A proc macro and a macro attribute to quickly time funcitions. Uses std::time::Instant so relies on std to work.

#[time_this]

This macro can be used to time any function you want using std::time::Instant. It may not work correctly with async fn and it definitely doesn't work with const fn (even if called in a non-const context. You can write a small wrapping fn if you need to time a const fn). It will print: * the time in ns if the function took less than 1μs. * the time in μs if the function took less than 1ms. * the time in ms if the function took longer than 1ms, but less than 1s. * the time in s if the function took more than a second, with two decimal digits.

```rust use timethis::timethis;

[time_this]

fn add(a: u32, b: u32) -> u32 { a + b }

fn main() { let result = add(3, 5); // function 'add()' took 37ns } ```

time!()

This macro can be used to time any expression you want using std::time::Instant. It returns the result of the expression, similar to dbg!(). It may not work correctly with async fn. Instead of printing the function name, it will print the file/line the expression that was timed at.

```rust use time_this::time;

fn add(a: u32, b: u32) -> u32 { a + b }

fn main() { let result = time!(add(3, 5)); // expression at [tests/tests.rs:33] took 28ns } ```