bt_open.c

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/*-
 * 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);
}