Add BoolFlag for rawdatastore.

service/rawdatastore/types.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package rawdatastore
 
+import (
+        "fmt"
+)
+
 // ByteString is a short byte slice (up to 1500 bytes) that can be indexed.
 type ByteString []byte
 
 // GeoPoint represents a location as latitude/longitude in degrees.
 //
 // You probably shouldn't use these, but their inclusion here is so that the
 // RawDatastore can interact (and round-trip) correctly with other datastore API
 // implementations.
 type GeoPoint struct {
         Lat, Lng float64
@@ skipping 13 matching lines @@
         // have the same behavior as single group transactions. In particular, it
         // is much more likely to see partially applied transactions in different
         // entity groups, in global queries.
         // It is valid to set XG to true even if the transaction is within a
         // single entity group.
         XG bool
         // Attempts controls the number of retries to perform when commits fail
         // due to a conflicting transaction. If omitted, it defaults to 3.
         Attempts int
 }
+
+// Toggle is a tri-state boolean (Auto/True/False), which allows structs
+// to control boolean flags for metadata in a non-ambiguous way.
+type Toggle byte
+
+// These are the allowed values for Toggle. Any other values are invalid.
+const (
+        Auto Toggle = iota
+        On
+        Off
+)
+
+func (b Toggle) String() string {
+        switch b {
+        case Auto:
+                return "Auto"
+        case On:
+                return "On"
+        case Off:
+                return "Off"
+        default:
+                return fmt.Sprintf("UNKNOWN_Toggle(%d)", b)
+        }
+}