Page.h

/*
 * Page.h
 *
 *  Created on: Feb 1, 2021
 *      Author: tugrul
 */

#ifndef PAGE_H_
#define PAGE_H_

#include<vector>
#include<memory>
#include"ClCommandQueue.h"
#include"ClContext.h"
#include"AlignedCpuArray.h"

// active page that holds data in RAM by pinned buffers
template<typename T>
class Page
{
public:
	// do not use this
	Page(){arr=nullptr; edited=false;targetGpuPage=-1;}

	// allocates pinned array for a "page", uses opencl way of pinning the array and is meant to be used in its own command queue
	Page(int sz,ClContext ctxP, ClCommandQueue cqP, const bool usePinnedArraysOnly=true){ arr=std::shared_ptr<AlignedCpuArray<T>>(new AlignedCpuArray<T>(*ctxP.ctxPtr(),cqP.getQueue(),sz,4096,usePinnedArraysOnly)); edited=false; targetGpuPage=-1;}

	// reading an element of virtual array
	// i: index of element
	T get(const int & i) const  noexcept { return arr->getArray()[i]; }

	// reading multiple elements, exclusively used for "read-only access",
	const std::vector<T> getN(const int & i, const int & n) const  noexcept {
		const auto ptr = arr->getArray()+i;
		return std::vector<T>(ptr,ptr+n);
	}

	// writing to an element of virtual array
	// i: index of element
	// val: element value to be written
	void edit(const int & i, const T & val) const  noexcept  { arr->getArray()[i]=val;}

	// writing multiple elements, exclusively used for "write-only access",
	void editN(const int & i, const std::vector<T> & val, const size_t & valIndex, const size_t & n) const  noexcept
	{
		std::copy(val.begin()+valIndex,val.begin()+valIndex+n,arr->getArray()+i);
	}

	// only copying, no allocation
	void readN(T * const out, const int & i, const int & n) const  noexcept  {
		const auto ptr = arr->getArray()+i;
		std::copy(ptr,ptr+n,out);
	}

	// only copying, no allocation
	void writeN(T * const in, const int & i, const size_t & n) const  noexcept
	{
		std::copy(in,in+n,arr->getArray()+i);
	}


	void markAsEdited()  noexcept {  edited=true;  }

	// checks if page is edited (if true, paging system will upload data to graphics card in case of a storage requirement of a different frozen page)
	bool isEdited() const noexcept { return edited; }

	// clears "edited" status, only used after getting fresh data from a frozen page
	void reset() noexcept { edited=false; }

	// this changes index of frozen page (in a graphics card) is being written/read
	void setTargetGpuPage(size_t g)  noexcept { targetGpuPage=g; }

	// this returns index of frozen page (in a graphics card) is being written/read
	size_t getTargetGpuPage() const  noexcept  { return targetGpuPage; }

	// internal logic, for get/set methods of VirtualArray
	T * const ptr() const  noexcept  { return arr->getArray(); }

	Page<T>& operator=(Page<T>&&) = default;
	Page<T>& operator=(Page<T>&) = default;
	Page(Page<T>&) = default;
	~Page(){}
private:
	std::shared_ptr<AlignedCpuArray<T>> arr;
	bool edited;// todo: should make this smart pointer too, if a different paging algorithm is going to be used
	size_t targetGpuPage; // todo: should make this smart pointer too, if a different paging algorithm is going to be used
};



#endif /* PAGE_H_ */