Use LZFSE for payload compression

[kkaefer]

Given that we can't use the original compressed response (#3886) on iOS, we should use Apple's LZFSE algorithm introduced in iOS 9 and OS X 10.11.

[jfirebaugh]

Use it where? For resources stored in the database? I don't think we should make the database storage platform-specific -- people want to be able to transfer offline caches between devices, which potentially includes transfers between iOS and Android devices.

[Motti-Shneor]

As of yesterday, Apple open-sourced lzfse! I don't yet know where to find the sources... but I heard the announcement.

[kkaefer]

It's open source: https://github.com/lzfse/lzfse

[kkaefer]

people want to be able to transfer offline caches between devices, which potentially includes transfers between iOS and Android devices.

I haven't encountered this use case so far; the only transfer I've seen is from a pre-built database (on desktop) to phones. Adding support for LZFSE would only take effect for new items stored in the cache, and we'd still be able to decompress gzip-compressed responses.

[stale]

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