[racket] Binary class: general approach to binary data parsing and writing

 I made package 'binary-class-exif'
It does nearly the same that racket-mediafile, but uses binary-class, and so may write changes back

I cant't understand, why it gives different result for exif:user-comment when reading canon-ixus.jpg from
examples from racket-mediafile.

binary-class-exif gives 136 zeros
racket-mediafile gives #(undefined-type 136 #"*\2\0\0"))

Sun, 15 Jun 2014 21:59:24 -0400 от Neil Van Dyke <neil at neilvandyke.org>:
>Roman, this looks good.
>
>I think one good test of your abstractions would be to parse JPEG Exif 
>with some MakerNotes. IIRC, you have to things like read a value that 
>is an offset from some other position (from top of file, start of 
>header, current position...), to follow linked lists, and to have 
>conditionals.
>
>Another test would be getting video metadata out of popular video stream 
>and container formats. This would also be very useful for working with 
>video files.
>
>Some documentation references are here:
>http://www.neilvandyke.org/racket-mediafile/#%28part._.Content_.Types%29
>I didn't come up with a generalized high-level abstraction, but looks 
>like you're on your way to doing it better than I did.
>
>Neil V.
>
>Roman Klochkov wrote at 06/15/2014 02:42 PM:
>> I've written universal library for parsing binary files or their parts 
>> into Racket objects.
>> You may install it with 'raco pkg install binary-class'. This library 
>> has verbose documentation and easy syntax.
>> You simply describe your data in terms of class fields and load the 
>> object from the file.
>>
>> I've written parsers for MP3 ID3 tags (binary-class-mp3 package) and 
>> DBF files (binary-class-dbf package, no docs yet, only Readme at 
>>  https://github.com/Kalimehtar/binary-class-dbf ). You may treat them as 
>> usage examples for the library.
>>
>> Please, give me feedback. Maybe I can do something better, or maybe 
>> somebody write another file format to the library.
>>
>>
>> -- 
>> Roman Klochkov
>


-- 
Roman Klochkov
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