bt_open.c

Go to the documentation of this file.

/*-
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *  This product includes software developed by the University of
 *  California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
 
#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.
 */
 
#include <sys/param.h>
#include <sys/stat.h>
 
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
 
#include "../include/db.h"
#include "btree.h"
 
#ifdef DEBUG
#undef  MINPSIZE
#define MINPSIZE    128
#endif
 
static int byteorder __P((void));
static int nroot __P((BTREE *));
static int tmp __P((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 (fcntl(t->bt_fd, F_SETFD, 1) == -1)
        goto err;
 
    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 _STATBUF_ST_BLKSIZE
            b.psize = sb.st_blksize;
#endif
            if (b.psize < MINPSIZE)
                b.psize = MINPSIZE;
            if (b.psize > MAX_PAGE_OFFSET + 1)
                b.psize = MAX_PAGE_OFFSET + 1;
        }
 
        /* 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;
    const char *envtmp;
    char *path;
    static const char fmt[] = "%s/bt.XXXXXX";
    size_t n;
 
    envtmp = getenv("TMPDIR");
    if (!envtmp)
      envtmp = "/tmp";
    n = strlen (envtmp) + sizeof fmt;
#ifdef  __GNUC__
    path = __builtin_alloca(n);
#else
    path = malloc(n);
#endif
    (void)snprintf(path, n, fmt, envtmp ? envtmp : "/tmp");
 
    (void)sigfillset(&set);
    (void)sigprocmask(SIG_BLOCK, &set, &oset);
    if ((fd = mkstemp(path)) != -1)
        (void)unlink(path);
    (void)sigprocmask(SIG_SETMASK, &oset, NULL);
#ifndef __GNUC__
    free(path);
#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);
}