使用C++类模板实现动态数组

#include <iostream>
#include <string>

using namespace std;
//使用类模板实现动态数组！
template<typename T, int N>
class Array{
private:
T* m_array;
int m_len;
public:
//构造函数，给数组申请空间
Array() : m_array(new T
), m_len(N){}

//拷贝构造函数
template<int X>
Array(const Array<T, X>& that)
{
m_len = that.size();
m_array = new T[m_len];
if (m_array == NULL)
{
cout << "have not enough free memory" << endl;
return;
}

memset(m_array, 0, m_len);
memcpy(m_array, that.get_data(), m_len*sizeof(T));
}

//重载 = 运算符，使得数组之间能够实现 = 操作！
template<int Y>
Array& operator = (const Array<T, Y>& other)
{
if (this != &other)
{
//为保证程序的可靠性，应该先用一个临时变量将数据复制成功之后再改变被赋值数组的值，
//这样可以保证在程序运行出错时，原数组不会受影响
array = new T[m_len];
if (array == NULL)
{
cout << "have not enough free memory" << endl;
return;
}

memset(array, 0, other.size());
memcpy(array, other.get_data(), other.size()*sizeof(T));

delete[] m_array;
m_array = array;
m_len = other.size();
}

return *this;
}

//重载下标运算符，使得下标运算符具有越界检测功能!
T& operator[](int index)
{
if (index > m_len - 1)
{
cout << "Array out of range, 0 to " << (m_len - 1) << " is legitimate scope." << endl;
return m_array[0];  //因为return的是m_array[0]，所以如果是在执行 = 操作，则数组第一位元素值就会发生变化！
}

return m_array[index];
}

//重载下标运算符，保证常数组也能实现相关操作
T& operator[](unsigned int index) const
{
if (index > m_len - 1)
{
cout << "Array out of range, 0 to " << (m_len - 1) << " is legitimate scope." << endl;
return m_array[0];
}

return m_array[index];
}

//用来扩大数组的容量
Array* add_memory(unsigned int len)
{
//增加一个中间变量
T* temp = new T[m_len + len];
if (temp == NULL)
{
cout << "have not enough free!" << endl;
return this;
}
//将原来的数据存储进这个中间变量中
memset(temp, 0, (m_len + len) * sizeof(T));
memcpy(temp, m_array, m_len*sizeof(T));
//删除原来的数组指针，并将中间变量temp赋值给成员变量m_array;
delete[] m_array;
m_array = temp;
m_len = m_len + len;
return this;
}

int size() const
{
return m_len;
}

T* get_data() const
{
return m_array;
}

friend ostream& operator<<(ostream& os, const Array<T, N>& array)
{
for (int i = 0; i < array.size(); i++)
{
os << array[i] << " ";
//保证输出格式
if (!(i + 1 % 5))
{
os << endl;
}
}

return os;
}
};

int main()
{
Array<int, 5> b;
b[0] = 1;
b[1] = 3;
b[2] = 4;
b[3] = 5;
b[4] = 6;
b[7] = 8;

cout << b[0] << endl;
cout << b << endl;

Array<int, 2> a(b);

cout << a << endl;
cout << a.size() << endl;
cout << b.size() << endl;

b.add_memory(10);
cout << b.size() << endl;
cout << b << endl;

Array<int, 5> c;
c = b;
cout << c << endl;
cout << c.size() << endl;

b[20] = 20;

system("pause");
return 0;
}