another file i/o question
What difference does it make whether a file is opened in text mode vs. binary mode? I seem to be finding the same results either way. When I write an int using write() the file contains the 4 bytes that make up the int. When I write the int using <<, the file contains the ascii codes for the digits that represent the int. The same things occur regardless of whether I use fout.open( "iotest.dat" ) or fout.open( "iotest.dat", ios::binary ). It seems that the only thing that matters is the output function, not the file type. Why?
Code:
#include <iostream>
#include <fstream>
using namespace std;
int main () {
int intval1 = 1919006563; // this is what I should get back when the chars are put together
int intval2, intval3;
unsigned char buffer[4];
void* vp;
cout << "First test - view contents of binary file written with unformatted output:\n";
ofstream fout( "iotest.dat", ios::binary );
if( fout == NULL ) {
cout << "couldn't open for output\n";
return 1;
}
buffer[0] = (unsigned char)99;
buffer[1] = (unsigned char)183;
buffer[2] = (unsigned char)97;
buffer[3] = (unsigned char)114;
vp = buffer;
fout.write( (const char*)vp, 4 );
vp = &intval1;
fout.write( (const char*)vp, 4 );
fout.close();
ifstream fin( "iotest.dat", ios::binary );
if( fin == NULL ) {
cout << "couldn't open for input\n";
return 1;
}
vp = &intval2;
fin.read( (char*)vp, 4 );
cout << intval2 << endl;
vp = buffer;
fin.read( (char*)vp, 4 );
for( int i = 0; i < 4; ++i ) {
cout << (int)buffer[i] << endl;
}
while( !fin.eof() ) {
fin.read( (char*)vp, 1 );
if( !fin.eof() )
cout << (int)buffer[0] << " ";
else cout << "reached eof";
}
cout << endl;
fin.close();
cout << "\nSecond test - view contents of binary file written with formatted output:\n";
fout.open( "iotest.dat", ios::binary );
if( fout == NULL ) {
cout << "couldn't open for output\n";
return 1;
}
fout << intval1;
fout << (unsigned char)99;
fout << (unsigned char)183;
fout << (unsigned char)97;
fout << (unsigned char)114;
fout.close();
fin.open( "iotest.dat", ios::binary );
if( fin == NULL ) {
cout << "couldn't open for input\n";
return 1;
}
while( !fin.eof() ) {
fin.read( (char*)vp, 1 );
if( !fin.eof() )
cout << (int)buffer[0] << " ";
else cout << "reached eof";
}
cout << endl;
fin.close();
cout << "\nThird test - view contents of text file with unformatted output:\n";
fout.open( "iotest.dat" );
if( fout == NULL ) {
cout << "couldn't open for output\n";
return 1;
}
buffer[0] = (unsigned char)99;
buffer[1] = (unsigned char)183;
buffer[2] = (unsigned char)97;
buffer[3] = (unsigned char)114;
vp = buffer;
fout.write( (const char*)vp, 4 );
vp = &intval1;
fout.write( (const char*)vp, 4 );
fout.close();
fin.open( "iotest.dat", ios::binary );
if( fin == NULL ) {
cout << "couldn't open for input\n";
return 1;
}
cout << "Unformatted input: ";
while( !fin.eof() ) {
fin.read( (char*)buffer, 1 );
if( !fin.eof() )
cout << (int)buffer[0] << " ";
else cout << "reached eof";
}
cout << endl;
fin.clear();
fin.seekg(0);
cout << "Formatted input: ";
while( fin >> buffer[0] )
cout << (int)buffer[0] << " ";
cout << endl;
fin.close();
cout << "\nFourth test - view contents of text file with formatted output:\n";
fout.open( "iotest.dat" );
if( fout == NULL ) {
cout << "couldn't open for output\n";
return 1;
}
buffer[0] = (unsigned char)99;
buffer[1] = (unsigned char)183;
buffer[2] = (unsigned char)97;
buffer[3] = (unsigned char)114;
for( int i = 0; i < 4; ++i )
fout << buffer[i];
fout << intval1;
fout.close();
fin.open( "iotest.dat", ios::binary );
if( fin == NULL ) {
cout << "couldn't open for input\n";
return 1;
}
cout << "Unformatted input: ";
while( !fin.eof() ) {
fin.read( (char*)buffer, 1 );
if( !fin.eof() )
cout << (int)buffer[0] << " ";
else cout << "reached eof";
}
cout << endl;
fin.clear();
fin.seekg(0);
cout << "Formatted input: ";
while( fin >> buffer[0] ) {
cout << (int)buffer[0] << " ";
}
cout << endl;
fin.close();
return 0;
}
