ShaderArrayIndexManager.h

#pragma once
 
// Standard.
#include <string>
#include <queue>
#include <mutex>
#include <memory>
 
namespace ne {
    class ShaderArrayIndexManager;
 
    class ShaderArrayIndex {
        friend class ShaderArrayIndexManager;
 
    public:
        ShaderArrayIndex() = delete;
 
        ShaderArrayIndex(const ShaderArrayIndex&) = delete;
        ShaderArrayIndex& operator=(const ShaderArrayIndex&) = delete;
 
        ShaderArrayIndex(ShaderArrayIndex&&) = delete;
        ShaderArrayIndex& operator=(ShaderArrayIndex&&) = delete;
 
        unsigned int getActualIndex() const;
 
        ~ShaderArrayIndex();
 
    private:
        ShaderArrayIndex(ShaderArrayIndexManager* pManager, unsigned int iIndexIntoShaderArray);
 
        ShaderArrayIndexManager* pManager = nullptr;
 
        unsigned int iIndexIntoShaderArray;
    };
 
    class ShaderArrayIndexManager {
        // Indices notify the manager in their destructor about no longer being used.
        friend class ShaderArrayIndex;
 
    public:
        ShaderArrayIndexManager() = delete;
 
        ShaderArrayIndexManager(const std::string& sName, unsigned int iArraySize);
 
        ~ShaderArrayIndexManager();
 
        std::unique_ptr<ShaderArrayIndex> reserveIndex();
 
    private:
        void onIndexNoLongerUsed(unsigned int iIndex);
 
        struct InternalData {
            InternalData() = default;
 
            std::queue<unsigned int> noLongerUsedIndices;
 
            unsigned int iNextFreeIndex = 0;
 
            size_t iActiveIndexCount = 0;
        };
 
        std::pair<std::recursive_mutex, InternalData> mtxData;
 
        const unsigned int iArraySize = 0;
 
        const std::string sName;
    };
}