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Subject: RE: JMimeMagic (was [fileUpload] file content-type)
Date: Mon, 29 May 2006 18:40:58 +0200
Message-ID: <F0D7281DAB048B438E8F5EC4ECEFBDDCCB8EBC@esmail.elsag.de>
Thread-Topic: JMimeMagic (was [fileUpload] file content-type)
Thread-Index: AcZ/1oj8JRufYAQ1QqGgvB0zp1KLPQDXZyxw
From: =?iso-8859-1?Q?J=F6rg_Schaible?= <Joerg.Schaible@Elsag-Solutions.com>
To: "Jakarta Commons Users List" <commons-user@jakarta.apache.org>

Hi David,

sorry for the delay, but I had to do some research again to give some =
more substantial answers.

David Castro wrote on Thursday, May 25, 2006 10:38 AM:

>> Hi Brain and Mark,
>>=20
>> Brian K. Wallace wrote on Tuesday, April 18, 2006 9:18 PM:
>>=20
>>=20
>>>> -----BEGIN PGP SIGNED MESSAGE-----
>>>> Hash: SHA1
>>>>=20
>>>> Just be conscious of the fact that, with all open source projects,
>>>> time is usually volunteer/as available/as the urge strikes. I
>>>> wouldn't start to get anxious for a couple of weeks. (some take
>>>> longer, but I'm anxious by then)
>>>>=20
>>>> As for forking -> commons, remember licensing issues. GPL/LGPL !=3D
>>>> ASL. In order for ASL to come into the picture you'd have to not
>>>> fork but start from scratch. IANAL, but that's how it's been
>>>> presented before.=20
>>>=20
>>=20
>> Starting from scratch would be possibly the best anyway. I
> had it also on my todo list on a very low priority ... but
> just, because I found that jMimeMagic has a really worse
> implemenattion - extremly slow and not working correctly. I
> have a good pile of image files it does not detect. Main
> reason is, that the implementation is simply
> What exactly is extremely slow and not working correctly?

After a quick look over the package you get the impression, that you =
imported the magic codes of file magic into the project. And then you're =
quite astonished, if the library does not detect simple formats (e.g. =
TIFF, Windows BMP), that are no problem for the C pendant. This is IMHO =
a problem, because there's simply no documentation, that states =
something else. When I detected jMimeMagic I just thought to use it as a =
black box.

> There are lots of things that don't detect out of the box right now,
> since only a subset of magic rules are defined in the magic.xml file.
>>  wrong. The original magic files have a clear idea of
> precedence of patterns - this has been lost completely in the
> conversion/implementation of jMimeMagic.
>>=20
> What is simply wrong about the implementation?  Precedence of matchers
> is a part of the current implementation, so I'm not sure what
> you mean.
> jMimeMagic wasn't a conversion, it was an implementation written from
> scratch.=20

But you could not decide, what you wanted to implement. See, file magic =
has two magic files, one to produce a format description and one for the =
mime type. Your implementation mixes the two approaches. Mime type =
detection is normally an action that should happen *fast*, but if I =
request the mime type for an MP3 you evaluate all the nested matchers =
that are totally moot for the mime type.

Looking at the code:

- what's the real difference between MagicMact and MagicMatcher? Even =
the javadoc is the same ...
- you're code is linked to Log4J. This is not good for libraries. See, =
some of our customers use completely own logging implementations, but =
with commons-logging you can at least write an easy bridge
- you never guard log.debug with log.isDebug - and you create *a lot* of =
debug output
- file magic has also its limits as already explained in this thread. =
You already introduced regexp support, but you don't use it properly =
e.g. for the HTML types so far

OK, some of the problems would have been solved by providing an own =
magic.xml file. E.g. one of my mistakes with the library was, that I =
assumed that the magic file was read every time you create a Magic =
instance and you would have to synchronize the initializartion of the =
instance if you want to share it. This assumtion was wrong, but only =
after looking at the code - not by reading the javadocs.

- J=F6rg

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