【STL源码剖析读书笔记】自己实现vector之MyVector
MyVector.h
#ifndef MY_VECTOR_H
#define MY_VECTOR_H
#define _SCL_SECURE_NO_WARNINGS //为了防止在VS2013中报错
#include<cstddef> //ptrdiff_t
#include<memory>
template<typename T>
void destroy(T* ptr){
ptr->~T();
}
template<typename ForwardIterator>
void destroy(ForwardIterator first, ForwardIterator last){
for (; first != last; ++first)
destroy(&*first);
}
template<typename T>
class MyVector{
public:
//嵌套型别定义
typedef T value_type;
typedef T* pointer;
typedef const T* const_pointer;
typedef T* iterator;
typedef const T* const_iterator;
typedef T& reference;
typedef const T& const_reference;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
protected:
iterator start; //目前使用空间的头
iterator finish;//目前使用空间的尾
iterator end_of_storage;//目前可用空间的尾
std::allocator<T> alloc; //空间分配器
public:
MyVector(); //默认构造函数
MyVector(size_type n, const T& value);//构造函数
MyVector(iterator first, iterator last);//构造函数
~MyVector(); //析构函数
MyVector(MyVector& vec); //拷贝构造函数
MyVector& operator=(MyVector& vec); //拷贝赋值运算符
public:
iterator begin(){ return start; }
const_iterator begin() const { return start; }
iterator end(){ return finish; }
const_iterator end() const { return finish; }
size_type size() const { return (size_type)(finish - start); }
size_type capacity() const { return (size_type)(end_of_storage - start); }
bool empty() const { return start == finish; }
reference operator[](size_type n){ return *(begin() + n); }
const_reference operator[](size_type n) const { return *(begin() + n); }
reference front() { return *begin(); }
const_reference front() const { return *begin(); }
reference back(){ return *(end() - 1); }
const_reference back() const { retunr *(end() - 1); }
void push_back(const T& value);
void pop_back();
void insert(iterator position,size_type n,const T& value);
iterator erase(iterator position);
iterator erase(iterator first,iterator last);
void resize(size_type new_size);
void resize(size_type new_size, const T& value);
void reserve(size_type new_size);
void clear();
private:
void free();
void reallocate();
};
//默认构造函数
template<typename T>
MyVector<T>::MyVector():start(nullptr),finish(nullptr),end_of_storage(nullptr){}
//构造函数
template<typename T>
MyVector<T>::MyVector(size_type n, const T& value){
start=alloc.allocate(n);
finish = end_of_storage = start + n;
for (iterator it = start; it != finish; ++start)
alloc.construct(it, value);
}
//构造函数
template<typename T>
MyVector<T>::MyVector(iterator first, iterator last){
size_type n = (size_type)(last - first);
start = alloc.allocate(n);
finish = end_of_storage = start + n;
std::uninitialized_copy(first, last, start);
}
//析构函数
template<typename T>
MyVector<T>::~MyVector(){
free();
}
template<typename T>
void MyVector<T>::free(){
destroy(start, finish);
alloc.deallocate(start, capacity());
}
//拷贝构造函数
template<typename T>
MyVector<T>::MyVector(MyVector& vec){
start = alloc.allocate(vec.size());
finish = end_of_storage = start + vec.size();
std::uninitialized_copy(vec.begin(), vec.end(), start);
}
//拷贝赋值运算符
template<typename T>
MyVector<T>& MyVector<T>::operator=(MyVector& vec){
if (vec != *this){
iterator new_start = alloc.allocate(vec.size());
std::uninitialized_copy(vec.begin(), vec.end(), new_start);
size_type old_size = size();
size_type old_capacity = capacity();
free();
start = new_start;
finish = start + old_size;
end_of_storage = start + old_capacity;
}
return *this;
}
//reallocate()
template<typename T>
void MyVector<T>::reallocate(){
size_type new_size = size() ? size() * 2 : 1;
iterator new_start = alloc.allocate(new_size);
iterator new_finish=std::uninitialized_copy(start, finish, new_start);
free();
start = new_start;
finish = new_finish;
end_of_storage = start + new_size;
}
//push_back(const T& value)
template<typename T>
void MyVector<T>::push_back(const T& value){
if (size() == capacity())
reallocate();
alloc.construct(finish++, value);
}
//pop_back()
template<typename T>
void MyVector<T>::pop_back(){
alloc.destroy(--finish);
}
//insert(iterator position, size_type n, const T& value)
template<typename T>
void MyVector<T>::insert(iterator position, size_type n, const T& value){
if (n <= (size_type)(capacity() - size())){
if (n > (size_type)(finish - position)){
std::uninitialized_fill(finish, finish + n - (size_type)(finish - position),value);
std::uninitialized_copy(position, finish, position + n);
std::uninitialized_fill(position, finish, value);
}
else{
std::copy_backward(position, finish, finish + n);
std::uninitialized_fill_n(position, n, value);
}
finish += n;
}
else{
size_type new_size = size() + (size() > n ? size() : n);
iterator new_start = alloc.allocate(new_size);
iterator new_finish = std::uninitialized_copy(start, position, new_start);
new_finish=std::uninitialized_fill_n(new_finish, n, value);
new_finish = std::uninitialized_copy(position, finish, new_finish);
free();
start = new_start;
finish = new_finish;
end_of_storage = start + new_size;
}
}
//erase(iterator position)
template<typename T>
typename MyVector<T>::iterator MyVector<T>::erase(iterator position){
if (position+1!=finish)
std::uninitialized_copy(position + 1, finish, position);
destroy(--finish);
return position;
}
//erase(iterator first, iterator last)
template<typename T>
typename MyVector<T>::iterator MyVector<T>::erase(iterator first, iterator last){
size_type n = (size_type)(last - first);
std::uninitialized_copy(last, finish, first);
destroy(finish - n, finish);
finish = finish - n;
return first;
}
//resize(size_type new_size)
template<typename T>
void MyVector<T>::resize(size_type new_size){
resize(new_size, T());
}
//resize(size_type new_size, const T& value)
template<typename T>
void MyVector<T>::resize(size_type new_size, const T& value){
if (new_size > size())
insert(finish, new_size - size(), value);
else
erase(begin() + new_size, finish);
}
//reserve(size_type new_size)
template<typename T>
void MyVector<T>::reserve(size_type new_size){
if (new_size > capacity()){
iterator new_start = alloc.allocate(new_size);
size_t old_size = size();
std::uninitialized_copy(start, finish, new_start);
free();
start = new_start;
finish = start + old_size;
end_of_storage = start + new_size;
}
}
//clear()
template<typename T>
void MyVector<T>::clear(){
erase(start, finish);
}
#endifmain.cpp
#include "MyVector.h"
#include<iostream>
using namespace std;
int main(){
MyVector<int> vec;
for (int i = 0; i != 10; ++i)
vec.push_back(i); //push_back()
MyVector<int>::iterator it;
MyVector<int> vec2(vec); //拷贝构造
for (it = vec2.begin(); it != vec2.end(); ++it) //begin(),end()
cout << *it << " "; //0 1 2 3 4 5 6 7 8 9
cout << endl;
MyVector<int> vec3 = vec; //拷贝赋值运算符
for (it = vec3.begin(); it != vec3.end(); ++it)
cout << *it << " "; //0 1 2 3 4 5 6 7 8 9
cout << endl;
for (it = vec.begin(); it != vec.end(); ++it)
cout << *it << " "; //0 1 2 3 4 5 6 7 8 9
cout << endl;
cout << "size:" << vec.size() << endl; //10 size()
cout << "capacity:" << vec.capacity() << endl; //16 capacity()
vec.reserve(10); //reserve()
cout << "capacity:" << vec.capacity() << endl; //16
vec.reserve(30);//reserve()
cout << "capacity:" << vec.capacity() << endl; //30
vec.pop_back(); //pop_back()
for (size_t i = 0; i <vec.size(); ++i)
cout << vec[i] << " ";//0 1 2 3 4 5 6 7 8
cout << endl;
cout << "front:" << vec.front() << endl; //0 front()
cout << "back:" << vec.back() << endl; //8 back()
vec.insert(vec.begin() + 5, 3, 10); //insert()
for (const auto& c : vec)
cout << c << " ";//0 1 2 3 4 10 10 10 5 6 7 8
cout << endl;
vec.erase(vec.begin() + 2, vec.begin() + 5); //erase()
for (it = vec.begin(); it != vec.end(); ++it)
cout << *it << " ";//0 1 10 10 10 5 6 7 8
cout << endl;
cout << "size:" << vec.size() << endl; //9
vec.resize(5); //resize()
for (it = vec.begin(); it != vec.end(); ++it)
cout << *it << " ";//0 1 10 10 10
cout << endl;
cout << "size:" << vec.size() << endl; //5
vec.resize(10);
for (it = vec.begin(); it != vec.end(); ++it)
cout << *it << " ";//0 1 10 10 10 0 0 0 0 0
cout << endl;
cout << "size:" << vec.size() << endl; //10
vec.clear(); //clear()
cout << (vec.empty() ? "vector empty" : "vector not empty") << endl; //empty
system("pause");
return 0;
}