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bt_open.c

/*-
 * 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/types.h>        /* XXX: param.h may not have included types.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 <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;
      int nr, 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 HAVE_ST_BLKSIZE
                  b.psize = sb.st_blksize;
#else
                  b.psize = 4 * 1024;
#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;
      char *envtmp;
      char path[MAXPATHLEN];

      envtmp = getenv("TMPDIR");
      (void)snprintf(path,
          sizeof(path), "%s/bt.XXXXXX", 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);
      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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