STL tutorial 4- input / output stream and object serialization

standard I/O= The standard input + standard output
file I/O= File input + File output

One 、 Standard I / O stream

cout Global object , Has been associated with the display

cerr There is no buffer ,clog There are buffers ,cin and cout There are also buffers

cin.peek(); Peeping into the buffer , Does not take from the buffer
cin.putback() Use is to use the front get perhaps getline Function to read characters from the input stream ch Return to the input stream , Insert to current pointer position

cout<<flush()// Refresh buffer
cout.put(‘a’).put(‘a’);// Output a character and support chain programming
cout.write(“aaa”,strlen(“aaa”));

Format output

1、 The way member methods

Code

void test06() {
    

	int number = 10;
	// The pattern of member methods 
	cout.unsetf(ios::dec);// Uninstall the default 10 Binary output mode 
	cout.setf(ios::oct);// Set to octal output 
	cout << number<<endl;
	cout.setf(ios::showbase);// Show some hidden contents 
	cout << number<<endl;
	cout.unsetf(ios::oct);// Unload octal 
	cout.setf(ios::hex);// Set to hexadecimal 
	cout << number << endl;
	cout.width(10);// Set bit width 
	cout.fill('*');// Set content fill 
	cout << number << endl;
	cout.setf(ios::left);// Set left alignment 
	cout << number << endl;

}

2、 Through the controller
Need to include header file #include

	int number2 = 10;
	cout << hex   // Set to 16 Base number 
		<< resetiosflags(ios::showbase)// Set the display symbol bit 
		<< setw(10)// Set the width to 10
		<< setfill('$')// Set the padding to $
		<<setiosflags(ios::left)
		<< number2
		<< endl;

Two 、 File operations

File read

Need to include header file #include < fstream >// File read and write
There are two ways to define file objects ,
1、ifstream ism(filePath,ios::in);
2、ifstream ism;
ism.open(filePath, ios::in);

	const char* filePath = "C:\\Users\\admin\\Desktop\\source.txt";
	ifstream ism(filePath,ios::in);// Open the file in read-only mode 

   // Or define an object , Open the file as a member of the object 
	/*ifstream ism; ism.open(filePath, ios::in);*/

	// Here, the object must be overloaded 
	if (!ism) {
    
		cout << " fail to open file " << endl;
	}
	// Reading documents   Thanks to the establishment of the pipeline 
	char ch;
	while ( ism.get(ch))
	{
    
		cout << ch;
	}
	// Finished closing files 
	ism.close();

File is written to

Defining the file write object is the same as defining the file read format
ofstream osm(targetPath, ios::out | ios::app); // have only out It's overlay mode , Add the back | ios::app It's the append mode
rearwards osm.put(ch); Add elements to it

void test07() {
    
	
	const char* filePath = "C:\\Users\\admin\\Desktop\\source.txt";
	const char* targetPath = "C:\\Users\\admin\\Desktop\\target.txt";
	ifstream ism(filePath,ios::in);// Open the file in read-only mode 
	ofstream osm(targetPath, ios::out | ios::app); // have only out It's overlay mode , Plus the following is the append mode 

   // Or define an object , Open the file as a member of the object 
	/*ifstream ism; ism.open(filePath, ios::in);*/

	// Here, the object must be overloaded 
	if (!ism) {
    
		cout << " fail to open file " << endl;
	}
	// Reading documents   Thanks to the establishment of the pipeline 
	char ch;
	while ( ism.get(ch))
	{
     
		cout << ch;
		osm.put(ch);
	}
	// Finished closing files 
	ism.close();
	osm.close();


}

Binary mode read / write

Create a new one Person class take p1 and p2 Write to file p1 and p2 Is stored in binary form , The common text mode reading mentioned above is actually stored in binary form
Even garbled code is stored in binary form window Go to carriage return and line feed /r/n Two symbols are used to mark the end of the line linux Just wrap on as a newline /n sign
Read files in text mode , Will automatically change the /r/n Switch to /n, Writing a file will /n Switch to /r/n
But in linxu It is the same in both text mode and binary mode

summary

Files are stored in binary mode , Even newly created objects in memory are in binary form , Then you can write the object to the file , The difference between opening files in text mode and binary mode is ,window Go to carriage return and line feed /r/n Two symbols are used to mark the end of the line ,linux Just wrap on as a newline /n sign . Read files in text mode , Will automatically change the /r/n Switch to /n, Writing a file will /n Switch to /r/n, But in linux It is the same in both text mode and binary mode