X-Git-Url: http://git.ozlabs.org/?a=blobdiff_plain;f=ccan%2Ftdb2%2Ftdb2.h;h=0940be1ceac40797435eaaa6241cbdd0e787484f;hb=8d8de08d9079f503256e1682dfa93bb22dcd4ad0;hp=50903a7641bfcc409c2c26d7d74a0a1c40210d60;hpb=a97da100b00206544c7a68593b64a49f2b854f7e;p=ccan

diff --git a/ccan/tdb2/tdb2.h b/ccan/tdb2/tdb2.h
index 50903a76..0940be1c 100644
--- a/ccan/tdb2/tdb2.h
+++ b/ccan/tdb2/tdb2.h
@@ -40,6 +40,8 @@ extern "C" {
 #include <stdint.h>
 /* For bool */
 #include <stdbool.h>
+/* For memcmp */
+#include <string.h>
 #endif
 #include <ccan/compiler/compiler.h>
 #include <ccan/typesafe_cb/typesafe_cb.h>
@@ -76,6 +78,7 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 #define TDB_NOMMAP   8 /* don't use mmap */
 #define TDB_CONVERT 16 /* convert endian */
 #define TDB_NOSYNC   64 /* don't use synchronous transactions */
+#define TDB_SEQNUM   128 /* maintain a sequence number */
 
 /**
  * tdb_close - close and free a tdb.
@@ -208,6 +211,16 @@ enum TDB_ERROR tdb_delete(struct tdb_context *tdb, struct tdb_data key);
  */
 bool tdb_exists(struct tdb_context *tdb, TDB_DATA key);
 
+/**
+ * tdb_deq - are struct tdb_data equal?
+ * @a: one struct tdb_data
+ * @b: another struct tdb_data
+ */
+static inline bool tdb_deq(struct tdb_data a, struct tdb_data b)
+{
+	return a.dsize == b.dsize && memcmp(a.dptr, b.dptr, a.dsize) == 0;
+}
+
 /**
  * tdb_transaction_start - start a transaction
  * @tdb: the tdb context returned from tdb_open()
@@ -311,6 +324,25 @@ enum TDB_ERROR tdb_parse_record_(struct tdb_context *tdb,
 							 TDB_DATA data,
 							 void *p),
 				 void *p);
+
+/**
+ * tdb_get_seqnum - get a database sequence number
+ * @tdb: the tdb context returned from tdb_open()
+ *
+ * This returns a sequence number: any change to the database from a
+ * tdb context opened with the TDB_SEQNUM flag will cause that number
+ * to increment.  Note that the incrementing is unreliable (it is done
+ * without locking), so this is only useful as an optimization.
+ *
+ * For example, you may have a regular database backup routine which
+ * does not operate if the sequence number is unchanged.  In the
+ * unlikely event of a failed increment, it will be backed up next
+ * time any way.
+ *
+ * Returns an enum TDB_ERROR (ie. negative) on error.
+ */
+int64_t tdb_get_seqnum(struct tdb_context *tdb);
+
 /**
  * tdb_firstkey - get the "first" key in a TDB
  * @tdb: the tdb context returned from tdb_open()
@@ -454,6 +486,26 @@ void tdb_add_flag(struct tdb_context *tdb, unsigned flag);
  */
 void tdb_remove_flag(struct tdb_context *tdb, unsigned flag);
 
+/**
+ * tdb_name - get the name of a tdb
+ * @tdb: the tdb context returned from tdb_open()
+ *
+ * This returns a copy of the name string, made at tdb_open() time.  If that
+ * argument was NULL (possible for a TDB_INTERNAL db) this will return NULL.
+ *
+ * This is mostly useful for logging.
+ */
+const char *tdb_name(const struct tdb_context *tdb);
+
+/**
+ * tdb_fd - get the file descriptor of a tdb
+ * @tdb: the tdb context returned from tdb_open()
+ *
+ * This returns the file descriptor for the underlying database file, or -1
+ * for TDB_INTERNAL.
+ */
+int tdb_fd(const struct tdb_context *tdb);
+
 /**
  * enum tdb_attribute_type - descriminator for union tdb_attribute.
  */
@@ -588,11 +640,6 @@ union tdb_attribute {
 	struct tdb_attribute_stats stats;
 };
 
-/**
- * tdb_null - a convenient value for errors.
- */
-extern struct tdb_data tdb_null;
-
 #ifdef  __cplusplus
 }
 #endif