[](https://docs.rs/coarsetime)
[](https://ci.appveyor.com/project/jedisct1/rust-coarsetime)
# coarsetime
A Rust crate to make time measurements, that focuses on speed.
This crate is a partial replacement for the `Time` and `Duration` structures
from the standard library, with the following differences:
* Speed is privileged over accuracy. In particular, `CLOCK_MONOTONIC_COARSE` is
used to retrieve the clock value on Linux systems, and transformations avoid
operations that can be slow on non-Intel systems.
* The number of system calls can be kept to a minimum. The "most recent
timestamp" is always kept in memory. It can be read with just a load operation,
and can be updated only as frequently as necessary.
# Installation
`coarsetime` is available on [crates.io](https://crates.io/crates/coarsetime)
and works on Rust stable, beta, and nightly.
Windows and Unix-like systems are supported.
Available feature:
* `wasi-abi2`: when targeting WASI, use the second preview of the ABI. Default is to use the regular WASI-core ABI.
# Documentation
[API documentation](https://docs.rs/coarsetime)
# Example
```rust
extern crate coarsetime;
use coarsetime::{Duration, Instant, Updater};
// Get the current instant. This may require a system call, but it may also
// be faster than the stdlib equivalent.
let now = Instant::now();
// Get the latest known instant. This operation is super fast.
// In this case, the value will be identical to `now`, because we haven't
// updated the latest known instant yet.
let ts1 = Instant::recent();
// Update the latest known instant. This may require a system call.
// Note that a call to `Instant::now()` also updates the stored instant.
Instant::update();
// Now, we may get a different instant. This call is also super fast.
let ts2 = Instant::recent();
// Compute the time elapsed between ts2 and ts1.
let elapsed_ts2_ts1 = ts2.duration_since(ts1);
// Operations such as `+` and `-` between `Instant` and `Duration` are also
// available.
let elapsed_ts2_ts1 = ts2 - ts1;
// Returns the time elapsed since ts1.
// This retrieves the actual current time, and may require a system call.
let elapsed_since_ts1 = ts1.elapsed();
// Returns the approximate time elapsed since ts1.
// This uses the latest known instant, and is super fast.
let elapsed_since_recent = ts1.elapsed_since_recent();
// Instant::update() should be called periodically, for example using an
// event loop. Alternatively, the crate provides an easy way to spawn a
// background task that will periodically update the latest known instant.
// Here, the update will happen every 250ms.
let updater = Updater::new(250).start().unwrap();
// From now on, Instant::recent() will always return an approximation of the
// current instant.
let ts3 = Instant::recent();
// Stop the task.
updater.stop().unwrap();
// Returns the elapsed time since the UNIX epoch
let unix_timestamp = Clock::now_since_epoch();
// Returns an approximation of the elapsed time since the UNIX epoch, based on
// the latest time update
let unix_timestamp_approx = Clock::recent_since_epoch();
```