How can I open a nodejs Duplex stream given a file descriptor?

Question

I'm porting an existing program to nodejs. In this program, I open a file descriptor and then hand it off to a thread which calls poll on it in order to determine when it's readable.

Instead of writing a custom C++ module, I'd really like to do this in pure javascript making use of Node's handy dandy Duplex stream.

For example I'd like to do something like this:

var device = new PollDuplexStream(fileDescriptor);

device.on('data', function(data) {
    // data handling logic here
});

...

var chunk = new Buffer(...);
device.write(chunk);

It seems like this should exist, but I'm not seeing where it does. Perhaps I'm just blind? What's the real world equivalent of PollDuplexStream from the example above?

Please note that I'm explicitly looking for a solution which starts with a file descriptor rather than a path, otherwise I'd just create my own from fs.createReadStream and fs.createWriteStream.

Also I don't care that it calls poll internally - in fact, I'd prefer that it use libuv's uv_poll_* internally.

then try `tty.ReadStream` and `tty.WriteStream`. Related discussion: https://github.com/joyent/node/issues/7101 — vkurchatkin, Jun 28 '14 at 12:21
`createReadStream` also takes a file descriptor as an argument, have you tried that? — loganfsmyth, Jun 28 '14 at 17:22
@loganfsmyth does createWriteSteam as well? Can you point me to the docs which shows that w/ an answer rather than a comment? If it works I'll happily accept — Ben Burns, Jun 28 '14 at 23:49
@vkurchatkin same to you - if you write up your answer as an answer rather than a comment, I can at least upvote it. Thought I'm not convinced this is the best solution, as what I'm reading is neither a tty, nor a socket. — Ben Burns, Jun 28 '14 at 23:50
@BenBurns You can see it in the example options in the docs: http://nodejs.org/api/fs.html#fs_fs_createreadstream_path_options `fd`. It isn't in the docs, but `createWriteStream` also supports it. — loganfsmyth, Jun 29 '14 at 19:10
See https://github.com/joyent/node/issues/7707 for fs.createReadStream notes/discussion and https://github.com/joyent/node/issues/7708 for fs.createWriteStream regarding the `fd` option. — natevw, Jul 23 '14 at 20:39
@natevw - search the text on the page of issue 7707 for "benjamincburns" ;-) — Ben Burns, Jul 24 '14 at 04:51
@natevw - nevermind, I see you responded to me... :facepalm: — Ben Burns, Jul 24 '14 at 04:52

score 0 · Answer 1 · answered Sep 24 '14 at 12:59

0

You'll need to create a binary addon which uses a uv_poll_t handle, which is able to poll for readability / writability for arbitrary file descriptors.

answered Sep 24 '14 at 12:59

saghul

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How can I open a nodejs Duplex stream given a file descriptor?

1 Answers1