e8af1a1812
- Vendor coarsetime crate with portable-atomic fallback - Use portable-atomic on targets without 64-bit atomics - Patch crates.io to use local coarsetime - Fixes MIPS build failure (AtomicU64 missing)
91 lines
3.4 KiB
Markdown
91 lines
3.4 KiB
Markdown
[](https://docs.rs/coarsetime)
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[](https://ci.appveyor.com/project/jedisct1/rust-coarsetime)
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# coarsetime
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A Rust crate to make time measurements, that focuses on speed, API stability and portability.
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This crate is a partial replacement for the `Time` and `Duration` structures
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from the standard library, with the following differences:
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* Speed is privileged over accuracy. In particular, `CLOCK_MONOTONIC_COARSE` is
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used to retrieve the clock value on Linux systems, and transformations avoid
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operations that can be slow on non-Intel systems.
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* The number of system calls can be kept to a minimum. The "most recent
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timestamp" is always kept in memory. It can be read with just a load operation,
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and can be updated only as frequently as necessary.
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* The API is stable, and the same for all platforms. Unlike the standard library, it doesn't silently compile functions that do nothing but panic at runtime on some platforms.
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# Installation
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`coarsetime` is available on [crates.io](https://crates.io/crates/coarsetime)
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and works on Rust stable, beta, and nightly.
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Windows and Unix-like systems are supported.
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Available feature:
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* `wasi-abi2`: when targeting WASI, use the second preview of the ABI. Default is to use the regular WASI-core ABI.
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# Documentation
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[API documentation](https://docs.rs/coarsetime)
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# Example
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```rust
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extern crate coarsetime;
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use coarsetime::{Duration, Instant, Updater};
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// Get the current instant. This may require a system call, but it may also
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// be faster than the stdlib equivalent.
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let now = Instant::now();
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// Get the latest known instant. This operation is super fast.
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// In this case, the value will be identical to `now`, because we haven't
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// updated the latest known instant yet.
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let ts1 = Instant::recent();
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// Update the latest known instant. This may require a system call.
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// Note that a call to `Instant::now()` also updates the stored instant.
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Instant::update();
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// Now, we may get a different instant. This call is also super fast.
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let ts2 = Instant::recent();
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// Compute the time elapsed between ts2 and ts1.
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let elapsed_ts2_ts1 = ts2.duration_since(ts1);
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// Operations such as `+` and `-` between `Instant` and `Duration` are also
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// available.
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let elapsed_ts2_ts1 = ts2 - ts1;
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// Returns the time elapsed since ts1.
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// This retrieves the actual current time, and may require a system call.
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let elapsed_since_ts1 = ts1.elapsed();
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// Returns the approximate time elapsed since ts1.
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// This uses the latest known instant, and is super fast.
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let elapsed_since_recent = ts1.elapsed_since_recent();
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// Instant::update() should be called periodically, for example using an
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// event loop. Alternatively, the crate provides an easy way to spawn a
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// background task that will periodically update the latest known instant.
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// Here, the update will happen every 250ms.
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let updater = Updater::new(250).start().unwrap();
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// From now on, Instant::recent() will always return an approximation of the
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// current instant.
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let ts3 = Instant::recent();
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// Stop the task.
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updater.stop().unwrap();
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// Returns the elapsed time since the UNIX epoch
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let unix_timestamp = Clock::now_since_epoch();
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// Returns an approximation of the elapsed time since the UNIX epoch, based on
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// the latest time update
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let unix_timestamp_approx = Clock::recent_since_epoch();
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```
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