Step 3

apps/LoopThroughWithOpenGLCompositing/runtime/persistence/PersistenceWriter.h

@@ -2,10 +2,65 @@
 
 #include "PersistenceRequest.h"
 
+#include <chrono>
+#include <condition_variable>
+#include <cstdint>
+#include <deque>
+#include <functional>
+#include <mutex>
 #include <string>
+#include <thread>
+#include <unordered_map>
+
+struct PersistenceWriterMetrics
+{
+	std::size_t pendingCount = 0;
+	uint64_t enqueuedCount = 0;
+	uint64_t coalescedCount = 0;
+	uint64_t writtenCount = 0;
+	uint64_t failedCount = 0;
+};
 
 class PersistenceWriter
 {
 public:
+	using SnapshotSink = std::function<bool(const PersistenceSnapshot&, std::string&)>;
+
+	explicit PersistenceWriter(
+		std::chrono::milliseconds debounceDelay = std::chrono::milliseconds(50),
+		SnapshotSink sink = SnapshotSink());
+	~PersistenceWriter();
+
 	bool WriteSnapshot(const PersistenceSnapshot& snapshot, std::string& error) const;
+	bool EnqueueSnapshot(const PersistenceSnapshot& snapshot, std::string& error);
+	void StopAndFlush();
+	PersistenceWriterMetrics GetMetrics() const;
+
+private:
+	struct PendingSnapshot
+	{
+		PersistenceSnapshot snapshot;
+		std::chrono::steady_clock::time_point readyAt;
+	};
+
+	bool ValidateSnapshot(const PersistenceSnapshot& snapshot, std::string& error) const;
+	bool WriteSnapshotThroughSink(const PersistenceSnapshot& snapshot, std::string& error) const;
+	void StartWorkerLocked();
+	void WorkerMain();
+	std::size_t PendingCountLocked() const;
+
+	std::chrono::milliseconds mDebounceDelay;
+	SnapshotSink mSink;
+	mutable std::mutex mMutex;
+	std::condition_variable mCondition;
+	std::thread mWorker;
+	bool mWorkerRunning = false;
+	bool mStopping = false;
+	bool mAcceptingRequests = true;
+	std::unordered_map<std::string, PendingSnapshot> mDebouncedSnapshots;
+	std::deque<PersistenceSnapshot> mImmediateSnapshots;
+	uint64_t mEnqueuedCount = 0;
+	uint64_t mCoalescedCount = 0;
+	uint64_t mWrittenCount = 0;
+	uint64_t mFailedCount = 0;
 };