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 and works on Rust stable, beta, and nightly.

Windows and Unix-like systems are supported.

Available features:

• nightly: optimizes for rust-nightly
• sierra: optimizes for macOS Sierra

Documentation

API documentation

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 elapsedts2ts1 = ts2.duration_since(ts1);

// Operations such as + and - between Instant and Duration are also // available. let elapsedts2ts1 = ts2 - ts1;

// Returns the time elapsed since ts1. // This retrieves the actual current time, and may require a system call. let elapsedsincets1 = ts1.elapsed();

// Returns the approximate time elapsed since ts1. // This uses the latest known instant, and is super fast. let elapsedsincerecent = ts1.elapsedsincerecent();

// 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 unixtimestamp = Clock::nowsince_epoch();

// Returns an approximation of the elapsed time since the UNIX epoch, based on // the latest time update let unixtimestampapprox = Clock::recentsinceepoch(); ```