"raw_metadata" is not raw after serialization

[ShuiRuTian]

Under "cache/index-v5/xx/yy/zzz", I found something like "raw_metadata":[0,18,32,112,97,......]"

It is the serialization of Vec, rather than binary like format.

Is this intentional? It looks like not very efficient.

[zkat]

https://github.com/zkat/cacache-rs/blob/main/src/index.rs#L46-L54

oh. I guess that's just how serde serializes Vec<u8>

[ShuiRuTian]

Maybe we could base64/hex encode/decode it firstly?

Base64 makes the length about 33% larger than origin bytes, but we will save a u8 with a character rather than usually 3 chars(I mean the 2 number and one extra comma, one or three number is also possible, but relatively rare.)

And hex will always use 2 characters for one u8, so it makes length 100% larger than origin bytes.

Hex might be faster to parse, Base64 is more compact.

Seems https://github.com/DaniPopes/const-hex/tree/master is an easy and fast crate for this, it uses SIMD for many archs.

[zkat]

base64 seems like a nicer option to me in general. I don't know if the difference in performance will matter, and storage will help a lot.