C++初阶（十二）string的模拟实现

一、string类的模拟实现

1、构造、拷贝构造、赋值运算符重载以及析构函数

2、迭代器类

3、增删查改类

4、io类

5、扩容类

6、完整代码

namespace bit
{
	class string
	{
	public:
		typedef char* iterator;
		typedef const char* const_iterator;
		const_iterator beagin() const
		{
			return _str;
		}
		const_iterator end() const
		{
			return _str + _size;;
		}
		iterator begin()
		{
			return _str;
		}
		iterator end()
		{
			return _str + _size;
		}


		void insert(size_t pos, char ch)
		{
			assert(pos <= _size);
			if (_size == _capacity)
			{
				reserve(_capacity == 0 ? 4 : _capacity *= 2);
			}
			size_t end = _size + 1;
			while (end >pos)
			{
				_str[end] = _str[end-1];
				end--;
			}
			_str[pos] = ch;
			_size++;
		}

		void insert(size_t pos, const char* ch)
		{
			assert(pos <= _size);
			size_t len = strlen(ch);
			if (_size + len > _capacity)
			{
				reserve(_size + len);
			}
			size_t  end = _size;
			while (end > pos)
			{
				_str[end + len] = _str[end];
				--end;
			}
			strncpy(_str + pos, ch, len);
			_size += len;	                                                                                                              
		}

		void erase(size_t pos, size_t len = npos)
		{
			assert(pos < _size);
			if (len == npos || pos + len > _size)
			{
				_str[pos] = '\0';
				_size = pos;
			}
			else
			{
				size_t begin = _size + len;
				while (begin <= _size)
				{
					_str[pos++] = _str[begin++];
				}
				_size -= len;
			}
		}
		void push_back(char ch)
		{
			if (_size == _capacity)
			{
				reserve(_capacity == 0 ? 4 : _capacity * 2);
			}
			_str[_size] = ch;
			++_size;
			_str[_size] = '\0';
		}
		void append(const char* str)
		{
			size_t len = strlen(str);
			if (_size + len > _capacity)
			{
				reserve(_size + len);
				strcpy(_str + _size, str);
				_size += len;
			}
		}
		string& operator+=(char ch)
		{
			push_back(ch);
			return *this;

		}
		string& operator+=(const char* ch)
		{
			append(ch);
			return *this;

		}



		string(const char* str = "")
			:_size(strlen(str))
			,_capacity(_size)
		{
			_str = new char[_size + 1];
			strcpy(_str, str);
		}
		~string()
		{
			delete[] _str;
			_str = nullptr;
			_size = 0;
			_capacity = 0;
		}
		string(const string& s)
			:_str(nullptr)
			, _size(0)
			, _capacity(0)
		{
			string tmp(s._str);
			swap(tmp);
		}
		string& operator=(string s)
		{
			swap(s);
			return *this;
		}
		
		void reserve(size_t n)
		{
			if (n > _capacity)
			{
				char* tmp = new char[n + 1];
				strcpy(tmp, _str);
				_str = tmp;
				_capacity = n;
			}
		}
		void resize(size_t n,char ch='\0')
		{
			if (n <= _size)
			{
				_str[n] = ch;
				_size = n;
			}
			else
			{
				reserve(n);
				while (_size < n)
				{
					_str[_size++] = ch;
				}
				_str[_size] = '\0';
			}
		}
		
			
		
		
		void clear()

		{
			_str[0] = '\0';
			_size = 0;
		}
		void swap(string& s)
		{
			std::swap(_str, s._str);
			std::swap(_size, s._size);
			std::swap(_capacity, s._capacity);

		}




		
		size_t find(char ch, size_t pos = 0)
		{
			for (size_t i = pos; i < _size; i++)
			{
				if (_str[i] == ch)
				{
					return i;
				}
			}
			return npos;
		}
		size_t find(const char* sub, size_t pos=0)
		{
			const char* p = strstr(_str + pos, sub);
			if (p)
			{
				return p - _str;
			}
			else
			{
				return npos;
			}

		}
		string substr(size_t pos, size_t len = npos)
		{
			string s;
			size_t end = pos + len;
			if (len == npos || pos + len >= _size)
			{
				len = _size - pos;
				end = _size;
			}
			s.reserve(len);
			for (size_t i = pos; i <= end; i++)
			{
				s += _str[i];
			}
			return s;
		}

		



	private:
		char* _str;
		size_t _size;
		size_t _capacity;
		const static size_t npos;
	};
	const size_t string::npos = -1;
	ostream& operator<< (ostream& out, string& s)
	{
		for (auto ch : s)
		{
			out << ch;
		}
		return out;
	}

	istream& operator>> (istream& in, string& s)
	{
		s.clear();
		char buff[129];
		size_t i = 0;
		char ch;
		ch = in.get();
		while (ch != ' ' && ch != '\0')
		{
			buff[i++] = ch;
			if (i == 128)
			{
				buff[i] = '\0';
				s += buff;
				i = 0;
			}
			s += ch;
			ch = in.get();
		}
		if (i != 0)
		{
			buff[i] = '\0';
			s += buff;
		}
		return in;
	}

}