question about streams

[lab1]

Hello,

I have a function that I would like to either send it a ifstream or a string (maybe a string stream)?

So say I have this code:

string test = "hello this is a string to be parsed";

if(testint == 0)
{
ifstream in(fileName);
}
else
{
// put string in a stream here?
}

ParseData(generic stream?);

Can someone help me fill in the missing pieces to this code? basically I need to parse either a file or a string and I was hoping to use the same code to do either with maybe a generic stream?

Thanks!

[Gabriel Fleseriu]

It's quite simple. In my example, the "parse" function simply prints the input, but it could do whatever. It works with a file, with the console or a stringstream:

#include <iostream>
#include <fstream>
#include <sstream>
using namespace std;


template <typename E, typename T>
void parse(basic_istream<E, T> &s)
{   
    E e;
    while(s.read(&e, 1)) cout<<e;
}

int main()
{
    ifstream f("c:\\boot.ini");
    parse(f);
    parse(cin);
    stringstream ss;
    ss << "abc";
    parse(ss);
    return 0;
}

[lab1]

Is there a way to do this without templates?

Can you show sample code without templates?

Thanks

[Gabriel Fleseriu]

What's wrong with templates? The standard library is full of them and they are one of the major strengthes of C++. And my example won't involve a more extensive use of templates than it does when used in real life (that is with parse() implemented).

To answer your question: yes, you can do it without templates. Pseudocode:

if(your_int == 0)
{
   FILE *f = fopen("filename");
   fread(f, buffer, size_of_file);
   parse(buffer); // buffer is of course a byte buffer
} else {
   put_string_in_buffer(s, buffer);
   parse(buffer);
}

Basically parse() always parses a buffer. All you need to do is to take out the functionality of filling that buffer.

[Philip Nicoletti]

I don't have any documentation in front of me right now,
but isn't std::istream a common base class ?

#include <string>
#include <sstream>
#include <iostream>
#include <fstream>

using namespace std;

void Parse(std::istream & in)
{
    string str;
    getline(in,str);
    std::cout << str << "\n";
}

int main()
{
    ifstream in("somefile");
    Parse(in);

    istringstream ss("this is a test");
    Parse(ss);

    return 0;
}