chardet VS hachoir

chardet is a library for decoding characters, once installed you can use the following to determine encoding:

The craziest issue I had was I couldn't predict what char encoding the text in my database was in. Most users entered Windows-1252, some text blobs were UTF-16, others were European character sets, and some were UTF-8. Some were Japanese SHIFT_JIS. Don't ask me how any of this happened. I retrospect, I should have dumped all the tables from MySQL and used the excellent PyPy Chardet [1] library to see what I was dealing with, do the conversions and then re-import the data. But then someone could copy UTF-16 from a Windows document and paste it in, so you have to convert going in to the database.

You have set Apache to UTF-8, PHP to UTF-8, MySQL to UTF-8, and the MySQL driver you are using to UTF-8. It's not clear how these setting interact. Are there silent conversions happening or do you always have to detect the encoding on data coming from the server? HTML pages have a character encoding specifier, but the BOM at the start of the file takes precedence (I think.) I got it to work by always detecting encoding for any text coming from the database and using iconv, but this turned out to be really slow and unreliable. It was truly the biggest mess by an order of magnitude than any other programming problem I faced in my career.

Would not attempt again.

[1] https://github.com/chardet/chardet

I found there is a https://github.com/chardet/chardet python library, which can be ported to Common Lisp.

Then use chardet to determine the encoding from the content

The library that Requests uses for content encoding detection has for the past 10 years been chardet which is licensed LGPL-2.1.

https://github.com/vstinner/hachoir/blob/main/hachoir/subfil...

File signature:

I contributed a number of file formats a few years ago (and attempted numerous others) but ran into a number of problems with certain file formats:

1. It's not possible to read from the file until a multiple byte termination sequence is detected. [1]

2. You can't read sections of a file where the termination condition is the presence of a sequence of bytes denoting the next unrelated section of the file (and you don't want to consume/read these bytes) [2]

3. The WebIDE at the time couldn't handle very large file format specifications such as Photoshop (PSD) [3]

4. Files containing compressed or encrypted sections require a compression/encryption algorithm to be hardcoded into Kaitai struct libraries for each programming language it can output to.

The WebIDE I particularly liked as it makes it easy to get started and share results. I also liked how Kaitai Struct allows easy definition of constraints (simple ones at least) into the file format specification so that you can say "this section of the file shall have a size not exceeding header.length * 2 bytes".

Some alternative binary file format specification attempts for those interested in seeing alternatives, each with their own set of problems/pros/cons:

1. 010 Editor [4]

2. Synalysis [5]

3. hachoir [6]

4. DFDL [7]

[1] https://github.com/kaitai-io/kaitai_struct/issues/158

[2] https://github.com/kaitai-io/kaitai_struct/issues/156

[3] https://raw.githubusercontent.com/davidhicks/kaitai_struct_f...

[4] https://www.sweetscape.com/010editor/repository/templates/

[5] https://github.com/synalysis/Grammars

[6] https://github.com/vstinner/hachoir/tree/main/hachoir/parser

[7] https://github.com/DFDLSchemas/

Another one sort of related is hachoir, and specifically the hachoir-metadata script: https://github.com/vstinner/hachoir