Class: PhusionPassenger::MessageChannel

Inherits:
Object
  • Object
show all
Defined in:
lib/phusion_passenger/message_channel.rb

Overview

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.

Defined Under Namespace

Classes: InvalidHashError

Constant Summary collapse

HEADER_SIZE =

:nodoc:

2
DELIMITER =

:nodoc:

"\0"
DELIMITER_NAME =

:nodoc:

"null byte"
UINT16_PACK_FORMAT =

:nodoc:

"n"
UINT32_PACK_FORMAT =

:nodoc:

"N"

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(io = nil) ⇒ MessageChannel

Create a new MessageChannel by wrapping the given IO object.



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# File 'lib/phusion_passenger/message_channel.rb', line 44

def initialize(io = nil)
	@io = io
	# Make it binary just in case.
	@io.binmode if @io
end

Instance Attribute Details

#io ⇒ Object

The wrapped IO object.



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# File 'lib/phusion_passenger/message_channel.rb', line 41

def io
  @io
end

Instance Method Details

#close ⇒ Object

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



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# File 'lib/phusion_passenger/message_channel.rb', line 316

def close
	@io.close
end

#closed? ⇒ Boolean

Checks whether the underlying IO stream is closed.

Returns:

  • (Boolean) 


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# File 'lib/phusion_passenger/message_channel.rb', line 321

def closed?
	return @io.closed?
end

#fileno ⇒ Object

Return the file descriptor of the underlying IO object.



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# File 'lib/phusion_passenger/message_channel.rb', line 310

def fileno
	return @io.fileno
end

#read ⇒ Object

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.



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# File 'lib/phusion_passenger/message_channel.rb', line 56

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 ⇒ Object

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.



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# File 'lib/phusion_passenger/message_channel.rb', line 107

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) ⇒ Object

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.



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# File 'lib/phusion_passenger/message_channel.rb', line 176

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) ⇒ Object

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.



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# File 'lib/phusion_passenger/message_channel.rb', line 253

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) ⇒ Object

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.



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# File 'lib/phusion_passenger/message_channel.rb', line 266

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) ⇒ Object

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.



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# File 'lib/phusion_passenger/message_channel.rb', line 224

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) ⇒ Object

Send a scalar message over the underlying IO object.

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



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# File 'lib/phusion_passenger/message_channel.rb', line 242

def write_scalar(data)
	@io.write([data.size].pack('N') << data)
	@io.flush
end