## root/libdb/bt_open.c

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## DEFINITIONS

This source file includes following definitions.

1. __bt_open
2. nroot
3. tmp
4. byteorder
5. __bt_fd

    /*-
     * Copyright (c) 1990, 1993, 1994
     *      The Regents of the University of California.  All rights reserved.
     *
     * This code is derived from software contributed to Berkeley by
     * Mike Olson.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */

    #if defined(LIBC_SCCS) && !defined(lint)
    static char sccsid[] = "@(#)bt_open.c   8.10 (Berkeley) 8/17/94";
    #endif /* LIBC_SCCS and not lint */

    /*
     * Implementation of btree access method for 4.4BSD.
     *
     * The design here was originally based on that of the btree access method
     * used in the Postgres database system at UC Berkeley.  This implementation
     * is wholly independent of the Postgres code.
     */

    #ifdef HAVE_CONFIG_H
    #include <config.h>
    #endif
    #include <sys/stat.h>

    #include <errno.h>
    #include <fcntl.h>
    #ifdef HAVE_LIMITS_H
    #include <limits.h>
    #endif
    #include <signal.h>
    #include <stdio.h>
    #ifdef STDC_HEADERS
    #include <stdlib.h>
    #endif
    #ifdef HAVE_STRING_H
    #include <string.h>
    #else
    #include <strings.h>
    #endif
    #ifdef HAVE_UNISTD_H
    #include <unistd.h>
    #endif

    #if (defined(_WIN32) && !defined(__CYGWIN__))
    #define mkstemp(p) open(_mktemp(p), _O_CREAT | _O_SHORT_LIVED | _O_EXCL)
    #endif

    #include "db.h"
    #include "btree.h"

    #ifdef DEBUG
    #undef  MINPSIZE
    #define MINPSIZE        128
    #endif

    static int byteorder(void);
    static int nroot(BTREE *);
    static int tmp(void);

    /*
     * __BT_OPEN -- Open a btree.
     *
     * Creates and fills a DB struct, and calls the routine that actually
     * opens the btree.
     *
     * Parameters:
     *      fname:  filename (NULL for in-memory trees)
     *      flags:  open flag bits
     *      mode:   open permission bits
     *      b:      BTREEINFO pointer
     *
     * Returns:
     *      NULL on failure, pointer to DB on success.
     *
     */
    DB *
    __bt_open(fname, flags, mode, openinfo, dflags)
            const char *fname;
            int flags, mode, dflags;
            const BTREEINFO *openinfo;
    {
            struct stat sb;
            BTMETA m;
            BTREE *t;
            BTREEINFO b;
            DB *dbp;
            pgno_t ncache;
            ssize_t nr;
            int machine_lorder;

            t = NULL;

            /*
             * Intention is to make sure all of the user's selections are okay
             * here and then use them without checking.  Can't be complete, since
             * we don't know the right page size, lorder or flags until the backing
             * file is opened.  Also, the file's page size can cause the cachesize
             * to change.
             */
            machine_lorder = byteorder();
            if (openinfo) {
                    b = *openinfo;

                    /* Flags: R_DUP. */
                    if (b.flags & ~(R_DUP))
                            goto einval;

                    /*
                     * Page size must be indx_t aligned and >= MINPSIZE.  Default
                     * page size is set farther on, based on the underlying file
                     * transfer size.
                     */
                    if (b.psize &&
                        (b.psize < MINPSIZE || b.psize > MAX_PAGE_OFFSET + 1 ||
                        b.psize & (sizeof(indx_t) - 1)))
                            goto einval;

                    /* Minimum number of keys per page; absolute minimum is 2. */
                    if (b.minkeypage) {
                            if (b.minkeypage < 2)
                                    goto einval;
                    } else
                            b.minkeypage = DEFMINKEYPAGE;

                    /* If no comparison, use default comparison and prefix. */
                    if (b.compare == NULL) {
                            b.compare = __bt_defcmp;
                            if (b.prefix == NULL)
                                    b.prefix = __bt_defpfx;
                    }

                    if (b.lorder == 0)
                            b.lorder = machine_lorder;
            } else {
                    b.compare = __bt_defcmp;
                    b.cachesize = 0;
                    b.flags = 0;
                    b.lorder = machine_lorder;
                    b.minkeypage = DEFMINKEYPAGE;
                    b.prefix = __bt_defpfx;
                    b.psize = 0;
            }

            /* Check for the ubiquitous PDP-11. */
            if (b.lorder != BIG_ENDIAN && b.lorder != LITTLE_ENDIAN)
                    goto einval;

            /* Allocate and initialize DB and BTREE structures. */
            if ((t = (BTREE *)malloc(sizeof(BTREE))) == NULL)
                    goto err;
            memset(t, 0, sizeof(BTREE));
            t->bt_fd = -1;                  /* Don't close unopened fd on error. */
            t->bt_lorder = b.lorder;
            t->bt_order = NOT;
            t->bt_cmp = b.compare;
            t->bt_pfx = b.prefix;
            t->bt_rfd = -1;

            if ((t->bt_dbp = dbp = (DB *)malloc(sizeof(DB))) == NULL)
                    goto err;
            memset(t->bt_dbp, 0, sizeof(DB));
            if (t->bt_lorder != machine_lorder)
                    F_SET(t, B_NEEDSWAP);

            dbp->type = DB_BTREE;
            dbp->internal = t;
            dbp->close = __bt_close;
            dbp->del = __bt_delete;
            dbp->fd = __bt_fd;
            dbp->get = __bt_get;
            dbp->put = __bt_put;
            dbp->seq = __bt_seq;
            dbp->sync = __bt_sync;

            /*
             * If no file name was supplied, this is an in-memory btree and we
             * open a backing temporary file.  Otherwise, it's a disk-based tree.
             */
            if (fname) {
                    switch (flags & O_ACCMODE) {
                    case O_RDONLY:
                            F_SET(t, B_RDONLY);
                            break;
                    case O_RDWR:
                            break;
                    case O_WRONLY:
                    default:
                            goto einval;
                    }

                    if ((t->bt_fd = open(fname, flags, mode)) < 0)
                            goto err;

            } else {
                    if ((flags & O_ACCMODE) != O_RDWR)
                            goto einval;
                    if ((t->bt_fd = tmp()) == -1)
                            goto err;
                    F_SET(t, B_INMEM);
            }

    #if !defined(_WIN32) && !defined(__DJGPP__)
            if (fcntl(t->bt_fd, F_SETFD, 1) == -1)
                    goto err;
    #endif

            if (fstat(t->bt_fd, &sb))
                    goto err;
            if (sb.st_size) {
                    if ((nr = read(t->bt_fd, &m, sizeof(BTMETA))) < 0)
                            goto err;
                    if (nr != sizeof(BTMETA))
                            goto eftype;

                    /*
                     * Read in the meta-data.  This can change the notion of what
                     * the lorder, page size and flags are, and, when the page size
                     * changes, the cachesize value can change too.  If the user
                     * specified the wrong byte order for an existing database, we
                     * don't bother to return an error, we just clear the NEEDSWAP
                     * bit.
                     */
                    if (m.magic == BTREEMAGIC)
                            F_CLR(t, B_NEEDSWAP);
                    else {
                            F_SET(t, B_NEEDSWAP);
                            M_32_SWAP(m.magic);
                            M_32_SWAP(m.version);
                            M_32_SWAP(m.psize);
                            M_32_SWAP(m.free);
                            M_32_SWAP(m.nrecs);
                            M_32_SWAP(m.flags);
                    }
                    if (m.magic != BTREEMAGIC || m.version != BTREEVERSION)
                            goto eftype;
                    if (m.psize < MINPSIZE || m.psize > MAX_PAGE_OFFSET + 1 ||
                        m.psize & (sizeof(indx_t) - 1))
                            goto eftype;
                    if (m.flags & ~SAVEMETA)
                            goto eftype;
                    b.psize = m.psize;
                    F_SET(t, m.flags);
                    t->bt_free = m.free;
                    t->bt_nrecs = m.nrecs;
            } else {
                    /*
                     * Set the page size to the best value for I/O to this file.
                     * Don't overflow the page offset type.
                     */
                    if (b.psize == 0) {
    #ifdef HAVE_STRUCT_STAT_ST_BLKSIZE
                            b.psize = sb.st_blksize;
                            if (b.psize < MINPSIZE)
                                    b.psize = MINPSIZE;
                            if (b.psize > MAX_PAGE_OFFSET + 1)
                                    b.psize = MAX_PAGE_OFFSET + 1;
    #else
                            b.psize = MINPSIZE;
    #endif
                    }

                    /* Set flag if duplicates permitted. */
                    if (!(b.flags & R_DUP))
                            F_SET(t, B_NODUPS);

                    t->bt_free = P_INVALID;
                    t->bt_nrecs = 0;
                    F_SET(t, B_METADIRTY);
            }

            t->bt_psize = b.psize;

            /* Set the cache size; must be a multiple of the page size. */
            if (b.cachesize && b.cachesize & (b.psize - 1))
                    b.cachesize += (~b.cachesize & (b.psize - 1)) + 1;
            if (b.cachesize < b.psize * MINCACHE)
                    b.cachesize = b.psize * MINCACHE;

            /* Calculate number of pages to cache. */
            ncache = (b.cachesize + t->bt_psize - 1) / t->bt_psize;

            /*
             * The btree data structure requires that at least two keys can fit on
             * a page, but other than that there's no fixed requirement.  The user
             * specified a minimum number per page, and we translated that into the
             * number of bytes a key/data pair can use before being placed on an
             * overflow page.  This calculation includes the page header, the size
             * of the index referencing the leaf item and the size of the leaf item
             * structure.  Also, don't let the user specify a minkeypage such that
             * a key/data pair won't fit even if both key and data are on overflow
             * pages.
             */
            t->bt_ovflsize = (t->bt_psize - BTDATAOFF) / b.minkeypage -
                (sizeof(indx_t) + NBLEAFDBT(0, 0));
            if (t->bt_ovflsize < NBLEAFDBT(NOVFLSIZE, NOVFLSIZE) + sizeof(indx_t))
                    t->bt_ovflsize =
                        NBLEAFDBT(NOVFLSIZE, NOVFLSIZE) + sizeof(indx_t);

            /* Initialize the buffer pool. */
            if ((t->bt_mp =
                mpool_open(NULL, t->bt_fd, t->bt_psize, ncache)) == NULL)
                    goto err;
            if (!F_ISSET(t, B_INMEM))
                    mpool_filter(t->bt_mp, __bt_pgin, __bt_pgout, t);

            /* Create a root page if new tree. */
            if (nroot(t) == RET_ERROR)
                    goto err;

            /* Global flags. */
            if (dflags & DB_LOCK)
                    F_SET(t, B_DB_LOCK);
            if (dflags & DB_SHMEM)
                    F_SET(t, B_DB_SHMEM);
            if (dflags & DB_TXN)
                    F_SET(t, B_DB_TXN);

            return (dbp);

    einval: errno = EINVAL;
            goto err;

    eftype: errno = EFTYPE;
            goto err;

    err:    if (t) {
                    if (t->bt_dbp)
                            free(t->bt_dbp);
                    if (t->bt_fd != -1)
                            (void)close(t->bt_fd);
                    free(t);
            }
            return (NULL);
    }

    /*
     * NROOT -- Create the root of a new tree.
     *
     * Parameters:
     *      t:      tree
     *
     * Returns:
     *      RET_ERROR, RET_SUCCESS
     */
    static int
    nroot(t)
            BTREE *t;
    {
            PAGE *meta, *root;
            pgno_t npg;

            if ((meta = mpool_get(t->bt_mp, 0, 0)) != NULL) {
                    mpool_put(t->bt_mp, meta, 0);
                    return (RET_SUCCESS);
            }
            if (errno != EINVAL)            /* It's OK to not exist. */
                    return (RET_ERROR);
            errno = 0;

            if ((meta = mpool_new(t->bt_mp, &npg)) == NULL)
                    return (RET_ERROR);

            if ((root = mpool_new(t->bt_mp, &npg)) == NULL)
                    return (RET_ERROR);

            if (npg != P_ROOT)
                    return (RET_ERROR);
            root->pgno = npg;
            root->prevpg = root->nextpg = P_INVALID;
            root->lower = BTDATAOFF;
            root->upper = t->bt_psize;
            root->flags = P_BLEAF;
            memset(meta, 0, t->bt_psize);
            mpool_put(t->bt_mp, meta, MPOOL_DIRTY);
            mpool_put(t->bt_mp, root, MPOOL_DIRTY);
            return (RET_SUCCESS);
    }

    static int
    tmp()
    {
            sigset_t set, oset;
            int fd;
            char *envtmp;
            char path[1024];

            envtmp = getenv("TMPDIR");
    #ifdef _WIN32
            if (envtmp == NULL)
                    envtmp = getenv("TMP");
    #endif
            if (envtmp && strlen(envtmp) + strlen("/bt.XXXXXX") >= sizeof(path))
                    return -1;
            (void)snprintf(path, sizeof(path),
                                    "%s/bt.XXXXXX", envtmp ? envtmp : "/tmp");

    #ifndef _WIN32
            (void)sigfillset(&set);
            (void)sigprocmask(SIG_BLOCK, &set, &oset);
    #endif
            if ((fd = mkstemp(path)) != -1)
                    (void)unlink(path);
    #ifndef _WIN32
            (void)sigprocmask(SIG_SETMASK, &oset, NULL);
    #endif
            return(fd);
    }

    static int
    byteorder()
    {
            u_int32_t x;
            u_char *p;

            x = 0x01020304;
            p = (u_char *)&x;
            switch (*p) {
            case 1:
                    return (BIG_ENDIAN);
            case 4:
                    return (LITTLE_ENDIAN);
            default:
                    return (0);
            }
    }

    int
    __bt_fd(dbp)
            const DB *dbp;
    {
            BTREE *t;

            t = dbp->internal;

            /* Toss any page pinned across calls. */
            if (t->bt_pinned != NULL) {
                    mpool_put(t->bt_mp, t->bt_pinned, 0);
                    t->bt_pinned = NULL;
            }

            /* In-memory database can't have a file descriptor. */
            if (F_ISSET(t, B_INMEM)) {
                    errno = ENOENT;
                    return (-1);
            }
            return (t->bt_fd);
    }

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