Module: Scarpe::WVRelayUtil

Included in:
Scarpe::Webview::ContainedService, Scarpe::Webview::RelayDisplayService
Defined in:
lib/scarpe/wv/webview_relay_util.rb

Overview

WVRelayUtil defines the datagram format for the sockets that connect a parent Shoes application with a child display server.

The class including this module should also include Shoes::Log so that it can be used.

Instance Method Summary collapse

Instance Method Details

#event_loop_for(t = 1.5) ⇒ Object

Loop for up to t seconds, reading data and waiting.

Parameters:

  • t (Float) (defaults to: 1.5) —

    the number of seconds to loop for



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# File 'lib/scarpe/wv/webview_relay_util.rb', line 127

def event_loop_for(t = 1.5)
  t_start = Time.now
  delay_time = t

  while Time.now - t_start < delay_time
    if ready_to_read?(0.1)
      respond_to_datagram
    else
      sleep 0.1
    end
  end
end

#ready_to_read?(timeout = 0.0) ⇒ Boolean

Checks whether the internal socket is ready to be read from. If timeout is greater than 0, this will block for up to that long.

Parameters:

  • timeout (Float) (defaults to: 0.0) —

    the longest to wait for more input to read

Returns:

  • (Boolean) —

    whether the socket has data ready for reading



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# File 'lib/scarpe/wv/webview_relay_util.rb', line 17

def ready_to_read?(timeout = 0.0)
  r, _, e = IO.select [@from], [], [@from, @to].uniq, timeout

  # On timeout, select returns nil instead of arrays.
  return if r.nil?

  unless e.empty?
    raise Scarpe::ConnectionError, "#{@i_am}: Got error on connection(s) from IO.select! Dying!"
  end

  !r.empty?
end

#receive_datagram ⇒ String

Read data from the internal socket. Read until a whole datagram has been received and then return it.

Returns:

  • (String) —

    the received datagram



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# File 'lib/scarpe/wv/webview_relay_util.rb', line 56

def receive_datagram
  @readbuf ||= String.new.encode(Encoding::BINARY)
  to_read = nil

  loop do
    # Have we read a packet length already, sitting in @readbuf?
    a_idx = @readbuf.index("a")
    if a_idx
      to_read = @readbuf[0..a_idx].to_i
      @readbuf = @readbuf[(a_idx + 1)..-1]
      break
    end

    # If not, read more bytes
    new_bytes = @from.read(10)
    if new_bytes.nil?
      # This is perfectly normal, if the connection closed
      raise Scarpe::AppShutdownError, "Got an unexpected EOF reading datagram! " +
        "Did the #{@i_am == :child ? "parent" : "child"} process die?"
    end
    @readbuf << new_bytes
  end

  loop do
    if @readbuf.bytesize >= to_read
      out = @readbuf.byteslice(0, to_read)
      @readbuf = @readbuf.byteslice(to_read, -1)
      return out
    end

    new_bytes = @from.read(to_read - @readbuf.bytesize)
    @readbuf << new_bytes
  end
rescue
  raise Scarpe::AppShutdownError, "Got exception #{$!.class} when receiving datagram... #{$!.inspect}"
end

#respond_to_datagram ⇒ Object

Read a datagram from the internal buffer and then dispatch it to the appropriate handler.



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# File 'lib/scarpe/wv/webview_relay_util.rb', line 95

def respond_to_datagram
  message = receive_datagram
  m_data = JSON.parse(message)

  if m_data["type"] == "event"
    kwargs_hash = {}
    m_data["kwargs"].each { |k, v| kwargs_hash[k.to_sym] = v }
    send_shoes_event(
      *m_data["args"],
      event_name: m_data["kwargs"]["event_name"],
      target: m_data["kwargs"]["event_target"],
      **kwargs_hash,
    )
  elsif m_data["type"] == "create"
    raise Scarpe::InvalidOperationError, "Parent process should never receive :create datagram!" if @i_am == :parent

    @wv_display.create_display_drawable_for(m_data["class_name"], m_data["id"], m_data["properties"])
  elsif m_data["type"] == "destroy"
    if @i_am == :parent
      @shutdown = true
    else
      @log.info("Shutting down...")
      exit 0
    end
  else
    @log.error("Unrecognized datagram type:event: #{m_data.inspect}!")
  end
end

#send_datagram(contents) ⇒ void

This method returns an undefined value.

Send bytes on the internal socket to the opposite side.

Parameters:

  • contents (String) —

    data to send



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# File 'lib/scarpe/wv/webview_relay_util.rb', line 34

def send_datagram(contents)
  str_data = JSON.dump contents
  dgram_str = (str_data.length.to_s + "a" + str_data).encode(Encoding::BINARY)
  to_write = dgram_str.bytesize
  written = 0

  until written == to_write
    count = @to.write(dgram_str.byteslice(written..-1))
    if count.nil? || count == 0
      raise Scarpe::DatagramSendError, "Something was wrong in send_datagram! Write returned #{count.inspect}!"
    end

    written += count
  end

  nil
end