Write support for deflate64

[brianhelba]

Is this library (zipfile-deflate64) capable of writing deflate64 (not just reading)? If not, are there any plans to add write support? The 7z command will work for me for testing, but if I want to generate files on the fly I doubt that would work cross-platform.

Originally posted by @adamjstewart in #19 (comment)

[brianhelba]

At present, zipfile-deflate64 only supports reading, as that's what my own use case required. However, support for writing DEFLATE64-encoded ZIP files seems reasonable to be within scope of this library.

The problem is implementing (and maintaining) the particulars of DEFLATE64 compression, as this is not provided by zlib/contrib/infback9. Ideally, we could find another compatible library which already implemented such low-level support, and use zipfile-deflate64 to patch together a Python zipfile-compatible interface for invoking it.

[cielavenir]

I tried to check https://github.com/jinfeihan57/p7zip/blob/master/CPP/7zip/Compress , but it seems not simple to adapt the deflate64mode conditional to zlib...

[cielavenir]

miurahr commented in miurahr/py7zr#419

I don't want to support write of deflate64 because it is still proprietary algorithm and inefficient. There is no reason to create new archive with deflate64 instead of zstandard or lzma2.

(Now that codecs7z provides deflate64 write) if his comment is true, it is useless to focus on merging deflate.c and infback9.c. Please write your opinion(s).

[miurahr]

There is a compression library for python that provide enhanced deflate, aka. deflate64(tm), https://pypi.org/project/inflate64/
@brianhelba v0.3.0 and later supports write.

[cielavenir]

zipfile 0.0.6.0 supports inflate64 module (note: it is used only when zipfile-deflate64 is not available)

[miurahr]

inflate64 implements enhanced deflate procedure by modifying zlib main deflate/inflate codes. These are independent from both infozip/infback9 and p7zip functions. You are welcome to join improving it.