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PhusionPassenger::MessageChannel

This class allows reading and writing structured messages over I/O channels. This is the Ruby implementation of ext/common/Utils/MessageIO.h; see that file for more information.

Attributes

io[RW]

The wrapped IO object.

Public Class Methods

new(io = nil) click to toggle source

Create a new MessageChannel by wrapping the given IO object.

# File lib/phusion_passenger/message_channel.rb, line 43
def initialize(io = nil)
  @io = io
  # Make it binary just in case.
  @io.binmode if @io
end

Public Instance Methods

close() click to toggle source

Close the underlying IO stream. Might raise SystemCallError or IOError when something goes wrong.

# File lib/phusion_passenger/message_channel.rb, line 315
def close
  @io.close
end
closed?() click to toggle source

Checks whether the underlying IO stream is closed.

# File lib/phusion_passenger/message_channel.rb, line 320
def closed?
  return @io.closed?
end
fileno() click to toggle source

Return the file descriptor of the underlying IO object.

# File lib/phusion_passenger/message_channel.rb, line 309
def fileno
  return @io.fileno
end
read() click to toggle source

Read an array message from the underlying file descriptor. Returns the array message as an array, or nil when end-of-stream has been reached.

Might raise SystemCallError, IOError or SocketError when something goes wrong.

# File lib/phusion_passenger/message_channel.rb, line 55
def read
  buffer = new_buffer
  if !@io.read(HEADER_SIZE, buffer)
    return nil
  end
  while buffer.size < HEADER_SIZE
    tmp = @io.read(HEADER_SIZE - buffer.size)
    if tmp.empty?
      return nil
    else
      buffer << tmp
    end
  end

  chunk_size = buffer.unpack(UINT16_PACK_FORMAT)[0]
  if !@io.read(chunk_size, buffer)
    return nil
  end
  while buffer.size < chunk_size
    tmp = @io.read(chunk_size - buffer.size)
    if tmp.empty?
      return nil
    else
      buffer << tmp
    end
  end

  message = []
  offset = 0
  delimiter_pos = buffer.index(DELIMITER, offset)
  while !delimiter_pos.nil?
    if delimiter_pos == 0
      message << ""
    else
      message << buffer[offset .. delimiter_pos - 1]
    end
    offset = delimiter_pos + 1
    delimiter_pos = buffer.index(DELIMITER, offset)
  end
  return message
rescue Errno::ECONNRESET
  return nil
end
read_hash() click to toggle source

Read an array message from the underlying file descriptor and return the result as a hash instead of an array. This assumes that the array message has an even number of elements. Returns nil when end-of-stream has been reached.

Might raise SystemCallError, IOError or SocketError when something goes wrong.

# File lib/phusion_passenger/message_channel.rb, line 106
def read_hash
  buffer = new_buffer
  if !@io.read(HEADER_SIZE, buffer)
    return nil
  end
  while buffer.size < HEADER_SIZE
    tmp = @io.read(HEADER_SIZE - buffer.size)
    if tmp.empty?
      return nil
    else
      buffer << tmp
    end
  end

  chunk_size = buffer.unpack(UINT16_PACK_FORMAT)[0]
  if !@io.read(chunk_size, buffer)
    return nil
  end
  while buffer.size < chunk_size
    tmp = @io.read(chunk_size - buffer.size)
    if tmp.empty?
      return nil
    else
      buffer << tmp
    end
  end

  result = {}
  offset = 0
  delimiter_pos = buffer.index(DELIMITER, offset)
  while !delimiter_pos.nil?
    if delimiter_pos == 0
      name = ""
    else
      name = buffer[offset .. delimiter_pos - 1]
    end

    offset = delimiter_pos + 1
    delimiter_pos = buffer.index(DELIMITER, offset)
    if delimiter_pos.nil?
      raise InvalidHashError
    elsif delimiter_pos == 0
      value = ""
    else
      value = buffer[offset .. delimiter_pos - 1]
    end

    result[name] = value
    offset = delimiter_pos + 1
    delimiter_pos = buffer.index(DELIMITER, offset)
  end
  return result
rescue Errno::ECONNRESET
  return nil
end
read_scalar(buffer = new_buffer, max_size = nil) click to toggle source

Read a scalar message from the underlying IO object. Returns the read message, or nil on end-of-stream.

Might raise SystemCallError, IOError or SocketError when something goes wrong.

The buffer argument specifies a buffer in which read_scalar stores the read data. It is good practice to reuse existing buffers in order to minimize stress on the garbage collector.

The max_size argument allows one to specify the maximum allowed size for the scalar message. If the received scalar message's size is larger than max_size, then a SecurityError will be raised.

# File lib/phusion_passenger/message_channel.rb, line 175
def read_scalar(buffer = new_buffer, max_size = nil)
  if !@io.read(4, buffer)
    return nil
  end
  while buffer.size < 4
    tmp = @io.read(4 - buffer.size)
    if tmp.empty?
      return nil
    else
      buffer << tmp
    end
  end

  size = buffer.unpack(UINT32_PACK_FORMAT)[0]
  if size == 0
    buffer.replace('')
    return buffer
  else
    if !max_size.nil? && size > max_size
      raise SecurityError, "Scalar message size (#{size}) " <<
        "exceeds maximum allowed size (#{max_size})."
    end
    if !@io.read(size, buffer)
      return nil
    end
    if buffer.size < size
      tmp = ''
      while buffer.size < size
        if !@io.read(size - buffer.size, tmp)
          return nil
        else
          buffer << tmp
        end
      end
    end
    return buffer
  end
rescue Errno::ECONNRESET
  return nil
end
recv_io(klass = IO, negotiate = true) click to toggle source

Receive an IO object (a file descriptor) from the channel. The other side must have sent an IO object by calling send_io(). Note that this only works on Unix sockets.

Might raise SystemCallError, IOError or SocketError when something goes wrong.

# File lib/phusion_passenger/message_channel.rb, line 252
def recv_io(klass = IO, negotiate = true)
  write("pass IO") if negotiate
  io = @io.recv_io(klass)
  write("got IO") if negotiate
  return io
end
send_io(io) click to toggle source

Send an IO object (a file descriptor) over the channel. The other side must receive the IO object by calling recv_io(). Note that this only works on Unix sockets.

Might raise SystemCallError, IOError or SocketError when something goes wrong.

# File lib/phusion_passenger/message_channel.rb, line 265
def send_io(io)
  # We read a message before actually calling #send_io
  # in order to prevent the other side from accidentally
  # read()ing past the normal data and reading our file
  # descriptor too.
  #
  # For example suppose that side A looks like this:
  #
  #   read(fd, buf, 1024)
  #   read_io(fd)
  #
  # and side B:
  #
  #   write(fd, buf, 100)
  #   send_io(fd_to_pass)
  #
  # If B completes both write() and send_io(), then A's read() call
  # reads past the 100 bytes that B sent. On some platforms, like
  # Linux, this will cause read_io() to fail. And it just so happens
  # that Ruby's IO#read method slurps more than just the given amount
  # of bytes.
  result = read
  if !result
    raise EOFError, "End of stream"
  elsif result != ["pass IO"]
    raise IOError, "IO passing pre-negotiation header expected"
  else
    @io.send_io(io)
    # Once you've sent the IO you expect to be able to close it on the
    # sender's side, even if the other side hasn't read the IO yet.
    # Not so: on some operating systems (I'm looking at you OS X) this
    # can cause the receiving side to receive a bad file descriptor.
    # The post negotiation protocol ensures that we block until the
    # other side has really received the IO.
    result = read
    if !result
      raise EOFError, "End of stream"
    elsif result != ["got IO"]
      raise IOError, "IO passing post-negotiation header expected"
    end
  end
end
write(name, *args) click to toggle source

Send an array message, which consists of the given elements, over the underlying file descriptor. name is the first element in the message, and args are the other elements. These arguments will internally be converted to strings by calling to_s().

Might raise SystemCallError, IOError or SocketError when something goes wrong.

# File lib/phusion_passenger/message_channel.rb, line 223
def write(name, *args)
  check_argument(name)
  args.each do |arg|
    check_argument(arg)
  end

  message = "#{name}#{DELIMITER}"
  args.each do |arg|
    message << arg.to_s << DELIMITER
  end
  @io.write([message.size].pack('n') << message)
  @io.flush
end
write_scalar(data) click to toggle source

Send a scalar message over the underlying IO object.

Might raise SystemCallError, IOError or SocketError when something goes wrong.

# File lib/phusion_passenger/message_channel.rb, line 241
def write_scalar(data)
  @io.write([data.size].pack('N') << data)
  @io.flush
end

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