Clock

Module clock

import clock

Two kinds of clock, deliberately kept apart.

There are two clocks, and confusing them is a bug. SystemClock reads civil time and can jump when the host is corrected — use it to timestamp and to do calendar work. MonotonicClock only moves forward and has a meaningless origin — use it to measure how long something took.

The attributes keep them apart at the type level: code that measures elapsed time requires HasMonotonicClock and therefore cannot be handed a wall clock by mistake.

Both are plain data holding a function, so a test supplies its own. fixed freezes time, stepping advances it predictably, and steppingMonotonic with a zero step makes every reading identical — which is how code under a timeout is tested without waiting for one.

Dependencies

• time

---

Contents

• Data — MonotonicClock, SystemClock
• Attributes — HasMonotonicClock, HasSystemClock
• Functions — fixed, instant, now, stepping, steppingMonotonic

---

Data

MonotonicClock

`clock/clock.zirr:22`

data MonotonicClock {
	now: fn() -> Instant
}

A clock that only ever moves forward, whose origin carries no meaning.

Fields

---

SystemClock

`clock/clock.zirr:17`

data SystemClock {
	now: fn() -> Timestamp
}

A clock reading civil time, which can jump when the host is corrected.

Fields

---

Attributes

HasMonotonicClock

`clock/clock.zirr:12`

attr HasMonotonicClock {
	clock(self: @HasMonotonicClock) -> MonotonicClock
}

Provides the monotonic clock, for measuring how long something took.
Kept apart from HasSystemClock because a wall clock can jump, so code measuring elapsed time must not be handed one.

Fields

---

HasSystemClock

`clock/clock.zirr:6`

attr HasSystemClock {
	clock(self: @HasSystemClock) -> SystemClock
}

Provides the wall clock, for timestamping and calendar work.

Fields

---

Functions

fixed

`clock/clock.zirr:37`

fn fixed(at: Timestamp) -> SystemClock

A wall clock frozen at one time, for tests that must see a fixed date.

---

instant

`clock/clock.zirr:32`

fn instant(c: MonotonicClock) -> Instant

The current monotonic reading. Subtract two to learn how much time passed between them.

---

now

`clock/clock.zirr:27`

fn now(c: SystemClock) -> Timestamp

The current wall-clock time.

---

stepping

`clock/clock.zirr:42`

fn stepping(from: Timestamp, step: Duration) -> SystemClock

A wall clock starting at from and advancing by step on every reading, for tests that need time to pass predictably.

---

steppingMonotonic

`clock/clock.zirr:53`

fn steppingMonotonic(step: Duration) -> MonotonicClock

A monotonic clock starting at the origin and advancing by step on every reading.
A step of zero makes every reading identical, which is how code under a timeout is tested without waiting.