Add simple lru cache into utils. (envoyproxy#8)

* Add simple lru cache into utils.

* Format files.

mixerclient/BUILD

@@ -33,6 +33,16 @@ cc_library(
  ],
 )
 
+cc_library(
+    name = "simple_lru_cache",
+    srcs = ["utils/google_macros.h"],
+    hdrs = [
+        "utils/simple_lru_cache.h",
+        "utils/simple_lru_cache_inl.h",
+    ],
+    visibility = ["//visibility:public"],
+)
+
 cc_test(
     name = "mixer_client_impl_test",
     size = "small",
@@ -43,3 +53,17 @@ cc_test(
         "//external:googletest_main",
     ],
 )
+
+cc_test(
+    name = "simple_lru_cache_test",
+    size = "small",
+    srcs = ["utils/simple_lru_cache_test.cc"],
+    linkopts = [
+        "-lm",
+        "-lpthread",
+    ],
+    deps = [
+        ":simple_lru_cache",
+        "//external:googletest_main",
+    ],
+)

mixerclient/utils/google_macros.h

@@ -0,0 +1,24 @@
+/* Copyright 2017 Google Inc. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef MIXERCLIENT_UTILS_GOOGLE_MACROS_H_
+#define MIXERCLIENT_UTILS_GOOGLE_MACROS_H_
+
+#undef GOOGLE_DISALLOW_EVIL_CONSTRUCTORS
+#define GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(TypeName) \
+  TypeName(const TypeName&);                        \
+  void operator=(const TypeName&)
+
+#endif  // MIXERCLIENT_UTILS_GOOGLE_MACROS_H_

mixerclient/utils/simple_lru_cache.h

@@ -0,0 +1,50 @@
+/* Copyright 2017 Google Inc. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// For inclusion in .h files.  The real class definition is in
+// simple_lru_cache_inl.h.
+
+#ifndef MIXERCLIENT_UTILS_SIMPLE_LRU_CACHE_H_
+#define MIXERCLIENT_UTILS_SIMPLE_LRU_CACHE_H_
+
+#include <functional>
+#include <unordered_map>  // for hash<>
+
+namespace istio {
+namespace mixer_client {
+
+namespace internal {
+template <typename T>
+struct SimpleLRUHash : public std::hash<T> {};
+}  // namespace internal
+
+template <typename Key, typename Value,
+          typename H = internal::SimpleLRUHash<Key>,
+          typename EQ = std::equal_to<Key> >
+class SimpleLRUCache;
+
+// Deleter is a functor that defines how to delete a Value*. That is, it
+// contains a public method:
+//  operator() (Value* value)
+// See example in the associated unittest.
+template <typename Key, typename Value, typename Deleter,
+          typename H = internal::SimpleLRUHash<Key>,
+          typename EQ = std::equal_to<Key> >
+class SimpleLRUCacheWithDeleter;
+
+}  // namespace mixer_client
+}  // namespace istio
+
+#endif  // MIXERCLIENT_UTILS_SIMPLE_LRU_CACHE_H_