tek/src/time.rs

/// Number of data frames in a second.
#[derive(Debug)]
pub struct Hz(pub u32);

/// One data frame.
#[derive(Debug)]
pub struct Frame(pub u32);

/// One microsecond.
#[derive(Debug)]
pub struct Usec(pub u64);

/// Beats per minute as `120000` = 120.000BPM
#[derive(Debug)]
pub struct Tempo(pub u64);

/// Time signature: N/Mths per bar.
#[derive(Debug)]
pub struct Signature(pub u32, pub u32);

/// NoteDuration in musical terms. Has definite usec value
/// for given bpm and sample rate.
pub enum NoteDuration {
    Nth(u16, u16),
    Dotted(Box<Self>),
    Tuplet(u16, Box<Self>),
}

impl Frame {
    #[inline]
    pub fn to_usec (&self, rate: &Hz) -> Usec {
        Usec((self.0 as u64 * 1000000) / rate.0 as u64)
    }
}

impl Usec {
    #[inline]
    pub fn to_frame (&self, rate: &Hz) -> Frame {
        Frame(((self.0 * rate.0 as u64) / 1000) as u32)
    }
}

impl Tempo {
    #[inline]
    pub fn usec_per_bar (&self, beats: u64) -> Usec {
        Usec(beats * self.usec_per_beat().0)
    }
    #[inline]
    pub fn usec_per_beat (&self) -> Usec {
        Usec(60_000_000_000 / self.0 as u64)
    }
    #[inline]
    pub fn usec_per_step (&self, divisor: u64) -> Usec {
        Usec(self.usec_per_beat().0 / divisor as u64)
    }
    #[inline]
    pub fn quantize (&self, step: &NoteDuration, time: Usec) -> Usec {
        let step = step.to_usec(self);
        let t = time.0 / step.0;
        Usec(step.0 * t)
    }
    #[inline]
    pub fn quantize_into <T, U> (&self, step: &NoteDuration, events: U)
        -> Vec<(Usec, T)>
            where U: std::iter::Iterator<Item=(Usec, T)> + Sized
    {
        events
            .map(|(time, event)|(self.quantize(step, time), event))
            .collect()
    }
}

impl NoteDuration {
    fn to_usec (&self, bpm: &Tempo) -> Usec {
        Usec(match self {
            Self::Nth(time, flies) =>
                bpm.usec_per_beat().0 * *time as u64 / *flies as u64,
            Self::Dotted(duration) =>
                duration.to_usec(bpm).0 * 3 / 2,
            Self::Tuplet(n, duration) =>
                duration.to_usec(bpm).0 * 2 / *n as u64,
        })
    }
    fn to_frame (&self, bpm: &Tempo, rate: &Hz) -> Frame {
        self.to_usec(bpm).to_frame(rate)
    }
}

struct Loop<T> {
    repeat:     bool,
    pre_start:  T,
    start:      T,
    end:        T,
    post_end:   T,
}