Standardize some magic bytes to identify a brotli stream

[jrmuizel]

This would be very useful for dealing with something like .tar.br fies.

[eustas]

Unfortunately, there is no magic bytes for brotli.
In future brotli streams will be wrapped in some framing format which will have magic bytes that could be used to identify it.

[eustas]

Mark Adler helped us much with proof-testing brotli and refining specification.
Here is his framing format proposal:
https://github.com/madler/brotli/blob/master/br-format-v3.txt

Signature in hexadecimal (four bytes):

ce b2 cf 81

[catlee]

That's very helpful, thank you!

Do you have any idea when the new framing could be introduced? And how to transition content and clients over to the new format?

[dsnet]

A framing or file format of some type sounds great.

Is there a process through which people are peer reviewing how the new framing format is being designed?

Has any thought been given to possibly re-using a "framing" format like the XZ file format where brotli is just one of the filter chains that can be used?

[stokito]

Hi, could you add the signature to the file tool?
It looks like you need to add it here:
https://github.com/file/file/blob/c7d910ee8879dfbe80fe14bfc13c8fa6c6fe1d32/src/compress.c
and here:
https://github.com/file/file/blob/c7d910ee8879dfbe80fe14bfc13c8fa6c6fe1d32/magic/Magdir/archive

I created a separate ticket for this #727

[jason-sachs]

This issue was closed in Oct 2016. What was the resolution?

[pavelloz]

Im also interested in detecting brotli archives in a convenient way.

[matijaskala]

I've written a wrapper program around brotli and have been using it locally on my system for quite some time

[simonmittag]

has this ever been implemented? identifying binary streams without relying on external headers (HTTP) is commonplace functionality