c++学习笔记(7)——关于类的实现（以vector为例）

#ifndef VEC_H#define VEC_H#pragma warning(disable:4996)//这里最好有这一句，否则uninitialized_copy 函数会被称为unsafe!也提示我们在出现unsafe的时候，要用这个屏蔽掉。#include <iostream>#include <algorithm>#include <memory>template <class T>class Vec{public:typedef T*iterator;typedef const T*const_iterator;typedef size_tsize_type;typedef Tvalue_type;typedef std::ptrdiff_tdifference_type;typedef T&reference;typedef const T&const_reference;Vec() { create(); }explicit Vec(std::size_t n, const T& val = T()) { create(n, val); }Vec(const Vec& v) { create(v.begin(), v.end()); }Vec& operator= (const Vec&);~Vec() { uncreate(); }T& operator[] (size_type i) { return data[i]; }const T& operator[] (size_type i) const { return data[i]; }void push_back(const T& val){if (avail == limit)grow();unchecked_append(val);}size_type size() const { return avail - data; }iterator begin() { return data; }const iterator begin() const { return data; }iterator end() { return avail; }const iterator end() const { return avail; }bool empty() const { return data == limit; }//iterator erase(iterator);void clear() { uncreate(); }private:iterator data;iterator avail;iterator limit;std::allocator<T> alloc;//这里一定要加std！！alloc方面的都是需要std的！void create();void create(size_type, const T&);void create(const_iterator, const_iterator);void uncreate();void grow();void unchecked_append(const T&);};template <class T>void Vec<T>::create(){data = avail = limit = 0;}template <class T>void Vec<T>::create(size_type n, const T& val){data = alloc.allocate(n);limit = avail = data + n;uninitialized_fill(data, limit, val);}template<class T>void Vec<T>::create(const_iterator i, const_iterator j){data = alloc.allocate(j - i);limit = avail = uninitialized_copy(i, j, data);}template <class T>void Vec<T>::uncreate(){if (data){iterator it = avail;while (it != data)alloc.destroy(--it);alloc.deallocate(data, limit - data);}data = limit =  avail = 0;}template <class T>void Vec<T>::grow(){size_type new_size = max(2 * (limit - data), ptrdiff_t(1));iterator new_data = alloc.allocate(new_size);iterator new_avail = uninitialized_copy(data, avail, new_data);uncreate();data = new_data;avail = new_avail;limit = data + new_size;}template <class T>void Vec<T>::unchecked_append(const T& val){alloc.construct(avail++, val);}template <class T>Vec<T>& Vec<T>::operator= (const Vec& rhs){if (&rhs != this){uncreate();create(rhs.begin(), rhs.end());}return *this;}#endif