download_back_buffer()

MAYAFLUX_API void MayaFlux::Buffers::download_back_buffer	(	const VKBufferResources::GenerationSlot &	slot,
		void *	data,
		size_t	size,
		std::shared_ptr< VKBuffer > &	staging
	)

Download a raw back_buffers slot to host memory.

Parameters

slot	Source slot, typically from VKBuffer::get_back_buffer().
size	Byte count to copy.
data	Destination pointer, at least size bytes.
staging	Persistent staging buffer for device-local slots. Ignored, and may be null, when slot.mapped_ptr is already valid.

Reads slot.mapped_ptr directly when present (host-visible slot, no transfer). Otherwise records a fenced copy into staging exactly as download_from_gpu_async does, using slot.buffer as the copy source.

Definition at line 294 of file StagingUtils.cpp.

{
    if (!data || size == 0)
        return;
 
    if (slot.mapped_ptr) {
        std::memcpy(data, slot.mapped_ptr, size);
        return;
    }
 
    auto buffer_service = Registry::BackendRegistry::instance()
                              .get_service<Registry::Service::BufferService>();
 
    if (!buffer_service
        || !buffer_service->execute_fenced
        || !buffer_service->wait_fenced
        || !buffer_service->release_fenced
        || !buffer_service->invalidate_range) {
        error<std::runtime_error>(
            Journal::Component::Buffers,
            Journal::Context::BufferProcessing,
            std::source_location::current(),
            "download_back_buffer: BufferService unavailable");
    }
 
    if (!staging || staging->get_size_bytes() < size)
        staging = create_staging_buffer(size);
 
    auto handle = buffer_service->copy_buffer_fenced(
        static_cast<void*>(slot.buffer),
        static_cast<void*>(staging->get_buffer()),
        size, 0, 0);
 
    buffer_service->wait_fenced(handle);
 
    auto& resources = staging->get_buffer_resources();
    buffer_service->invalidate_range(resources.memory, 0, size);
 
    std::memcpy(data, staging->get_mapped_ptr(), size);
    buffer_service->release_fenced(handle);
}

References MayaFlux::Buffers::VKBufferResources::GenerationSlot::buffer, MayaFlux::Journal::BufferProcessing, MayaFlux::Journal::Buffers, create_staging_buffer(), MayaFlux::Registry::BackendRegistry::get_service(), MayaFlux::Registry::BackendRegistry::instance(), and MayaFlux::Buffers::VKBufferResources::GenerationSlot::mapped_ptr.

Referenced by MayaFlux::Buffers::BufferDownloadProcessor::download_back_buffers(), MayaFlux::Buffers::RelaxationStepProcessor::on_after_execute(), and MayaFlux::Buffers::VolumeGridBuffer::read_field().

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