Update.

[glibc.git] / db2 / btree / bt_recno.c

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

#include "config.h"

#ifndef lint
static const char sccsid[] = "@(#)bt_recno.c    10.37 (Sleepycat) 5/23/98";
#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"

static int __ram_add __P((DB *, db_recno_t *, DBT *, u_int32_t, u_int32_t));
static int __ram_c_close __P((DBC *));
static int __ram_c_del __P((DBC *, u_int32_t));
static int __ram_c_get __P((DBC *, DBT *, DBT *, u_int32_t));
static int __ram_c_put __P((DBC *, DBT *, DBT *, u_int32_t));
static int __ram_fmap __P((DB *, db_recno_t));
static int __ram_get __P((DB *, DB_TXN *, DBT *, DBT *, u_int32_t));
static int __ram_iget __P((DB *, DBT *, DBT *));
static int __ram_put __P((DB *, DB_TXN *, DBT *, DBT *, u_int32_t));
static int __ram_source __P((DB *, RECNO *, const char *));
static int __ram_sync __P((DB *, u_int32_t));
static int __ram_update __P((DB *, db_recno_t, int));
static int __ram_vmap __P((DB *, db_recno_t));
static int __ram_writeback __P((DB *));

/*
 * If we're renumbering records, then we have to detect in the cursor that a
 * record was deleted, and adjust the cursor as necessary.  If not renumbering
 * records, then we can detect this by looking at the actual record, so we
 * ignore the cursor delete flag.
 */
#define CD_SET(dbp, cp) {                                               \
        if (F_ISSET(dbp, DB_RE_RENUMBER))                               \
                F_SET(cp, CR_DELETED);                                  \
}
#define CD_CLR(dbp, cp) {                                               \
        if (F_ISSET(dbp, DB_RE_RENUMBER))                               \
                F_CLR(cp, CR_DELETED);                                  \
}
#define CD_ISSET(dbp, cp)                                               \
        (F_ISSET(dbp, DB_RE_RENUMBER) && F_ISSET(cp, CR_DELETED))

/*
 * __ram_open --
 *      Recno open function.
 *
 * PUBLIC: int __ram_open __P((DB *, DBTYPE, DB_INFO *));
 */
int
__ram_open(dbp, type, dbinfo)
        DB *dbp;
        DBTYPE type;
        DB_INFO *dbinfo;
{
        BTREE *t;
        RECNO *rp;
        int ret;

        COMPQUIET(type, DB_RECNO);

        ret = 0;

        /* Allocate and initialize the private RECNO structure. */
        if ((rp = (RECNO *)__db_calloc(1, sizeof(*rp))) == NULL)
                return (ENOMEM);

        if (dbinfo != NULL) {
                /*
                 * 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 (dbinfo->re_source == NULL) {
                        rp->re_fd = -1;
                        F_SET(rp, RECNO_EOF);
                } else {
                        if ((ret =
                            __ram_source(dbp, rp, dbinfo->re_source)) != 0)
                        goto err;
                }

                /* Copy delimiter, length and padding values. */
                rp->re_delim =
                    F_ISSET(dbp, DB_RE_DELIMITER) ? dbinfo->re_delim : '\n';
                rp->re_pad = F_ISSET(dbp, DB_RE_PAD) ? dbinfo->re_pad : ' ';

                if (F_ISSET(dbp, DB_RE_FIXEDLEN)) {
                        if ((rp->re_len = dbinfo->re_len) == 0) {
                                __db_err(dbp->dbenv,
                                    "record length must be greater than 0");
                                ret = EINVAL;
                                goto err;
                        }
                } else
                        rp->re_len = 0;
        } else {
                rp->re_delim = '\n';
                rp->re_pad = ' ';
                rp->re_fd = -1;
                F_SET(rp, RECNO_EOF);
        }

        /* Open the underlying btree. */
        if ((ret = __bam_open(dbp, DB_RECNO, dbinfo)) != 0)
                goto err;

        /* Set the routines necessary to make it look like a recno tree. */
        dbp->cursor = __ram_cursor;
        dbp->del = __ram_delete;
        dbp->get = __ram_get;
        dbp->put = __ram_put;
        dbp->sync = __ram_sync;

        /* Link in the private recno structure. */
        ((BTREE *)dbp->internal)->bt_recno = rp;

        /* If we're snapshotting an underlying source file, do it now. */
        if (dbinfo != NULL && F_ISSET(dbinfo, DB_SNAPSHOT))
                if ((ret = __ram_snapshot(dbp)) != 0 && ret != DB_NOTFOUND)
                        goto err;

        return (0);

err:    /* If we mmap'd a source file, discard it. */
        if (rp->re_smap != NULL)
                (void)__db_unmapfile(rp->re_smap, rp->re_msize);

        /* If we opened a source file, discard it. */
        if (rp->re_fd != -1)
                (void)__db_close(rp->re_fd);
        if (rp->re_source != NULL)
                FREES(rp->re_source);

        /* If we allocated room for key/data return, discard it. */
        t = dbp->internal;
        if (t != NULL && t->bt_rkey.data != NULL)
                __db_free(t->bt_rkey.data);

        FREE(rp, sizeof(*rp));

        return (ret);
}

/*
 * __ram_cursor --
 *      Recno db->cursor function.
 *
 * PUBLIC: int __ram_cursor __P((DB *, DB_TXN *, DBC **));
 */
int
__ram_cursor(dbp, txn, dbcp)
        DB *dbp;
        DB_TXN *txn;
        DBC **dbcp;
{
        RCURSOR *cp;
        DBC *dbc;

        DEBUG_LWRITE(dbp, txn, "ram_cursor", NULL, NULL, 0);

        if ((dbc = (DBC *)__db_calloc(1, sizeof(DBC))) == NULL)
                return (ENOMEM);
        if ((cp = (RCURSOR *)__db_calloc(1, sizeof(RCURSOR))) == NULL) {
                __db_free(dbc);
                return (ENOMEM);
        }

        cp->dbc = dbc;
        cp->recno = RECNO_OOB;

        dbc->dbp = dbp;
        dbc->txn = txn;
        dbc->internal = cp;
        dbc->c_close = __ram_c_close;
        dbc->c_del = __ram_c_del;
        dbc->c_get = __ram_c_get;
        dbc->c_put = __ram_c_put;

        /*
         * All cursors are queued from the master DB structure.  Add the
         * cursor to that queue.
         */
        CURSOR_SETUP(dbp);
        TAILQ_INSERT_HEAD(&dbp->curs_queue, dbc, links);
        CURSOR_TEARDOWN(dbp);

        *dbcp = dbc;
        return (0);
}

/*
 * __ram_get --
 *      Recno db->get function.
 */
static int
__ram_get(argdbp, txn, key, data, flags)
        DB *argdbp;
        DB_TXN *txn;
        DBT *key, *data;
        u_int32_t flags;
{
        DB *dbp;
        int ret;

        DEBUG_LWRITE(argdbp, txn, "ram_get", key, NULL, flags);

        /* Check for invalid flags. */
        if ((ret = __db_getchk(argdbp, key, data, flags)) != 0)
                return (ret);

        GETHANDLE(argdbp, txn, &dbp, ret);

        ret = __ram_iget(dbp, key, data);

        PUTHANDLE(dbp);
        return (ret);
}

/*
 * __ram_iget --
 *      Internal ram get function, called for both standard and cursor
 *      get after the flags have been checked.
 */
static int
__ram_iget(dbp, key, data)
        DB *dbp;
        DBT *key, *data;
{
        BTREE *t;
        PAGE *h;
        db_indx_t indx;
        db_recno_t recno;
        int exact, ret, stack;

        stack = 0;
        t = dbp->internal;

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

        /* Search the tree for the record. */
        if ((ret = __bam_rsearch(dbp, &recno, S_FIND, 1, &exact)) != 0)
                goto done;
        if (!exact)
                return (DB_NOTFOUND);
        stack = 1;

        h = t->bt_csp->page;
        indx = t->bt_csp->indx;

        /* If the record has already been deleted, we couldn't have found it. */
        if (B_DISSET(GET_BKEYDATA(h, indx)->type)) {
                ret = DB_KEYEMPTY;
                goto done;
        }

        /* Return the data item. */
        ret = __db_ret(dbp,
            h, indx, data, &t->bt_rdata.data, &t->bt_rdata.ulen);
        ++t->lstat.bt_get;

done:   /* Discard the stack. */
        if (stack)
                __bam_stkrel(dbp);

        return (ret);
}

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

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

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

        GETHANDLE(argdbp, txn, &dbp, ret);

        /*
         * 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.
         */
        ret = LF_ISSET(DB_APPEND) ?
            __ram_snapshot(dbp) : __ram_getno(dbp, key, &recno, 1);

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

        /* If we're appending to the tree, we have to return the record. */
        if (ret == 0 && LF_ISSET(DB_APPEND)) {
                t = dbp->internal;
                ret = __db_retcopy(key, &recno, sizeof(recno),
                    &t->bt_rkey.data, &t->bt_rkey.ulen, dbp->db_malloc);
        }

        PUTHANDLE(dbp);
        return (ret);
}

/*
 * __ram_sync --
 *      Recno db->sync function.
 */
static int
__ram_sync(argdbp, flags)
        DB *argdbp;
        u_int32_t flags;
{
        DB *dbp;
        int ret;

        DEBUG_LWRITE(argdbp, NULL, "ram_sync", NULL, NULL, flags);

        /* Sync the underlying btree. */
        if ((ret = __bam_sync(argdbp, flags)) != 0)
                return (ret);

        /* Copy back the backing source file. */
        GETHANDLE(argdbp, NULL, &dbp, ret);
        ret = __ram_writeback(dbp);
        PUTHANDLE(dbp);

        return (ret);
}

/*
 * __ram_close --
 *      Recno db->close function.
 *
 * PUBLIC: int __ram_close __P((DB *));
 */
int
__ram_close(argdbp)
        DB *argdbp;
{
        RECNO *rp;

        DEBUG_LWRITE(argdbp, NULL, "ram_close", NULL, NULL, 0);

        rp = ((BTREE *)argdbp->internal)->bt_recno;

        /* Close any underlying mmap region. */
        if (rp->re_smap != NULL)
                (void)__db_unmapfile(rp->re_smap, rp->re_msize);

        /* Close any backing source file descriptor. */
        if (rp->re_fd != -1)
                (void)__db_close(rp->re_fd);

        /* Free any backing source file name. */
        if (rp->re_source != NULL)
                FREES(rp->re_source);

        /* Free allocated memory. */
        FREE(rp, sizeof(RECNO));
        ((BTREE *)argdbp->internal)->bt_recno = NULL;

        /* Close the underlying btree. */
        return (__bam_close(argdbp));
}

/*
 * __ram_c_close --
 *      Recno cursor->close function.
 */
static int
__ram_c_close(dbc)
        DBC *dbc;
{
        DEBUG_LWRITE(dbc->dbp, dbc->txn, "ram_c_close", NULL, NULL, 0);

        return (__ram_c_iclose(dbc->dbp, dbc));
}

/*
 * __ram_c_iclose --
 *      Close a single cursor -- internal version.
 *
 * PUBLIC: int __ram_c_iclose __P((DB *, DBC *));
 */
int
__ram_c_iclose(dbp, dbc)
        DB *dbp;
        DBC *dbc;
{
        /* Remove the cursor from the queue. */
        CURSOR_SETUP(dbp);
        TAILQ_REMOVE(&dbp->curs_queue, dbc, links);
        CURSOR_TEARDOWN(dbp);

        /* Discard the structures. */
        FREE(dbc->internal, sizeof(RCURSOR));
        FREE(dbc, sizeof(DBC));

        return (0);
}

/*
 * __ram_c_del --
 *      Recno cursor->c_del function.
 */
static int
__ram_c_del(dbc, flags)
        DBC *dbc;
        u_int32_t flags;
{
        DBT key;
        RCURSOR *cp;
        int ret;

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

        cp = dbc->internal;

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

        /* If already deleted, return failure. */
        if (CD_ISSET(dbc->dbp, cp))
                return (DB_KEYEMPTY);

        /* Build a normal delete request. */
        memset(&key, 0, sizeof(key));
        key.data = &cp->recno;
        key.size = sizeof(db_recno_t);
        if ((ret = __ram_delete(dbc->dbp, dbc->txn, &key, 0)) == 0)
                CD_SET(dbc->dbp, cp);

        return (ret);
}

/*
 * __ram_c_get --
 *      Recno cursor->c_get function.
 */
static int
__ram_c_get(dbc, key, data, flags)
        DBC *dbc;
        DBT *key, *data;
        u_int32_t flags;
{
        BTREE *t;
        DB *dbp;
        RCURSOR *cp, copy;
        int ret;

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

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

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

        GETHANDLE(dbc->dbp, dbc->txn, &dbp, ret);
        t = dbp->internal;

        /* Initialize the cursor for a new retrieval. */
        copy = *cp;

retry:  /* Update the record number. */
        switch (flags) {
        case DB_CURRENT:
                if (CD_ISSET(dbp, cp)) {
                        PUTHANDLE(dbp);
                        return (DB_KEYEMPTY);
                }
                break;
        case DB_NEXT:
                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:
                if (cp->recno != RECNO_OOB) {
                        if (cp->recno == 1)
                                return (DB_NOTFOUND);
                        --cp->recno;
                        break;
                }
                /* FALLTHROUGH */
        case DB_LAST:
                flags = DB_PREV;
                if (((ret = __ram_snapshot(dbp)) != 0) && ret != DB_NOTFOUND)
                        goto err;
                if ((ret = __bam_nrecs(dbp, &cp->recno)) != 0)
                        goto err;
                if (cp->recno == 0)
                        return (DB_NOTFOUND);
                break;
        case DB_SET:
        case DB_SET_RANGE:
                if ((ret = __ram_getno(dbp, key, &cp->recno, 0)) != 0)
                        goto err;
                break;
        }

        /*
         * Return the key if the user didn't give us one, and then pass it
         * into __ram_iget().
         */
        if (flags != DB_SET && flags != DB_SET_RANGE &&
            (ret = __db_retcopy(key, &cp->recno, sizeof(cp->recno),
            &t->bt_rkey.data, &t->bt_rkey.ulen, dbp->db_malloc)) != 0)
                return (ret);

        /*
         * The cursor was reset, so the delete adjustment is no
         * longer necessary.
         */
        CD_CLR(dbp, cp);

        /*
         * Retrieve the record.
         *
         * Skip any keys that don't really exist.
         */
        if ((ret = __ram_iget(dbp, key, data)) != 0)
                if (ret == DB_KEYEMPTY &&
                    (flags == DB_NEXT || flags == DB_PREV))
                        goto retry;

err:    if (ret != 0)
                *cp = copy;

        PUTHANDLE(dbp);
        return (ret);
}

/*
 * __ram_c_put --
 *      Recno cursor->c_put function.
 */
static int
__ram_c_put(dbc, key, data, flags)
        DBC *dbc;
        DBT *key, *data;
        u_int32_t flags;
{
        BTREE *t;
        RCURSOR *cp, copy;
        DB *dbp;
        int exact, ret;
        void *arg;

        DEBUG_LWRITE(dbc->dbp, dbc->txn, "ram_c_put", NULL, data, flags);

        cp = dbc->internal;

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

        GETHANDLE(dbc->dbp, dbc->txn, &dbp, ret);
        t = dbp->internal;

        /* Initialize the cursor for a new retrieval. */
        copy = *cp;

        /*
         * To split, we need a valid key for the page.  Since it's a cursor,
         * we have to build one.
         *
         * The split code discards all short-term locks and stack pages.
         */
        if (0) {
split:          arg = &cp->recno;
                if ((ret = __bam_split(dbp, arg)) != 0)
                        goto err;
        }

        if ((ret = __bam_rsearch(dbp, &cp->recno, S_INSERT, 1, &exact)) != 0)
                goto err;
        if (!exact) {
                ret = DB_NOTFOUND;
                goto err;
        }
        if ((ret = __bam_iitem(dbp, &t->bt_csp->page,
            &t->bt_csp->indx, key, data, flags, 0)) == DB_NEEDSPLIT) {
                if ((ret = __bam_stkrel(dbp)) != 0)
                        goto err;
                goto split;
        }
        if ((ret = __bam_stkrel(dbp)) != 0)
                goto err;

        switch (flags) {
        case DB_AFTER:
                /* Adjust the cursors. */
                __ram_ca(dbp, cp->recno, CA_IAFTER);

                /* Set this cursor to reference the new record. */
                cp->recno = copy.recno + 1;
                break;
        case DB_BEFORE:
                /* Adjust the cursors. */
                __ram_ca(dbp, cp->recno, CA_IBEFORE);

                /* Set this cursor to reference the new record. */
                cp->recno = copy.recno;
                break;
        }

        /*
         * The cursor was reset, so the delete adjustment is no
         * longer necessary.
         */
        CD_CLR(dbp, cp);

err:    if (ret != 0)
                *cp = copy;

        PUTHANDLE(dbp);
        return (ret);
}

/*
 * __ram_ca --
 *      Adjust cursors.
 *
 * PUBLIC: void __ram_ca __P((DB *, db_recno_t, ca_recno_arg));
 */
void
__ram_ca(dbp, recno, op)
        DB *dbp;
        db_recno_t recno;
        ca_recno_arg op;
{
        DBC *dbc;
        RCURSOR *cp;

        /*
         * Adjust the cursors.  See the comment in __bam_ca_delete().
         */
        CURSOR_SETUP(dbp);
        for (dbc = TAILQ_FIRST(&dbp->curs_queue);
            dbc != NULL; dbc = TAILQ_NEXT(dbc, links)) {
                cp = (RCURSOR *)dbc->internal;
                switch (op) {
                case CA_DELETE:
                        if (recno > cp->recno)
                                --cp->recno;
                        break;
                case CA_IAFTER:
                        if (recno > cp->recno)
                                ++cp->recno;
                        break;
                case CA_IBEFORE:
                        if (recno >= cp->recno)
                                ++cp->recno;
                        break;
                }
        }
        CURSOR_TEARDOWN(dbp);
}

#ifdef DEBUG
/*
 * __ram_cprint --
 *      Display the current recno cursor list.
 *
 * PUBLIC: int __ram_cprint __P((DB *));
 */
int
__ram_cprint(dbp)
        DB *dbp;
{
        DBC *dbc;
        RCURSOR *cp;

        CURSOR_SETUP(dbp);
        for (dbc = TAILQ_FIRST(&dbp->curs_queue);
            dbc != NULL; dbc = TAILQ_NEXT(dbc, links)) {
                cp = (RCURSOR *)dbc->internal;
                fprintf(stderr,
                    "%#0x: recno: %lu\n", (u_int)cp, (u_long)cp->recno);
        }
        CURSOR_TEARDOWN(dbp);

        return (0);
}
#endif /* DEBUG */

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

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

        /*
         * Btree can neither create records or read them in.  Recno can
         * do both, see if we can find the record.
         */
        return (dbp->type == DB_RECNO ?
            __ram_update(dbp, recno, can_create) : 0);
}

/*
 * __ram_snapshot --
 *      Read in any remaining records from the backing input file.
 *
 * PUBLIC: int __ram_snapshot __P((DB *));
 */
int
__ram_snapshot(dbp)
        DB *dbp;
{
        return (__ram_update(dbp, DB_MAX_RECORDS, 0));
}

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

        t = dbp->internal;
        rp = t->bt_recno;

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

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

        t->bt_rdata.dlen = 0;
        t->bt_rdata.doff = 0;
        t->bt_rdata.flags = 0;
        if (F_ISSET(dbp, DB_RE_FIXEDLEN)) {
                if (t->bt_rdata.ulen < rp->re_len) {
                        t->bt_rdata.data = t->bt_rdata.data == NULL ?
                            (void *)__db_malloc(rp->re_len) :
                            (void *)__db_realloc(t->bt_rdata.data, rp->re_len);
                        if (t->bt_rdata.data == NULL) {
                                t->bt_rdata.ulen = 0;
                                return (ENOMEM);
                        }
                        t->bt_rdata.ulen = rp->re_len;
                }
                t->bt_rdata.size = rp->re_len;
                memset(t->bt_rdata.data, rp->re_pad, rp->re_len);
        } else
                t->bt_rdata.size = 0;

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

/*
 * __ram_source --
 *      Load information about the backing file.
 */
static int
__ram_source(dbp, rp, fname)
        DB *dbp;
        RECNO *rp;
        const char *fname;
{
        size_t size;
        u_int32_t bytes, mbytes, oflags;
        int ret;

        if ((ret = __db_appname(dbp->dbenv,
            DB_APP_DATA, NULL, fname, 0, NULL, &rp->re_source)) != 0)
                return (ret);

        oflags = F_ISSET(dbp, DB_AM_RDONLY) ? DB_RDONLY : 0;
        if ((ret =
            __db_open(rp->re_source, oflags, oflags, 0, &rp->re_fd)) != 0) {
                __db_err(dbp->dbenv, "%s: %s", rp->re_source, strerror(ret));
                goto err;
        }

        /*
         * XXX
         * 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 = __db_ioinfo(rp->re_source,
            rp->re_fd, &mbytes, &bytes, NULL)) != 0) {
                __db_err(dbp->dbenv, "%s: %s", rp->re_source, strerror(ret));
                goto err;
        }
        if (mbytes == 0 && bytes == 0) {
                F_SET(rp, RECNO_EOF);
                return (0);
        }

        size = mbytes * MEGABYTE + bytes;
        if ((ret = __db_mapfile(rp->re_source,
            rp->re_fd, (size_t)size, 1, &rp->re_smap)) != 0)
                goto err;
        rp->re_cmap = rp->re_smap;
        rp->re_emap = (u_int8_t *)rp->re_smap + (rp->re_msize = size);
        rp->re_irec = F_ISSET(dbp, DB_RE_FIXEDLEN) ?  __ram_fmap : __ram_vmap;
        return (0);

err:    FREES(rp->re_source)
        return (ret);
}

/*
 * __ram_writeback --
 *      Rewrite the backing file.
 */
static int
__ram_writeback(dbp)
        DB *dbp;
{
        RECNO *rp;
        DBT key, data;
        db_recno_t keyno;
        ssize_t nw;
        int fd, ret, t_ret;
        u_int8_t delim, *pad;

        rp = ((BTREE *)dbp->internal)->bt_recno;

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

        /* If there's no backing source file, we're done. */
        if (rp->re_source == NULL) {
                F_CLR(rp, RECNO_MODIFIED);
                return (0);
        }

        /*
         * Read any remaining records into the tree.
         *
         * XXX
         * 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(), or, since db_open() isn't transaction protected, as part
         * of the first DB operation.  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_snapshot(dbp)) != 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 (rp->re_smap != NULL) {
                (void)__db_unmapfile(rp->re_smap, rp->re_msize);
                rp->re_smap = NULL;
        }

        /* Get rid of any backing file descriptor, just on GP's. */
        if (rp->re_fd != -1) {
                (void)__db_close(rp->re_fd);
                rp->re_fd = -1;
        }

        /* Open the file, truncating it. */
        if ((ret = __db_open(rp->re_source,
            DB_SEQUENTIAL | DB_TRUNCATE,
            DB_SEQUENTIAL | DB_TRUNCATE, 0, &fd)) != 0) {
                __db_err(dbp->dbenv, "%s: %s", rp->re_source, strerror(ret));
                return (ret);
        }

        /*
         * 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 = rp->re_delim;
        if (F_ISSET(dbp, DB_RE_FIXEDLEN)) {
                if ((pad = (u_int8_t *)__db_malloc(rp->re_len)) == NULL) {
                        ret = ENOMEM;
                        goto err;
                }
                memset(pad, rp->re_pad, rp->re_len);
        } else
                COMPQUIET(pad, NULL);
        for (keyno = 1;; ++keyno) {
                switch (ret = dbp->get(dbp, NULL, &key, &data, 0)) {
                case 0:
                        if ((ret =
                            __db_write(fd, data.data, data.size, &nw)) != 0)
                                goto err;
                        if (nw != (ssize_t)data.size) {
                                ret = EIO;
                                goto err;
                        }
                        break;
                case DB_KEYEMPTY:
                        if (F_ISSET(dbp, DB_RE_FIXEDLEN)) {
                                if ((ret =
                                    __db_write(fd, pad, rp->re_len, &nw)) != 0)
                                        goto err;
                                if (nw != (ssize_t)rp->re_len) {
                                        ret = EIO;
                                        goto err;
                                }
                        }
                        break;
                case DB_NOTFOUND:
                        ret = 0;
                        goto done;
                }
                if (!F_ISSET(dbp, DB_RE_FIXEDLEN)) {
                        if ((ret = __db_write(fd, &delim, 1, &nw)) != 0)
                                goto err;
                        if (nw != 1) {
                                ret = EIO;
                                goto err;
                        }
                }
        }

err:
done:   /* Close the file descriptor. */
        if ((t_ret = __db_close(fd)) != 0 || ret == 0)
                ret = t_ret;

        if (ret == 0)
                F_CLR(rp, RECNO_MODIFIED);
        return (ret);
}

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

        if ((ret = __bam_nrecs(dbp, &recno)) != 0)
                return (ret);

        t = dbp->internal;
        rp = t->bt_recno;
        if (t->bt_rdata.ulen < rp->re_len) {
                t->bt_rdata.data = t->bt_rdata.data == NULL ?
                    (void *)__db_malloc(rp->re_len) :
                    (void *)__db_realloc(t->bt_rdata.data, rp->re_len);
                if (t->bt_rdata.data == NULL) {
                        t->bt_rdata.ulen = 0;
                        return (ENOMEM);
                }
                t->bt_rdata.ulen = rp->re_len;
        }

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

        sp = (u_int8_t *)rp->re_cmap;
        ep = (u_int8_t *)rp->re_emap;
        while (recno < top) {
                if (sp >= ep) {
                        F_SET(rp, RECNO_EOF);
                        return (DB_NOTFOUND);
                }
                len = rp->re_len;
                for (p = t->bt_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 (rp->re_last >= recno) {
                        if (len != 0)
                                memset(p, rp->re_pad, len);

                        ++recno;
                        if ((ret = __ram_add(dbp, &recno, &data, 0, 0)) != 0)
                                return (ret);
                }
                ++rp->re_last;
        }
        rp->re_cmap = sp;
        return (0);
}

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

        t = dbp->internal;
        rp = t->bt_recno;

        if ((ret = __bam_nrecs(dbp, &recno)) != 0)
                return (ret);

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

        delim = rp->re_delim;

        sp = (u_int8_t *)rp->re_cmap;
        ep = (u_int8_t *)rp->re_emap;
        while (recno < top) {
                if (sp >= ep) {
                        F_SET(rp, RECNO_EOF);
                        return (DB_NOTFOUND);
                }
                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 (rp->re_last >= recno) {
                        data.size = sp - (u_int8_t *)data.data;
                        ++recno;
                        if ((ret = __ram_add(dbp, &recno, &data, 0, 0)) != 0)
                                return (ret);
                }
                ++rp->re_last;
                ++sp;
        }
        rp->re_cmap = sp;
        return (0);
}

/*
 * __ram_add --
 *      Add records into the tree.
 */
static int
__ram_add(dbp, recnop, data, flags, bi_flags)
        DB *dbp;
        db_recno_t *recnop;
        DBT *data;
        u_int32_t flags, bi_flags;
{
        BKEYDATA *bk;
        BTREE *t;
        PAGE *h;
        db_indx_t indx;
        int exact, isdeleted, ret, stack;

        t = dbp->internal;

retry:  /* Find the slot for insertion. */
        if ((ret = __bam_rsearch(dbp, recnop,
            S_INSERT | (LF_ISSET(DB_APPEND) ? S_APPEND : 0), 1, &exact)) != 0)
                return (ret);
        h = t->bt_csp->page;
        indx = t->bt_csp->indx;
        stack = 1;

        /*
         * If DB_NOOVERWRITE is set and the item already exists in the tree,
         * return an error unless the item has been marked for deletion.
         */
        isdeleted = 0;
        if (exact) {
                bk = GET_BKEYDATA(h, indx);
                if (B_DISSET(bk->type)) {
                        isdeleted = 1;
                        __bam_ca_replace(dbp, h->pgno, indx, REPLACE_SETUP);
                } else
                        if (LF_ISSET(DB_NOOVERWRITE)) {
                                ret = DB_KEYEXIST;
                                goto err;
                        }
        }

        /*
         * Select the arguments for __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 = __bam_iitem(dbp,
            &h, &indx, NULL, data, exact ? DB_CURRENT : DB_BEFORE, bi_flags)) {
        case 0:
                /*
                 * Done.  Clean up the cursor and adjust the internal page
                 * counts.
                 */
                if (isdeleted)
                        __bam_ca_replace(dbp, h->pgno, indx, REPLACE_SUCCESS);
                break;
        case DB_NEEDSPLIT:
                /*
                 * We have to split the page.  Back out the cursor setup,
                 * discard the stack of pages, and do the split.
                 */
                if (isdeleted)
                        __bam_ca_replace(dbp, h->pgno, indx, REPLACE_FAILED);

                (void)__bam_stkrel(dbp);
                stack = 0;

                if ((ret = __bam_split(dbp, recnop)) != 0)
                        break;

                goto retry;
                /* NOTREACHED */
        default:
                if (isdeleted)
                        __bam_ca_replace(dbp, h->pgno, indx, REPLACE_FAILED);
                break;
        }

err:    if (stack)
                __bam_stkrel(dbp);

        return (ret);
}