C++ - Implementing my own stream

Question

Hello! My problem can be described the following way:

I have some data which actually is an array and could be represented as char* data with some size

I also have some legacy code (function) that takes some abstract std::istream object as a param and uses that stream to retrieve data to operate.

So, my question is the following - what would be the easy way to map my data to some std::istream object so that I can pass it to my function? I thought about creating a std::stringstream object from my data, but that means copying and (as I assume) isn't the best solution.

Any ideas how this could be done so that my std::istream operates on the data directly?

Thank you.

Answer 1

You can implement a derived std::streambuf class, and use it with an input stream.

Answer 2

If you're looking at actually creating your own stream, I'd look at the Boost.Iostreams library. It makes it easy to create your own stream objects.

Answer 3

Use string stream:

#include <sstream>

int main()
{
    char[]  data = "PLOP PLOP PLOP";
    int     size = 13;  // PS I know this is not the same as strlen(data);

    std::stringstream  stream(std::string(data, size));

    // use stream as an istream;
}

If you want to be real effecient you can muck with the stream buffer directly. I have not tried this and do not have a compiler to test with, but the folowing should work:

#include <sstream>

int main()
{
    char[]  data = "PLOP PLOP PLOP";
    int     size = 13;  // PS I know this is not the same as strlen(data);

    std::stringstream  stream;
    stream.rdbuf()->pubsetbuf(data, size);

    // use stream as an istream;
}