we've reached the
                         * beginning of the tree.  If we've reached the first
                         * of a page of duplicates, continue from the btree
                         * leaf page where we found this page of duplicates.
                         */
                        pgno = cp->page->prev_pgno;
                        if (pgno == PGNO_INVALID) {
                                /* If in a btree leaf page, it's SOF. */
                                if (cp->dpgno == PGNO_INVALID)
                                        return (DB_NOTFOUND);

                                /* Continue from the last btree leaf page. */
                                cp->dpgno = PGNO_INVALID;

                                adjust = P_INDX;
                                pgno = cp->pgno;
                                indx = cp->indx;
                                set_indx = 0;
                        } else
                                set_indx = 1;

                        DISCARD(dbc, cp);
                        if ((ret = __bam_lget(dbc,
                            0, pgno, DB_LOCK_READ, &cp->lock)) != 0)
                                return (ret);
                        if ((ret =
                            memp_fget(dbp->mpf, &pgno, 0, &cp->page)) != 0)
                                return (ret);

                        if (set_indx)
                                indx = NUM_ENT(cp->page);
                        if (indx == 0)
                                continue;
                }

                /* Ignore deleted records. */
                indx -= adjust;
                if (IS_DELETED(cp, indx))
                        continue;

                /*
                 * If we're not in a duplicates page, check to see if we've
                 * found a page of duplicates, in which case we move to the
                 * last entry.
                 */
                if (cp->dpgno == PGNO_INVALID) {
                        cp->pgno = cp->page->pgno;
                        cp->indx = indx;

                        if ((ret = __bam_dup(dbc, cp, indx, 1)) != 0)
                                return (ret);
                        if (cp->dpgno != PGNO_INVALID) {
                                indx = cp->dindx + O_INDX;
                                adjust = O_INDX;
                                continue;
                        }
                } else {
                        cp->dpgno = cp->page->pgno;
                        cp->dindx = indx;
                }
                break;
        }
        return (0);
}

/*
 * __bam_c_search --
 *      Move to a specified record.
 */
static int
__bam_c_search(dbc, cp, key, flags, exactp)
        DBC *dbc;
        CURSOR *cp;
        const DBT *key;
        u_int32_t flags;
        int *exactp;
{
        BTREE *t;
        DB *dbp;
        DB_LOCK lock;
        PAGE *h;
        db_recno_t recno;
        db_indx_t indx;
        u_int32_t sflags;
        int cmp, needexact, ret;

        dbp = dbc->dbp;
        t = dbp->internal;

        /* Find an entry in the database. */
        switch (flags) {
        case DB_SET_RECNO:
                if ((ret = __ram_getno(dbc, key, &recno, 0)) != 0)
                        return (ret);
                sflags = F_ISSET(dbc, DBC_RMW) ? S_FIND_WR : S_FIND;
                needexact = *exactp = 1;
                ret = __bam_rsearch(dbc, &recno, sflags, 1, exactp);
                break;
        case DB_SET:
        case DB_GET_BOTH:
                sflags = F_ISSET(dbc, DBC_RMW) ? S_FIND_WR : S_FIND;
                needexact = *exactp = 1;
                goto search;
        case DB_SET_RANGE:
                sflags = F_ISSET(dbc, DBC_RMW) ? S_FIND_WR : S_FIND;
                needexact = *exactp = 0;
                goto search;
        case DB_KEYFIRST:
                sflags = S_KEYFIRST;
                goto fast_search;
        case DB_KEYLAST:
                sflags = S_KEYLAST;
fast_search:    needexact = *exactp = 0;
                /*
                 * If the application has a history of inserting into the first
                 * or last pages of the database, we check those pages first to
                 * avoid doing a full search.
                 *
                 * Record numbers can't be fast-tracked, the entire tree has to
                 * be locked.
                 */
                h = NULL;
                lock = LOCK_INVALID;
                if (F_ISSET(dbp, DB_BT_RECNUM))
                        goto search;

                /* Check if the application has a history of sorted input. */
                if (t->bt_lpgno == PGNO_INVALID)
                        goto search;

                /*
                 * Lock and retrieve the page on which we did the last insert.
                 * It's okay if it doesn't exist, or if it's not the page type
                 * we expected, it just means that the world changed.
                 */
                if (__bam_lget(dbc, 0, t->bt_lpgno, DB_LOCK_WRITE, &lock))
                        goto fast_miss;
                if (memp_fget(dbp->mpf, &t->bt_lpgno, 0, &h))
                        goto fast_miss;
                if (TYPE(h) != P_LBTREE)
                        goto fast_miss;
                if (NUM_ENT(h) == 0)
                        goto fast_miss;

                /*
                 * What we do here is test to see if we're at the beginning or
                 * end of the tree and if the new item sorts before/after the
                 * first/last page entry.  We don't try and catch inserts into
                 * the middle of the tree (although we could, as long as there
                 * were two keys on the page and we saved both the index and
                 * the page number of the last insert).
                 */
                if (h->next_pgno == PGNO_INVALID) {
                        indx = NUM_ENT(h) - P_INDX;
                        if ((cmp =
                            __bam_cmp(dbp, key, h, indx, t->bt_compare)) < 0)
                                goto try_begin;
                        if (cmp > 0) {
                                indx += P_INDX;
                                goto fast_hit;
                        }

                        /*
                         * Found a duplicate.  If doing DB_KEYLAST, we're at
                         * the correct position, otherwise, move to the first
                         * of the duplicates.
                         */
                        if (flags == DB_KEYLAST)
                                goto fast_hit;
                        for (;
                            indx > 0 && h->inp[indx - P_INDX] == h->inp[indx];
                            indx -= P_INDX)
                                ;
                        goto fast_hit;
                }
try_begin:      if (h->prev_pgno == PGNO_INVALID) {
                        indx = 0;
                        if ((cmp =
                            __bam_cmp(dbp, key, h, indx, t->bt_compare)) > 0)
                                goto fast_miss;
                        if (cmp < 0)
                                goto fast_hit;
                        /*
                         * Found a duplicate.  If doing DB_KEYFIRST, we're at
                         * the correct position, otherwise, move to the last
                         * of the duplicates.
                         */
                        if (flags == DB_KEYFIRST)
                                goto fast_hit;
                        for (;
                            indx < (db_indx_t)(NUM_ENT(h) - P_INDX) &&
                            h->inp[indx] == h->inp[indx + P_INDX];
                            indx += P_INDX)
                                ;
                        goto fast_hit;
                }
                goto fast_miss;

fast_hit:       /* Set the exact match flag, we may have found a duplicate. */
                *exactp = cmp == 0;

                /* Enter the entry in the stack. */
                BT_STK_CLR(cp);
                BT_STK_ENTER(cp, h, indx, lock, ret);
                break;

fast_miss:      if (h != NULL)
                        (void)memp_fput(dbp->mpf, h, 0);
                if (lock != LOCK_INVALID)
                        (void)__BT_LPUT(dbc, lock);

search:         ret = __bam_search(dbc, key, sflags, 1, NULL, exactp);
                break;
        default:                                /* XXX: Impossible. */
                abort();
                /* NOTREACHED */
        }
        if (ret != 0)
                return (ret);

        /*
         * Initialize the cursor to reference it.  This has to be done
         * before we return (even with DB_NOTFOUND) because we have to
         * free the page(s) we locked in __bam_search.
         */
        cp->page = cp->csp->page;
        cp->pgno = cp->csp->page->pgno;
        cp->indx = cp->csp->indx;
        cp->lock = cp->csp->lock;
        cp->dpgno = PGNO_INVALID;

        /*
         * If we inserted a key into the first or last slot of the tree,
         * remember where it was so we can do it more quickly next time.
         */
        if (flags == DB_KEYFIRST || flags == DB_KEYLAST)
                t->bt_lpgno =
                    ((cp->page->next_pgno == PGNO_INVALID &&
                    cp->indx >= NUM_ENT(cp->page)) ||
                    (cp->page->prev_pgno == PGNO_INVALID && cp->indx == 0)) ?
                    cp->pgno : PGNO_INVALID;

        /* If we need an exact match and didn't find one, we're done. */
        if (needexact && *exactp == 0)
                return (DB_NOTFOUND);

        return (0);
}

/*
 * __bam_dup --
 *      Check for an off-page duplicates entry, and if found, move to the
 *      first or last entry.
 *
 * PUBLIC: int __bam_dup __P((DBC *, CURSOR *, u_int32_t, int));
 */
int
__bam_dup(dbc, cp, indx, last_dup)
        DBC *dbc;
        CURSOR *cp;
        u_int32_t indx;
        int last_dup;
{
        BOVERFLOW *bo;
        DB *dbp;
        db_pgno_t pgno;
        int ret;

        dbp = dbc->dbp;

        /*
         * Check for an overflow entry.  If we find one, move to the
         * duplicates page, and optionally move to the last record on
         * that page.
         *
         * !!!
         * We don't lock duplicates pages, we've already got the correct
         * lock on the main page.
         */
        bo = GET_BOVERFLOW(cp->page, indx + O_INDX);
        if (B_TYPE(bo->type) != B_DUPLICATE)
                return (0);

        pgno = bo->pgno;
        if ((ret = memp_fput(dbp->mpf, cp->page, 0)) != 0)
                return (ret);
        cp->page = NULL;
        if (last_dup) {
                if ((ret = __db_dend(dbc, pgno, &cp->page)) != 0)
                        return (ret);
                indx = NUM_ENT(cp->page) - O_INDX;
        } else {
                if ((ret = memp_fget(dbp->mpf, &pgno, 0, &cp->page)) != 0)
                        return (ret);
                indx = 0;
        }

        /* Update the cursor's duplicate information. */
        cp->dpgno = cp->page->pgno;
        cp->dindx = indx;

        return (0);
}

/*
 * __bam_c_physdel --
 *      Actually do the cursor deletion.
 */
static int
__bam_c_physdel(dbc, cp, h)
        DBC *dbc;
        CURSOR *cp;
        PAGE *h;
{
        enum { DELETE_ITEM, DELETE_PAGE, NOTHING_FURTHER } cmd;
        BOVERFLOW bo;
        DB *dbp;
        DBT dbt;
        DB_LOCK lock;
        db_indx_t indx;
        db_pgno_t pgno, next_pgno, prev_pgno;
        int delete_page, local_page, ret;

        dbp = dbc->dbp;

        delete_page = ret = 0;

        /* Figure out what we're deleting. */
        if (cp->dpgno == PGNO_INVALID) {
                pgno = cp->pgno;
                indx = cp->indx;
        } else {
                pgno = cp->dpgno;
                indx = cp->dindx;
        }

        /*
         * If the item is referenced by another cursor, set that cursor's
         * delete flag and leave it up to it to do the delete.
         *
         * !!!
         * This test for > 0 is a tricky.  There are two ways that we can
         * be called here.  Either we are closing the cursor or we've moved
         * off the page with the deleted entry.  In the first case, we've
         * already removed the cursor from the active queue, so we won't see
         * it in __bam_ca_delete. In the second case, it will be on a different
         * item, so we won't bother with it in __bam_ca_delete.
         */
        if (__bam_ca_delete(dbp, pgno, indx, 1) > 0)
                return (0);

        /*
         * If this is concurrent DB, upgrade the lock if necessary.
         */
        if (F_ISSET(dbp, DB_AM_CDB) && F_ISSET(dbc, DBC_RMW) &&
            (ret = lock_get(dbp->dbenv->lk_info,
            dbc->locker, DB_LOCK_UPGRADE, &dbc->lock_dbt, DB_LOCK_WRITE,
            &dbc->mylock)) != 0)
                return (EAGAIN);

        /*
         * If we don't already have the page locked, get it and delete the
         * items.
         */
        if ((h == NULL || h->pgno != pgno)) {
                if ((ret = __bam_lget(dbc, 0, pgno, DB_LOCK_WRITE, &lock)) != 0)
                        return (ret);
                if ((ret = memp_fget(dbp->mpf, &pgno, 0, &h)) != 0)
                        return (ret);
                local_page = 1;
        } else
                local_page = 0;

        /*
         * If we're deleting a duplicate entry and there are other duplicate
         * entries remaining, call the common code to do the work and fix up
         * the parent page as necessary.  Otherwise, do a normal btree delete.
         *
         * There are 5 possible cases:
         *
         * 1. It's not a duplicate item: do a normal btree delete.
         * 2. It's a duplicate item:
         *      2a: We delete an item from a page of duplicates, but there are
         *          more items on the page.
         *      2b: We delete the last item from a page of duplicates, deleting
         *          the last duplicate.
         *      2c: We delete the last item from a page of duplicates, but there
         *          is a previous page of duplicates.
         *      2d: We delete the last item from a page of duplicates, but there
         *          is a following page of duplicates.
         *
         * In the case of:
         *
         *  1: There's nothing further to do.
         * 2a: There's nothing further to do.
         * 2b: Do the normal btree delete instead of a duplicate delete, as
         *     that deletes both the duplicate chain and the parent page's
         *     entry.
         * 2c: There's nothing further to do.
         * 2d: Delete the duplicate, and update the parent page's entry.
         */
        if (TYPE(h) == P_DUPLICATE) {
                pgno = PGNO(h);
                prev_pgno = PREV_PGNO(h);
                next_pgno = NEXT_PGNO(h);

                if (NUM_ENT(h) == 1 &&
                    prev_pgno == PGNO_INVALID && next_pgno == PGNO_INVALID)
                        cmd = DELETE_PAGE;
                else {
                        cmd = DELETE_ITEM;

                        /* Delete the duplicate. */
                        if ((ret = __db_drem(dbc, &h, indx, __bam_free)) != 0)
                                goto err;

                        /*
                         * 2a: h != NULL, h->pgno == pgno
                         * 2b: We don't reach this clause, as the above test
                         *     was true.
                         * 2c: h == NULL, prev_pgno != PGNO_INVALID
                         * 2d: h != NULL, next_pgno != PGNO_INVALID
                         *
                         * Test for 2a and 2c: if we didn't empty the current
                         * page or there was a previous page of duplicates, we
                         * don't need to touch the parent page.
                         */
                        if ((h != NULL && pgno == h->pgno) ||
                            prev_pgno != PGNO_INVALID)
                                cmd = NOTHING_FURTHER;
                }

                /*
                 * Release any page we're holding and its lock.
                 *
                 * !!!
                 * If there is no subsequent page in the duplicate chain, then
                 * __db_drem will have put page "h" and set it to NULL.
                */
                if (local_page) {
                        if (h != NULL)
                                (void)memp_fput(dbp->mpf, h, 0);
                        (void)__BT_TLPUT(dbc, lock);
                        local_page = 0;
                }

                if (cmd == NOTHING_FURTHER)
                        goto done;

                /* Acquire the parent page and switch the index to its entry. */
                if ((ret =
                    __bam_lget(dbc, 0, cp->pgno, DB_LOCK_WRITE, &lock)) != 0)
                        goto err;
                if ((ret = memp_fget(dbp->mpf, &cp->pgno, 0, &h)) != 0) {
                        (void)__BT_TLPUT(dbc, lock);
                        goto err;
                }
                local_page = 1;
                indx = cp->indx;

                if (cmd == DELETE_PAGE)
                        goto btd;

                /*
                 * Copy, delete, update, add-back the parent page's data entry.
                 *
                 * XXX
                 * This may be a performance/logging problem.  We should add a
                 * log message which simply logs/updates a random set of bytes
                 * on a page, and use it instead of doing a delete/add pair.
                 */
                indx += O_INDX;
                bo = *GET_BOVERFLOW(h, indx);
                (void)__db_ditem(dbc, h, indx, BOVERFLOW_SIZE);
                bo.pgno = next_pgno;
                memset(&dbt, 0, sizeof(dbt));
                dbt.data = &bo;
                dbt.size = BOVERFLOW_SIZE;
                (void)__db_pitem(dbc, h, indx, BOVERFLOW_SIZE, &dbt, NULL);
                (void)memp_fset(dbp->mpf, h, DB_MPOOL_DIRTY);
                goto done;
        }

btd:    /*
         * If the page is going to be emptied, delete it.  To delete a leaf
         * page we need a copy of a key from the page.  We use the 0th page
         * index since it's the last key that the page held.
         *
         * We malloc the page information instead of using the return key/data
         * memory because we've already set them -- the reason we've already
         * set them is because we're (potentially) about to do a reverse split,
         * which would make our saved page information useless.
         *
         * !!!
         * The following operations to delete a page might deadlock.  I think
         * that's OK.  The problem is if we're deleting an item because we're
         * closing cursors because we've already deadlocked and want to call
         * txn_abort().  If we fail due to deadlock, we leave a locked empty
         * page in the tree, which won't be empty long because we're going to
         * undo the delete.
         */
        if (NUM_ENT(h) == 2 && h->pgno != PGNO_ROOT) {
                memset(&dbt, 0, sizeof(DBT));
                dbt.flags = DB_DBT_MALLOC | DB_DBT_INTERNAL;
                if ((ret = __db_ret(dbp, h, 0, &dbt, NULL, NULL)) != 0)
                        goto err;
                delete_page = 1;
        }

        /*
         * Do a normal btree delete.
         *
         * !!!
         * Delete the key item first, otherwise the duplicate checks in
         * __bam_ditem() won't work!
         */
        if ((ret = __bam_ditem(dbc, h, indx)) != 0)
                goto err;
        if ((ret = __bam_ditem(dbc, h, indx)) != 0)
                goto err;

        /* Discard any remaining locks/pages. */
        if (local_page) {
                (void)memp_fput(dbp->mpf, h, 0);
                (void)__BT_TLPUT(dbc, lock);
                local_page = 0;
        }

        /* Delete the page if it was emptied. */
        if (delete_page)
                ret = __bam_dpage(dbc, &dbt);

err:
done:   if (delete_page)
                __os_free(dbt.data, dbt.size);

        if (local_page) {
                /*
                 * It's possible for h to be NULL, as __db_drem may have
                 * been relinking pages by the time that it deadlocked.
                 */
                if (h != NULL)
                        (void)memp_fput(dbp->mpf, h, 0);
                (void)__BT_TLPUT(dbc, lock);
        }

        if (F_ISSET(dbp, DB_AM_CDB) && F_ISSET(dbc, DBC_RMW))
                (void)__lock_downgrade(dbp->dbenv->lk_info, dbc->mylock,
                    DB_LOCK_IWRITE, 0);

        return (ret);
}

/*
 * __bam_c_getstack --
 *      Acquire a full stack for a cursor.
 */
static int
__bam_c_getstack(dbc, cp)
        DBC *dbc;
        CURSOR *cp;
{
        DB *dbp;
        DBT dbt;
        PAGE *h;
        db_pgno_t pgno;
        int exact, ret;

        dbp = dbc->dbp;
        h = NULL;
        memset(&dbt, 0, sizeof(DBT));
        ret = 0;

        /* Get the page with the current item on it. */
        pgno = cp->pgno;
        if ((ret = memp_fget(dbp->mpf, &pgno, 0, &h)) != 0)
                return (ret);

        /* Get a copy of a key from the page. */
        dbt.flags = DB_DBT_MALLOC | DB_DBT_INTERNAL;
        if ((ret = __db_ret(dbp, h, 0, &dbt, NULL, NULL)) != 0)
                goto err;

        /* Get a write-locked stack for that page. */
        exact = 0;
        ret = __bam_search(dbc, &dbt, S_KEYFIRST, 1, NULL, &exact);

        /* We no longer need the key or the page. */
err:    if (h != NULL)
                (void)memp_fput(dbp->mpf, h, 0);
        if (dbt.data != NULL)
                __os_free(dbt.data, dbt.size);
        return (ret);
}