I wanted to provide a generic interface for reading from a device. The most simple interface I can think of would be: virtual std::string read(const std::size_t) = 0;. Also, std::istream can be used and could be preferable. However, what if you wanted to make this interface asynchronous? I don't think std::istream is possible, but the other interface can be: virtual std::future<std::string> read(const std::size_t) = 0. The interface should handle the case where a second read was done before the prior read completed. In that situation the interface either blocks until the other future is set or tries to have a small queue so the client can continue working unblocked. I wanted to do the latter. Perhaps it wasn't the best idea because it was slow (used boost::futures). Although, I had no time to analyze the performance issues either.

There are certainly ways to achieve that asynchronous interface using scatter gather and containers (return a future<vector<string> > or similar), but the obvious interfaces were too messy for my liking. I became big on NOT messing up interfaces for performance gains, I am generally convinced that both are achievable. At the time, I thought finding a method of queuing reads was the best way to achieve both.

Lee