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fswatch.rb

require "Win32API"

class FilesystemWatcher

	FILE_NOTIFY_CHANGE_FILE_NAME   = 0x00000001
	FILE_NOTIFY_CHANGE_DIR_NAME    = 0x00000002
	FILE_NOTIFY_CHANGE_ATTRIBUTES  = 0x00000004
	FILE_NOTIFY_CHANGE_SIZE        = 0x00000008
	FILE_NOTIFY_CHANGE_LAST_WRITE  = 0x00000010
	FILE_NOTIFY_CHANGE_LAST_ACCESS = 0x00000020
	FILE_NOTIFY_CHANGE_CREATION    = 0x00000040
	FILE_NOTIFY_CHANGE_SECURITY    = 0x00000100

	WAIT_OBJECT_0    = 0x00000000
	WAIT_ABANDONED_0 = 0x00000080
	WAIT_TIMEOUT     = 0x00000102
	WAIT_FAILED      = -1
	
	INFINITE = 0xFFFFFFFF
	
	INVALID_HANDLE_VALUE = -1

	# p    : *void (ポインタ)
	# i    : int, DWORD, BOOL など
	# l, n : long, HANDLE など
	# v    : void
	FindFirstChangeNotification = Win32API.new "kernel32", "FindFirstChangeNotification", %w(p i i),     "n"
	FindNextChangeNotification  = Win32API.new "kernel32", "FindNextChangeNotification",  %w(n),         "i"
	FindCloseChangeNotification = Win32API.new "kernel32", "FindCloseChangeNotification", %w(n),         "i"
	WaitForSingleObjectEx       = Win32API.new "kernel32", "WaitForSingleObjectEx",       %w(n i i),     "i"
	WaitForMultipleObjectsEx    = Win32API.new "kernel32", "WaitForMultipleObjectsEx",    %w(n p i l i), "i"

	def initialize
		@handle_map = {}
	end

	def watch(filename, subtree=true, attachment=nil, flags=
		FILE_NOTIFY_CHANGE_FILE_NAME  |
		FILE_NOTIFY_CHANGE_DIR_NAME   |
		FILE_NOTIFY_CHANGE_ATTRIBUTES |
		FILE_NOTIFY_CHANGE_SIZE       |
		FILE_NOTIFY_CHANGE_LAST_WRITE |
		FILE_NOTIFY_CHANGE_CREATION )

		handle = FindFirstChangeNotification.call(filename, (subtree ? 1: 0), flags)
		if handle == INVALID_HANDLE_VALUE
			raise RuntimeError.new "Failed to call WINAPI:FindFirstChangeNotification(...)."
		end
		@handle_map[handle] = attachment
		handle
	end

	def unwatch(handle)
		unless @handle_map.key? handle
			raise ArgumentError.new "Unregistered handle object:#{handle}"
		end
		FindCloseChangeNotification.call handle
		@handle_map.delete handle
	end

	def close
		@handle_map.each_key {|handle|
			FindCloseChangeNotification.call handle
		}
	end

	def wait(timeout=INFINITE)
		result = WaitForMultipleObjectsEx.call(
				@handle_map.size, @handle_map.keys.pack("V*"), 0, timeout, 0)
		if result == WAIT_FAILED
			raise RuntimeError.new "Failed to call WINAPI:WaitForMultipleObjectsEx(...)."
		end
		@handle_map.each {|handle, attachment|
			next unless WAIT_OBJECT_0 == WaitForSingleObjectEx.call(handle, 0, 0)
			if FindNextChangeNotification.call(handle) == 0
				raise RuntimeError.new "Failed to call WINAPI:FindNextChangeNotification(...)."
			end
			yield [handle, attachment]
		}
	end

end