c++--string类的模拟实现

//mystring.h
#define _CRT_SECURE_NO_WARNINGS 1
#pragma once
#include<iostream>
#include<assert.h>
using namespace std;

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();
		string(const char* str = "");
		string(const string& s);
		~string();

		const char* c_str() const;

		void reserve(size_t n);

		size_t size() const;
		char& operator[](size_t pos);
		string& operator=(const string& s);

		void print()const;

		void push_back(char ch);
		void append(const char* str);

		void insert(size_t pos, char ch);
		void insert(size_t pos, const char* str);
	private:
		char* _str;
		int _size;
		int _capacity;

	};
}

//mystring.cpp
#include"mystring.h"

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

	string::string(const string& s)
	{
		_str = new char[s._capacity+1];
		strcpy(_str, s._str);
		_capacity = s._capacity;
		_size = s._size;

	}


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

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

	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)
	{
		if (this != &s)
		{
			char* tmp = new char[s._capacity+1];
			strcpy(tmp, s._str);
			delete[] _str;
			_str = tmp;
			_capacity = s._capacity;
			_size = s._size;
		}
		return *this;
	}

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

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

	void string::push_back(char ch)
	{
		/*if (_size == _capacity)
		{
			size_t newcapacity = _capacity == 0 ? 4 : _capacity * 2;
			reserve(newcapacity);
		}
		_str[_size] = ch;
		_str[_size + 1] = '\0';
		_size++;*/
		insert(_size, ch);
	}

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

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

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


	void string::print() const
	{
		for (auto e : *this)
		{
			cout << e << " ";
		}
		cout << endl;
	}
}

//test.cpp
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include"mystring.h"
using namespace std;


int main()
{
	bit::string s1("hello world");
	s1.push_back('x');
	s1.print();

	s1.append("hello");
	cout << endl;

	bit::string::iterator it = s1.begin();
	while (it != s1.end())
	{
		cout << *it << " ";
		++it;
	}

	cout << endl;

	s1.insert(0, 'i');
	cout << s1.c_str();


	return 0;
}