flower/source/engine/rhi/sampler_cache.h

#pragma once

#include "bindless.h"
#include "rhi_misc.h"
#include <util/cityhash/city.h>

namespace engine
{
	class VulkanContext;

	class SamplerCache
	{
	public:
		struct SamplerWithIndex
		{
			VkSampler sampler; // sampler handle.
			uint32_t index; // index in bindless set.
		};

	private:
		VulkanContext* m_context;

        struct SamplerCreateInfo
        {
            VkSamplerCreateInfo info;

            bool operator==(const SamplerCreateInfo& other) const
            {
                return other.hash() == hash();
            }

            uint64_t hash() const
            {
                return CityHash64((const char*)&info, sizeof(info));
            }
        };

        struct SamplerCreateInfoHash
        {
            uint64_t operator()(const SamplerCreateInfo& k) const
            {
                return k.hash();
            }
        };

		// Bindless index and sampler combine.
		using Cache = std::unordered_map<SamplerCreateInfo, SamplerWithIndex, SamplerCreateInfoHash>;

		// Cache all sampler.
		Cache m_cache;

		// Common sampler.
		VkDescriptorSet m_cacheCommonDescriptor = VK_NULL_HANDLE;
		VkDescriptorSetLayout m_cacheCommonDescriptorSetLayout = VK_NULL_HANDLE;

		void initCommonDescriptorSet();

	public:
		void init(VulkanContext* context);
		void release();

		VkSampler createSampler(VkSamplerCreateInfo info);
		VkSampler createSampler(VkSamplerCreateInfo info, uint32_t& bindless);
		SamplerWithIndex createSamplerAndUpdateToBindless(VkSamplerCreateInfo info);

		// Common descriptor set.
		// See layout in /shader/common_sampler.glsl
        VkDescriptorSet getCommonDescriptorSet() const { return m_cacheCommonDescriptor;  }
        VkDescriptorSetLayout getCommonDescriptorSetLayout() const { return m_cacheCommonDescriptorSetLayout; }
	};
}