模仿實現C++庫函數----String 類----用 寫時拷貝 實現

模仿實現C++庫函數----String 類----用 寫時拷貝 實現

#define _CRT_SECURE_NO_WARNINGS 1

#include<iostream>
#include<assert.h>
#define DEFAULTNUME 3
using namespace std;

class String
{
public:

	int& GetCount()
	{
		return *(((int *)_str) - 1);
	}

	char* GetStr()
	{
		return _str;
	}

	//找到字符 ch  並返回它的下標
	int Find(char ch)
	{
		if (_str == NULL)
		{
			return -1;
		}
		else
		{
			int count = 0;
			char* str = _str;
			while (str && count < _size)
			{
				if (*str == ch)
				{
					return count;
				}
				str++;
				count++;
			}
		}
		return -1;
	}

	//實現下標訪問
	char& operator[](int pos)
	{
     	char* cur = _str;
		cur = cur + pos ;
		return *cur;
	}

	bool operator<(const String& s)
	{
		char* pSourse = this->_str;
		char* pDest = s._str;

		if (pSourse == NULL)
		{
			return false;
		}
		else if (pDest == NULL)
		{
			return true;
		}
		else
		{
			while ((*pSourse != NULL) && (pDest != NULL))
			{
				if (*pSourse < *pDest)
				{
					return true;
				}
				else if (*pSourse > *pDest)
				{
					return false;
				}
				else
				{
					pSourse++;
					pDest++;
				}
			}
		}

		if (*pSourse == NULL && *pDest != NULL)
		{
			return true;
		}
		else
		{
			return false;
		}

	}

	bool operator==(const String& s)
	{
		char* pSource = _str;
		char* pDest = s._str;

		if (_size == s._size)
		{
			while (*pSource == *pDest && *pSource != NULL && *pDest != NULL)
			{
				pSource++;
				pDest++;
			}
			if (*pSource == NULL && *pDest == NULL)
			{
				return true;
			}
		}

		return false;
	}

	bool operator>(const String& s)
	{
		return !((*this < s) && (*this == s));
	}

	bool operator>=(const String& s)
	{
		return ((*this > s) && (*this == s));
	}

	bool operator<=(const String& s)
	{
		return ((*this < s) && (*this == s));
	}

	bool operator!=(const String& s)
	{
		return !(*this == s);
	}

	char* CheckCapacity(int capacity)
	{
		if (capacity > _capacity)
		{
			char* cur = new char[capacity + DEFAULTNUME];
			return cur;
		}
		return _str;//>>>>>>>>>>>>>>>>>>>改 
	}

	void  Insert(int pos, const char* s)
	{
		*(((int *)_str) - 1) -= 1;

		int len = strlen(s);
		char* p = CheckCapacity(_size + len + 1);
		strcpy(p, _str);
		_str = p;
		p = NULL;

		//移動原字符串  空出來空間給待插入的字符串
		int moveCount = _size - pos  + len + 1;// moveCount 為移動次數
		int i = _size;//  i  為移動的元素位置
		while (moveCount--)//把pos位置及pos後面的  字符 集體向後移一位
		{
			_str[i + len] = _str[i];
			i--;
		}

		//插入待插入的字符串
		//int insertCount = len;   //  insertCount  為字符插入次數
		//int posSource = pos;//  posSource 為原字符串的下標
		//int posDest = 0;// posDest 為待插入的字符串s的下標
		//while (insertCount--)
		//{
		//	_str[posSource - 1] = s[posDest];
		//	posSource++;
		//	posDest++;
		//}                            //>>>用strncpy就可以實現（多注意常用的庫函數啊！） 

		char* tem = _str + pos - 1;
		strncpy(tem, s,len);

		_size += len;
		_capacity = _size + 4; //4 為 '\0' + DEFAULTNUME 的個數

	}

	void  Insert(size_t pos, const char ch)
	{
		*(((int *)_str) - 1) -= 1;

		char* p = new char[_capacity + 1];
		strcpy(p, _str);
		_str = p;
		p = NULL;

		int count = _size - pos + 2;// count 為移動次數
		int i = _size;//移動的元素位置
		while (count--)//把pos位置及pos後面的  字符 集體向後移一位
		{
			_str[i + 1] = _str[i];
			i--;
		}

		_str[pos - 1] = ch;
		_size++;
		_capacity = _size + 4; //4 為 '\0' + DEFAULTNUME 的個數

	}
	String& operator+=(const String& s)
	{
		*(((int *)_str) - 1) -= 1;

		char* cur = CheckCapacity(_size + s._size + 5);
		cur = cur + 4;
		strcpy(cur, _str);//拷貝原字符串

		_str = cur;
		Insert(_size + 1, s._str);//拷貝s._str字符串

		*((int*)cur - 1) = 1;
		cur = NULL;
		_size += s._size;
		_capacity = _size + 4;  //4 為 '\0' + DEFAULTNUME 的個數

		return *this;
	}

public:

	String(char* str = "")
		:_str(new char[_size + 5])
	{
		_str = _str + 4;
		strcpy(_str, str);
		_size = strlen(str);
		_capacity = _size + 1;
		//GetCount() = 1;//  為什麼 錯了？
		*(((int *)_str) - 1) += 1;//用++為什麼錯了
	}

	String(const String& s)
	{
		_str = s._str;
		_size = s._size;
		_capacity = _size + 1;
		int count = GetCount();
		GetCount()++;
	}

	~String()
	{
		if (--GetCount() == 0 && _str != NULL)
		{
			delete[] _str;
			_str = NULL;//>>>>>>>>>>>>>>>>>改 
		}
	}

	String& operator=(const String& s)
	{
		if (this != &s)
		{
			_str = s._str;
			_size = s._size;
			_capacity = _size + 1;
			int count = GetCount();
			//GetCount()++;
			*(((int *)_str) - 1) += 1;
		}
		return *this;
	}

private:
	void Check(int a);//實現引用計數
	char* _str;
	int _size;
	int _capacity;
};

//test 構造函數  拷貝構造函數 析構函數 賦值操作符重載 引用計數
void test1()
{
	String s1("abcd");
	cout << s1.GetStr() << endl;
	String s2 = s1;
	cout << s2.GetStr() << endl;
	String s3;
	cout << s3.GetStr() << endl;
	s3 = s1;
	cout << s3.GetStr() << endl;
}

//test  Find  operator[](只讀操作)  
void test2()
{
	String s1("abcdefg");
	cout << s1.Find('b') << endl;
	cout << s1.Find('g') << endl;
	cout << s1.Find('h') << endl;
	cout << s1[2] << endl;
	cout << s1[6] << endl;
	cout << s1[9] << endl;

}

//test  operator< operator== operator>
//test  operator<=  operator>= operator!=
void test3()
{
	String s1("abcd");
	String s2("abc");
	String s3("abcd");
	String s4("acd");
	cout << (s2 < s1) << endl;
	cout << (s1 < s2) << endl;
	cout << (s1 < s3) << endl;
	cout << (s1 < s4) << endl;
	cout << (s1 == s3) << endl;
	cout << (s1 == s2) << endl;
}

//test  operator+=  Insert  
void test4()
{
	String s1("tan");
	String s2("xiaohui is superman");
	cout << (s1 += s2).GetStr() << endl;
	//s1.Insert(2, "ooooo");
	//cout << s1.GetStr() << endl;
	s1.Insert(4, '-');
	cout << s1.GetStr() << endl;
	
}
int main()
{
	
	//test1();
	//test2();
	//test3();
	test4();
	system("pause");
	return 0;
}