#include "tdb1_private.h"
-/* all contexts, to ensure no double-opens (fcntl locks don't nest!) */
-static struct tdb1_context *tdb1s = NULL;
-
/* We use two hashes to double-check they're using the right hash function. */
-void tdb1_header_hash(struct tdb1_context *tdb,
+void tdb1_header_hash(struct tdb_context *tdb,
uint32_t *magic1_hash, uint32_t *magic2_hash)
{
- TDB1_DATA hash_key;
uint32_t tdb1_magic = TDB1_MAGIC;
- hash_key.dptr = (unsigned char *)TDB1_MAGIC_FOOD;
- hash_key.dsize = sizeof(TDB1_MAGIC_FOOD);
- *magic1_hash = tdb->hash_fn(&hash_key);
-
- hash_key.dptr = (unsigned char *)TDB1_CONV(tdb1_magic);
- hash_key.dsize = sizeof(tdb1_magic);
- *magic2_hash = tdb->hash_fn(&hash_key);
+ *magic1_hash = tdb_hash(tdb, TDB_MAGIC_FOOD, sizeof(TDB_MAGIC_FOOD));
+ *magic2_hash = tdb_hash(tdb, TDB1_CONV(tdb1_magic), sizeof(tdb1_magic));
/* Make sure at least one hash is non-zero! */
if (*magic1_hash == 0 && *magic2_hash == 0)
}
/* initialise a new database with a specified hash size */
-static int tdb1_new_database(struct tdb1_context *tdb, int hash_size)
+static int tdb1_new_database(struct tdb_context *tdb, int hash_size)
{
struct tdb1_header *newdb;
size_t size;
/* We make it up in memory, then write it out if not internal */
size = sizeof(struct tdb1_header) + (hash_size+1)*sizeof(tdb1_off_t);
if (!(newdb = (struct tdb1_header *)calloc(size, 1))) {
- tdb->ecode = TDB1_ERR_OOM;
+ tdb->last_error = TDB_ERR_OOM;
return -1;
}
/* Make sure older tdbs (which don't check the magic hash fields)
* will refuse to open this TDB. */
- if (tdb->flags & TDB1_INCOMPATIBLE_HASH)
+ if (tdb->hash_fn == tdb1_incompatible_hash)
newdb->rwlocks = TDB1_HASH_RWLOCK_MAGIC;
- if (tdb->flags & TDB1_INTERNAL) {
- tdb->map_size = size;
- tdb->map_ptr = (char *)newdb;
- memcpy(&tdb->header, newdb, sizeof(tdb->header));
+ if (tdb->flags & TDB_INTERNAL) {
+ tdb->file->fd = -1;
+ tdb->file->map_size = size;
+ tdb->file->map_ptr = (char *)newdb;
+ memcpy(&tdb->tdb1.header, newdb, sizeof(tdb->tdb1.header));
/* Convert the `ondisk' version if asked. */
TDB1_CONV(*newdb);
return 0;
}
- if (lseek(tdb->fd, 0, SEEK_SET) == -1)
+ if (lseek(tdb->file->fd, 0, SEEK_SET) == -1)
goto fail;
- if (ftruncate(tdb->fd, 0) == -1)
+ if (ftruncate(tdb->file->fd, 0) == -1)
goto fail;
/* This creates an endian-converted header, as if read from disk */
TDB1_CONV(*newdb);
- memcpy(&tdb->header, newdb, sizeof(tdb->header));
+ memcpy(&tdb->tdb1.header, newdb, sizeof(tdb->tdb1.header));
/* Don't endian-convert the magic food! */
- memcpy(newdb->magic_food, TDB1_MAGIC_FOOD, strlen(TDB1_MAGIC_FOOD)+1);
+ memcpy(newdb->magic_food, TDB_MAGIC_FOOD, strlen(TDB_MAGIC_FOOD)+1);
/* we still have "ret == -1" here */
- if (tdb1_write_all(tdb->fd, newdb, size))
+ if (tdb1_write_all(tdb->file->fd, newdb, size))
ret = 0;
fail:
-static int tdb1_already_open(dev_t device,
- ino_t ino)
-{
- struct tdb1_context *i;
-
- for (i = tdb1s; i; i = i->next) {
- if (i->device == device && i->inode == ino) {
- return 1;
- }
- }
-
- return 0;
-}
-
/* open the database, creating it if necessary
The open_flags and mode are passed straight to the open call on the
try to call tdb1_error or tdb1_errname, just do strerror(errno).
@param name may be NULL for internal databases. */
-struct tdb1_context *tdb1_open(const char *name, int hash_size, int tdb1_flags,
+struct tdb_context *tdb1_open(const char *name, int hash_size, int tdb1_flags,
int open_flags, mode_t mode)
{
return tdb1_open_ex(name, hash_size, tdb1_flags, open_flags, mode, NULL, NULL);
}
-/* a default logging function */
-static void null_log_fn(struct tdb1_context *tdb, enum tdb1_debug_level level, const char *fmt, ...) PRINTF_ATTRIBUTE(3, 4);
-static void null_log_fn(struct tdb1_context *tdb, enum tdb1_debug_level level, const char *fmt, ...)
+static bool hash_correct(struct tdb_context *tdb,
+ uint32_t *m1, uint32_t *m2)
{
+ tdb1_header_hash(tdb, m1, m2);
+ return (tdb->tdb1.header.magic1_hash == *m1 &&
+ tdb->tdb1.header.magic2_hash == *m2);
}
-static bool check_header_hash(struct tdb1_context *tdb,
- bool default_hash, uint32_t *m1, uint32_t *m2)
+static bool check_header_hash(struct tdb_context *tdb,
+ uint32_t *m1, uint32_t *m2)
{
- tdb1_header_hash(tdb, m1, m2);
- if (tdb->header.magic1_hash == *m1 &&
- tdb->header.magic2_hash == *m2) {
+ if (hash_correct(tdb, m1, m2))
return true;
- }
-
- /* If they explicitly set a hash, always respect it. */
- if (!default_hash)
- return false;
- /* Otherwise, try the other inbuilt hash. */
+ /* If they use one inbuilt, try the other inbuilt hash. */
if (tdb->hash_fn == tdb1_old_hash)
- tdb->hash_fn = tdb1_jenkins_hash;
- else
+ tdb->hash_fn = tdb1_incompatible_hash;
+ else if (tdb->hash_fn == tdb1_incompatible_hash)
tdb->hash_fn = tdb1_old_hash;
- return check_header_hash(tdb, false, m1, m2);
+ else
+ return false;
+ return hash_correct(tdb, m1, m2);
}
-struct tdb1_context *tdb1_open_ex(const char *name, int hash_size, int tdb1_flags,
+struct tdb_context *tdb1_open_ex(const char *name, int hash_size, int tdb1_flags,
int open_flags, mode_t mode,
const struct tdb1_logging_context *log_ctx,
tdb1_hash_func hash_fn)
{
- struct tdb1_context *tdb;
+ struct tdb_context *tdb;
struct stat st;
- int rev = 0, locked = 0;
- unsigned char *vp;
- uint32_t vertest;
+ int rev = 0;
unsigned v;
const char *hash_alg;
uint32_t magic1, magic2;
- if (!(tdb = (struct tdb1_context *)calloc(1, sizeof *tdb))) {
+ if (!(tdb = (struct tdb_context *)calloc(1, sizeof *tdb))) {
/* Can't log this */
errno = ENOMEM;
goto fail;
}
+ tdb->file = calloc(1, sizeof *tdb->file);
+ if (!tdb->file) {
+ free(tdb);
+ errno = ENOMEM;
+ goto fail;
+ }
tdb1_io_init(tdb);
- tdb->fd = -1;
+ tdb->file->fd = -1;
tdb->name = NULL;
- tdb->map_ptr = NULL;
- tdb->flags = tdb1_flags;
+ tdb->file->map_ptr = NULL;
+ tdb->flags = tdb1_flags|TDB_VERSION1;
tdb->open_flags = open_flags;
+ tdb->lock_fn = tdb_fcntl_lock;
+ tdb->unlock_fn = tdb_fcntl_unlock;
if (log_ctx) {
- tdb->log = *log_ctx;
- } else {
- tdb->log.log_fn = null_log_fn;
- tdb->log.log_private = NULL;
- }
+ tdb->log_fn = log_ctx->log_fn;
+ tdb->log_data = log_ctx->log_private;
+ } else
+ tdb->log_fn = NULL;
- if (name == NULL && (tdb1_flags & TDB1_INTERNAL)) {
+ if (name == NULL && (tdb1_flags & TDB_INTERNAL)) {
name = "__TDB1_INTERNAL__";
}
if (name == NULL) {
tdb->name = (char *)"__NULL__";
- TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_open_ex: called with name == NULL\n"));
+ tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_USE_ERROR,
+ "tdb1_open_ex: called with name == NULL");
tdb->name = NULL;
errno = EINVAL;
goto fail;
* work in case of an error.
*/
tdb->name = (char *)name;
- TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_open_ex: can't strdup(%s)\n",
- name));
+ tdb_logerr(tdb, TDB_ERR_OOM, TDB_LOG_ERROR,
+ "tdb1_open_ex: can't strdup(%s)", name);
tdb->name = NULL;
errno = ENOMEM;
goto fail;
}
+ tdb->hash_seed = 0;
if (hash_fn) {
tdb->hash_fn = hash_fn;
- hash_alg = "the user defined";
+ if (hash_fn == tdb1_incompatible_hash)
+ hash_alg = "tdb1_incompatible_hash";
+ else
+ hash_alg = "the user defined";
} else {
- /* This controls what we use when creating a tdb. */
- if (tdb->flags & TDB1_INCOMPATIBLE_HASH) {
- tdb->hash_fn = tdb1_jenkins_hash;
- } else {
- tdb->hash_fn = tdb1_old_hash;
- }
- hash_alg = "either default";
+ tdb->hash_fn = tdb1_old_hash;
+ hash_alg = "default";
}
/* cache the page size */
- tdb->page_size = getpagesize();
- if (tdb->page_size <= 0) {
- tdb->page_size = 0x2000;
+ tdb->tdb1.page_size = getpagesize();
+ if (tdb->tdb1.page_size <= 0) {
+ tdb->tdb1.page_size = 0x2000;
}
- tdb->max_dead_records = (tdb1_flags & TDB1_VOLATILE) ? 5 : 0;
+ /* FIXME: Used to be 5 for TDB_VOLATILE. */
+ tdb->tdb1.max_dead_records = 0;
if ((open_flags & O_ACCMODE) == O_WRONLY) {
- TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_open_ex: can't open tdb %s write-only\n",
- name));
+ tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_USE_ERROR,
+ "tdb1_open_ex: can't open tdb %s write-only",
+ name);
errno = EINVAL;
goto fail;
}
if (hash_size == 0)
hash_size = TDB1_DEFAULT_HASH_SIZE;
if ((open_flags & O_ACCMODE) == O_RDONLY) {
- tdb->read_only = 1;
- /* read only databases don't do locking or clear if first */
- tdb->flags |= TDB1_NOLOCK;
- tdb->flags &= ~TDB1_CLEAR_IF_FIRST;
- }
-
- if ((tdb->flags & TDB1_ALLOW_NESTING) &&
- (tdb->flags & TDB1_DISALLOW_NESTING)) {
- tdb->ecode = TDB1_ERR_NESTING;
- TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_open_ex: "
- "allow_nesting and disallow_nesting are not allowed together!"));
- errno = EINVAL;
- goto fail;
- }
-
- if (getenv("TDB_NO_FSYNC")) {
- tdb->flags |= TDB1_NOSYNC;
- }
-
- /*
- * TDB1_ALLOW_NESTING is the default behavior.
- * Note: this may change in future versions!
- */
- if (!(tdb->flags & TDB1_DISALLOW_NESTING)) {
- tdb->flags |= TDB1_ALLOW_NESTING;
+ tdb->flags |= TDB_RDONLY;
+ /* read only databases don't do locking */
+ tdb->flags |= TDB_NOLOCK;
}
/* internal databases don't mmap or lock, and start off cleared */
- if (tdb->flags & TDB1_INTERNAL) {
- tdb->flags |= (TDB1_NOLOCK | TDB1_NOMMAP);
- tdb->flags &= ~TDB1_CLEAR_IF_FIRST;
+ if (tdb->flags & TDB_INTERNAL) {
+ tdb->flags |= (TDB_NOLOCK | TDB_NOMMAP);
if (tdb1_new_database(tdb, hash_size) != 0) {
- TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_open_ex: tdb1_new_database failed!"));
+ tdb_logerr(tdb, tdb->last_error, TDB_LOG_ERROR,
+ "tdb1_open_ex: tdb1_new_database failed!");
goto fail;
}
goto internal;
}
- if ((tdb->fd = open(name, open_flags, mode)) == -1) {
- TDB1_LOG((tdb, TDB1_DEBUG_WARNING, "tdb1_open_ex: could not open file %s: %s\n",
- name, strerror(errno)));
+ if ((tdb->file->fd = open(name, open_flags, mode)) == -1) {
+ tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
+ "tdb1_open_ex: could not open file %s: %s",
+ name, strerror(errno));
goto fail; /* errno set by open(2) */
}
/* on exec, don't inherit the fd */
- v = fcntl(tdb->fd, F_GETFD, 0);
- fcntl(tdb->fd, F_SETFD, v | FD_CLOEXEC);
+ v = fcntl(tdb->file->fd, F_GETFD, 0);
+ fcntl(tdb->file->fd, F_SETFD, v | FD_CLOEXEC);
/* ensure there is only one process initialising at once */
- if (tdb1_nest_lock(tdb, TDB1_OPEN_LOCK, F_WRLCK, TDB1_LOCK_WAIT) == -1) {
- TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_open_ex: failed to get open lock on %s: %s\n",
- name, strerror(errno)));
+ if (tdb1_nest_lock(tdb, TDB1_OPEN_LOCK, F_WRLCK, TDB_LOCK_WAIT) == -1) {
+ tdb_logerr(tdb, tdb->last_error, TDB_LOG_ERROR,
+ "tdb1_open_ex: failed to get open lock on %s: %s",
+ name, strerror(errno));
goto fail; /* errno set by tdb1_brlock */
}
- /* we need to zero database if we are the only one with it open */
- if ((tdb1_flags & TDB1_CLEAR_IF_FIRST) &&
- (!tdb->read_only) &&
- (locked = (tdb1_nest_lock(tdb, TDB1_ACTIVE_LOCK, F_WRLCK, TDB1_LOCK_NOWAIT|TDB1_LOCK_PROBE) == 0))) {
- open_flags |= O_CREAT;
- if (ftruncate(tdb->fd, 0) == -1) {
- TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_open_ex: "
- "failed to truncate %s: %s\n",
- name, strerror(errno)));
- goto fail; /* errno set by ftruncate */
- }
- }
-
errno = 0;
- if (read(tdb->fd, &tdb->header, sizeof(tdb->header)) != sizeof(tdb->header)
- || strcmp(tdb->header.magic_food, TDB1_MAGIC_FOOD) != 0) {
+ if (read(tdb->file->fd, &tdb->tdb1.header, sizeof(tdb->tdb1.header)) != sizeof(tdb->tdb1.header)
+ || strcmp(tdb->tdb1.header.magic_food, TDB_MAGIC_FOOD) != 0) {
if (!(open_flags & O_CREAT) || tdb1_new_database(tdb, hash_size) == -1) {
if (errno == 0) {
errno = EIO; /* ie bad format or something */
}
goto fail;
}
- rev = (tdb->flags & TDB1_CONVERT);
- } else if (tdb->header.version != TDB1_VERSION
- && !(rev = (tdb->header.version==TDB1_BYTEREV(TDB1_VERSION)))) {
+ rev = (tdb->flags & TDB_CONVERT);
+ } else if (tdb->tdb1.header.version != TDB1_VERSION
+ && !(rev = (tdb->tdb1.header.version==TDB1_BYTEREV(TDB1_VERSION)))) {
/* wrong version */
errno = EIO;
goto fail;
}
- vp = (unsigned char *)&tdb->header.version;
- vertest = (((uint32_t)vp[0]) << 24) | (((uint32_t)vp[1]) << 16) |
- (((uint32_t)vp[2]) << 8) | (uint32_t)vp[3];
- tdb->flags |= (vertest==TDB1_VERSION) ? TDB1_BIGENDIAN : 0;
if (!rev)
- tdb->flags &= ~TDB1_CONVERT;
+ tdb->flags &= ~TDB_CONVERT;
else {
- tdb->flags |= TDB1_CONVERT;
- tdb1_convert(&tdb->header, sizeof(tdb->header));
+ tdb->flags |= TDB_CONVERT;
+ tdb1_convert(&tdb->tdb1.header, sizeof(tdb->tdb1.header));
}
- if (fstat(tdb->fd, &st) == -1)
+ if (fstat(tdb->file->fd, &st) == -1)
goto fail;
- if (tdb->header.rwlocks != 0 &&
- tdb->header.rwlocks != TDB1_HASH_RWLOCK_MAGIC) {
- TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_open_ex: spinlocks no longer supported\n"));
+ if (tdb->tdb1.header.rwlocks != 0 &&
+ tdb->tdb1.header.rwlocks != TDB1_HASH_RWLOCK_MAGIC) {
+ tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
+ "tdb1_open_ex: spinlocks no longer supported");
goto fail;
}
- if ((tdb->header.magic1_hash == 0) && (tdb->header.magic2_hash == 0)) {
+ if ((tdb->tdb1.header.magic1_hash == 0) && (tdb->tdb1.header.magic2_hash == 0)) {
/* older TDB without magic hash references */
tdb->hash_fn = tdb1_old_hash;
- } else if (!check_header_hash(tdb, !hash_fn, &magic1, &magic2)) {
- TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_open_ex: "
- "%s was not created with %s hash function we are using\n"
- "magic1_hash[0x%08X %s 0x%08X] "
- "magic2_hash[0x%08X %s 0x%08X]\n",
- name, hash_alg,
- tdb->header.magic1_hash,
- (tdb->header.magic1_hash == magic1) ? "==" : "!=",
- magic1,
- tdb->header.magic2_hash,
- (tdb->header.magic2_hash == magic2) ? "==" : "!=",
- magic2));
+ } else if (!check_header_hash(tdb, &magic1, &magic2)) {
+ tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_USE_ERROR,
+ "tdb1_open_ex: "
+ "%s was not created with %s hash function we are using\n"
+ "magic1_hash[0x%08X %s 0x%08X] "
+ "magic2_hash[0x%08X %s 0x%08X]",
+ name, hash_alg,
+ tdb->tdb1.header.magic1_hash,
+ (tdb->tdb1.header.magic1_hash == magic1) ? "==" : "!=",
+ magic1,
+ tdb->tdb1.header.magic2_hash,
+ (tdb->tdb1.header.magic2_hash == magic2) ? "==" : "!=",
+ magic2);
errno = EINVAL;
goto fail;
}
- /* Is it already in the open list? If so, fail. */
- if (tdb1_already_open(st.st_dev, st.st_ino)) {
- TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_open_ex: "
- "%s (%d,%d) is already open in this process\n",
- name, (int)st.st_dev, (int)st.st_ino));
- errno = EBUSY;
- goto fail;
- }
-
- tdb->map_size = st.st_size;
- tdb->device = st.st_dev;
- tdb->inode = st.st_ino;
+ tdb->file->map_size = st.st_size;
+ tdb->file->device = st.st_dev;
+ tdb->file->inode = st.st_ino;
tdb1_mmap(tdb);
- if (locked) {
- if (tdb1_nest_unlock(tdb, TDB1_ACTIVE_LOCK, F_WRLCK, false) == -1) {
- TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_open_ex: "
- "failed to release ACTIVE_LOCK on %s: %s\n",
- name, strerror(errno)));
- goto fail;
- }
-
- }
-
- /* We always need to do this if the CLEAR_IF_FIRST flag is set, even if
- we didn't get the initial exclusive lock as we need to let all other
- users know we're using it. */
-
- if (tdb1_flags & TDB1_CLEAR_IF_FIRST) {
- /* leave this lock in place to indicate it's in use */
- if (tdb1_nest_lock(tdb, TDB1_ACTIVE_LOCK, F_RDLCK, TDB1_LOCK_WAIT) == -1) {
- goto fail;
- }
- }
/* if needed, run recovery */
if (tdb1_transaction_recover(tdb) == -1) {
/* Internal (memory-only) databases skip all the code above to
* do with disk files, and resume here by releasing their
* open lock and hooking into the active list. */
- if (tdb1_nest_unlock(tdb, TDB1_OPEN_LOCK, F_WRLCK, false) == -1) {
+ if (tdb1_nest_unlock(tdb, TDB1_OPEN_LOCK, F_WRLCK) == -1) {
goto fail;
}
- tdb->next = tdb1s;
- tdb1s = tdb;
return tdb;
fail:
if (!tdb)
return NULL;
- if (tdb->map_ptr) {
- if (tdb->flags & TDB1_INTERNAL)
- SAFE_FREE(tdb->map_ptr);
+ if (tdb->file->map_ptr) {
+ if (tdb->flags & TDB_INTERNAL)
+ SAFE_FREE(tdb->file->map_ptr);
else
tdb1_munmap(tdb);
}
- if (tdb->fd != -1)
- if (close(tdb->fd) != 0)
- TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_open_ex: failed to close tdb->fd on error!\n"));
- SAFE_FREE(tdb->lockrecs);
+ if (tdb->file->fd != -1)
+ if (close(tdb->file->fd) != 0)
+ tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
+ "tdb1_open_ex: failed to close tdb->fd on error!");
+ if (tdb->file) {
+ SAFE_FREE(tdb->file->lockrecs);
+ SAFE_FREE(tdb->file);
+ }
SAFE_FREE(tdb->name);
SAFE_FREE(tdb);
errno = save_errno;
* Set the maximum number of dead records per hash chain
*/
-void tdb1_set_max_dead(struct tdb1_context *tdb, int max_dead)
+void tdb1_set_max_dead(struct tdb_context *tdb, int max_dead)
{
- tdb->max_dead_records = max_dead;
+ tdb->tdb1.max_dead_records = max_dead;
}
/**
*
* @returns -1 for error; 0 for success.
**/
-int tdb1_close(struct tdb1_context *tdb)
+int tdb1_close(struct tdb_context *tdb)
{
- struct tdb1_context **i;
int ret = 0;
- if (tdb->transaction) {
+ if (tdb->tdb1.transaction) {
tdb1_transaction_cancel(tdb);
}
- if (tdb->map_ptr) {
- if (tdb->flags & TDB1_INTERNAL)
- SAFE_FREE(tdb->map_ptr);
+ if (tdb->file->map_ptr) {
+ if (tdb->flags & TDB_INTERNAL)
+ SAFE_FREE(tdb->file->map_ptr);
else
tdb1_munmap(tdb);
}
SAFE_FREE(tdb->name);
- if (tdb->fd != -1) {
- ret = close(tdb->fd);
- tdb->fd = -1;
- }
- SAFE_FREE(tdb->lockrecs);
-
- /* Remove from contexts list */
- for (i = &tdb1s; *i; i = &(*i)->next) {
- if (*i == tdb) {
- *i = tdb->next;
- break;
- }
+ if (tdb->file->fd != -1) {
+ ret = close(tdb->file->fd);
+ tdb->file->fd = -1;
}
+ SAFE_FREE(tdb->file->lockrecs);
+ SAFE_FREE(tdb->file);
memset(tdb, 0, sizeof(*tdb));
SAFE_FREE(tdb);
projects / ccan / blobdiff