Class: EventMachine::WebSocketCodec::Decoder

Inherits:
Object
  • Object
show all
Includes:
Protocol
Defined in:
lib/em-ws-client/decoder.rb

Overview

Internal: A WebSocket frame decoder based on RFC 6455

Constant Summary

Constants included from Protocol

Protocol::BINARY_FRAME, Protocol::CLOSE, Protocol::CONTINUATION, Protocol::PING, Protocol::PONG, Protocol::TEXT_FRAME

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Decoder

Returns a new instance of Decoder.



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# File 'lib/em-ws-client/decoder.rb', line 11

def initialize
  @fragmented = false
  @buffer = ""
  @chunks = nil
  @callbacks = {}
end

Instance Method Details

#<<(data) ⇒ Object

Public: Feed the decoder raw data from the wire

data - The raw websocket frame data

Examples

decoder << raw

Returns nothing



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# File 'lib/em-ws-client/decoder.rb', line 33

def << data

  # put the data into the buffer, as
  # we might be replaying
  if data
    @buffer << data
  end

  # Don't do work if we don't have to
  if @buffer.length < 2
    return
  end

  # decode the first 2 bytes, with
  # opcode, lengthgth, masking bit, and frag bit
  h1, h2 = @buffer.unpack("CC")

  # check the fragmentation bit to see
  # if this is a message fragment
  fin = ((h1 & 0x80) == 0x80)

  # used to keep track of our position in the buffer
  offset = 2

  # see above for possible opcodes
  opcode = (h1 & 0x0F)

  # the leading length idicator
  length = (h2 & 0x7F)

  # masking bit, is the data masked with
  # a specified masking key?
  masked = ((h2 & 0x80) == 0x80)

  # Find errors and fail fast
  if h1 & 0b01110000 != 0
    return emit :error, 1002, "RSV bits must be 0"
  end

  if opcode > 7
    if !fin
      return emit :error, 1002, "Control frame cannot be fragmented"
    elsif length > 125
      return emit :error, 1002, "Control frame is too large #{length}"
    elsif opcode > 0xA
      return emit :error, 1002, "Unexpected reserved opcode #{opcode}"
    elsif opcode == CLOSE && length == 1
      return emit :error, 1002, "Close control frame with payload of length 1"
    end
  else
    if opcode != CONTINUATION && opcode != TEXT_FRAME && opcode != BINARY_FRAME
      return emit :error, 1002, "Unexpected reserved opcode #{opcode}"
    end
  end

  # Get the actual size of the payload
  if length > 125
    if length == 126
      length = @buffer.unpack("@#{offset}n").first
      offset += 2
    else
      length = @buffer.unpack("@#{offset}L!>").first
      offset += 8
    end
  end

  # unpack the masking key
  if masked
    key = @buffer.unpack("@#{offset}N").first
    offset += 4
  end

  # replay on next frame
  if @buffer.size < (length + offset)
    return false
  end

  # Read the important bits
  payload = @buffer.unpack("@#{offset}C#{length}")

  # Unmask the data if it"s masked
  if masked
    payload.bytesize.times do |i|
      payload[i] = ((payload[i] ^ (key >> ((3 - (i % 4)) * 8))) & 0xFF)
    end
  end
  
  payload = payload.pack("C*")

  case opcode
  when CONTINUATION

    # We shouldn't get a contination without
    # knowing whether or not it's binary or text
    unless @fragmented
      return emit :error, 1002, "Unexepected continuation"
    end

    if @fragmented == :text
      @chunks << payload.force_encoding("UTF-8")
    else
      @chunks << payload
    end

    if fin
      if @fragmented == :text && !valid_utf8?(@chunks)
        return emit :error, 1007, "Invalid UTF"
      end

      emit :frame, @chunks, @fragmented == :binary
      @chunks = nil
      @fragmented = false
    end

  when TEXT_FRAME
    # We shouldn't get a text frame when we
    # are expecting a continuation
    if @fragmented
      return emit :error, 1002, "Unexepected frame"
    end

    # emit or buffer
    if fin
      unless valid_utf8?(payload)
        return emit :error, 1007, "Invalid UTF Hmm"
      end

      emit :frame, payload, false
    else
      @chunks = payload.force_encoding("UTF-8")
      @fragmented = :text
    end

  when BINARY_FRAME
    # We shouldn't get a text frame when we
    # are expecting a continuation
    if @fragmented
      return emit :error, 1002, "Unexepected frame"
    end

    # emit or buffer
    if fin
      emit :frame, payload, true
    else
      @chunks = payload
      @fragmented = :binary
    end

  when CLOSE
    code, explain = payload.unpack("nA*")
    if explain && !valid_utf8?(explain)
      emit :close, 1007
    else
      emit :close, response_close_code(code)
    end

  when PING
    emit :ping, payload

  when PONG
    emit :pong, payload

  end

  # Remove data we made use of and call back
  # TODO: remove recursion
  @buffer = @buffer[offset + length..-1] || ""
  if not @buffer.empty?
    self << nil
  end

end

#onclose(&block) ⇒ Object 



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# File 'lib/em-ws-client/decoder.rb', line 18

def onclose &block; @callbacks[:close] = block; end

#onerror(&block) ⇒ Object 



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# File 'lib/em-ws-client/decoder.rb', line 22

def onerror &block; @callbacks[:error] = block; end

#onframe(&block) ⇒ Object 



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# File 'lib/em-ws-client/decoder.rb', line 21

def onframe &block; @callbacks[:frame] = block; end

#onping(&block) ⇒ Object 



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# File 'lib/em-ws-client/decoder.rb', line 19

def onping &block; @callbacks[:ping] = block; end

#onpong(&block) ⇒ Object 



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# File 'lib/em-ws-client/decoder.rb', line 20

def onpong &block; @callbacks[:pong] = block; end