bt_recno.c

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/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1997, 1998, 1999, 2000
 *      Sleepycat Software.  All rights reserved.
 */

#include "config.h"

#ifndef lint
static const char revid[] = "$Id: bt__recno_8c-source.html,v 1.1 2008/06/08 10:13:41 sebdiaz Exp $";
#endif /* not lint */

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

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

#include "db_int.h"
#include "db_page.h"
#include "btree.h"
#include "db_ext.h"
#include "db_shash.h"
#include "lock.h"
#include "lock_ext.h"
#include "qam.h"

static int  __ram_add __P((DBC *, db_recno_t *, DBT *, u_int32_t, u_int32_t));
static void __ram_ca __P((DBC *, db_recno_t, ca_recno_arg));
static int  __ram_delete __P((DB *, DB_TXN *, DBT *, u_int32_t));
static int  __ram_fmap __P((DBC *, db_recno_t));
static int  __ram_put __P((DB *, DB_TXN *, DBT *, DBT *, u_int32_t));
static int  __ram_source __P((DB *));
static int  __ram_update __P((DBC *, db_recno_t, int));
static int  __ram_vmap __P((DBC *, db_recno_t));

/*
 * In recno, there are two meanings to the on-page "deleted" flag.  If we're
 * re-numbering records, it means the record was implicitly created.  We skip
 * over implicitly created records if doing a cursor "next" or "prev", and
 * return DB_KEYEMPTY if they're explicitly requested..  If not re-numbering
 * records, it means that the record was implicitly created, or was deleted.
 * We skip over implicitly created or deleted records if doing a cursor "next"
 * or "prev", and return DB_KEYEMPTY if they're explicitly requested.
 *
 * If we're re-numbering records, then we have to detect in the cursor that
 * a record was deleted, and adjust the cursor as necessary on the next get.
 * If we're not re-numbering records, then we can detect that a record has
 * been deleted by looking at the actual on-page record, so we completely
 * ignore the cursor's delete flag.  This is different from the B+tree code.
 * It also maintains whether the cursor references a deleted record in the
 * cursor, and it doesn't always check the on-page value.
 */
#define CD_SET(dbp, cp) {                                               \
        if (F_ISSET(cp, C_RENUMBER))                                    \
                F_SET(cp, C_DELETED);                                   \
}
#define CD_CLR(dbp, cp) {                                               \
        if (F_ISSET(cp, C_RENUMBER))                                    \
                F_CLR(cp, C_DELETED);                                   \
}
#define CD_ISSET(dbp, cp)                                               \
        (F_ISSET(cp, C_RENUMBER) && F_ISSET(cp, C_DELETED))

/*
 * CDB___ram_open --
 *      Recno open function.
 *
 * PUBLIC: int CDB___ram_open __P((DB *, const char *, db_pgno_t, u_int32_t));
 */
int
CDB___ram_open(dbp, name, base_pgno, flags)
        DB *dbp;
        const char *name;
        db_pgno_t base_pgno;
        u_int32_t flags;
{
        BTREE *t;
        DBC *dbc;
        int ret, t_ret;

        t = dbp->bt_internal;

        /* Initialize the remaining fields/methods of the DB. */
        dbp->del = __ram_delete;
        dbp->put = __ram_put;
        dbp->stat = CDB___bam_stat;

        /* Start up the tree. */
        if ((ret = CDB___bam_read_root(dbp, name, base_pgno, flags)) != 0)
                goto err;

        /*
         * If the user specified a source tree, open it and map it in.
         *
         * !!!
         * We don't complain if the user specified transactions or threads.
         * It's possible to make it work, but you'd better know what you're
         * doing!
         */
        if (t->re_source != NULL && (ret = __ram_source(dbp)) != 0)
                goto err;

        /* If we're snapshotting an underlying source file, do it now. */
        if (F_ISSET(dbp, DB_RE_SNAPSHOT)) {
                /* Allocate a cursor. */
                if ((ret = dbp->cursor(dbp, NULL, &dbc, 0)) != 0)
                        goto err;

                /* Do the snapshot. */
                if ((ret = __ram_update(dbc,
                    DB_MAX_RECORDS, 0)) != 0 && ret == DB_NOTFOUND)
                        ret = 0;

                /* Discard the cursor. */
                if ((t_ret = dbc->c_close(dbc)) != 0 && ret == 0)
                        ret = t_ret;

                if (ret != 0)
                        goto err;
        }

        return (0);

err:    /* If we mmap'd a source file, discard it. */
        if (t->re_smap != NULL)
                (void)CDB___os_unmapfile(dbp->dbenv, t->re_smap, t->re_msize);

        /* If we opened a source file, discard it. */
        if (F_ISSET(&t->re_fh, DB_FH_VALID))
                (void)CDB___os_closehandle(&t->re_fh);
        if (t->re_source != NULL)
                CDB___os_freestr(t->re_source);

        return (ret);
}

/*
 * __ram_delete --
 *      Recno db->del function.
 */
static int
__ram_delete(dbp, txn, key, flags)
        DB *dbp;
        DB_TXN *txn;
        DBT *key;
        u_int32_t flags;
{
        BTREE_CURSOR *cp;
        DBC *dbc;
        db_recno_t recno;
        int ret, t_ret;

        PANIC_CHECK(dbp->dbenv);

        /* Check for invalid flags. */
        if ((ret = CDB___db_delchk(dbp,
            key, flags, F_ISSET(dbp, DB_AM_RDONLY))) != 0)
                return (ret);

        /* Acquire a cursor. */
        if ((ret = dbp->cursor(dbp, txn, &dbc, DB_WRITELOCK)) != 0)
                return (ret);

        DEBUG_LWRITE(dbc, txn, "ram_delete", key, NULL, flags);

        /* Check the user's record number and fill in as necessary. */
        if ((ret = CDB___ram_getno(dbc, key, &recno, 0)) != 0)
                goto err;

        /* Do the delete. */
        cp = (BTREE_CURSOR *)dbc->internal;
        cp->recno = recno;

        ret = CDB___ram_c_del(dbc);

        /* Release the cursor. */
err:    if ((t_ret = dbc->c_close(dbc)) != 0 && ret == 0)
                ret = t_ret;

        return (ret);
}

/*
 * __ram_put --
 *      Recno db->put function.
 */
static int
__ram_put(dbp, txn, key, data, flags)
        DB *dbp;
        DB_TXN *txn;
        DBT *key, *data;
        u_int32_t flags;
{
        DBC *dbc;
        db_recno_t recno;
        int ret, t_ret;

        PANIC_CHECK(dbp->dbenv);

        /* Check for invalid flags. */
        if ((ret = CDB___db_putchk(dbp,
            key, data, flags, F_ISSET(dbp, DB_AM_RDONLY), 0)) != 0)
                return (ret);

        /* Allocate a cursor. */
        if ((ret = dbp->cursor(dbp, txn, &dbc, DB_WRITELOCK)) != 0)
                return (ret);

        DEBUG_LWRITE(dbc, txn, "ram_put", key, data, flags);

        /*
         * If we're appending to the tree, make sure we've read in all of
         * the backing source file.  Otherwise, check the user's record
         * number and fill in as necessary.
         */
        if (flags == DB_APPEND) {
                if ((ret = __ram_update(
                    dbc, DB_MAX_RECORDS, 0)) != 0 && ret == DB_NOTFOUND)
                        ret = 0;
        } else
                ret = CDB___ram_getno(dbc, key, &recno, 1);

        /* Add the record. */
        if (ret == 0)
                ret = __ram_add(dbc, &recno, data, flags, 0);

        /* Discard the cursor. */
        if ((t_ret = dbc->c_close(dbc)) != 0 && ret == 0)
                ret = t_ret;

        /* Return the record number if we're appending to the tree. */
        if (ret == 0 && flags == DB_APPEND)
                ret = CDB___db_retcopy(dbp, key, &recno, sizeof(recno),
                    &dbc->rkey.data, &dbc->rkey.ulen);

        return (ret);
}

/*
 * CDB___ram_c_del --
 *      Recno cursor->c_del function.
 *
 * PUBLIC: int CDB___ram_c_del __P((DBC *));
 */
int
CDB___ram_c_del(dbc)
        DBC *dbc;
{
        BKEYDATA bk;
        BTREE *t;
        BTREE_CURSOR *cp;
        DB *dbp;
        DBT hdr, data;
        EPG *epg;
        int exact, ret, stack;

        dbp = dbc->dbp;
        cp = (BTREE_CURSOR *)dbc->internal;
        t = dbp->bt_internal;
        stack = 0;

        /*
         * The semantics of cursors during delete are as follows: if record
         * numbers are mutable (C_RENUMBER is set), deleting a record causes
         * the cursor to automatically point to the immediately following
         * record.  In this case it is possible to use a single cursor for
         * repeated delete operations, without intervening operations.
         *
         * If record numbers are not mutable, then records are replaced with
         * a marker containing a delete flag.  If the record referenced by
         * this cursor has already been deleted, we will detect that as part
         * of the delete operation, and fail.
         */

        /* Search the tree for the key; delete only deletes exact matches. */
        if ((ret = CDB___bam_rsearch(dbc, &cp->recno, S_DELETE, 1, &exact)) != 0)
                goto err;
        if (!exact) {
                ret = DB_NOTFOUND;
                goto err;
        }
        stack = 1;
        cp->page = cp->csp->page;
        cp->pgno = cp->csp->page->pgno;
        cp->indx = cp->csp->indx;

        /*
         * If re-numbering records, the on-page deleted flag can only mean
         * that this record was implicitly created.  Applications aren't
         * permitted to delete records they never created, return an error.
         *
         * If not re-numbering records, the on-page deleted flag means that
         * this record was implicitly created, or, was deleted at some time.
         * The former is an error because applications aren't permitted to
         * delete records they never created, the latter is an error because
         * if the record was "deleted", we could never have found it.
         */
        if (B_DISSET(GET_BKEYDATA(cp->page, cp->indx)->type)) {
                ret = DB_KEYEMPTY;
                goto err;
        }

        if (F_ISSET(cp, C_RENUMBER)) {
                /* Delete the item, adjust the counts, adjust the cursors. */
                if ((ret = CDB___bam_ditem(dbc, cp->page, cp->indx)) != 0)
                        goto err;
                CDB___bam_adjust(dbc, -1);
                __ram_ca(dbc, cp->recno, CA_DELETE);

                /*
                 * If the page is empty, delete it.
                 *
                 * We never delete a root page.  First, root pages of primary
                 * databases never go away, recno or otherwise.  However, if
                 * it's the root page of an off-page duplicates database, then
                 * it can be deleted.   We don't delete it here because we have
                 * no way of telling the primary database page holder (e.g.,
                 * the hash access method) that its page element should cleaned
                 * up because the underlying tree is gone.  So, we keep the page
                 * around until the last cursor referencing the empty tree is
                 * are closed, and then clean it up.
                 */
                if (NUM_ENT(cp->page) == 0 && PGNO(cp->page) != cp->root) {
                        /*
                         * We already have a locked stack of pages.  However,
                         * there are likely entries in the stack that aren't
                         * going to be emptied by removing the single reference
                         * to the emptied page (or one of its parents).
                         */
                        for (epg = cp->sp; epg <= cp->csp; ++epg)
                                if (NUM_ENT(epg->page) <= 1)
                                        break;

                        /*
                         * We want to delete a single item out of the last page
                         * that we're not deleting, back up to that page.
                         */
                        ret = CDB___bam_dpages(dbc, --epg);

                        /*
                         * Regardless of the return from CDB___bam_dpages, it will
                         * discard our stack and pinned page.
                         */
                        stack = 0;
                        cp->page = NULL;
                }
        } else {
                /* Use a delete/put pair to replace the record with a marker. */
                if ((ret = CDB___bam_ditem(dbc, cp->page, cp->indx)) != 0)
                        goto err;

                B_TSET(bk.type, B_KEYDATA, 1);
                bk.len = 0;
                memset(&hdr, 0, sizeof(hdr));
                hdr.data = &bk;
                hdr.size = SSZA(BKEYDATA, data);
                memset(&data, 0, sizeof(data));
                data.data = (void *)"";
                data.size = 0;
                if ((ret = CDB___db_pitem(dbc,
                    cp->page, cp->indx, BKEYDATA_SIZE(0), &hdr, &data)) != 0)
                        goto err;
        }

        F_SET(t, RECNO_MODIFIED);

err:    if (stack)
                CDB___bam_stkrel(dbc, STK_CLRDBC);

        return (ret);
}

/*
 * CDB___ram_c_get --
 *      Recno cursor->c_get function.
 *
 * PUBLIC: int CDB___ram_c_get
 * PUBLIC:     __P((DBC *, DBT *, DBT *, u_int32_t, db_pgno_t *));
 */
int
CDB___ram_c_get(dbc, key, data, flags, pgnop)
        DBC *dbc;
        DBT *key, *data;
        u_int32_t flags;
        db_pgno_t *pgnop;
{
        BTREE_CURSOR *cp;
        DB *dbp;
        int cmp, exact, ret;

        COMPQUIET(pgnop, NULL);

        dbp = dbc->dbp;
        cp = (BTREE_CURSOR *)dbc->internal;

retry:  switch (flags) {
        case DB_CURRENT:
                /*
                 * If we're in a normal Recno tree with mutable record numbers,
                 * we need make no correction if we just deleted a record, we
                 * will return the record following the deleted one by virtue
                 * of renumbering the tree.
                 *
                 * If we're in an off-page duplicate Recno tree, we are using
                 * mutable records, but we don't implicitly move the cursor if
                 * we delete one.
                 */
                if (F_ISSET(dbc, DBC_OPD) && F_ISSET(cp, C_DELETED))
                        return (DB_KEYEMPTY);
                break;
        case DB_NEXT_DUP:
                /*
                 * If we're not in an off-page dup set, we know there's no
                 * next duplicate since recnos don't have them.  If we
                 * are in an off-page dup set, the next item assuredly is
                 * a dup, so we set flags to DB_NEXT and keep going.
                 */
                if (!F_ISSET(dbc, DBC_OPD))
                        return (DB_NOTFOUND);
                /* FALLTHROUGH */
        case DB_NEXT_NODUP:
                /*
                 * Recno databases don't have duplicates, set flags to DB_NEXT
                 * and keep going.
                 */
                /* FALLTHROUGH */
        case DB_NEXT:
                flags = DB_NEXT;
                /*
                 * If record numbers are mutable: if we just deleted a record,
                 * we have to avoid incrementing the record number so that we
                 * return the right record by virtue of renumbering the tree.
                 */
                if (CD_ISSET(dbp, cp))
                        break;

                if (cp->recno != RECNO_OOB) {
                        ++cp->recno;
                        break;
                }
                /* FALLTHROUGH */
        case DB_FIRST:
                flags = DB_NEXT;
                cp->recno = 1;
                break;
        case DB_PREV_NODUP:
                /*
                 * Recno databases don't have duplicates, set flags to DB_PREV
                 * and keep going.
                 */
                /* FALLTHROUGH */
        case DB_PREV:
                flags = DB_PREV;
                if (cp->recno != RECNO_OOB) {
                        if (cp->recno == 1) {
                                ret = DB_NOTFOUND;
                                goto err;
                        }
                        --cp->recno;
                        break;
                }
                /* FALLTHROUGH */
        case DB_LAST:
                flags = DB_PREV;
                if (((ret = __ram_update(dbc,
                    DB_MAX_RECORDS, 0)) != 0) && ret != DB_NOTFOUND)
                        goto err;
                if ((ret = CDB___bam_nrecs(dbc, &cp->recno)) != 0)
                        goto err;
                if (cp->recno == 0) {
                        ret = DB_NOTFOUND;
                        goto err;
                }
                break;
        case DB_GET_BOTHC:
                /*
                 * If we're doing a join and these are offpage dups,
                 * we want to keep searching forward from after the
                 * current cursor position.  Increment the recno by 1,
                 * then proceed as for a DB_SET.
                 *
                 * Otherwise, we know there are no additional matching
                 * data, as recnos don't have dups.  return DB_NOTFOUND.
                 */
                if (F_ISSET(dbc, DBC_OPD)) {
                        cp->recno++;
                        break;
                } else
                        ret = DB_NOTFOUND;
                        goto err;
                /* NOTREACHED */
        case DB_GET_BOTH:
                /*
                 * If we're searching a set of off-page dups, we start
                 * a new linear search from the first record.  Otherwise,
                 * we compare the single data item associated with the
                 * requested record for a match.
                 */
                if (F_ISSET(dbc, DBC_OPD)) {
                        cp->recno = 1;
                        break;
                }
                /* FALLTHROUGH */
        case DB_SET:
        case DB_SET_RANGE:
                if ((ret = CDB___ram_getno(dbc, key, &cp->recno, 0)) != 0)
                        goto err;
                break;
        default:
                ret = CDB___db_unknown_flag(dbp->dbenv, "CDB___ram_c_get", flags);
                goto err;
        }

        /*
         * For DB_PREV, DB_LAST, DB_SET and DB_SET_RANGE, we have already
         * called __ram_update() to make sure sufficient records have been
         * read from the backing source file.  Do it now for DB_CURRENT (if
         * the current record was deleted we may need more records from the
         * backing file for a DB_CURRENT operation), DB_FIRST and DB_NEXT.
         */
        if ((flags == DB_NEXT || flags == DB_CURRENT) && ((ret =
            __ram_update(dbc, cp->recno, 0)) != 0) && ret != DB_NOTFOUND)
                goto err;

        for (;; ++cp->recno) {
                /* Search the tree for the record. */
                if ((ret = CDB___bam_rsearch(dbc, &cp->recno,
                    F_ISSET(dbc, DBC_RMW) ? S_FIND_WR : S_FIND,
                    1, &exact)) != 0)
                        goto err;
                if (!exact) {
                        ret = DB_NOTFOUND;
                        goto err;
                }

                /*
                 * Copy the page into the cursor, discarding any lock we
                 * are currently holding.
                 */
                cp->page = cp->csp->page;
                cp->pgno = cp->csp->page->pgno;
                cp->indx = cp->csp->indx;
                (void)__TLPUT(dbc, cp->lock);
                cp->lock = cp->csp->lock;
                cp->lock_mode = cp->csp->lock_mode;

                /*
                 * If re-numbering records, the on-page deleted flag means this
                 * record was implicitly created.  If not re-numbering records,
                 * the on-page deleted flag means this record was implicitly
                 * created, or, it was deleted at some time.  Regardless, we
                 * skip such records if doing cursor next/prev operations or
                 * walking through off-page duplicates, and fail if they were
                 * requested explicitly by the application.
                 */
                if (B_DISSET(GET_BKEYDATA(cp->page, cp->indx)->type))
                        switch (flags) {
                        case DB_NEXT:
                        case DB_PREV:
                                (void)CDB___bam_stkrel(dbc, STK_CLRDBC);
                                goto retry;
                        case DB_GET_BOTH:
                                (void)CDB___bam_stkrel(dbc, STK_CLRDBC);
                                continue;
                        default:
                                ret = DB_KEYEMPTY;
                                goto err;
                        }

                if (flags == DB_GET_BOTH || flags == DB_GET_BOTHC) {
                        if ((ret = CDB___bam_cmp(dbp, data,
                            cp->page, cp->indx, CDB___bam_defcmp, &cmp)) != 0)
                                return (ret);
                        if (cmp == 0)
                                break;
                        if (!F_ISSET(dbc, DBC_OPD)) {
                                ret = DB_NOTFOUND;
                                goto err;
                        }
                        (void)CDB___bam_stkrel(dbc, STK_CLRDBC);
                } else
                        break;
        }

        /* Return the key if the user didn't give us one. */
        if (!F_ISSET(dbc, DBC_OPD)) {
                if (flags != DB_SET && flags != DB_SET_RANGE)
                        ret = CDB___db_retcopy(dbp,
                             key, &cp->recno, sizeof(cp->recno),
                             &dbc->rkey.data, &dbc->rkey.ulen);
                F_SET(key, DB_DBT_ISSET);
        }

        /* The cursor was reset, no further delete adjustment is necessary. */
err:    CD_CLR(dbp, cp);

        return (ret);
}

/*
 * CDB___ram_c_put --
 *      Recno cursor->c_put function.
 *
 * PUBLIC: int CDB___ram_c_put __P((DBC *, DBT *, DBT *, u_int32_t, db_pgno_t *));
 */
int
CDB___ram_c_put(dbc, key, data, flags, pgnop)
        DBC *dbc;
        DBT *key, *data;
        u_int32_t flags;
        db_pgno_t *pgnop;
{
        BTREE_CURSOR *cp;
        DB *dbp;
        int exact, ret, t_ret;
        void *arg;

        COMPQUIET(pgnop, NULL);

        dbp = dbc->dbp;
        cp = (BTREE_CURSOR *)dbc->internal;

        /*
         * DB_KEYFIRST and DB_KEYLAST will only be set if we're dealing with
         * an off-page duplicate tree, they can't be specified at user level.
         * Translate them into something else.
         */
        switch (flags) {
        case DB_KEYFIRST:
                cp->recno = 1;
                flags = DB_BEFORE;
                break;
        case DB_KEYLAST:
                return (__ram_add(dbc, &cp->recno, data, DB_APPEND, 0));
        }

split:  if ((ret = CDB___bam_rsearch(dbc, &cp->recno, S_INSERT, 1, &exact)) != 0)
                goto err;
        if (!exact) {
                ret = DB_NOTFOUND;
                goto err;
        }
        cp->page = cp->csp->page;
        cp->pgno = cp->csp->page->pgno;
        cp->indx = cp->csp->indx;

        ret = CDB___bam_iitem(dbc, key, data, flags, 0);
        t_ret = CDB___bam_stkrel(dbc, STK_CLRDBC);

        if (t_ret != 0 && (ret == 0 || ret == DB_NEEDSPLIT))
                ret = t_ret;
        else if (ret == DB_NEEDSPLIT) {
                arg = &cp->recno;
                if ((ret = CDB___bam_split(dbc, arg)) != 0)
                        goto err;
                goto split;
        }
        if (ret != 0)
                goto err;

        switch (flags) {                        /* Adjust the cursors. */
        case DB_AFTER:
                __ram_ca(dbc, cp->recno, CA_IAFTER);
                ++cp->recno;
                break;
        case DB_BEFORE:
                __ram_ca(dbc, cp->recno, CA_IBEFORE);
                --cp->recno;
                break;
        }

        /* Return the key if we've created a new record. */
        if (!F_ISSET(dbc, DBC_OPD) && (flags == DB_AFTER || flags == DB_BEFORE))
                ret = CDB___db_retcopy(dbp, key, &cp->recno,
                    sizeof(cp->recno), &dbc->rkey.data, &dbc->rkey.ulen);

        /* The cursor was reset, no further delete adjustment is necessary. */
err:    CD_CLR(dbp, cp);

        return (ret);
}

/*
 * __ram_ca --
 *      Adjust cursors.
 */
static void
__ram_ca(dbc_arg, recno, op)
        DBC *dbc_arg;
        db_recno_t recno;
        ca_recno_arg op;
{
        BTREE_CURSOR *cp;
        DB *dbp;
        DBC *dbc;
        db_recno_t nrecs;

        dbp = dbc_arg->dbp;

        /*
         * Adjust the cursors.  See the comment in CDB___bam_ca_delete().
         */
        MUTEX_THREAD_LOCK(dbp->mutexp);
        for (dbc = TAILQ_FIRST(&dbp->active_queue);
            dbc != NULL; dbc = TAILQ_NEXT(dbc, links)) {
                cp = (BTREE_CURSOR *)dbc->internal;
                if (dbc_arg->internal->root != cp->root)
                        continue;

                switch (op) {
                case CA_DELETE:
                        if (recno < cp->recno)
                                --cp->recno;
                        if (recno == cp->recno) {
                                /*
                                 * If we're in an off-page duplicate Recno tree,
                                 * we are using mutable records, but we don't
                                 * implicitly move the cursor if we delete one.
                                 */
                                if (!F_ISSET(dbc, DBC_OPD) &&
                                    CDB___bam_nrecs(dbc, &nrecs) == 0 &&
                                    recno > nrecs)
                                        --cp->recno;
                                else
                                        CD_SET(dbp, cp);
                        }
                        break;
                case CA_IAFTER:
                        if (recno < cp->recno)
                                ++cp->recno;
                        break;
                case CA_IBEFORE:
                        if (recno <= cp->recno)
                                ++cp->recno;
                        break;
                }
        }
        MUTEX_THREAD_UNLOCK(dbp->mutexp);
}

/*
 * CDB___ram_getno --
 *      Check the user's record number, and make sure we've seen it.
 *
 * PUBLIC: int CDB___ram_getno __P((DBC *, const DBT *, db_recno_t *, int));
 */
int
CDB___ram_getno(dbc, key, rep, can_create)
        DBC *dbc;
        const DBT *key;
        db_recno_t *rep;
        int can_create;
{
        DB *dbp;
        db_recno_t recno;

        dbp = dbc->dbp;

        /* Check the user's record number. */
        if ((recno = *(db_recno_t *)key->data) == 0) {
                CDB___db_err(dbp->dbenv, "illegal record number of 0");
                return (EINVAL);
        }
        if (rep != NULL)
                *rep = recno;

        /*
         * Btree can neither create records nor read them in.  Recno can
         * do both, see if we can find the record.
         */
        return (dbc->dbtype == DB_RECNO ?
            __ram_update(dbc, recno, can_create) : 0);
}

/*
 * __ram_update --
 *      Ensure the tree has records up to and including the specified one.
 */
static int
__ram_update(dbc, recno, can_create)
        DBC *dbc;
        db_recno_t recno;
        int can_create;
{
        BTREE *t;
        BTREE_CURSOR *cp;
        DB *dbp;
        db_recno_t nrecs;
        int ret;

        dbp = dbc->dbp;
        cp = (BTREE_CURSOR *)dbc->internal;
        t = dbp->bt_internal;

        /*
         * If we can't create records and we've read the entire backing input
         * file, we're done.
         */
        if (!can_create && !F_ISSET(t, RECNO_READFILE))
                return (0);

        /*
         * If we haven't seen this record yet, try to get it from the original
         * file.
         */
        if ((ret = CDB___bam_nrecs(dbc, &nrecs)) != 0)
                return (ret);
        if (F_ISSET(t, RECNO_READFILE) && recno > nrecs) {
                if ((ret = t->re_irec(dbc, recno)) != 0)
                        return (ret);
                if ((ret = CDB___bam_nrecs(dbc, &nrecs)) != 0)
                        return (ret);
        }

        /*
         * If we can create records, create empty ones up to the requested
         * record.
         */
        if (!can_create || recno <= nrecs + 1)
                return (0);

        dbc->rdata.dlen = 0;
        dbc->rdata.doff = 0;
        dbc->rdata.flags = 0;
        if (F_ISSET(dbp, DB_RE_FIXEDLEN)) {
                if (dbc->rdata.ulen < t->re_len) {
                        if ((ret = CDB___os_realloc(dbp->dbenv,
                            t->re_len, NULL, &dbc->rdata.data)) != 0) {
                                dbc->rdata.ulen = 0;
                                dbc->rdata.data = NULL;
                                return (ret);
                        }
                        dbc->rdata.ulen = t->re_len;
                }
                dbc->rdata.size = t->re_len;
                memset(dbc->rdata.data, t->re_pad, t->re_len);
        } else
                dbc->rdata.size = 0;

        while (recno > ++nrecs)
                if ((ret = __ram_add(dbc,
                    &nrecs, &dbc->rdata, 0, BI_DELETED)) != 0)
                        return (ret);
        return (0);
}

/*
 * __ram_source --
 *      Load information about the backing file.
 */
static int
__ram_source(dbp)
        DB *dbp;
{
        BTREE *t;
        size_t size;
        u_int32_t bytes, mbytes;
        char *source;
        int ret;

        t = dbp->bt_internal;
        source = t->re_source;

        /*
         * !!!
         * The caller has full responsibility for cleaning up on error --
         * (it has to anyway, in case it fails after this routine succeeds).
         */
        ret = CDB___db_appname(dbp->dbenv,
            DB_APP_DATA, NULL, source, 0, NULL, &t->re_source);

        CDB___os_freestr(source);

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

        /*
         * !!!
         * It's possible that the backing source file is read-only.  We don't
         * much care other than we'll complain if there are any modifications
         * when it comes time to write the database back to the source.
         */
        ret = CDB___os_open(dbp->dbenv, t->re_source,
            F_ISSET(dbp, DB_AM_RDONLY) ? DB_OSO_RDONLY : 0, 0, &t->re_fh);
        if (ret != 0 && !F_ISSET(dbp, DB_AM_RDONLY))
                ret = CDB___os_open(dbp->dbenv,
                    t->re_source, DB_OSO_RDONLY, 0, &t->re_fh);
        if (ret != 0) {
                CDB___db_err(dbp->dbenv, "%s: %s", t->re_source, CDB_db_strerror(ret));
                return (ret);
        }

        /*
         * !!!
         * We'd like to test to see if the file is too big to mmap.  Since we
         * don't know what size or type off_t's or size_t's are, or the largest
         * unsigned integral type is, or what random insanity the local C
         * compiler will perpetrate, doing the comparison in a portable way is
         * flatly impossible.  Hope that mmap fails if the file is too large.
         */
        if ((ret = CDB___os_ioinfo(dbp->dbenv, t->re_source,
            &t->re_fh, &mbytes, &bytes, NULL)) != 0) {
                CDB___db_err(dbp->dbenv, "%s: %s", t->re_source, CDB_db_strerror(ret));
                return (ret);
        }
        if (mbytes == 0 && bytes == 0)
                return (0);

        size = mbytes * MEGABYTE + bytes;
        if ((ret = CDB___os_mapfile(dbp->dbenv, t->re_source,
            &t->re_fh, (size_t)size, 1, &t->re_smap)) != 0)
                return (ret);
        t->re_cmap = t->re_smap;
        t->re_emap = (u_int8_t *)t->re_smap + (t->re_msize = size);
        t->re_irec = F_ISSET(dbp, DB_RE_FIXEDLEN) ?  __ram_fmap : __ram_vmap;
        F_SET(t, RECNO_READFILE);
        return (0);
}

/*
 * CDB___ram_writeback --
 *      Rewrite the backing file.
 *
 * PUBLIC: int CDB___ram_writeback __P((DB *));
 */
int
CDB___ram_writeback(dbp)
        DB *dbp;
{
        BTREE *t;
        DB_ENV *dbenv;
        DB_FH fh;
        DBC *dbc;
        DBT key, data;
        db_recno_t keyno;
        size_t nw;
        int ret, t_ret;
        u_int8_t delim, *pad;

        t = dbp->bt_internal;
        dbenv = dbp->dbenv;

        /* If the file wasn't modified, we're done. */
        if (!F_ISSET(t, RECNO_MODIFIED))
                return (0);

        /* If there's no backing source file, we're done. */
        if (t->re_source == NULL) {
                F_CLR(t, RECNO_MODIFIED);
                return (0);
        }

        /* Allocate a cursor. */
        if ((ret = dbp->cursor(dbp, NULL, &dbc, 0)) != 0)
                return (ret);

        /*
         * Read any remaining records into the tree.
         *
         * !!!
         * This is why we can't support transactions when applications specify
         * backing (re_source) files.  At this point we have to read in the
         * rest of the records from the file so that we can write all of the
         * records back out again, which could modify a page for which we'd
         * have to log changes and which we don't have locked.  This could be
         * partially fixed by taking a snapshot of the entire file during the
         * DB->open as DB->open is transaction protected.  But, if a checkpoint
         * occurs then, the part of the log holding the copy of the file could
         * be discarded, and that would make it impossible to recover in the
         * face of disaster.  This could all probably be fixed, but it would
         * require transaction protecting the backing source file, i.e. mpool
         * would have to know about it, and we don't want to go there.
         */
        if ((ret =
            __ram_update(dbc, DB_MAX_RECORDS, 0)) != 0 && ret != DB_NOTFOUND)
                return (ret);

        /*
         * !!!
         * Close any underlying mmap region.  This is required for Windows NT
         * (4.0, Service Pack 2) -- if the file is still mapped, the following
         * open will fail.
         */
        if (t->re_smap != NULL) {
                (void)CDB___os_unmapfile(dbenv, t->re_smap, t->re_msize);
                t->re_smap = NULL;
        }

        /* Get rid of any backing file descriptor, just on GP's. */
        if (F_ISSET(&t->re_fh, DB_FH_VALID))
                (void)CDB___os_closehandle(&t->re_fh);

        /* Open the file, truncating it. */
        if ((ret = CDB___os_open(dbenv,
            t->re_source, DB_OSO_SEQ | DB_OSO_TRUNC, 0, &fh)) != 0) {
                CDB___db_err(dbenv, "%s: %s", t->re_source, CDB_db_strerror(ret));
                goto err;
        }

        /*
         * We step through the records, writing each one out.  Use the record
         * number and the dbp->get() function, instead of a cursor, so we find
         * and write out "deleted" or non-existent records.
         */
        memset(&key, 0, sizeof(key));
        memset(&data, 0, sizeof(data));
        key.size = sizeof(db_recno_t);
        key.data = &keyno;

        /*
         * We'll need the delimiter if we're doing variable-length records,
         * and the pad character if we're doing fixed-length records.
         */
        delim = t->re_delim;
        if (F_ISSET(dbp, DB_RE_FIXEDLEN)) {
                if ((ret = CDB___os_malloc(dbenv, t->re_len, NULL, &pad)) != 0)
                        goto err;
                memset(pad, t->re_pad, t->re_len);
        } else
                COMPQUIET(pad, NULL);
        for (keyno = 1;; ++keyno) {
                switch (ret = dbp->get(dbp, NULL, &key, &data, 0)) {
                case 0:
                        if ((ret = CDB___os_write(dbenv,
                            &fh, data.data, data.size, &nw)) != 0)
                                goto err;
                        if (nw != (size_t)data.size) {
                                ret = EIO;
                                goto write_err;
                        }
                        break;
                case DB_KEYEMPTY:
                        if (F_ISSET(dbp, DB_RE_FIXEDLEN)) {
                                if ((ret = CDB___os_write(dbenv,
                                    &fh, pad, t->re_len, &nw)) != 0)
                                        goto write_err;
                                if (nw != (size_t)t->re_len) {
                                        ret = EIO;
                                        goto write_err;
                                }
                        }
                        break;
                case DB_NOTFOUND:
                        ret = 0;
                        goto done;
                }
                if (!F_ISSET(dbp, DB_RE_FIXEDLEN)) {
                        if ((ret = CDB___os_write(dbenv, &fh, &delim, 1, &nw)) != 0)
                                goto write_err;
                        if (nw != 1) {
                                ret = EIO;
write_err:                      CDB___db_err(dbp->dbenv,
                                    "Write failed to backing file");
                                goto err;
                        }
                }
        }

err:
done:   /* Close the file descriptor. */
        if (F_ISSET(&fh, DB_FH_VALID) &&
            (t_ret = CDB___os_closehandle(&fh)) != 0 && ret == 0)
                ret = t_ret;

        /* Discard the cursor. */
        if ((t_ret = dbc->c_close(dbc)) != 0 && ret == 0)
                ret = t_ret;

        if (ret == 0)
                F_CLR(t, RECNO_MODIFIED);

        return (ret);
}

/*
 * __ram_fmap --
 *      Get fixed length records from a file.
 */
static int
__ram_fmap(dbc, top)
        DBC *dbc;
        db_recno_t top;
{
        BTREE *t;
        BTREE_CURSOR *cp;
        DB *dbp;
        DBT data;
        db_recno_t recno;
        u_int32_t len;
        u_int8_t *sp, *ep, *p;
        int is_modified, ret;

        dbp = dbc->dbp;
        cp = (BTREE_CURSOR *)dbc->internal;
        t = dbp->bt_internal;

        if ((ret = CDB___bam_nrecs(dbc, &recno)) != 0)
                return (ret);

        if (dbc->rdata.ulen < t->re_len) {
                if ((ret = CDB___os_realloc(dbp->dbenv,
                    t->re_len, NULL, &dbc->rdata.data)) != 0) {
                        dbc->rdata.ulen = 0;
                        dbc->rdata.data = NULL;
                        return (ret);
                }
                dbc->rdata.ulen = t->re_len;
        }

        is_modified = F_ISSET(t, RECNO_MODIFIED);

        memset(&data, 0, sizeof(data));
        data.data = dbc->rdata.data;
        data.size = t->re_len;

        sp = (u_int8_t *)t->re_cmap;
        ep = (u_int8_t *)t->re_emap;
        while (recno < top) {
                if (sp >= ep) {
                        F_CLR(t, RECNO_READFILE);
                        ret = DB_NOTFOUND;
                        goto err;
                }
                len = t->re_len;
                for (p = dbc->rdata.data;
                    sp < ep && len > 0; *p++ = *sp++, --len)
                        ;

                /*
                 * Another process may have read this record from the input
                 * file and stored it into the database already, in which
                 * case we don't need to repeat that operation.  We detect
                 * this by checking if the last record we've read is greater
                 * or equal to the number of records in the database.
                 *
                 * XXX
                 * We should just do a seek since the records are fixed length.
                 */
                if (t->re_last >= recno) {
                        if (len != 0)
                                memset(p, t->re_pad, len);

                        ++recno;
                        if ((ret = __ram_add(dbc, &recno, &data, 0, 0)) != 0)
                                goto err;
                }
                ++t->re_last;
        }
        t->re_cmap = sp;

err:    if (!is_modified)
                F_CLR(t, RECNO_MODIFIED);

        return (0);
}

/*
 * __ram_vmap --
 *      Get variable length records from a file.
 */
static int
__ram_vmap(dbc, top)
        DBC *dbc;
        db_recno_t top;
{
        BTREE *t;
        DBT data;
        db_recno_t recno;
        u_int8_t *sp, *ep;
        int delim, is_modified, ret;

        t = dbc->dbp->bt_internal;

        if ((ret = CDB___bam_nrecs(dbc, &recno)) != 0)
                return (ret);

        delim = t->re_delim;
        is_modified = F_ISSET(t, RECNO_MODIFIED);

        memset(&data, 0, sizeof(data));

        sp = (u_int8_t *)t->re_cmap;
        ep = (u_int8_t *)t->re_emap;
        while (recno < top) {
                if (sp >= ep) {
                        F_CLR(t, RECNO_READFILE);
                        ret = DB_NOTFOUND;
                        goto err;
                }
                for (data.data = sp; sp < ep && *sp != delim; ++sp)
                        ;

                /*
                 * Another process may have read this record from the input
                 * file and stored it into the database already, in which
                 * case we don't need to repeat that operation.  We detect
                 * this by checking if the last record we've read is greater
                 * or equal to the number of records in the database.
                 */
                if (t->re_last >= recno) {
                        data.size = sp - (u_int8_t *)data.data;
                        ++recno;
                        if ((ret = __ram_add(dbc, &recno, &data, 0, 0)) != 0)
                                goto err;
                }
                ++t->re_last;
                ++sp;
        }
        t->re_cmap = sp;

err:    if (!is_modified)
                F_CLR(t, RECNO_MODIFIED);

        return (ret);
}

/*
 * __ram_add --
 *      Add records into the tree.
 */
static int
__ram_add(dbc, recnop, data, flags, bi_flags)
        DBC *dbc;
        db_recno_t *recnop;
        DBT *data;
        u_int32_t flags, bi_flags;
{
        BKEYDATA *bk;
        BTREE_CURSOR *cp;
        int exact, ret, stack;

        cp = (BTREE_CURSOR *)dbc->internal;

retry:  /* Find the slot for insertion. */
        if ((ret = CDB___bam_rsearch(dbc, recnop,
            S_INSERT | (flags == DB_APPEND ? S_APPEND : 0), 1, &exact)) != 0)
                return (ret);
        stack = 1;
        cp->page = cp->csp->page;
        cp->pgno = cp->csp->page->pgno;
        cp->indx = cp->csp->indx;

        /*
         * If re-numbering records, the on-page deleted flag means this record
         * was implicitly created.  If not re-numbering records, the on-page
         * deleted flag means this record was implicitly created, or, it was
         * deleted at some time.
         *
         * If DB_NOOVERWRITE is set and the item already exists in the tree,
         * return an error unless the item was either marked for deletion or
         * only implicitly created.
         */
        if (exact) {
                bk = GET_BKEYDATA(cp->page, cp->indx);
                if (!B_DISSET(bk->type) && flags == DB_NOOVERWRITE) {
                        ret = DB_KEYEXIST;
                        goto err;
                }
        }

        /*
         * Select the arguments for CDB___bam_iitem() and do the insert.  If the
         * key is an exact match, or we're replacing the data item with a
         * new data item, replace the current item.  If the key isn't an exact
         * match, we're inserting a new key/data pair, before the search
         * location.
         */
        switch (ret = CDB___bam_iitem(dbc,
            NULL, data, exact ? DB_CURRENT : DB_BEFORE, bi_flags)) {
        case 0:
                /*
                 * Don't adjust anything.
                 *
                 * If we inserted a record, no cursors need adjusting because
                 * the only new record it's possible to insert is at the very
                 * end of the tree.  The necessary adjustments to the internal
                 * page counts were made by CDB___bam_iitem().
                 *
                 * If we overwrote a record, no cursors need adjusting because
                 * future DBcursor->get calls will simply return the underlying
                 * record (there's no adjustment made for the DB_CURRENT flag
                 * when a cursor get operation immediately follows a cursor
                 * delete operation, and the normal adjustment for the DB_NEXT
                 * flag is still correct).
                 */
                break;
        case DB_NEEDSPLIT:
                /* Discard the stack of pages and split the page. */
                (void)CDB___bam_stkrel(dbc, STK_CLRDBC);
                stack = 0;

                if ((ret = CDB___bam_split(dbc, recnop)) != 0)
                        goto err;

                goto retry;
                /* NOTREACHED */
        default:
                goto err;
        }

err:    if (stack)
                CDB___bam_stkrel(dbc, STK_CLRDBC);

        return (ret);
}

---