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-rw-r--r--libdb/db_btree.c272
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diff --git a/libdb/db_btree.c b/libdb/db_btree.c
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+/*
+ * db_btree.c: low level btree interface routines for man.
+ *
+ * Copyright (C) 1994, 1995 Graeme W. Wilford. (Wilf.)
+ * Copyright (C) 2002 Colin Watson.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * Mon Aug 8 20:35:30 BST 1994 Wilf. (G.Wilford@ee.surrey.ac.uk)
+ */
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif /* HAVE_CONFIG_H */
+
+/* below this line are routines only useful for the BTREE interface */
+#ifdef BTREE
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+
+#include <sys/file.h> /* for flock() */
+#include <sys/types.h> /* for open() */
+#include <sys/stat.h>
+
+#if HAVE_FCNTL_H
+# include <fcntl.h>
+#endif
+
+#include <unistd.h>
+
+#include "stat-time.h"
+#include "timespec.h"
+
+#include "manconfig.h"
+
+#include "error.h"
+#include "hashtable.h"
+
+#include "mydbm.h"
+#include "db_storage.h"
+
+struct hashtable *loop_check_hash;
+
+/* the Berkeley database libraries do nothing to arbitrate between concurrent
+ database accesses, so we do a simple flock(). If the db is opened in
+ anything but O_RDONLY mode, an exclusive lock is enabled. Otherwise, the
+ lock is shared. A file cannot have both locks at once, and the non
+ blocking method is used ": Try again". This adopts GNU dbm's approach. */
+
+/* release the lock and close the database */
+int btree_close (DB *db)
+{
+ (void) flock ((db->fd) (db), LOCK_UN);
+ return (db->close) (db);
+}
+
+/* open a btree type database, with file locking. */
+DB *btree_flopen (char *filename, int flags, int mode)
+{
+ DB *db;
+ BTREEINFO b;
+ int lock_op;
+ int lock_failed;
+
+ b.flags = 0; /* do not allow any duplicate keys */
+
+ b.cachesize = 0; /* default size */
+ b.maxkeypage = 0; /* default */
+ b.minkeypage = 0; /* default */
+ b.psize = 0; /* default page size (2048?) */
+ b.compare = NULL; /* builtin compare() function */
+ b.prefix = NULL; /* builtin function */
+ b.lorder = 0; /* byte order of host */
+
+ if (flags & ~O_RDONLY) {
+ /* flags includes O_RDWR or O_WRONLY, need an exclusive lock */
+ lock_op = LOCK_EX | LOCK_NB;
+ } else {
+ lock_op = LOCK_SH | LOCK_NB;
+ }
+
+ if (!(flags & O_CREAT)) {
+ /* Berkeley DB thinks that a zero-length file means that
+ * somebody else is writing it, and sleeps for a few
+ * seconds to give the writer a chance. All very well, but
+ * the common case is that the database is just zero-length
+ * because mandb was interrupted or ran out of disk space or
+ * something like that - so we check for this case by hand
+ * and ignore the database if it's zero-length.
+ */
+ struct stat iszero;
+ if (stat (filename, &iszero) < 0)
+ return NULL;
+ if (iszero.st_size == 0) {
+ errno = EINVAL;
+ return NULL;
+ }
+ }
+
+ if (flags & O_TRUNC) {
+ /* opening the db is destructive, need to lock first */
+ int fd;
+
+ db = NULL;
+ lock_failed = 1;
+ fd = open (filename, flags & ~O_TRUNC, mode);
+ if (fd != -1) {
+ if (!(lock_failed = flock (fd, lock_op)))
+ db = dbopen (filename, flags, mode,
+ DB_BTREE, &b);
+ close (fd);
+ }
+ } else {
+ db = dbopen (filename, flags, mode, DB_BTREE, &b);
+ if (db)
+ lock_failed = flock ((db->fd) (db), lock_op);
+ }
+
+ if (!db)
+ return NULL;
+
+ if (lock_failed) {
+ gripe_lock (filename);
+ btree_close (db);
+ return NULL;
+ }
+
+ return db;
+}
+
+/* do a replace when we have the duplicate flag set on the database -
+ we must do a del and insert, as a direct insert will not wipe out the
+ old entry */
+int btree_replace (DB *db, datum key, datum cont)
+{
+ return (db->put) (db, (DBT *) &key, (DBT *) &cont, 0);
+}
+
+int btree_insert (DB *db, datum key, datum cont)
+{
+ return (db->put) (db, (DBT *) &key, (DBT *) &cont, R_NOOVERWRITE);
+}
+
+/* generic fetch routine for the btree database */
+datum btree_fetch (DB *db, datum key)
+{
+ datum data;
+
+ memset (&data, 0, sizeof data);
+
+ if ((db->get) (db, (DBT *) &key, (DBT *) &data, 0)) {
+ memset (&data, 0, sizeof data);
+ return data;
+ }
+
+ return copy_datum (data);
+}
+
+/* return 1 if the key exists, 0 otherwise */
+int btree_exists (DB *db, datum key)
+{
+ datum data;
+ return ((db->get) (db, (DBT *) &key, (DBT *) &data, 0) ? 0 : 1);
+}
+
+/* initiate a sequential access */
+static datum btree_findkey (DB *db, u_int flags)
+{
+ datum key, data;
+
+ memset (&key, 0, sizeof key);
+ memset (&data, 0, sizeof data);
+
+ if (flags == R_FIRST) {
+ if (loop_check_hash) {
+ hashtable_free (loop_check_hash);
+ loop_check_hash = NULL;
+ }
+ }
+ if (!loop_check_hash)
+ loop_check_hash = hashtable_create (&free);
+
+ if (((db->seq) (db, (DBT *) &key, (DBT *) &data, flags))) {
+ memset (&key, 0, sizeof key);
+ return key;
+ }
+
+ if (hashtable_lookup (loop_check_hash,
+ MYDBM_DPTR (key), MYDBM_DSIZE (key))) {
+ /* We've seen this key already, which is broken. Return NULL
+ * so the caller doesn't go round in circles.
+ */
+ debug ("Corrupt database! Already seen %*s. "
+ "Attempting to recover ...\n",
+ (int) MYDBM_DSIZE (key), MYDBM_DPTR (key));
+ memset (&key, 0, sizeof key);
+ return key;
+ }
+
+ hashtable_install (loop_check_hash,
+ MYDBM_DPTR (key), MYDBM_DSIZE (key), NULL);
+
+ return copy_datum (key);
+}
+
+/* return the first key in the db */
+datum btree_firstkey (DB *db)
+{
+ return btree_findkey (db, R_FIRST);
+}
+
+/* return the next key in the db. NB. This routine only works if the cursor
+ has been previously set by btree_firstkey() since it was last opened. So
+ if we close/reopen a db mid search, we have to manually set up the
+ cursor again. */
+datum btree_nextkey (DB *db)
+{
+ return btree_findkey (db, R_NEXT);
+}
+
+/* compound nextkey routine, initialising key and content */
+int btree_nextkeydata (DB *db, datum *key, datum *cont)
+{
+ int status;
+
+ if ((status = (db->seq) (db, (DBT *) key, (DBT *) cont, R_NEXT)) != 0)
+ return status;
+
+ *key = copy_datum (*key);
+ *cont = copy_datum (*cont);
+
+ return 0;
+}
+
+struct timespec btree_get_time (DB *db)
+{
+ struct stat st;
+
+ if (fstat ((db->fd) (db), &st) < 0) {
+ struct timespec t;
+ t.tv_sec = -1;
+ t.tv_nsec = -1;
+ return t;
+ }
+ return get_stat_mtime (&st);
+}
+
+void btree_set_time (DB *db, const struct timespec time)
+{
+ struct timespec times[2];
+
+ times[0] = time;
+ times[1] = time;
+ futimens ((db->fd) (db), times);
+}
+
+#endif /* BTREE */