Cargo Features

xmas-elf has no features set by default.

[dependencies]
xmas-elf = { version = "0.9.1", features = ["compression"] }
compression = flate2

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

flate2 compression?