main177.cpp

#include <iostream>
#include <fstream>
#include <vector>
#include <iterator>
#include <string>
#include <algorithm>//for for_each()

//#define end "\n"//简单测试一下而已
using namespace std;
static void ShowStr(const string &s)
{
	cout<<s<<endl;
};
static bool store(ofstream &fout,string &s)
{
	if(fout.good())
	{
	int len=s.length();
	fout.write((char*)&len,sizeof(size_t));
	fout.write(s.data(),len);//看api
	return true;
	}
	return false;
}
/*用类我无法实现这个功能，谁实现了麻烦告诉我下
class Store{
private:
	
	//ifstream fin;//接受的应该是ifstream对象
	//fstream fst;
public:
	ofstream fout;
	//Store(){};
	Store(ofstream &os):fout(os){};//构造函数
	//Store(const Store &s)
	bool operator()(const string &s)
	{
		int len=s.length();
		//fout.write((char*)&len,sizeof(size_t));
		//fout.write(s.data(),len);//看api

		return true;
	}

};*/
static bool GetStrs(ifstream &fin,vector<string> &str)
{
	int len;
	//while(!fin.eof()&&fin.good())
	while(fin.read((char*)&len,sizeof(size_t)))//用这个作为判断的时候才能正确执行，
												//难道fin有特殊的？
	{
		//string t;
		//int len;	
		//fin.read((char*)&len,sizeof(size_t));
		//cout<<len<<endl;
		string t="";//t的值每次都要更新
		while(len--)
		{
			char ch;
			ch=fin.get();
			t=t+ch;
		}
		str.push_back(t);

	}
	if(fin.eof())
		return true;
	else
		return false;

};

void main177()
{
	vector<string> vostr;
	string temp;

	cout<<"Enter string (q to quit):"<<endl;
	while(getline(cin,temp)&&temp!="q")
 	{
		vostr.push_back(temp);
	}
		cout<<"Her is your input:"<<endl;
		for_each(vostr.begin(),vostr.end(),ShowStr);

		ofstream fout("str.dat",ios_base::out|ios_base::binary|ios_base::app);
		//ofstream fout("strings.dat",ios_base::out|ios_base::binary);//是|而不是||
		//for_each(vostr.begin(),vostr.end(),Store(fout));
		//由Strore(fout)可知Strore应该是一个类
		//Store的具体实现不太会，对于函数符中如何传递的原理不太懂
		vector<string>::iterator it=vostr.begin();
		for(;it!=vostr.end();++it)
		{
			store(fout,*it);//用这个实现
		}
		fout.close();

		
		vector<string> vistr;
		ifstream fin("str.dat",ios_base::in|ios_base::binary);
		if(!fin.is_open())
		{
			cerr<<"Could not open file for input."<<endl;
			exit(EXIT_FAILURE);
		}
		GetStrs(fin,vistr);
		cout<<endl<<"Here are the strings read fronm the file:"<<endl;
		for_each(vistr.begin(),vistr.end(),ShowStr);

		fin.close();
		
		cin.get();


}

 

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下面是一个网友的改进，感谢分享！

class Store{
private:
std::ofstream &os;
public:
Store(std::ofstream &os_) : os(os_){}
void operator()(const std::string & str){
int n = str.length();
os.write((char *)&n, sizeof(int));
os.write(str.c_str(), str.length());
}
};

—2014.9.16

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//写的错误或者不好的地方请多多指导，可以在下面留言或者给我发邮件，指出我的错误以及不足，以便我修改，更好的分享给大家，谢谢。

转载请注明出处：https://www.royalchen.com/

author:royalchen

Email:royalchen@royalchen.com

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