encrypted compression "none" vs "store"

[danielweck]

https://github.com/readium/webpub-manifest/blob/master/extensions/epub.md#encrypted

The current Readium2 TypeScript / NodeJS implementation uses "none", not "store".
Update: Kotlin, Swift and Go too.

[danielweck]

Typescript:

https://github.com/readium/r2-shared-js/blob/41eb2bf265d0145ef17a6affd159f2e79ea6d7ed/src/parser/epub.ts#L1488-L1492

if (prop.Compression.Method === "8") {
    encrypted.Compression = "deflate";
} else {
    encrypted.Compression = "none";
}

[danielweck]

Go:

https://github.com/readium/r2-streamer-go/blob/e4bf2ff6f829c2e6a87d62d83e4edf7bb876859c/parser/epub.go#L631-L635

if prop.Compression.Method == "8" {
    encrypted.Compression = "deflate"
} else {
    encrypted.Compression = "none"
}

[danielweck]

Kotlin:

https://github.com/readium/r2-streamer-kotlin/blob/097db8477680b434360283efc032e509c6a485af/r2-streamer/src/main/java/org/readium/r2/streamer/parser/epub/EncryptionParser.kt#L32

encryption.compression = if (method == "8") "deflate" else "none"

[danielweck]

Swift:

https://github.com/readium/r2-streamer-swift/blob/de36714b6137ff73c7f2b46700363771322fbfba/Sources/parser/EncryptionParser.swift#L84

encryption.compression = (method == "8" ? "deflate" : "none")

[HadrienGardeur]

OK, I'm fine using none as well, it just needs to be documented.

How far do we want to go though in the JSON Schema? Should we limit this value to an enum with only deflate and none?

[danielweck]

I think this is safe for now.
http://www.idpf.org/epub/31/spec/epub-ocf.html#sec-enc-compression

Value is either "0" (no compression) or "8" (Deflate algorithm).

[HadrienGardeur]

It's safe for EPUB but we might need to support other packaging formats in the future.