Remove the hacky HashableDimensionKey.

+ Add a real HashableDimensionKey as a wrapper of the dimension.
So we can get rid of the maps that we kept.

Pay down technical debt and reduce memory usage.

Test: statsd_test & manual
Change-Id: I233280cf1e2ce93da6a8cd4e8514abb066f4016d
diff --git a/cmds/statsd/src/HashableDimensionKey.h b/cmds/statsd/src/HashableDimensionKey.h
new file mode 100644
index 0000000..85215552
--- /dev/null
+++ b/cmds/statsd/src/HashableDimensionKey.h
@@ -0,0 +1,102 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#pragma once
+
+#include <utils/JenkinsHash.h>
+#include "frameworks/base/cmds/statsd/src/stats_log.pb.h"
+
+namespace android {
+namespace os {
+namespace statsd {
+
+class HashableDimensionKey {
+public:
+    explicit HashableDimensionKey(const std::vector<KeyValuePair>& keyValuePairs)
+        : mKeyValuePairs(keyValuePairs){};
+
+    HashableDimensionKey(){};
+
+    HashableDimensionKey(const HashableDimensionKey& that)
+        : mKeyValuePairs(that.getKeyValuePairs()){};
+
+    HashableDimensionKey& operator=(const HashableDimensionKey& from) = default;
+
+    std::string toString() const;
+
+    inline const std::vector<KeyValuePair>& getKeyValuePairs() const {
+        return mKeyValuePairs;
+    }
+
+    bool operator==(const HashableDimensionKey& that) const;
+
+    bool operator<(const HashableDimensionKey& that) const;
+
+    inline const char* c_str() const {
+        return toString().c_str();
+    }
+
+private:
+    std::vector<KeyValuePair> mKeyValuePairs;
+};
+
+}  // namespace statsd
+}  // namespace os
+}  // namespace android
+
+namespace std {
+
+using android::os::statsd::HashableDimensionKey;
+using android::os::statsd::KeyValuePair;
+
+template <>
+struct hash<HashableDimensionKey> {
+    std::size_t operator()(const HashableDimensionKey& key) const {
+        android::hash_t hash = 0;
+        for (const auto& pair : key.getKeyValuePairs()) {
+            hash = android::JenkinsHashMix(hash, android::hash_type(pair.key()));
+            hash = android::JenkinsHashMix(
+                    hash, android::hash_type(static_cast<int32_t>(pair.value_case())));
+            switch (pair.value_case()) {
+                case KeyValuePair::ValueCase::kValueStr:
+                    hash = android::JenkinsHashMix(
+                            hash,
+                            static_cast<uint32_t>(std::hash<std::string>()(pair.value_str())));
+                    break;
+                case KeyValuePair::ValueCase::kValueInt:
+                    hash = android::JenkinsHashMix(hash, android::hash_type(pair.value_int()));
+                    break;
+                case KeyValuePair::ValueCase::kValueLong:
+                    hash = android::JenkinsHashMix(
+                            hash, android::hash_type(static_cast<int64_t>(pair.value_long())));
+                    break;
+                case KeyValuePair::ValueCase::kValueBool:
+                    hash = android::JenkinsHashMix(hash, android::hash_type(pair.value_bool()));
+                    break;
+                case KeyValuePair::ValueCase::kValueFloat: {
+                    float floatVal = pair.value_float();
+                    hash = android::JenkinsHashMixBytes(hash, (uint8_t*)&floatVal, sizeof(float));
+                    break;
+                }
+                case KeyValuePair::ValueCase::VALUE_NOT_SET:
+                    break;
+            }
+        }
+        return hash;
+    }
+};
+
+}  // namespace std