ovsdb-idl: Transition to better interfaces for reading table columns.

The existing ovsdb_idl_txn_read() was somewhat difficult and expensive to
use, because it always made a copy of the data in the column.  This was
necessary at the time it was introduced, because there was no way for it
to return a "default" value for columns that had not yet been populated
without allocating data and hence requiring the caller to free it.

Now that ovsdb_datum_default() exists, this is no longer required.  This
commit introduces a pair of new functions, ovsdb_idl_read() and
ovsdb_idl_get(), that return a pointer to existing data and do not do any
copying.  It also transitions all of ovsdb_idl_txn_read()'s callers to
the new interfaces.

1 files changed, 8 insertions, 3 deletions

diff --git a/lib/ovsdb-idl.h b/lib/ovsdb-idl.h
index 7832e4ee..c09ba9b0 100644
--- a/lib/ovsdb-idl.h
+++ b/lib/ovsdb-idl.h
@@ -33,6 +33,7 @@
 #include <stdbool.h>
 #include <stdint.h>
 #include "compiler.h"
+#include "ovsdb-types.h"
 
 struct json;
 struct ovsdb_datum;
@@ -59,6 +60,13 @@ const struct ovsdb_idl_row *ovsdb_idl_first_row(
     const struct ovsdb_idl *, const struct ovsdb_idl_table_class *);
 const struct ovsdb_idl_row *ovsdb_idl_next_row(const struct ovsdb_idl_row *);
 
+const struct ovsdb_datum *ovsdb_idl_read(const struct ovsdb_idl_row *,
+                                         const struct ovsdb_idl_column *);
+const struct ovsdb_datum *ovsdb_idl_get(const struct ovsdb_idl_row *,
+                                        const struct ovsdb_idl_column *,
+                                        enum ovsdb_atomic_type key_type,
+                                        enum ovsdb_atomic_type value_type);
+
 enum ovsdb_idl_txn_status {
     TXN_UNCHANGED,              /* Transaction didn't include any changes. */
     TXN_INCOMPLETE,             /* Commit in progress, please wait. */
@@ -90,9 +98,6 @@ int64_t ovsdb_idl_txn_get_increment_new_value(const struct ovsdb_idl_txn *);
 const struct uuid *ovsdb_idl_txn_get_insert_uuid(const struct ovsdb_idl_txn *,
                                                  const struct uuid *);
 
-void ovsdb_idl_txn_read(const struct ovsdb_idl_row *,
-                        const struct ovsdb_idl_column *,
-                        struct ovsdb_datum *);
 void ovsdb_idl_txn_write(const struct ovsdb_idl_row *,
                          const struct ovsdb_idl_column *,
                          struct ovsdb_datum *);