gplib/include/gp/iterator.hpp

#pragma once

#include <stddef.h>
#include <stdint.h>

enum class iterator_type_t{
	contiguous_iterator,
	non_contiguous_iterator,
	lazy_iterator
};

template<typename T, int sign = 1>
struct pointer_iterator final
{
	T* data;
	typedef T value_type;
	typedef std::size_t difference_type;
	static constexpr iterator_type_t iterator_type = iterator_type_t::contiguous_iterator;

	constexpr pointer_iterator()
	: data{nullptr}
	{}

	constexpr pointer_iterator(const pointer_iterator& oth)
	: data{oth.data}
	{}

	constexpr pointer_iterator(T* ptr)
	: data{ptr}
	{}

	constexpr T& operator*()
	{
		return *data;
	}

	constexpr pointer_iterator& operator++()
	{
		data += sign;
		return *this;
	}

	constexpr pointer_iterator operator++(int)
	{
		auto p = *this;
		data += sign;
		return p;
	}

	constexpr pointer_iterator& operator--()
	{
		data -= sign;
		return *this;
	}

	constexpr pointer_iterator operator--(int)
	{
		auto p = *this;
		data -= sign;
		return p;
	}

	constexpr pointer_iterator operator+(const std::size_t offset)
	{
		return pointer_iterator{data+sign*offset};
	}

	constexpr pointer_iterator operator+(const int offset)
	{
		return pointer_iterator{data+sign*offset};
	}

	constexpr pointer_iterator operator-(const std::size_t offset)
	{
		return pointer_iterator{data-sign*offset};
	}

	constexpr pointer_iterator operator-(const int offset)
	{
		return pointer_iterator{data-sign*offset};
	}

	constexpr difference_type operator-(const pointer_iterator& oth) const
	{
		return ((T*)data-(T*)oth.data)*sign;
	}

	constexpr bool operator==(const pointer_iterator oth)
	{
		return data==oth.data;
	}

	constexpr bool operator!=(pointer_iterator oth)
	{
		return data!=oth.data;
	}

	constexpr bool before_or_equal(const pointer_iterator oth)
	{
		return reinterpret_cast<std::intptr_t>(data) <= reinterpret_cast<std::intptr_t>(oth.data);
	}

	constexpr bool operator<=(const pointer_iterator oth)
	{
		return before_or_equal(oth);
	}
};

template<typename T, int sign = 1>
struct const_pointer_iterator final
{
	const T* data;
	typedef T value_type;
	typedef std::size_t difference_type;
	static constexpr iterator_type_t iterator_type = iterator_type_t::contiguous_iterator;

	constexpr const_pointer_iterator(const const_pointer_iterator& oth)
	: data{oth.data}
	{}

	constexpr const_pointer_iterator(const T* ptr)
	: data{ptr}
	{}

	constexpr const T& operator*()
	{
		return *data;
	}

	constexpr const_pointer_iterator& operator++()
	{
		data += sign;
		return *this;
	}

	constexpr const_pointer_iterator operator++(int)
	{
		auto p = data;
		data += sign;
		return const_pointer_iterator{p};
	}

	constexpr const_pointer_iterator& operator--()
	{
		data -= sign;
		return *this;
	}

	constexpr const_pointer_iterator operator--(int)
	{
		auto p = data;
		data -= sign;
		return const_pointer_iterator{p};
	}

	constexpr const_pointer_iterator operator+(const std::size_t offset)
	{
		return const_pointer_iterator{data+sign*offset};
	}

	constexpr const_pointer_iterator operator+(const int offset)
	{
		return const_pointer_iterator{data+sign*offset};
	}

	constexpr const_pointer_iterator operator-(const std::size_t offset)
	{
		return const_pointer_iterator{data-sign*offset};
	}

	constexpr const_pointer_iterator operator-(const int offset)
	{
		return const_pointer_iterator{data-sign*offset};
	}

	constexpr difference_type operator-(const const_pointer_iterator& oth) const
	{
		return ((T*)data-(T*)oth.data)*sign;
	}

	constexpr bool operator==(const const_pointer_iterator oth)
	{
		return data==oth.data;
	}

	constexpr bool operator!=(const_pointer_iterator oth)
	{
		return data!=oth.data;
	}

	constexpr bool before_or_equal(const const_pointer_iterator oth)
	{
		return reinterpret_cast<std::intptr_t>(data) <= reinterpret_cast<std::intptr_t>(oth.data);
	}

	constexpr bool operator<=(const const_pointer_iterator oth)
	{
		return before_or_equal(oth);
	}
};