Copy data from fstream to stringstream with no buffer?

Question

Is there anyway I can transfer data from an fstream (a file) to a stringstream (a stream in the memory)?

Currently, I'm using a buffer, but this requires double the memory, because you need to copy the data to a buffer, then copy the buffer to the stringstream, and until you delete the buffer, the data is duplicated in the memory.

std::fstream fWrite(fName,std::ios::binary | std::ios::in | std::ios::out);  
    fWrite.seekg(0,std::ios::end); //Seek to the end  
    int fLen = fWrite.tellg(); //Get length of file  
    fWrite.seekg(0,std::ios::beg); //Seek back to beginning  
    char* fileBuffer = new char[fLen];  
    fWrite.read(fileBuffer,fLen);  
    Write(fileBuffer,fLen); //This writes the buffer to the stringstream  
    delete fileBuffer;`

Does anyone know how I can write a whole file to a stringstream without using an inbetween buffer?

Answer 1

 ifstream f(fName);
 stringstream s;
 if (f) {
     s << f.rdbuf();    
     f.close();
 }

Answer 2

// need to include <algorithm> and <iterator>, and of course <fstream> and <sstream>
ifstream fin("input.txt");
ostringstream sout;
copy(istreambuf_iterator<char>(fin),
     istreambuf_iterator<char>(),
     ostreambuf_iterator<char>(sout));

Answer 3

In the documentation for ostream, there are several overloads for operator<<. One of them takes a streambuf* and reads all of the streambuffer's contents.

Here is a sample use (compiled and tested):

#include <exception>
#include <iostream>
#include <fstream>
#include <sstream>

int main ( int, char ** )
try
{
        // Will hold file contents.
    std::stringstream contents;

        // Open the file for the shortest time possible.
    { std::ifstream file("/path/to/file", std::ios::binary);

            // Make sure we have something to read.
        if ( !file.is_open() ) {
            throw (std::exception("Could not open file."));
        }

            // Copy contents "as efficiently as possible".
        contents << file.rdbuf();
    }

        // Do something "useful" with the file contents.
    std::cout << contents.rdbuf();
}
catch ( const std::exception& error )
{
    std::cerr << error.what() << std::endl;
    return (EXIT_FAILURE);
}