awedio 0.6.0

A low-overhead and adaptable audio playback library
Documentation 
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use std::time::Duration;

use crate::Sound;

use super::Wrapper;

/// Play the  first part of an inner Sound measured in seconds then stop even
/// if the inner sound still has samples remaining. Finishes early if the inner
/// sound finishes before duration. Any time the inner sample is paused does not
/// count against the duration (i.e. duration only includes time of samples).
pub struct FinishAfter<S: Sound> {
    inner: S,
    samples_remaining: u64,
    total_duration: Duration,
    current_channel_count: u16,
    current_sample_rate: u32,
}

impl<S> FinishAfter<S>
where
    S: Sound,
{
    /// Only play the first `duration` of inner before finishing.
    pub fn new(inner: S, duration: Duration) -> Self {
        let current_channel_count = inner.channel_count();
        let current_sample_rate = inner.sample_rate();
        let samples_remaining = num_samples(duration, current_channel_count, current_sample_rate);
        FinishAfter {
            inner,
            samples_remaining,
            total_duration: duration,
            current_channel_count,
            current_sample_rate,
        }
    }

    /// Get a reference to the wrapped inner Sound.
    pub fn inner(&self) -> &S {
        &self.inner
    }

    /// Get a mutable reference to the wrapped inner Sound.
    pub fn inner_mut(&mut self) -> &mut S {
        &mut self.inner
    }

    /// Unwrap and return the previously wrapped Sound.
    pub fn into_inner(self) -> S {
        self.inner
    }
}

impl<S> Sound for FinishAfter<S>
where
    S: Sound,
{
    fn channel_count(&self) -> u16 {
        self.inner.channel_count()
    }

    fn sample_rate(&self) -> u32 {
        self.inner.sample_rate()
    }

    fn next_sample(&mut self) -> Result<crate::NextSample, crate::Error> {
        if self.samples_remaining == 0 {
            return Ok(crate::NextSample::Finished);
        }
        let next = self.inner.next_sample()?;
        match next {
            crate::NextSample::Sample(_) => {
                self.samples_remaining -= 1;
            }
            crate::NextSample::MetadataChanged => {
                let total_old_samples = num_samples(
                    self.total_duration,
                    self.current_channel_count,
                    self.current_sample_rate,
                );
                let num_samples_played = total_old_samples - self.samples_remaining;
                let seconds_played = num_samples_played as f64
                    / self.current_channel_count as f64
                    / self.current_sample_rate as f64;
                let duration_played = Duration::from_secs_f64(seconds_played);
                let duration_remaining = self.total_duration - duration_played;
                self.current_channel_count = self.inner.channel_count();
                self.current_sample_rate = self.inner.sample_rate();
                self.samples_remaining = num_samples(
                    duration_remaining,
                    self.current_channel_count,
                    self.current_sample_rate,
                );
            }
            crate::NextSample::Paused => (),
            crate::NextSample::Finished => (),
        }
        Ok(next)
    }

    fn on_start_of_batch(&mut self) {
        self.inner.on_start_of_batch()
    }
}

pub fn num_samples(duration: Duration, num_channels: u16, num_samples: u32) -> u64 {
    const MICROS_PER_SEC: u64 = 1_000_000;
    let micros = duration.as_secs() * MICROS_PER_SEC + duration.subsec_micros() as u64;
    micros * num_channels as u64 * num_samples as u64 / MICROS_PER_SEC
}

impl<S: Sound> Wrapper for FinishAfter<S> {
    type Inner = S;

    fn inner(&self) -> &Self::Inner {
        &self.inner
    }

    fn inner_mut(&mut self) -> &mut Self::Inner {
        &mut self.inner
    }

    fn into_inner(self) -> Self::Inner {
        self.inner
    }
}

#[cfg(test)]
#[path = "./tests/finish_after.rs"]
mod tests;