injectable-timeinjectable-time is a library to support dependency-injecting a time source.
It provides a trait TimeSource with one function, now(). The library uses i64 instead of an os-dependent time type so it can run host-side and in Fuchsia.
It provides three structs, UtcTime, MonotonicTime, and FakeTime, which implement TimeSource. FakeTime has functions set_ticks and add_ticks which can be used in tests.
The now() function of FakeTime returns the last number that was set_ticks by set_ticks(). It does not increment on multiple calls to now().
The now() function of UtcTime returns the number of nanoseconds since the Unix epoch.
The now() function of MonotonicTime returns a number of nanoseconds which monotonically increases at approximately a 1:1 rate with the wall clock.
Any struct that needs an injectable time source can store a &'a dyn TimeSource. Note the lack of mut.
A struct can also simply store a T: TimeSource. FakeTime can be clone()'d.
See the unit tests in injectable_time.rs for a usage example.
This project should be automatically included in builds.
injectable-time can be used by depending on the //src/lib/injectable-time gn target and then using the injectable-time crate in a Rust project.
injectable-time is not available in the sdk and is intended to be used only by diagnostics binaries.
Unit tests for injectable-time are available in the injectable-time package:
$ fx test injectable_time_lib_test
You'll need to include //src/lib/injectable-time:tests in your build, either by using fx args to put it under universe_package_labels, or by fx set_ticks [....] --with //src/lib/injectable-time:tests.