[paramiko] Using select() to determine when channel write buffer not full

[Dwayne Litzenberger]

Hi there!

When working with a native socket, if I want to check if a send() would not 
block, I can do something like this:

    (rr, ww, ee) = select.select([], [sock], [], 0)

That obviously doesn't work with Paramiko channels, since (from what I can 
tell) the file descriptor returned by Channel.fileno() isn't actually used 
for I/O.

Imagine that I want to copy data coming in at high speed over a socket to a 
much slower Paramiko channel.  What I would like to do is something like 
this, but it doesn't seem to be possible:

    writeBuf = ""
    while loop:
        if writeBuf != "":
            channel.set_notify_on_writable(True)
        else:
            channel.set_notify_on_writable(False)
        rr = [abort_fd, channel, sock]
        if len(writeBuf) >= 8192:
            # Don't allow writeBuf to grow infinitely
            rr.remove(sock)
        (rr, ww, ee) = select.select(rr, [], [], 0)
        if abort_fd in rr:
            # Another thread has requested that we abort
            break
        if sock in rr:
            # Data is ready to be read from the socket
            writeBuf += sock.recv(8192)
        if channel in rr:
            if channel.recv_ready():
                # do stuff
            if channel.recv_stderr_ready():
                # do stuff
            if channel.send_ready():
                count = channel.send(writeBuf)
                writeBuf = writeBuf[count:]
        # ...

Is anything similar possible?

-- 
Dwayne Litzenberger, B.A.Sc.
Information Technology Analyst

Open Systems Canada Limited
1627 Broad Street
Regina, SK S4P1X3
Office: 306.359.6725
http://www.oscl.ca/