1 files changed, 115 insertions, 0 deletions
diff --git a/libartbase/base/flags.cc b/libartbase/base/flags.cc
new file mode 100644
index 0000000000..079694c835
--- /dev/null
+++ b/libartbase/base/flags.cc
@@ -0,0 +1,115 @@
+/*
+ * Copyright (C) 2021 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.
+ */
+
+#include "flags.h"
+
+#include <algorithm>
+
+#include "android-base/parsebool.h"
+#include "android-base/properties.h"
+
+#pragma clang diagnostic push
+#pragma clang diagnostic error "-Wconversion"
+
+namespace {
+constexpr const char* kServerConfigurableFlagsPrefix = "persist.device_config.runtime_native_boot.";
+constexpr const char* kUndefinedValue = "UNSET";
+
+// The various ParseValue functions store the parsed value into *destination. If parsing fails for
+// some reason, ParseValue makes no changes to *destination.
+
+void ParseValue(const std::string_view value, std::optional<bool>* destination) {
+  switch (::android::base::ParseBool(value)) {
+    case ::android::base::ParseBoolResult::kError:
+      return;
+    case ::android::base::ParseBoolResult::kTrue:
+      *destination = true;
+      return;
+    case ::android::base::ParseBoolResult::kFalse:
+      *destination = false;
+      return;
+  }
+}
+
+}  // namespace
+
+namespace art {
+
+template <>
+std::forward_list<FlagBase*> FlagBase::ALL_FLAGS{};
+
+// gFlags must be defined after FlagBase::ALL_FLAGS so the constructors run in the right order.
+Flags gFlags;
+
+template <typename Value>
+Flag<Value>::Flag(const std::string& name, Value default_value) : default_{default_value} {
+  command_line_argument_name_ = "-X" + name + "=_";
+  std::replace(command_line_argument_name_.begin(), command_line_argument_name_.end(), '.', '-');
+  system_property_name_ = "dalvik.vm." + name;
+
+  std::string server_setting = name;
+  std::replace(server_setting.begin(), server_setting.end(), '.', '_');
+  std::replace(server_setting.begin(), server_setting.end(), '-', '_');
+  server_setting_name_ = kServerConfigurableFlagsPrefix + server_setting;
+
+  ALL_FLAGS.push_front(this);
+}
+
+template <typename Value>
+Value Flag<Value>::operator()() {
+  if (!initialized_) {
+    Reload();
+  }
+  if (from_command_line_.has_value()) {
+    return from_command_line_.value();
+  }
+  if (from_server_setting_.has_value()) {
+    return from_server_setting_.value();
+  }
+  if (from_system_property_.has_value()) {
+    return from_system_property_.value();
+  }
+  return default_;
+}
+
+template <typename Value>
+void Flag<Value>::Reload() {
+  // Check system properties and server configured value.
+  from_system_property_ = std::nullopt;
+  const std::string sysprop = ::android::base::GetProperty(system_property_name_, kUndefinedValue);
+  if (sysprop != kUndefinedValue) {
+    ParseValue(sysprop, &from_system_property_);
+  }
+
+  // Check the server-side configuration
+  from_server_setting_ = std::nullopt;
+  // Read the device_config setting directly to avoid a dependency on server_configurable_flags.
+  const std::string server_config =
+      ::android::base::GetProperty(server_setting_name_, kUndefinedValue);
+  if (server_config != kUndefinedValue) {
+    ParseValue(server_config, &from_server_setting_);
+  }
+
+  // Command line argument cannot be reloaded. It must be set during initial command line parsing.
+
+  initialized_ = true;
+}
+
+template class Flag<bool>;
+
+}  // namespace art
+
+#pragma clang diagnostic pop  // -Wconversion