Class: Protocol::WebSocket::Framer

Inherits:
Object
  • Object
show all
Defined in:
lib/protocol/websocket/framer.rb

Overview

Wraps an underlying Async::IO::Stream for reading and writing binary data into structured frames.

Instance Method Summary collapse

Constructor Details

#initialize(stream, frames = FRAMES) ⇒ Framer

Initialize a new framer wrapping the given stream.



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# File 'lib/protocol/websocket/framer.rb', line 35

def initialize(stream, frames = FRAMES)
	@stream = stream
	@frames = frames
end

Instance Method Details

#close ⇒ Object

Close the underlying stream.



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# File 'lib/protocol/websocket/framer.rb', line 41

def close
	@stream.close
end

#flush ⇒ Object

Flush the underlying stream.



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# File 'lib/protocol/websocket/framer.rb', line 46

def flush
	@stream.flush
end

#read_frame(maximum_frame_size = MAXIMUM_ALLOWED_FRAME_SIZE) ⇒ Object

Read a frame from the underlying stream.



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# File 'lib/protocol/websocket/framer.rb', line 52

def read_frame(maximum_frame_size = MAXIMUM_ALLOWED_FRAME_SIZE)
	buffer = @stream.read(2)
	
	unless buffer and buffer.bytesize == 2
		raise EOFError, "Could not read frame header!"
	end
	
	first_byte = buffer.getbyte(0)
	second_byte = buffer.getbyte(1)
	
	finished = (first_byte & 0b1000_0000 != 0)
	flags = (first_byte & 0b0111_0000) >> 4
	opcode = first_byte & 0b0000_1111
	
	if opcode >= 0x3 && opcode <= 0x7
		raise ProtocolError, "Non-control opcode = #{opcode} is reserved!"
	elsif opcode >= 0xB
		raise ProtocolError, "Control opcode = #{opcode} is reserved!"
	end
	
	mask = (second_byte & 0b1000_0000 != 0)
	length = second_byte & 0b0111_1111
	
	if opcode & 0x8 != 0
		if length > 125
			raise ProtocolError, "Invalid control frame payload length: #{length} > 125!"
		elsif !finished
			raise ProtocolError, "Fragmented control frame!"
		end
	end
	
	if length == 126
		if mask
			buffer = @stream.read(6) or raise EOFError, "Could not read length and mask!"
			length = buffer.unpack1("n")
			mask = buffer.byteslice(2, 4)
		else
			buffer = @stream.read(2) or raise EOFError, "Could not read length!"
			length = buffer.unpack1("n")
		end
	elsif length == 127
		if mask
			buffer = @stream.read(12) or raise EOFError, "Could not read length and mask!"
			length = buffer.unpack1("Q>")
			mask = buffer.byteslice(8, 4)
		else
			buffer = @stream.read(8) or raise EOFError, "Could not read length!"
			length = buffer.unpack1("Q>")
		end
	elsif mask
		mask = @stream.read(4) or raise EOFError, "Could not read mask!"
	end
	
	if length > maximum_frame_size
		raise ProtocolError, "Invalid payload length: #{length} > #{maximum_frame_size}!"
	end
	
	payload = @stream.read(length) or raise EOFError, "Could not read payload!"
	
	if payload.bytesize != length
		raise EOFError, "Incorrect payload length: #{length} != #{payload.bytesize}!"
	end
	
	klass = @frames[opcode] || Frame
	return klass.new(finished, payload, flags: flags, opcode: opcode, mask: mask)
end

#write_frame(frame) ⇒ Object

Write a frame to the underlying stream.



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# File 'lib/protocol/websocket/framer.rb', line 122

def write_frame(frame)
	if frame.mask and frame.mask.bytesize != 4
		raise ProtocolError, "Invalid mask length!"
	end
	
	length = frame.length
	
	if length <= 125
		short_length = length
	elsif length.bit_length <= 16
		short_length = 126
	else
		short_length = 127
	end
	
	buffer = [
		(frame.finished ? 0b1000_0000 : 0) | (frame.flags << 4) | frame.opcode,
		(frame.mask ? 0b1000_0000 : 0) | short_length,
	].pack("CC")
	
	if short_length == 126
		buffer << [length].pack("n")
	elsif short_length == 127
		buffer << [length].pack("Q>")
	end
	
	buffer << frame.mask if frame.mask
	
	@stream.write(buffer)
	@stream.write(frame.payload)
end