`module FlowControlled`

Provides flow control functionality for HTTP/2 connections and streams. This module implements window-based flow control as defined in RFC 7540.

Definitions

`def available_size`

Get the available window size for sending data.

Signature

returns　Integer: The number of bytes that can be sent.

Implementation

def available_size
	@remote_window.available
end

`def available_frame_size(maximum_frame_size = self.maximum_frame_size)`

This could be negative if the window has been overused due to a change in initial window size.

Implementation

def available_frame_size(maximum_frame_size = self.maximum_frame_size)
	available_size = self.available_size
	
	# puts "available_size=#{available_size} maximum_frame_size=#{maximum_frame_size}"
	
	if available_size < maximum_frame_size
		return available_size
	else
		return maximum_frame_size
	end
end

`def consume_remote_window(frame)`

Keep track of the amount of data sent, and fail if is too much.

Implementation

def consume_remote_window(frame)
	amount = frame.length
	
	# Frames with zero length with the END_STREAM flag set (that is, an empty DATA frame) MAY be sent if there is no available space in either flow-control window.
	if amount.zero? and frame.end_stream?
		# It's okay, we can send. No need to consume, it's empty anyway.
	elsif amount >= 0 and amount <= @remote_window.available
		@remote_window.consume(amount)
	else
		raise FlowControlError, "Trying to send #{frame.length} bytes, exceeded window size: #{@remote_window.available} (#{@remote_window})"
	end
end

`def update_local_window(frame)`

Update the local window after receiving data.

Signature

parameter　frame　Frame: The frame that was received.

Implementation

def update_local_window(frame)
	consume_local_window(frame)
	request_window_update
end

`def consume_local_window(frame)`

Consume local window space for a received frame.

Signature

parameter　frame　Frame: The frame that consumed window space.

Implementation

def consume_local_window(frame)
	# For flow-control calculations, the 9-octet frame header is not counted.
	amount = frame.length
	@local_window.consume(amount)
end

`def request_window_update`

Request a window update if the local window is limited.

Implementation

def request_window_update
	if @local_window.limited?
		self.send_window_update(@local_window.wanted)
	end
end

`def send_window_update(window_increment)`

Notify the remote end that we are prepared to receive more data:

Implementation

def send_window_update(window_increment)
	frame = WindowUpdateFrame.new(self.id)
	frame.pack window_increment
	
	write_frame(frame)
	
	@local_window.expand(window_increment)
end

`def receive_window_update(frame)`

Process a received WINDOW_UPDATE frame.

Signature

parameter　frame　WindowUpdateFrame: The window update frame to process.
raises　ProtocolError: If the window increment is invalid.

Implementation

def receive_window_update(frame)
	amount = frame.unpack
	
	if amount != 0
		@remote_window.expand(amount)
	else
		raise ProtocolError, "Invalid window size increment: #{amount}!"
	end
end

`def window_updated(size)`

The window has been expanded by the given amount.

Signature

parameter　size　Integer: the maximum amount of data to send.

Implementation

def window_updated(size)
	return false
end