[Haskell-beginners] parsing exif file: binary, binary-strict, or cereal?

Emmanuel Touzery etouzery at gmail.com
Sun Apr 13 15:18:29 UTC 2014

well, it went fast :-)
already ported.

regarding strictness, i hope just doing that is enough:

data IfEntry = IfEntry
        entryTag :: !Word16,
        entryFormat :: !Word16,
        entryNoComponents :: !Word32,
        entryContents :: !Word32
    } deriving Show

Though from past experience, I'm far from sure.

I'll add comments soon and then push it to hackage.


On Sun, Apr 13, 2014 at 5:08 PM, Emmanuel Touzery <etouzery at gmail.com>wrote:

> On Sun, Apr 13, 2014 at 4:30 PM, Yitzchak Gale <gale at sefer.org> wrote:
>> Emmanuel Touzery wrote:
>> >  I could not find a pure haskell library to parse EXIF so I wrote one
>> > (pretty basic so far):
>> > https://github.com/emmanueltouzery/hsexif
>> Very nice! Why not upload it to hackage to make it easier
>> for others to share and collaborate?
> Yes, that's the plan as soon as I get the basics right and that I write
> some short documentation. Hopefully very quickly.
>> > I wrote it with binary-strict. I also considered binary, but I would
>> like
>> > the library not to throw an exception if the file that it's given is
>> not a
>> > JPEG or is a JPEG without EXIF, but rather return an Either. I didn't
>> manage
>> > to do that with binary
>> Perhaps the function Data.Binary.Get.runGetOrFail is what
>> you are looking for? Or perhaps the incremental strict interface?
> Ah yes... Actually I was a bit mislead because I found an haskell wiki
> stating that with binary it was impossible to catch the exceptions except
> in the IO monad and I took that at face value. I think runGetOrFail is what
> I want, I'll test it, thank you!
>> >  And then I realized that binary-strict was last updated in 2010, it
>> seems
>> > cereal is recommended for strict binary file parsing nowadays.
>> >  So, what should I do? Leave it as it is? Port to cereal? Port to
>> binary?
>> The binary-strict library is no longer maintained, since binary now also
>> provides a strict interface. Both binary and cereal are good choices.
>> Probably porting to binary would be easiest if you've already written
>> it for binary-strict, assuming runGetOrFail or the incremental interface
>> does what you want.
> Ok, then I'll try the non-strict binary first then. Most JPG files will be
> only a couple of megabytes and it wouldn't be THAT bad loading them
> entirely in memory but then, it seems a bit of a shame. With lazy though
> I'll have to work a bit on my strictness annotations I think.
> Thanks for the hints! Hopefully I can port it to lazy binary and publish
> it on hackage soon enough...
> Emmanuel
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