win32utils devel - Apr 2012 - FFI and wide character output buffers

Hi all,

I''ve seen how to deal with wide input strings with FFI, but
I''m not
sure how to deal with output buffers for wide character functions. I
tried this:

class Windows
  extend FFI::Library

  ffi_lib :kernel32

  attach_function :GetTempPathA, [:ulong, :pointer], :long
  attach_function :GetTempPathW, [:ulong, :pointer], :long

  def self.temp_path
    buf = 0.chr * 256
    buf.encode!("UTF-16LE")
    ptr = FFI::MemoryPointer.from_string(buf)

    # segfault or interpreter failure here
    if GetTempPathW(ptr.size, ptr) == 0
      raise SystemCallError, FFI.errno, "GetTempPathW"
    end

    p ptr.read_string
  end
end

Windows.temp_path

Any suggestions?

Regards,

Dan

On Thu, Apr 19, 2012 at 12:54 PM, Daniel Berger <djberg96 at gmail.com>
wrote:
> Hi all,
>
> I''ve seen how to deal with wide input strings with FFI, but
I''m not
> sure how to deal with output buffers for wide character functions. I
> tried this:
>
> class Windows
> ?extend FFI::Library
>
> ?ffi_lib :kernel32
>
> ?attach_function :GetTempPathA, [:ulong, :pointer], :long
> ?attach_function :GetTempPathW, [:ulong, :pointer], :long
>
> ?def self.temp_path
> ? ?buf = 0.chr * 256
> ? ?buf.encode!("UTF-16LE")
> ? ?ptr = FFI::MemoryPointer.from_string(buf)
>
> ? ?# segfault or interpreter failure here
> ? ?if GetTempPathW(ptr.size, ptr) == 0
> ? ? ?raise SystemCallError, FFI.errno, "GetTempPathW"
> ? ?end
>
> ? ?p ptr.read_string
> ?end
> end
>
> Windows.temp_path
>
> Any suggestions?
Disregard. Changing the second arg from :pointer to :buffer_out and
just using an encoded string worked.

Regards,

Dan