module Net::SSH::BufferedIo

This module is used to extend sockets and other IO objects, to allow them to be buffered for both read and write. This abstraction makes it quite easy to write a select-based event loop (see Net::SSH::Connection::Session#listen_to).

The general idea is that instead of calling read directly on an IO that has been extended with this module, you call fill (to add pending input to the internal read buffer), and then read_available (to read from that buffer). Likewise, you don't call write directly, you call enqueue to add data to the write buffer, and then send_pending or wait_for_pending_sends to actually send the data across the wire.

In this way you can easily use the object as an argument to IO.select, calling fill when it is available for read, or send_pending when it is available for write, and then call enqueue and read_available during the idle times.

socket = TCPSocket.new(address, port)
socket.extend(Net::SSH::BufferedIo)

ssh.listen_to(socket)

ssh.loop do
  if socket.available > 0
    puts socket.read_available
    socket.enqueue("response\n")
  end
end

Note that this module must be used to extend an instance, and should not be included in a class. If you do want to use it via an include, then you must make sure to invoke the private initialize_buffered_io method in your class' initialize method:

class Foo < IO
  include Net::SSH::BufferedIo

  def initialize
    initialize_buffered_io
    # ...
  end
end

Public Instance Methods

available() click to toggle source

Returns the number of bytes available to be read from the input buffer. (See read_available.)

# File lib/net/ssh/buffered_io.rb, line 83
def available
  input.available
end

enqueue(data) click to toggle source

Enqueues data in the output buffer, to be written when send_pending is called. Note that the data is not sent immediately by this method!

# File lib/net/ssh/buffered_io.rb, line 89
def enqueue(data)
  output.append(data)
end

fill(n=8192) click to toggle source

Tries to read up to n bytes of data from the remote end, and appends the data to the input buffer. It returns the number of bytes read, or 0 if no data was available to be read.

# File lib/net/ssh/buffered_io.rb, line 64
def fill(n=8192)
  input.consume!
  data = recv(n)
  debug { "read #{data.length} bytes" }
  input.append(data)
  return data.length
rescue EOFError => e
  @input_errors << e
  return 0
end

pending_write?() click to toggle source

Returns true if there is data waiting in the output buffer, and false otherwise.

# File lib/net/ssh/buffered_io.rb, line 95
def pending_write?
  output.length > 0
end

read_available(length=nil) click to toggle source

Read up to length bytes from the input buffer. If length is nil, all available data is read from the buffer. (See available.)

# File lib/net/ssh/buffered_io.rb, line 77
def read_available(length=nil)
  input.read(length || available)
end

send_pending() click to toggle source

Sends as much of the pending output as possible. Returns true if any data was sent, and false otherwise.

# File lib/net/ssh/buffered_io.rb, line 101
def send_pending
  if output.length > 0
    sent = send(output.to_s, 0)
    debug { "sent #{sent} bytes" }
    output.consume!(sent)
    return sent > 0
  else
    return false
  end
end

wait_for_pending_sends() click to toggle source

Calls send_pending repeatedly, if necessary, blocking until the output buffer is empty.

# File lib/net/ssh/buffered_io.rb, line 114
def wait_for_pending_sends
  send_pending
  while output.length > 0
    result = IO.select(nil, [self]) or next
    next unless result[1].any?
    send_pending
  end
end