restructure

apps/RenderCadenceCompositor/render/readback/PboReadbackRing.cpp

@@ -0,0 +1,138 @@
+#include "PboReadbackRing.h"
+
+#include <algorithm>
+
+PboReadbackRing::~PboReadbackRing()
+{
+	Shutdown();
+}
+
+bool PboReadbackRing::Initialize(std::size_t depth, std::size_t byteCount)
+{
+	Shutdown();
+	if (depth == 0 || byteCount == 0)
+		return false;
+
+	mSlots.resize(depth);
+	mByteCount = byteCount;
+	for (Slot& slot : mSlots)
+	{
+		glGenBuffers(1, &slot.pbo);
+		if (slot.pbo == 0)
+		{
+			Shutdown();
+			return false;
+		}
+		glBindBuffer(GL_PIXEL_PACK_BUFFER, slot.pbo);
+		glBufferData(GL_PIXEL_PACK_BUFFER, static_cast<GLsizeiptr>(mByteCount), nullptr, GL_STREAM_READ);
+	}
+	glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);
+	return true;
+}
+
+void PboReadbackRing::Shutdown()
+{
+	for (Slot& slot : mSlots)
+	{
+		if (slot.fence)
+			glDeleteSync(slot.fence);
+		if (slot.pbo != 0)
+			glDeleteBuffers(1, &slot.pbo);
+		slot = {};
+	}
+	mSlots.clear();
+	mWriteIndex = 0;
+	mReadIndex = 0;
+	mByteCount = 0;
+}
+
+bool PboReadbackRing::QueueReadback(GLuint framebuffer, unsigned width, unsigned height, uint64_t frameIndex)
+{
+	if (mSlots.empty())
+		return false;
+
+	Slot& slot = mSlots[mWriteIndex];
+	if (slot.inFlight || slot.acquired)
+	{
+		++mQueueMisses;
+		return false;
+	}
+
+	glBindFramebuffer(GL_READ_FRAMEBUFFER, framebuffer);
+	glPixelStorei(GL_PACK_ALIGNMENT, 4);
+	glPixelStorei(GL_PACK_ROW_LENGTH, 0);
+	glBindBuffer(GL_PIXEL_PACK_BUFFER, slot.pbo);
+	glBufferData(GL_PIXEL_PACK_BUFFER, static_cast<GLsizeiptr>(mByteCount), nullptr, GL_STREAM_READ);
+	glReadPixels(0, 0, static_cast<GLsizei>(width), static_cast<GLsizei>(height), GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, nullptr);
+	slot.fence = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
+	slot.inFlight = slot.fence != nullptr;
+	slot.frameIndex = frameIndex;
+	glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);
+
+	if (!slot.inFlight)
+		return false;
+
+	mWriteIndex = (mWriteIndex + 1) % mSlots.size();
+	return true;
+}
+
+bool PboReadbackRing::TryAcquireCompleted(CompletedReadback& readback)
+{
+	if (mSlots.empty())
+		return false;
+
+	for (std::size_t checked = 0; checked < mSlots.size(); ++checked)
+	{
+		Slot& slot = mSlots[mReadIndex];
+		if (!slot.inFlight || slot.acquired || slot.fence == nullptr)
+		{
+			mReadIndex = (mReadIndex + 1) % mSlots.size();
+			continue;
+		}
+
+		const GLenum waitResult = glClientWaitSync(slot.fence, 0, 0);
+		if (waitResult != GL_ALREADY_SIGNALED && waitResult != GL_CONDITION_SATISFIED)
+			return false;
+
+		slot.acquired = true;
+		readback.pbo = slot.pbo;
+		readback.frameIndex = slot.frameIndex;
+		readback.byteCount = mByteCount;
+		return true;
+	}
+	return false;
+}
+
+void PboReadbackRing::ReleaseCompleted(const CompletedReadback& readback)
+{
+	for (std::size_t index = 0; index < mSlots.size(); ++index)
+	{
+		Slot& slot = mSlots[index];
+		if (!slot.acquired || slot.pbo != readback.pbo)
+			continue;
+		ResetSlot(slot);
+		mReadIndex = (index + 1) % mSlots.size();
+		return;
+	}
+}
+
+void PboReadbackRing::DrainCompleted()
+{
+	for (std::size_t pass = 0; pass < mSlots.size() * 2; ++pass)
+	{
+		CompletedReadback readback;
+		if (!TryAcquireCompleted(readback))
+			break;
+		ReleaseCompleted(readback);
+	}
+}
+
+void PboReadbackRing::ResetSlot(Slot& slot)
+{
+	if (slot.fence)
+		glDeleteSync(slot.fence);
+	slot.fence = nullptr;
+	slot.inFlight = false;
+	slot.acquired = false;
+	slot.frameIndex = 0;
+}