metasploit-framework/lib/rex/sync/thread_safe.rb

require 'timeout'

module Rex

###
# 
# This module provides a set of methods for performing various blocking
# operations in a manner that is compatible with ruby style threads.
#
###
module ThreadSafe

	DefaultCycle = 0.2

	#
	# Wraps calls to select with a lower timeout period and does the
	# calculations to walk down to zero timeout.  This has a little room for
	# improvement in that it should probably check how much time actually
	# elapsed during the select call considering ruby threading wont be exactly
	# accurate perhaps.
	#
	def self.select(rfd = nil, wfd = nil, efd = nil, t = nil)
		left = t

		begin
			orig_size = rfd.length if (rfd)

			# Poll the set supplied to us at least once.
			begin
				rv = ::IO.select(rfd, wfd, efd, DefaultCycle)
			rescue IOError
				# If a stream was detected as being closed, re-raise the error as
				# a StreamClosedError with the specific file descriptor that was
				# detected as being closed.  This is to better handle the case of
				# a closed socket being detected so that it can be cleaned up and
				# removed.
				if (rfd)
					rfd.each { |fd|
						raise StreamClosedError.new(fd) if (fd.closed?)
					}
				end

				# If the original rfd length is not the same as the current
				# length, then the list may have been altered and as such may not
				# contain the socket that caused the IOError.  This is a bad way
				# to do this since it's possible that the array length could be
				# back to the size that it was originally and yet have had the
				# socket that caused the IOError to be removed.
				return nil if (rfd and rfd.length != orig_size)

				# Re-raise the exception since we didn't handle it here.
				raise $!
			end

			return rv if (rv)

			# Decrement the amount of time left by the polling cycle
			left -= DefaultCycle if (left)

			# Keep chugging until we run out of time, if time was supplied.
		end while ((left == nil) or (left > 0))

		# Nothin.
		nil
	end

	#
	# Simulates a sleep operation by selecting on nil until a timeout period
	# expires.
	#
	def self.sleep(seconds)
		self.select(nil, nil, nil, seconds)

		seconds
	end

end

end