How do you read from a ifstream asynchronously in C++?

Question

The ifstream is reading from a UNIX pipe, currently the communication is done by sending a signal to the reading application, but I would like to get rid of the signals and use proper async io.

In C I would use the select() function with a timeout, so I could react immediately when there is something to read, and waith for IO otherwise.

In C++ I can't access the fd of the file, so I can't use select(). What's the most reasonable approach to doing this? Do I have to use some sort of Boost library, or can this be done using the standard C++ libraries?

Answer 1

std::ifstream does not support asynchronous operations, it is designed for synchronous IO. You could build async IO around it using additional threads and IO queue, but in general this is not a good idea for efficiency reasons.

For asynchronous IO you might want to look at Boost.ASIO , in particular its stream_descriptor , which can be used to adopt arbitrary stream file descriptors like pipes.