Brotli support

[stokito]

Do you have any plans to add a support of the Brotli compression algorithm?

[kientzle]

Brotli looks like it might be worth adding: There's an RFC for it and I see it's already supported by some tools.

Key requirements:

• Must have a well-designed initial signature for automatic detection.
• Must compress/decompress a stream.
• Should have a well-designed API (zlib's API is well done; most compression libraries seem to be copying it)

[stokito]

Unfortunately at the moment Brotli doesn't have a magic signature google/brotli#727
Is this a strict requirement?
It would be great to have the Brotli support in libarchive because it is used by KDE Ark archive manager and to make adoption of Brotli wider we need all desktop environments to support it.
Brotli is already supported by GNOME File Roller and MATE Engrampa.

[kientzle]

Without a magic signature, libarchive cannot automatically recognize the file type, so it cannot automatically decompress. (Libarchive does not consider the file name, only the contents.)

[kientzle]

I don't think we can support brotli if it lacks a magic signature.