string类的模拟实现

目录

string.h

string.cpp

string.h

#define _CRT_SECURE_NO_WARNINGS 1
#pragma once
#include <iostream>
#include <assert.h>

namespace bit
{
	class string
	{
	public:
		typedef char* iterator;
		typedef const char* const_iterator;

		iterator begin();
		iterator end();
		
		const_iterator begin() const;
		const_iterator end() const;

		string(const char* str = "");

		~string();

		const char* c_str()const;

		size_t size()const;

		char& operator[](size_t pos);
		const char& operator[](size_t pos) const;

		string& operator=(const string& s);

		void reserve(size_t n);

		void push_back(char ch);

		void append(const char* str);

		string& operator+=(char ch);
		string& operator+=(const char* str);

		void insert(size_t pos, char ch);
		void insert(size_t pos, const char* str);

		void erase(size_t pos = 0, size_t len = npos);

		size_t find(char ch, size_t pos = 0);
		size_t find(const char* str, size_t pos = 0);

		void swap(string& s);

		string substr(size_t pos = 0, size_t len = npos);

		bool operator<(const string& s) const;
		bool operator>(const string& s) const;
		bool operator<=(const string& s) const;
		bool operator>=(const string& s) const;
		bool operator==(const string& s) const;
		bool operator!=(const string& s) const;

		void clear();

	private:
		char* _str;
		size_t _size;
		size_t _capacity;
		const static size_t npos;
	};
	std::istream& operator>> (std::istream& is, string& str);
	std::ostream& operator<< (std::ostream& os, const string& str);
}

string.cpp

#include "string.h"
namespace bit
{

	const size_t string::npos = -1;

	string::string(const char* str)
		:_size(strlen(str))
	{
		_str = new char[_size + 1];
		_capacity = _size;
		strcpy(_str, str);
	}

	string::~string()
	{
		delete[] _str;
		_str = nullptr;
		_size = _capacity = 0;
	}

	const char* string::c_str()const
	{
		return _str;
	}

	size_t string::size()const
	{
		return _size;
	}

	char& string::operator[](size_t pos)
	{
		assert(pos < _size);
		return _str[pos];
	}

	const char& string::operator[](size_t pos) const
	{
		assert(pos < _size);
		return _str[pos];
	}

	string::iterator string::begin()
	{
		return _str;
	}
	string::iterator string::end()
	{
		return _str + _size;
	}

	string::const_iterator string::begin() const
	{
		return _str;
	}
	string::const_iterator string::end() const
	{
		return _str + _size;
	}

	string& string::operator=(const string& s)
	{
		while (this != &s)
		{
			char* tmp = new char[_capacity + 1];
			strcpy(tmp, s.c_str());
			delete[]_str;
			_str = tmp;
			_capacity = s._capacity;
			_size = s._size;
		}
		return *this;
	}


	void string::reserve(size_t n)
	{
		if (n >= _capacity)
		{
			char* tmp = new char[n + 1];
			strcpy(tmp, _str);
			delete[] _str;
			_str = tmp;
			_capacity = n;
		}
	}

	void string::push_back(char ch)
	{
		return insert(_size, ch);
	}

	void string::append(const char* str)
	{
		return insert(_size, str);
	}

	string& string::operator+=(char ch)
	{
		push_back(ch);
		return *this;
	}

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

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

	void string::insert(size_t pos, const char* str)
	{
		size_t len = strlen(str);
		if (len + _size > _capacity)
		{
			reserve(len + _size);
		}

		size_t end = _size + len;
		while (pos < end - len + 1)
		{
			_str[end] = _str[end - len];
			--end;
		}
		memcpy(_str + pos, str, len);
		_size += len;
	}

	void string::erase(size_t pos, size_t len)
	{
		if (pos + len >= _size)
		{
			_str[pos] = '\0';
			_size = pos;
		}
		else
		{
			strcpy(_str + pos, _str + pos + len);
			_size -= len;
		}
		
	}

	size_t string::find(char ch, size_t pos)
	{
		size_t i = 0;
		for (i = pos; i < _size; i++)
		{
			if (_str[i] == ch)
			{
				return i;
			}
		}
		return npos;
	}

	size_t string::find(const char* str, size_t pos)
	{
		char* p = strstr(_str + pos, str);
		return  p - _str;
	}

	void string::swap(string& s)
	{
		std::swap(_str, s._str);
		std::swap(_size, s._size);
		std::swap(_capacity, s._capacity);

	}

	string string::substr(size_t pos, size_t len)
	{
		if (pos + len >= _size)
		{
			string sub(_str + pos);
			return sub;
		}
		else
		{
			string sub;
			sub.reserve(len);
			for (size_t i = 0; i < len; i++)
			{
				sub += _str[pos + i];
			}
			return sub;
		}
	}

	bool string::operator<(const string& s) const
	{
		return strcmp(_str, s.c_str()) < 0;
	}

	bool string::operator>(const string& s) const
	{
		return !(*this <= 0);
	}

	bool string::operator<=(const string& s) const
	{
		return !(*this > 0);
	}

	bool string::operator>=(const string& s) const
	{
		return !(*this < 0);
	}

	bool string::operator==(const string& s) const
	{
		return strcmp(_str, s.c_str()) == 0;
	}

	bool string::operator!=(const string& s) const
	{
		return !(*this == 0);
	}

	void string::clear()
	{
		_str[0] = '\0';
		_size = 0;
	}

	std::istream& operator>> (std::istream& is, string& str)
	{
		str.clear();
		char ch = is.get();
		while (ch != ' ' && ch != '\n')
		{
			str += ch;
			ch = is.get();
		}

		return is;
	}

	std::ostream& operator<< (std::ostream& os, const string& str)
	{
		for (size_t i = 0; i < str.size(); i++)
		{
			os << str[i];
		}
		return os;
	}
 }