STL中vector的模拟实现

#pragma once

#include<assert.h>

namespace lhw
{
	template<class T>
	class vector
	{
		typedef T* iterator;
		typedef const T* const_iterator;
	public:
		vector()
			:_start(nullptr)
			,_finish(nullptr)
			,_end_of_storage(nullptr)
		{}

		vector(size_t n,const T& val)
			:_start(nullptr)
			, _finish(nullptr)
			, _end_of_storage(nullptr)
		{
			reserve(n);
			for (size_t i = 0; i < n; i++)
			{
				push_back(val);
			}
		}

		template<class InputIterator>
		vector(InputIterator first, InputIterator last)
			:_start(nullptr)
			, _finish(nullptr)
			, _end_of_storage(nullptr)
		{
			while (last != first)
			{
				push_back(*first);
				first++;
			}
		}

		vector(const vector<T>& v)
		{
			_start = new T[v.capacity()];
			for (size_t i = 0; i < v.size(); i++)
			{
				_start[i] = v._start[i];
			}
			_finish = _start + v.size();
			_end_of_storage = _start + v.capacity();
		}

		vector<T>& operator=(const vector<T>& v)
		{
			if (this != &v)
			{
				delete[] _start;
				_str = new T[v.capacity()];
				for (size_t i = 0; i < v.size(); i++)
				{
					_str[i] = v._start[i];
				}
				_finish = _start + v.size();
				_end_of_storage = _start + v.capacity();
			}
			return *this;
		}

		vector<T>& operator=(const vector<T>& v)
		{
			swap(v);
			return *this;
		}

		~vector()
		{
			if (_start)
			{
				delete[] _str;
				_start = _finish = _end_of_storage = nullptr;
			}
		}

		iterator begin()
		{
			return _start;
		}

		const_iterator begin()const 
		{
			return _start;
		}

		iterator end()
		{
			return _finish;
		}

		const_iterator end()const
		{
			return _finish;
		}

		size_t size()
		{
			return _finish - _start;
		}

		size_t capacity()
		{
			return _end_of_storage - _start;
		}

		void reserve(size_t n)
		{
			if (n > capacity())
			{
				T* tmp = new T[n];
				size_t sz = size();
				if (_start)
				{
					for (size_t i = 0; i < size(); i++)
					{
						tmp[i] = _start[i];
					}
					delete[] _start;
				}
				_start = tmp;
				_finish = _start + sz;
				_end_of_storage = _start + n;
			}
		}

		void resize(size_t n, T& val)
		{
			if (n < size())
			{
				_finsih = _start + n;
			}
			else
			{
				if (n > capacity())
				{
					reserve(n);
				}
				while (_finish < _start + n)
				{
					*_finish = val;
					_finish++;
				}
			}
		}

		bool empty()
		{
			return _start == _finish;
		}

		void push_back(const T& val)
		{
			if (_start == _finish)
			{
				size_t newcapacity = capacity() == 0 ? 4 : 2 * capacity();
				reserve(newcapacity);
			}
			*_finish = val;
			_finish++;
		}

		void pop_back()
		{
			assert(_start == _finish);
			_finish--;
		}

		void insert(iterator pos, const T& val)
		{
			assert(pos <= _finish);
			if (_finish == _end_of_storage)
			{
				size_t len = pos - _start;
				size_t newcapacity = capacity() == 0 ? 4 : 2 * capacity();
				reserve(newcapacity);
				pos = _start + len;
			}
			iterator end = _finish - 1;
			while (end >= pos)
			{
				*(end + 1) = *end;
				end--;
			}
			*pos = val;
			_finish++;
		}

		iterator erase(iterator pos)
		{
			assert(!empty());
			iterator it = pos;
			while (it + 1 != _finish)
			{
				*it = *(it + 1);
				it++;
			}
			_finish--;
			return pos;
		}

		void swap(vector<T>& v)
		{
			::swap(_start, v._start);
			::swap(_finish, v._finish);
			::swap(_end_of_storage, v._end_of_storage);
		}

		T& operator[](size_t i)
		{
			assert(i < size());
			return _start[i];
		}

		const T& operator[](size_t i)const
		{
			assert(i < size());
			return _start[i];
		}

	private:
		iterator _start;
		iterator _finish;
		iterator _end_of_storage;
	};
}