Question

C++ file I/O is tougher than C file I/O. So in C++, creating a new library for file I/O is useful or not? I mean <fstream> Can anyone please tell are there any benefits in C++ file I/O ?

Answer 1

Opinion

I don’t know of any real project that uses C++ streams. They are too slow and difficult to use. There are several newer libraries like FastFormat and the Boost version that claim to be better there was a piece in the last ACCU Overload magazine about them. Personally I have used the c FILE library for the last 15 years or so in C++ and I can see no reason yet to change.

Speed

Here is small test program (I knock together quickly) to show the basic speed problem:

#include <stdio.h> #include <time.h>  #include<iostream> #include<fstream>  using namespace std;  int main( int argc, const char* argv[] )     {     const int max = 1000000;     const char* teststr = "example";      int start = time(0);     FILE* file = fopen( "example1", "w" );     for( int i = 0; i < max; i++ )         {         fprintf( file, "%s:%d\n", teststr, i );         }     fclose( file );     int end = time(0);      printf( "C FILE: %ds\n", end-start );      start = time(0);     ofstream outdata;     outdata.open("example2.dat");     for( int i = 0; i < max; i++ )         {         outdata << teststr << ":" << i << endl;         }     outdata.close();     end = time(0);      printf( "C++ Streams: %ds\n", end-start );      return 0;     } 

And the results on my PC:

C FILE: 5s C++ Streams: 260s  Process returned 0 (0x0)   execution time : 265.282 s Press any key to continue. 

As we can see just this simple example is 52x slower. I hope that there are ways to make it faster!

NOTE: changing endl to ‘\n’ in my example improved C++ streams making it only 3x slower than the FILE* streams (thanks jalf) there may be ways to make it faster.

Difficulty to use

I can’t argue that printf() is not terse but it is more flexible (IMO) and simpler to understand, once you get past the initial WTF for the macro codes.

double pi = 3.14285714;      cout << "pi = " << setprecision(5)  << pi << '\n'; printf( "%.5f\n", pi );      cout << "pi = " << fixed << showpos << setprecision(3) << pi << '\n';  printf( "%+.3f\n", pi );      cout << "pi = " << scientific << noshowpos << pi<< '\n'; printf( "%e\n", pi ); 

The Question

Yes, may be there is need of a better C++ library, may be FastFormat is that library, only time will tell.

dave