本篇练习涉及到的知识点
- 写文本文件
- 4种方式读文本文件
- 写二进制文件
- 读二进制文件（例如写入自定义类的实例，和浮点数）
- char* p = "abc";// valid in C, invalid in C
#include<iostream>
#include<fstream>
#include<string>
using namespace std;
class Person
{
public:
Person(char* name,int age,char* gender)
{
m_name = name;
m_age = age;
m_gender = gender;
}
Person()
{
}
get_age()
{
return m_age;
}
public:
char* m_name;
char* m_gender;
private:
int m_age;
};
void write_text();
void write_binary();
//以下4种方式均可写文本文件
void read1_text();
void read2_text();
void read3_text();
void read4_text();
void read_binary();
int main()
{
write_text();
cout<<endl;
read1_text();//0.3s
cout<<endl;
read2_text();//0.3s
cout<<endl;
read3_text();//0.3s
cout<<endl;
read4_text();//0.3s
cout<<endl;
write_binary();
cout<<endl;
read_binary();
return 0;
}
void write_text()
{
ofstream ofs;
ofs.open("E:\test1.txt", ios::out);
for(int i = 0; i <5;)
{
ofs<< i <<endl;
}
ofs<< "王八" <<endl;
ofs.close();
cout<<"文本文件写入成功!"<<endl;
}
void read1_text()
{
ifstream ifs("E:\test1.txt", ios::in);//也在ifstream构造函数中指定参数，可省去open调用
//ifs.open("E:\test1.txt", ios::in);
if (!ifs.is_open())
{
cout<<"文本文件打开失败！"<<endl;
return;
}
cout<<"文本文件打开成功！下面依次读取每一行"<<endl;
char buffer[1024]= {0};
while(ifs >> buffer)//循环读取每一行（不含'n'），存到字符数组
{
cout<< buffer <<endl;
}
ifs.close();
}
void read2_text()
{
//也在ifstream构造函数中指定参数，即可省去open调用
ifstream ifs("E:\test1.txt", ios::in);
if (!ifs.is_open())
{
cout<<"文本文件打开失败！"<<endl;
return;
}
cout<<"文本文件打开成功！下面依次读取每一行"<<endl;
char buffer[1024]= {0};
//循环读取每一行（不含'n',），存到字符数组(但是限定了最多读取多少字节）
while(ifs.getline(buffer,sizeof(buffer)))
{
cout<< buffer<<endl;
}
ifs.close();
}
void read3_text()
{
ifstream ifs("E:\test1.txt", ios::in);
if (!ifs.is_open())
{
cout<<"文本文件打开失败！"<<endl;
return;
}
cout<<"文本文件打开成功！下面依次读取每一行"<<endl;
string buffer;
//循环读取每一行（不含'n',），存到字符数组(但是限定了最多读取多少字节）
while(getline(ifs, buffer))
{
cout<< buffer<<endl;
}
ifs.close();
}
void read4_text(void)
{
ifstream ifs("E:\test1.txt", ios::in);
if (!ifs.is_open())
{
cout<<"文本文件打开失败！"<<endl;
return;
}
cout<<"文本文件打开成功！下面依次读取每一行"<<endl;
char c;
//循环读取每个字符（包含'n',），赋值给字符变量c
while((c = ifs.get())!=EOF)
{
cout<< c;
}
ifs.close();
}
void write_binary()//写二进制文件
{
ofstream ofs;
ofs.open("E:\test2.bin", ios::out | ios::binary);
Person p1 = {(char*)"法外狂徒张三", 28, (char*)"男"};//字符数组常量强制转换成字符指针
ofs.write((const char*)&p1, sizeof(Person));//写入对象
float x1 = 0.999f;
ofs.write((const char*)&x1, sizeof(float));
ofs.close();
cout<<"二进制文件写入成功!"<<endl;
}
void read_binary()//读二进制文件
{
ifstream ifs("E:\test2.bin", ios::in | ios::binary);
if (!ifs.is_open())
{
cout<<"二进制文件打开失败！"<<endl;
return;
}
cout<<"二进制文件打开成功！"<<endl;
Person p;
//读二进制数据，注意须强制类型转换 (char*)
ifs.read((char*) &p, sizeof(Person));
float x = 0;
ifs.read((char*) &x, sizeof(float));
ifs.close();
cout<< "p.name: "<< p.m_name << endl;
cout<< "p.gender: "<< p.m_gender << endl;
cout<< "p.age: "<< p.get_age()<< endl;
cout<< "x: "<< x << endl;
char name[1024] ={0};
int i;
for(; i< int(sizeof(name)); i )//将 字符指针指向的值复制到字符数组中
{
name[i] = *(p.m_name );
if(name[i] == ' ') break;
}
cout<<name<<" 共"<<i<<"字节";
char* ps1 = "abc";// valid in C, invalid in C
char* ps2 = (char*)"abc";// OK .注意括号！
char const *cp = "abc";// OK
}
