win32utils devel - Nov 2008 - GetFinalPathNameByHandle for XP and earlier

Hi all,

How''s this look? I based it on 
http://msdn.microsoft.com/en-us/library/aa366789(VS.85).aspx.

I''m undecided as to when I should raise an error versus when I should
just let
it fall through, but this is how it is for now.

You''ll need the latest windows-pr from CVS, btw.

Regards,

Dan

PS - Where should I put it? In Windows::File directly? In a separate helper
module?

require ''windows/file''
require ''windows/file_mapping''
require ''windows/volume''
require ''windows/process''
require ''windows/limits''
require ''windows/handle''
require ''windows/error''
require ''windows/memory''

include Windows::File
include Windows::FileMapping
include Windows::Volume
include Windows::Process
include Windows::Limits
include Windows::Handle
include Windows::Error
include Windows::Memory

# The buf, buf_size, and flags arguments are ignored, but are
# present in order to keep the function parameters identical
# to the function defined for Windows Vista and later.
#
def GetFinalPathNameByHandle(handle, buf, buf_size, flags)
    size_ptr = [0].pack(''Q'')

    unless GetFileSizeEx(handle, size_ptr)
       raise get_last_error
    end

    if size_ptr.unpack(''Q'')[0] <= 0
       raise ''file size must be greater than zero''
    end

    map = CreateFileMapping(handle, nil, PAGE_READONLY, 0, 1, nil)
    final_path = nil

    if map && map > 0
       pmem = MapViewOfFile(map, FILE_MAP_READ, 0, 0, 1)

       if pmem
          begin
             buf = 0.chr * MAXPATH

             # Buf will contain the full path, but with the device name instead
             # of the drive letter that we ultimately want.
             if GetMappedFileName(GetCurrentProcess(), pmem, buf, MAXPATH) >
0
                buf.strip!
                dbuf = 0.chr * 512

                # Get a list of logical devices
                if GetLogicalDriveStrings(dbuf.size, dbuf) > 0
                   devices = dbuf.split("\0")
                   devices.delete_if{ |d| d.empty? || d.size > 3 }

                   # Match the drive letter to a device. Once we find a match to
                   # the device returned by GetMappedFileName, replace the
device
                   # name from our original buffer with the drive letter.
                   devices.each{ |device|
                      name = 0.chr * MAXPATH
                      device.chop! # Remove trailing slash

                      if QueryDosDevice(device, name, name.size) > 0
                         name.strip!
                         if buf.include?(name)
                            final_path = device << buf[name.length..-1]
                            break
                         end
                      end
                   }
                end
             else
                raise get_last_error
             end
          ensure
             UnmapViewOfFile(pmem)
          end
       end
    else
       raise get_last_error
    end

    final_path
end

# Test program

file = File.join(Dir.pwd, ''test.txt'')

handle = CreateFile(
    file,
    GENERIC_READ | GENERIC_WRITE,
    FILE_SHARE_READ,
    nil,
    OPEN_ALWAYS,
    nil,
    nil
)

if handle == INVALID_HANDLE_VALUE
    raise get_last_error
end

p GetFinalPathNameByHandle(handle, nil, nil, nil)

CloseHandle(handle)

Hi,

2008/11/22 Daniel Berger <djberg96 at gmail.com>:
> Hi all,
>
> How''s this look? I based it on
> http://msdn.microsoft.com/en-us/library/aa366789(VS.85).aspx.
>
> I''m undecided as to when I should raise an error versus when I
should just
> let it fall through, but this is how it is for now.
>
> You''ll need the latest windows-pr from CVS, btw.
>
I remembered that this issue was discussed at May, 2008.

Why not use my code in
http://rubyforge.org/pipermail/win32utils-devel/2008-May/001091.html ?

Regards,

Park Heesob

Heesob Park wrote:
> Hi,
> 
> 2008/11/22 Daniel Berger <djberg96 at gmail.com>:
>> Hi all,
>>
>> How''s this look? I based it on
>> http://msdn.microsoft.com/en-us/library/aa366789(VS.85).aspx.
>>
>> I''m undecided as to when I should raise an error versus when I
should just
>> let it fall through, but this is how it is for now.
>>
>> You''ll need the latest windows-pr from CVS, btw.
>>
> I remembered that this issue was discussed at May, 2008.
> 
> Why not use my code in
> http://rubyforge.org/pipermail/win32utils-devel/2008-May/001091.html ?
You know, I thought we had talked about it, but when I searched I
couldn''t find
it. Obviously I didn''t try hard enough.

Thanks. I like your implementation better. :)

Regards,

Dan