FFI symlink detection

win_symlink_detect.rb

require 'ffi'

FILE_ATTRIBUTE_REPARSE_POINT = 0x400
IO_REPARSE_TAG_SYMLINK = 0xA000000C
INVALID_FILE_ATTRIBUTES = 0xFFFFFFFF
INVALID_HANDLE_VALUE = 0xFFFFFFFF # -1 is also valid

module Win_Test
	extend FFI::Library

	MAX_PATH = 260

	class FILETIME < FFI::Struct
	  layout :dw_low_date_time, :uint32,
		:dw_high_date_time, :uint32,
	end	


	class WIN32_FIND_DATA < FFI::Struct
	  layout :dw_file_attributes, :uint32,
		:ft_creation_time, FILETIME,
		:ft_last_access_time, FILETIME,
		:ft_last_write_time, FILETIME,
		:n_file_size_high, :uint32,
		:n_file_size_low, :uint32,
		:dw_reserved_0, :uint32,
		:dw_reserved_1, :uint32,
		:c_file_name, [:char, MAX_PATH],
		:c_alternate_file_name, [:char, 14],
	end


	ffi_lib 'kernel32'
	ffi_convention :stdcall
	
=begin
DWORD WINAPI GetFileAttributes(
  __in  LPCTSTR lpFileName
);
=end

	attach_function :get_file_attribute, :GetFileAttributesW, [:pointer], :uint32
	# FindFirstFileW returns a pointer - but the part that matters is the
	# address it points to, not the value it contains, so declair as ulong
	# to do comparisons against it
	attach_function :find_first_file, :FindFirstFileW, [:pointer, :pointer], :ulong
	attach_function :get_last_error, :GetLastError, [], :uint
end

#path = 'testfile.txt'
path = 'newtestfile.txt'

#puts path.encoding.name
#path = path.encode('UTF-16LE')
#puts path.encoding.name

value = Win_Test.get_file_attribute(path.encode('UTF-16LE'))		

puts value

if (value == INVALID_FILE_ATTRIBUTES)
	
	#this prints invalid at random times, depending on what I modify in the file
	#can even be code I change below!
	puts "Invalid"
	#puts Win_Test.get_last_error

end	

#puts value

if ((value & FILE_ATTRIBUTE_REPARSE_POINT) != 0)
	puts "worked"

	data = Win_Test::WIN32_FIND_DATA.new
	handle = Win_Test.find_first_file(path, data)

	# do I have to worry about closing the handle?

	if handle == INVALID_HANDLE_VALUE
		#puts handle
		puts "Invalid Handle"
	end

	#puts handle
	#puts data
	#puts data[:dw_file_attributes]
	#puts data[:dw_reserved_0]
	if data[:dw_reserved_0] == IO_REPARSE_TAG_SYMLINK
		puts "Symlink"
	else
		puts "Not symlink"	
	end	

	# do I have to worry about closing the handle?
	# does FFI take care of that?

else
	puts "failed"	
end