V2 working

apps/RenderCadenceCompositor/render/PboReadbackRing.h

@@ -0,0 +1,52 @@
+#pragma once
+
+#include "GLExtensions.h"
+
+#include <cstddef>
+#include <cstdint>
+#include <vector>
+
+class PboReadbackRing
+{
+public:
+	struct CompletedReadback
+	{
+		GLuint pbo = 0;
+		uint64_t frameIndex = 0;
+		std::size_t byteCount = 0;
+	};
+
+	PboReadbackRing() = default;
+	PboReadbackRing(const PboReadbackRing&) = delete;
+	PboReadbackRing& operator=(const PboReadbackRing&) = delete;
+	~PboReadbackRing();
+
+	bool Initialize(std::size_t depth, std::size_t byteCount);
+	void Shutdown();
+
+	bool QueueReadback(GLuint framebuffer, unsigned width, unsigned height, uint64_t frameIndex);
+	bool TryAcquireCompleted(CompletedReadback& readback);
+	void ReleaseCompleted(const CompletedReadback& readback);
+	void DrainCompleted();
+
+	std::size_t Depth() const { return mSlots.size(); }
+	uint64_t QueueMisses() const { return mQueueMisses; }
+
+private:
+	struct Slot
+	{
+		GLuint pbo = 0;
+		GLsync fence = nullptr;
+		bool inFlight = false;
+		bool acquired = false;
+		uint64_t frameIndex = 0;
+	};
+
+	void ResetSlot(Slot& slot);
+
+	std::vector<Slot> mSlots;
+	std::size_t mWriteIndex = 0;
+	std::size_t mReadIndex = 0;
+	std::size_t mByteCount = 0;
+	uint64_t mQueueMisses = 0;
+};