From: Alex Young <alex@...>
Date: 2011-12-20T00:18:00+09:00
Subject: Re: Windows, CreateFile and IO objects

Jeremy Bopp wrote in post #1037344:
> On 12/19/2011 08:32 AM, Alex Young wrote:
>> I'm porting some code from Linux to Windows which relies on direct
>> access to a CD's block device.  This "just works" on Linux if I
>> File.open("/dev/cdrom"), but I can't see how to make it work on Windows.
>>
>> While manually running a dl/imported CreateFile works and gives me a
>> valid handle, just running File.open("\\\\.\\D:", "r") crashes the
>> interpreter (1.9.3-p0), as does IO.sysopen.
>>
>> Is there a built-in way to turn an open handle into a File object?  I
>> blindly tried IO.for_fd, but that fails and I got no further.
>
> I'm not expert on this, but my quick look in MSDN seems to indicate that
> you need to use DeviceIoControl to handle reads and writes to the device
> handle once you get it from CreateFile:

Drat.  I was afraid of that.

> Regular files wouldn't be accessed using that function, so that's
> probably why Ruby chokes on file objects you create with those special
> device paths.
>
> If you want the object you may eventually create in Ruby to work mostly
> like an IO object, take a look at my io-like gem:
>
> https://rubygems.org/gems/io-like
>
> Unfortunately, it doesn't support the Ruby 1.9 IO API yet, but it should
> get you the basics without a ton of work. :-)
>

That looks interesting, I'll give it a shot.  Do you know if this is
likely to break horribly?

  class MyFunkyBlockDevice < IO
    include IO::Like
  end

For some fairly boring reasons I do actually want an IO subclass, but I
only need reading and seeking to work.

Thanks,
--
Alex

-- 
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