Add ready/try methods to NamedPipeClient

[Jake-Shadle]

Motivation

As discussed in other issues related to named pipes, a very common use case for named pipes is using them similarly to unix domain sockets, however the initial named pipe support in 1.7 was intentionally bare bones and thus didn't support doing both read and write operations on the same pipe in the same task, but which is supported for UnixStream and other net types via the ready/try_read/try_write etc family of methods.

Solution

This PR just copies the following methods from UnixStream to NamedPipeClient with 0 changes other than in the doc comments, as well as adding an example and a test.

• ready
• readable
• poll_read_ready
• try_read
• try_read_vectored
• writable
• poll_write_ready
• try_write
• try_write_vectored

[Darksonn]

You have only added the methods for the NamedPipeClient, but there's also a NamedPipeServer.

[Jake-Shadle]

This was intentional just to keep it to the smallest cohesive change, I wanted to avoid stalling the PR as much as possible, but I can of course add those as well if you would like.

[Darksonn]

The methods and documentation look fine.

[carllerche]

LGTM, ideally we could get @udoprog to weigh in.

[udoprog]

Thanks!

Looks good to me as well. There are some minor documentation inconsistencies, but since they're essentially carried over from copying the documentation of TcpStream (or similar) I don't really find that particularly offensive.

One note is that it would be nice to get less functions that are no_run to get improved test coverage, but it would require that tests to spin up a server side as well which might be a bit noisy.

Just nits and no blockers though as far as I'm concerned since they're all documentation. The set of methods added makes perfect sense to me.

[Jake-Shadle]

I went through and cleaned up all of the docs, they were all copied from UnixStream, which seems to use socket/stream interchangeably in its docs, but now all the docs for the namedpipeclient just use pipe.