Page 301 - DCAP404 _Object Oriented Programming

Object-oriented Programming

Notes are taken. The size parameter is an integer value that specifies the number of characters to be
read or written from/to the memory block.

Example:
// reading a complete binary file
#include <iostream>

#include <fstream>
using namespace std;

ifstream::pos_type size;
char * memblock;

int main () {
ifstream file (“example.bin”, ios::in|ios::binary|ios::ate);
if (file.is_open())

{
size = file.tellg();
memblock = new char [size];
file.seekg (0, ios::beg);
file.read (memblock, size);
file.close();

cout << “the complete file content is in memory”;

delete[] memblock;
}
else cout << “Unable to open file”;
return 0;
} the complete file content is in memory
In this example the entire file is read and stored in a memory block. Let’s examine how this is
done:
First, the file is open with the ios::ate flag, which means that the get pointer will be positioned
at the end of the file. This way, when we call to member tellg(), we will directly obtain the size
of the file. Notice the type we have used to declare variable size:
ifstream::pos_type size;

ifstream::pos_type is a specific type used for buffer and file positioning and is the type returned
by file.tellg(). This type is defined as an integer type, therefore we can conduct on it the same
operations we conduct on any other integer value, and can safely be converted to another

294 LOVELY PROFESSIONAL UNIVERSITY