Merge "Implement android::base::WaitForProperty." am: 01003d40fc (1f6d1c43) · Commits · e / os / android_system_core

base/include/android-base/properties.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -58,6 +58,9 @@ template <typename T> T GetUintProperty(const std::string& key,
		// 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`, .
		void WaitForProperty(const std::string& key, const std::string& expected_value);

		} // namespace base
		} // namespace android

base/properties.cpp

+41 −0

Original line number	Diff line number	Diff line
		@@ -14,9 +14,12 @@
		* limitations under the License.
		*/

		#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_

		#include "android-base/properties.h"

		#include <sys/system_properties.h>
		#include <sys/_system_properties.h>

		#include <string>

		@@ -78,5 +81,43 @@ bool SetProperty(const std::string& key, const std::string& value) {
		return (__system_property_set(key.c_str(), value.c_str()) == 0);
		}

		struct WaitForPropertyData {
		bool done;
		const std::string* expected_value;
		unsigned last_read_serial;
		};

		static void WaitForPropertyCallback(void* data_ptr, const char, const char value, unsigned serial) {
		WaitForPropertyData* data = reinterpret_cast<WaitForPropertyData*>(data_ptr);
		if (*data->expected_value == value) {
		data->done = true;
		} else {
		data->last_read_serial = serial;
		}
		}

		void WaitForProperty(const std::string& key, const std::string& expected_value) {
		// Find the property's prop_info*.
		const prop_info* pi;
		unsigned global_serial = 0;
		while ((pi = __system_property_find(key.c_str())) == nullptr) {
		// The property doesn't even exist yet.
		// Wait for a global change and then look again.
		global_serial = __system_property_wait_any(global_serial);
		}

		WaitForPropertyData data;
		data.expected_value = &expected_value;
		data.done = false;
		while (true) {
		// Check whether the property has the value we're looking for?
		__system_property_read_callback(pi, WaitForPropertyCallback, &data);
		if (data.done) return;

		// It didn't so wait for it to change before checking again.
		__system_property_wait(pi, data.last_read_serial);
		}
		}

		} // namespace base
		} // namespace android

base/properties_test.cpp

+20 −0

Original line number	Diff line number	Diff line
		@@ -18,7 +18,12 @@

		#include <gtest/gtest.h>

		#include <atomic>
		#include <chrono>
		#include <string>
		#include <thread>

		using namespace std::chrono_literals;

		TEST(properties, smoke) {
		android::base::SetProperty("debug.libbase.property_test", "hello");
		@@ -119,3 +124,18 @@ TEST(properties, GetUintProperty_uint8_t) { CheckGetUintProperty<uint8_t>(); }
		TEST(properties, GetUintProperty_uint16_t) { CheckGetUintProperty<uint16_t>(); }
		TEST(properties, GetUintProperty_uint32_t) { CheckGetUintProperty<uint32_t>(); }
		TEST(properties, GetUintProperty_uint64_t) { CheckGetUintProperty<uint64_t>(); }

		TEST(properties, WaitForProperty) {
		std::atomic<bool> flag{false};
		std::thread thread([&]() {
		std::this_thread::sleep_for(100ms);
		android::base::SetProperty("debug.libbase.WaitForProperty_test", "a");
		while (!flag) std::this_thread::yield();
		android::base::SetProperty("debug.libbase.WaitForProperty_test", "b");
		});

		android::base::WaitForProperty("debug.libbase.WaitForProperty_test", "a");
		flag = true;
		android::base::WaitForProperty("debug.libbase.WaitForProperty_test", "b");
		thread.join();
		}

libcutils/properties.cpp

+1 −1

Original line number	Diff line number	Diff line
		@@ -129,7 +129,7 @@ struct callback_data {
		void* cookie;
		};

		static void trampoline(void* raw_data, const char* name, const char* value) {
		static void trampoline(void* raw_data, const char* name, const char* value, unsigned /serial/) {
		callback_data* data = reinterpret_cast<callback_data*>(raw_data);
		data->callback(name, value, data->cookie);
		}