Categories: Open C/C++ | Code Examples | Files/Data

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Overview

This code snippet shows how to use Open C++ file I/O classes for binary file read and write operations. The stream class fstream can be used for both read and write file I/O operations. Ifstream is only capable of file read operations and ofstream is only capable of file write operations. A header file <fstream> must be included in the application before these classes can be used. To operate as a binary file, the open() method is called with the parameter ios::binary. These file streams have two special methods for input and output binary data: read() and write(). In addition to read/write built-in data types, these classes can be used to read/write classes and structures to the file.

Note: In order to use this code, you need to install the Open C/C++ plug-in.

This snippet can be self-signed.

MMP file

The following libraries are required:

STATICLIBRARY   libcrt0.lib
 
LIBRARY  libstdcpp.lib
LIBRARY  libc.lib
LIBRARY  euser.lib

Source file

#include <fstream>  //ifstream, ofstream
#include <iostream> //cout
 
using namespace std;
 
//ExampleStruct
typedef struct 
{
    char chr;
    int num; 
} ExampleStruct;
 
//ExampleClass
class ExampleClass
{
public:
    ExampleClass(): m_chr(' '), m_num(0){}
    ExampleClass(char c, int n): m_chr(c), m_num(n){}
 
    friend ostream& operator<<(ostream&, const ExampleClass&);
private:
   char m_chr;
   int m_num; 
};
 
ostream& operator<<(ostream& out, const ExampleClass& c)
{
    out << "c.chr:" << c.m_chr << endl;
    out << "c.num:" << c.m_num << endl;
    
    return out;
}
 
void write_binary_output_example()
{
    char chr = 'A';
    int num = 1;
    ExampleStruct s = {'B', 2};
    ExampleClass c('C', 3);
    
    ofstream file("example.bin", ios::binary);
    
    //The first parameter of method write() is
    //a pointer to char representing the address of 
    //an array of bytes where the data elements to be 
    //written are taken from.
 
    //The second parameter is an integer value that specifies
    //the number of characters to be written to the memory block.
    
    file.write((char *)(&chr), sizeof(chr));
    file.write((char *)(&num), sizeof(num));
    file.write((char *)(&s), sizeof(s));
    file.write((char *)(&c), sizeof(c));
    
    file.close();
}
 
void read_binary_input_example()
{
    char chr = ' ';
    int num = 0;
    ExampleStruct s;
    ExampleClass c;
    
    ifstream file("example.bin", ios::binary);
 
    //The first parameter of the method read() is
    //a pointer to char representing the address of 
    //an array of bytes where the read data elements
    //are stored to.
    
    //The second parameter is an integer value that specifies 
    //the number of characters to be read from the memory block.
    
    file.read((char *)(&chr), sizeof(chr));
    cout << "chr:" << chr << endl;
 
    file.read((char *)(&num), sizeof(num));
    cout << "num:" << num << endl;
    
    file.read((char *)(&s), sizeof(s));
    cout << "s.chr:" << s.chr << endl;
    cout << "s.num:" << s.num << endl;
    
    file.read((char *)(&c), sizeof(c));
    cout << c << endl;
    
    file.close();
}
 
int main()
{   
    write_binary_output_example();
    
    read_binary_input_example();
    
   //getchar(); 
    
    return 0;
}

Postconditions

The Open C++ I/O classes ifstream and ofstream are used to read and write binary data from/to the created file simple.bin and content of the file is displayed as standard output.

See also

• CS001114 - Reading and writing text files in Open C++
• CS001116 - Checking the file I/O status in Open C++