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

13 Apr 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.

emmanuel

On Sun, Apr 13, 2014 at 5:08 PM, Emmanuel Touzery wrote:
...
On Sun, Apr 13, 2014 at 4:30 PM, Yitzchak Gale  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The binary-strict library is no longer maintained, since binary now also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