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//! Core abstractions of the Real-Time Interrupt-driven Concurrency (RTIC) Monotonic timers, used
//! internally for scheduling and users can use them for time.
//!
//! You can write generic *libraries* and HALs using the `Monotinc` trait in this crate. If you
//! want to write application code then you'll need an *implementation* of the RTIC framework for a
//! particular architecture. Currently, there are implementations for these architectures and OSes:
//!
//! - [ARM Cortex-M](https://crates.io/crates/cortex-m-rtic)

#![deny(missing_docs)]
#![deny(rust_2018_compatibility)]
#![deny(rust_2018_idioms)]
#![deny(warnings)]
#![no_std]

pub use embedded_time::{self, duration::*, Clock, Instant};

/// # A monotonic clock / counter definition.
///
/// ## Codegen extensions provided
///
/// The RTIC codegen will implement an infallible `Monotonic::now()` that simply gets the value
/// from the `Clock::try_now()`, and an `Monotonic::zero()` which returns the *zero* time for use
/// in `#[init]`.
///
/// ## Correctness
///
/// When implementing this trait it is important to decide if one want to have a fixed baseline and
/// utilize the `reset` method. If not, one can implement `reset` as an empty method. If
/// `reset` is **not empty**, it is **not allowed** for `try_now()`/`now()` to return
/// nonsensical values if called before `reset` is invoked by the runtime. Therefore implementation
/// authors should have methods in place for making sure of this, for example a flag in the timer
/// which tracks if the `reset` method has been called yet, and if not always return `0`.
///
/// The `embedded_time::Clock` implementation must be **infallible**.
pub trait Monotonic: Clock {
    /// This tells RTIC if it should disable the interrupt bound to the monotonic if there are no
    /// scheduled tasks. One may want to set this to `false` if one is using the `on_interrupt`
    /// method to perform housekeeping and need overflow interrupts to happen, such as when
    /// extending a 16 bit timer to 32/64 bits, even if there are no scheduled tasks.
    const DISABLE_INTERRUPT_ON_EMPTY_QUEUE: bool = true;

    /// Optionally resets the counter to *zero* for a fixed baseline in a system.
    ///
    /// This method will be called *exactly once* by the RTIC runtime after `#[init]` returns and
    /// before tasks can start.
    ///
    /// ## Correctness
    ///
    /// The user may not call this method.
    unsafe fn reset(&mut self);

    /// Set the compare value of the timer interrupt.
    fn set_compare(&mut self, instant: &Instant<Self>);

    /// Clear the compare interrupt flag.
    fn clear_compare_flag(&mut self);

    /// Optional. Commonly used for performing housekeeping of a timer when it has been extended,
    /// e.g. a 16 bit timer extended to 32/64 bits. This will be called at the end of the interrupt
    /// handler after all other operations have finished.
    fn on_interrupt(&mut self) {}

    /// Optional. This is used to save power, this is called when the Monotonic interrupt is
    /// enabled.
    fn enable_timer(&mut self) {}

    /// Optional. This is used to save power, this is called when the Monotonic interrupt is
    /// disabled.
    fn disable_timer(&mut self) {}
}