injectable-time

injectable-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 a function set which can be used in tests.

The now() function of FakeTime returns the last number that was set by set(). 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.

See the unit tests in injectable_time.rs for a usage example.

Building

This project should be automatically included in builds.

Using

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.

Testing

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 [....] --with //src/lib/injectable-time:tests.