create propeties.h

base/include/android-base/properties.h

@@ -0,0 +1,77 @@
+/*
+ * Copyright (C) 2016 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.
+ */
+
+#ifndef ANDROID_BASE_PROPERTIES_H
+#define ANDROID_BASE_PROPERTIES_H
+
+#include <sys/cdefs.h>
+
+#if !defined(__BIONIC__)
+#error Only bionic supports system properties.
+#endif
+
+#include <chrono>
+#include <limits>
+#include <string>
+
+namespace android {
+namespace base {
+
+// Returns the current value of the system property `key`,
+// or `default_value` if the property is empty or doesn't exist.
+std::string GetProperty(const std::string& key, const std::string& default_value);
+
+// Returns true if the system property `key` has the value "1", "y", "yes", "on", or "true",
+// false for "0", "n", "no", "off", or "false", or `default_value` otherwise.
+bool GetBoolProperty(const std::string& key, bool default_value);
+
+// Returns the signed integer corresponding to the system property `key`.
+// If the property is empty, doesn't exist, doesn't have an integer value, or is outside
+// the optional bounds, returns `default_value`.
+template <typename T> T GetIntProperty(const std::string& key,
+                                       T default_value,
+                                       T min = std::numeric_limits<T>::min(),
+                                       T max = std::numeric_limits<T>::max());
+
+// Returns the unsigned integer corresponding to the system property `key`.
+// If the property is empty, doesn't exist, doesn't have an integer value, or is outside
+// the optional bound, returns `default_value`.
+template <typename T> T GetUintProperty(const std::string& key,
+                                        T default_value,
+                                        T max = std::numeric_limits<T>::max());
+
+// Sets the system property `key` to `value`.
+// Note that system property setting is inherently asynchronous so a return value of `true`
+// isn't particularly meaningful, and immediately reading back the value won't necessarily
+// tell you whether or not your call succeeded. A `false` return value definitely means failure.
+bool SetProperty(const std::string& key, const std::string& value);
+
+// Waits for the system property `key` to have the value `expected_value`.
+// Times out after `relative_timeout`.
+// Returns true on success, false on timeout.
+bool WaitForProperty(const std::string& key, const std::string& expected_value,
+                     std::chrono::milliseconds relative_timeout = std::chrono::milliseconds::max());
+
+// Waits for the system property `key` to be created.
+// Times out after `relative_timeout`.
+// Returns true on success, false on timeout.
+bool WaitForPropertyCreation(const std::string& key, std::chrono::milliseconds relative_timeout =
+                                                         std::chrono::milliseconds::max());
+
+} // namespace base
+} // namespace android
+
+#endif // ANDROID_BASE_PROPERTIES_H