impl/memory: Implement Queries

impl/memory/stringset.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 memory
+
+type stringSet map[string]struct{}
+
+func (s stringSet) has(value string) bool {
+        _, ret := s[value]
+        return ret
+}
+
+// add adds to the set and returns true iff the value was not there before (i.e.
+// it returns true if add actually modifies the stringSet).
+func (s stringSet) add(value string) bool {
+        ret := !s.has(value)
+        s[value] = struct{}{}
+        return ret
+}
+
+func (s stringSet) rm(value string) {
+        delete(s, value)
+}
+
+func (s stringSet) dup() stringSet {
+        ret := make(stringSet, len(s))
+        for v := range s {
+                ret.add(v)
+        }
+        return ret
+}
+
+func (s stringSet) getOne() string {
+        for k := range s {
+                return k
+        }
+        return ""
+}