Re: [Madeleine-devel] Binary Mode

[Martin T. <ma...@ta...>]

Hi Anders,

 > I take it from this that binary-mode is something that only affects
 > reading?
Binary-mode also affects writing.
So I was wondering why it worked without it and tried to reproduce the 
error and couldn't! Marshal seems to works no matter which combination 
binary/text mode was set for reading or writing.
So why didn't it work in Madeleine?

- Marshal.dump and Marshal.load both change the IO Stream to binary mode;
Ruby source marshal.c:
	if (rb_respond_to(port, s_binmode)) {
	    rb_funcall2(port, s_binmode, 0, 0);
	}
-> So it should work not matter in which mode the stream is opened.

- In Madeline there is a "while !file.eof? read" loop.
It seems that the bug occurs only on the following conditions:
   - file opened in text mode
   - file.eof? called before Marshal.load
   - serialized data contains line-end
   - only on Windows?
This bug is definitely NOT in Madeleine but in Ruby (or more likely the 
Windows implementation), but opening in binary mode is a workaround for 
it. (also changing to binmode when writing could do no harm).

See below for a test script which can reproduce the error:
(sorry for the code, I'm a Ruby newbie)

Martin.


Result:
--------
write wb, read rb
OK

write w, read rb
OK

write w, read r
marshal data too short
Error!

write wb, read r
marshal data too short
Error!

------------------
NAME = "test.dat"
TEST = "\r\n \n \r \r\r\r \n\n\n \n\r"

def test(mode_write, mode_read)
	puts "write #{mode_write}, read #{mode_read}"
	save(mode_write)
			
	result = load(mode_read)
	puts (result == TEST ? "OK" : "Error!")
	puts
end

def load(mode)
	File.open(NAME, mode) { |file|	
		begin
			file.eof?
			# if the last line is removed: no error

			return Marshal.load(file)			
		rescue
			puts $!			
		end
	}
	
end

def save(mode)
	File.delete(NAME) if File.exists?(NAME)
	
	File.open(NAME, mode) { |file|		
		Marshal.dump(TEST, file)				
	}
end

test("wb", "rb")
test("w", "rb")
test("w", "r")
test("wb", "r")
--------------