tdb2: tdb_set_attribute, tdb_unset_attribute and tdb_get_attribute

[ccan] / ccan / tdb2 / tdb2.h

diff --git a/ccan/tdb2/tdb2.h b/ccan/tdb2/tdb2.h
index 47ec3041b85723b49e45c8b10458ee57c1f8cacc..296410e74196573a955470b78c422daa870f8be5 100644 (file)
--- a/ccan/tdb2/tdb2.h
+++ b/ccan/tdb2/tdb2.h
@@ -288,6 +288,9 @@ enum TDB_ERROR tdb_transaction_commit(struct tdb_context *tdb);
  * tdb_transaction_commit): if this succeeds then a transaction will only
  * fail if the write() or fsync() calls fail.
  *
+ * If this fails you must still call tdb_transaction_cancel() to cancel
+ * the transaction.
+ *
  * See Also:
  *     tdb_transaction_commit()
  */
@@ -579,6 +582,61 @@ void tdb_add_flag(struct tdb_context *tdb, unsigned flag);
  */
 void tdb_remove_flag(struct tdb_context *tdb, unsigned flag);
 
+/**
+ * enum tdb_attribute_type - descriminator for union tdb_attribute.
+ */
+enum tdb_attribute_type {
+       TDB_ATTRIBUTE_LOG = 0,
+       TDB_ATTRIBUTE_HASH = 1,
+       TDB_ATTRIBUTE_SEED = 2,
+       TDB_ATTRIBUTE_STATS = 3,
+       TDB_ATTRIBUTE_OPENHOOK = 4,
+       TDB_ATTRIBUTE_FLOCK = 5
+};
+
+/**
+ * tdb_get_attribute - get an attribute for an existing tdb
+ * @tdb: the tdb context returned from tdb_open()
+ * @attr: the union tdb_attribute to set.
+ *
+ * This gets an attribute from a TDB which has previously been set (or
+ * may return the default values).  Set @attr.base.attr to the
+ * attribute type you want get.
+ *
+ * Currently this does not work for TDB_ATTRIBUTE_OPENHOOK.
+ */
+enum TDB_ERROR tdb_get_attribute(struct tdb_context *tdb,
+                                union tdb_attribute *attr);
+
+/**
+ * tdb_set_attribute - set an attribute for an existing tdb
+ * @tdb: the tdb context returned from tdb_open()
+ * @attr: the union tdb_attribute to set.
+ *
+ * This sets an attribute on a TDB, overriding any previous attribute
+ * of the same type.  It returns TDB_ERR_EINVAL if the attribute is
+ * unknown or invalid.
+ *
+ * Note that TDB_ATTRIBUTE_HASH, TDB_ATTRIBUTE_SEED and
+ * TDB_ATTRIBUTE_OPENHOOK cannot currently be set after tdb_open.
+ */
+enum TDB_ERROR tdb_set_attribute(struct tdb_context *tdb,
+                                const union tdb_attribute *attr);
+
+/**
+ * tdb_unset_attribute - reset an attribute for an existing tdb
+ * @tdb: the tdb context returned from tdb_open()
+ * @type: the attribute type to unset.
+ *
+ * This unsets an attribute on a TDB, returning it to the defaults
+ * (where applicable).
+ *
+ * Note that it only makes sense for TDB_ATTRIBUTE_LOG and TDB_ATTRIBUTE_FLOCK
+ * to be unset.
+ */
+void tdb_unset_attribute(struct tdb_context *tdb,
+                        enum tdb_attribute_type type);
+
 /**
  * tdb_name - get the name of a tdb
  * @tdb: the tdb context returned from tdb_open()
@@ -599,16 +657,6 @@ const char *tdb_name(const struct tdb_context *tdb);
  */
 int tdb_fd(const struct tdb_context *tdb);
 
-/**
- * enum tdb_attribute_type - descriminator for union tdb_attribute.
- */
-enum tdb_attribute_type {
-       TDB_ATTRIBUTE_LOG = 0,
-       TDB_ATTRIBUTE_HASH = 1,
-       TDB_ATTRIBUTE_SEED = 2,
-       TDB_ATTRIBUTE_STATS = 3
-};
-
 /**
  * struct tdb_attribute_base - common fields for all tdb attributes.
  */
@@ -642,8 +690,8 @@ struct tdb_attribute_log {
        struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_LOG */
        void (*fn)(struct tdb_context *tdb,
                   enum tdb_log_level level,
-                  void *data,
-                  const char *message);
+                  const char *message,
+                  void *data);
        void *data;
 };
 
@@ -716,6 +764,41 @@ struct tdb_attribute_stats {
        uint64_t    lock_nonblock;
 };
 
+/**
+ * struct tdb_attribute_openhook - tdb special effects hook for open
+ *
+ * This attribute contains a function to call once we have the OPEN_LOCK
+ * for the tdb, but before we've examined its contents.  If this succeeds,
+ * the tdb will be populated if it's then zero-length.
+ *
+ * This is a hack to allow support for TDB1-style TDB_CLEAR_IF_FIRST
+ * behaviour.
+ */
+struct tdb_attribute_openhook {
+       struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_OPENHOOK */
+       enum TDB_ERROR (*fn)(int fd, void *data);
+       void *data;
+};
+
+/**
+ * struct tdb_attribute_flock - tdb special effects hook for file locking
+ *
+ * This attribute contains function to call to place locks on a file; it can
+ * be used to support non-blocking operations or lock proxying.
+ *
+ * They should return 0 on success, -1 on failure and set errno.
+ *
+ * An error will be logged on error if errno is neither EAGAIN nor EINTR
+ * (normally it would only return EAGAIN if waitflag is false, and
+ * loop internally on EINTR).
+ */
+struct tdb_attribute_flock {
+       struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_FLOCK */
+       int (*lock)(int fd,int rw, off_t off, off_t len, bool waitflag, void *);
+       int (*unlock)(int fd, int rw, off_t off, off_t len, void *);
+       void *data;
+};
+
 /**
  * union tdb_attribute - tdb attributes.
  *
@@ -723,7 +806,8 @@ struct tdb_attribute_stats {
  *
  * See also:
  *     struct tdb_attribute_log, struct tdb_attribute_hash,
- *     struct tdb_attribute_seed, struct tdb_attribute_stats.
+ *     struct tdb_attribute_seed, struct tdb_attribute_stats,
+ *     struct tdb_attribute_openhook, struct tdb_attribute_flock.
  */
 union tdb_attribute {
        struct tdb_attribute_base base;
@@ -731,6 +815,8 @@ union tdb_attribute {
        struct tdb_attribute_hash hash;
        struct tdb_attribute_seed seed;
        struct tdb_attribute_stats stats;
+       struct tdb_attribute_openhook openhook;
+       struct tdb_attribute_flock flock;
 };
 
 #ifdef  __cplusplus