Crate pw_time 

pw_time

pw_time provides time types and a system clock.

• Clock - A monotonically increasing clock with its own scale between internal “ticks” and human time.
• Instant<Clock> - A sample of a specific instant on a given Clock.
• Duration<Clock> - A span of time whose internal representation is scaled to the given Clock.
• SystemClock - The clock used by the core system/RTOS.

Examples

use pw_time::{SystemClock, Instant, Duration, Clock};

let start = SystemClock::now();
let duration = Duration::from_millis(500);
let end = start + duration;
assert_eq!(end - start, duration);

Design

Clocks

pw_time is designed to allow type-safe handling of systems with multiple clock domains. Each clock domain is defined by a Clock. Instant and Duration are generic of a Clock and can not be mixed.

Representation

pw_time uses 64 bit internal types to represent Instants (unsigned) and Durations (signed). The scale of this internal value is defined by the Clock::TICKS_PER_SEC. Future work may move from this scalar scale to a ratio based one similar to C++’s std::chrono types.

Const conversion

Duration’s from_* constructors are const and are designed to be optimized into single “tick native” values by the compiler.

Panic behavior

pw_time is designed to never cause a Rust panic because this can lead to code size bloat on size constrained systems. Instead it relies on pw_assert to allow system specific panic behavior.

Structs

Duration

A span of time represented by a signed tick count.

Instant

A measurement of a monotonically non-decreasing clock.

SystemClock

The clock used by the core system/RTOS

Traits

Clock

A trait for retrieving the current system or hardware time.