On Sun, Sep 11, 2011 at 4:48 AM, Nobuyoshi Nakada <nobu / ruby-lang.org> wrote:
> Hi,
>
> At Sun, 11 Sep 2011 00:58:53 +0900,
> Luis Lavena wrote in [ruby-core:39451]:
>> My question: can this behavior be changed for Windows?
>>
>> Asking this because we are not reading and resolving symlink,
>> junctions or hardlinks in Ruby for Windows, so doing the entire
>> traversal and check seems a bit expensive (several stat() calls)
>
> I think resolving symlinks and junctions should be implemented
> in the future.
>

Perhaps for Ruby 2.0, because introducing such change right now will
result in lot of problems.

Right a symlink *is* a reparse point, like junctions and these can be
pointing to different driver letters or network shares.

Problems:

1) Current symlink functionality requires not only Vista or greater
but also elevation of privileges to create them.

2) Some directory symlinks can point to UNC paths or other drive letters.

> # "Resolving hardlinks" makes no sense on any platforms.
>
>> This means: build absolute path, expand if required, combine with
>> GetFileAttributesEx to check for existance.
>
> Is this what you want?
>
>  ¨Βιμε®στατ¨αβσομυτείπατθ Ζιμε®αβσομυτείπατθ¨πατθίξανε©©αβσομυτείπατ>

Something similar, mainly because File.absolute_path is performing a
FindFirstFileA (globbing operation to resolve shortnames using ANSI)
and then winnt_stat() is doing FindFirstFileW (another globbing
operation) to obtain stats:

API							Duration
GetCurrentDirectoryA ( 0, NULL )			0.0000056
GetCurrentDirectoryA ( 200, 0x02cb3f00 )		0.0000056
FindFirstFileA ( "V:/a/b/d/e/foo.rb", 0x0028e980 )	0.0002077
FindClose ( 0x00773930 )				0.0000583
FindFirstFileW ( "V:\a\b\d\e\foo.rb", 0x0028e7d0 )	0.0000901
FindClose ( 0x00773930 )				0.0001246

===

From what I see here, neither File.absolute_path or File.expand_path
should be performing FS-operations (they don't on UNIX), the only one
that does is File.realpath because it resolves symlinks.

I want zero operations for File.expand_path and File.absolute_path
while keeping File.realpath to a moderate number, current
implementation:

(given V:\a\b\c\d\e\foo.rb exists):

>> File.realpath("foo.rb")
=> "V:/a/b/d/e/foo.rb"

Produces:

API							Duration
GetCurrentDirectoryA ( 0, NULL )			0.0000061
GetCurrentDirectoryA ( 200, 0x02cb3f00 )		0.0000061
FindFirstFileW ( "V:\a", 0x0028e6e0 )			0.0001736
FindClose ( 0x00773930 )				0.0000509
FindFirstFileW ( "V:\a\b", 0x0028e6e0 )			0.0000798
FindClose ( 0x00773930 )				0.0000387
FindFirstFileW ( "V:\a\b\d", 0x0028e6d0 )		0.0000737
FindClose ( 0x00773930 )				0.0000392
FindFirstFileW ( "V:\a\b\d\e", 0x0028e6d0 )		0.0001680
FindClose ( 0x00773930 )				0.0000387
FindFirstFileW ( "V:\a\b\d\e\foo.rb", 0x0028e6c0 )	0.0000784
FindClose ( 0x00773930 )				0.0000378

-- 
Luis Lavena
AREA 17
-
Perfection in design is achieved not when there is nothing more to add,
but rather when there is nothing more to take away.
Antoine de Saint-ExupρΣy