audio_blocks/sequential/

view.rs

use rtsan_standalone::nonblocking;

use core::{marker::PhantomData, ptr::NonNull};

use crate::{AudioBlock, Sample, iter::StridedSampleIter};

/// A read-only view of sequential audio data.
///
/// * **Layout:** `[ch0, ch0, ch0, ch1, ch1, ch1]`
/// * **Interpretation:** All samples from `ch0` are stored first, followed by all from `ch1`, etc.
/// * **Terminology:** Described “channels first” in the sense that all data for one channel appears before any data for the next.
/// * **Usage:** Used in DSP pipelines where per-channel processing is easier and more efficient.
///
/// # Example
///
/// ```
/// use audio_blocks::*;
///
/// let data = vec![0.0, 0.0, 0.0, 1.0, 1.0, 1.0];
///
/// let block = AudioBlockSequentialView::from_slice(&data, 2);
///
/// assert_eq!(block.channel(0), &[0.0, 0.0, 0.0]);
/// assert_eq!(block.channel(1), &[1.0, 1.0, 1.0]);
/// ```
pub struct AudioBlockSequentialView<'a, S: Sample> {
    data: &'a [S],
    num_channels: u16,
    num_frames: usize,
    num_channels_allocated: u16,
    num_frames_allocated: usize,
}

impl<'a, S: Sample> AudioBlockSequentialView<'a, S> {
    /// Creates a new audio block from a slice of sequential audio data.
    ///
    /// # Parameters
    /// * `data` - The slice containing sequential audio samples
    /// * `num_channels` - Number of audio channels in the data
    ///
    /// # Panics
    /// Panics if the length of `data` is not evenly divisible by `num_channels`.
    #[nonblocking]
    pub fn from_slice(data: &'a [S], num_channels: u16) -> Self {
        assert!(
            num_channels > 0 && data.len() % num_channels as usize == 0,
            "data length {} must be divisible by num_channels {}",
            data.len(),
            num_channels
        );
        let num_frames = data.len() / num_channels as usize;
        Self {
            data,
            num_channels,
            num_frames,
            num_channels_allocated: num_channels,
            num_frames_allocated: num_frames,
        }
    }

    /// Creates a new audio block from a slice with limited visibility.
    ///
    /// This function allows creating a view that exposes only a subset of the allocated channels
    /// and frames, which is useful for working with a logical section of a larger buffer.
    ///
    /// # Parameters
    /// * `data` - The slice containing sequential audio samples
    /// * `num_channels_visible` - Number of audio channels to expose in the view
    /// * `num_frames_visible` - Number of audio frames to expose in the view
    /// * `num_channels_allocated` - Total number of channels allocated in the data buffer
    /// * `num_frames_allocated` - Total number of frames allocated in the data buffer
    ///
    /// # Panics
    /// * Panics if the length of `data` doesn't equal `num_channels_allocated * num_frames_allocated`
    /// * Panics if `num_channels_visible` exceeds `num_channels_allocated`
    /// * Panics if `num_frames_visible` exceeds `num_frames_allocated`
    #[nonblocking]
    pub fn from_slice_limited(
        data: &'a [S],
        num_channels_visible: u16,
        num_frames_visible: usize,
        num_channels_allocated: u16,
        num_frames_allocated: usize,
    ) -> Self {
        assert_eq!(
            data.len(),
            num_channels_allocated as usize * num_frames_allocated
        );
        assert!(num_channels_visible <= num_channels_allocated);
        assert!(num_frames_visible <= num_frames_allocated);
        Self {
            data,
            num_channels: num_channels_visible,
            num_frames: num_frames_visible,
            num_channels_allocated,
            num_frames_allocated,
        }
    }

    /// Creates a new audio block from a raw pointers.
    ///
    /// # Safety
    ///
    /// The caller must ensure that:
    /// - `ptr` points to valid memory containing at least `num_channels_allocated * num_frames_allocated` elements
    /// - The memory referenced by `ptr` must be valid for the lifetime of the returned `SequentialView`
    /// - The memory must not be mutated through other pointers while this view exists
    #[nonblocking]
    pub unsafe fn from_ptr(ptr: *const S, num_channels: u16, num_frames: usize) -> Self {
        Self {
            data: unsafe { std::slice::from_raw_parts(ptr, num_channels as usize * num_frames) },
            num_channels,
            num_frames,
            num_channels_allocated: num_channels,
            num_frames_allocated: num_frames,
        }
    }

    /// Creates a new audio block from a pointer with a limited amount of channels and/or frames.
    ///
    /// # Safety
    ///
    /// The caller must ensure that:
    /// - `ptr` points to valid memory containing at least `num_channels_allocated * num_frames_allocated` elements
    /// - The memory referenced by `ptr` must be valid for the lifetime of the returned `SequentialView`
    /// - The memory must not be mutated through other pointers while this view exists
    #[nonblocking]
    pub unsafe fn from_ptr_limited(
        ptr: *const S,
        num_channels_visible: u16,
        num_frames_visible: usize,
        num_channels_allocated: u16,
        num_frames_allocated: usize,
    ) -> Self {
        assert!(num_channels_visible <= num_channels_allocated);
        assert!(num_frames_visible <= num_frames_allocated);
        Self {
            data: unsafe {
                std::slice::from_raw_parts(
                    ptr,
                    num_channels_allocated as usize * num_frames_allocated,
                )
            },
            num_channels: num_channels_visible,
            num_frames: num_frames_visible,
            num_channels_allocated,
            num_frames_allocated,
        }
    }

    /// Returns a slice for a single channel.
    ///
    /// # Panics
    ///
    /// Panics if channel index is out of bounds.
    #[nonblocking]
    pub fn channel(&self, channel: u16) -> &[S] {
        assert!(channel < self.num_channels);
        let start = channel as usize * self.num_frames_allocated;
        let end = start + self.num_frames;
        &self.data[start..end]
    }

    /// Returns an iterator over all channels in the block.
    ///
    /// Each channel is represented as a slice of samples.
    #[nonblocking]
    pub fn channels(&self) -> impl Iterator<Item = &[S]> {
        self.data
            .chunks(self.num_frames_allocated)
            .take(self.num_channels as usize)
            .map(|frame| &frame[..self.num_frames])
    }

    /// Provides direct access to the underlying memory as a sequential slice.
    ///
    /// This function gives access to all allocated data, including any reserved capacity
    /// beyond the visible range.
    #[nonblocking]
    pub fn raw_data(&self) -> &[S] {
        &self.data
    }

    #[nonblocking]
    pub fn view(&self) -> AudioBlockSequentialView<'_, S> {
        AudioBlockSequentialView::from_slice_limited(
            self.data,
            self.num_channels,
            self.num_frames,
            self.num_channels_allocated,
            self.num_frames_allocated,
        )
    }
}

impl<S: Sample> AudioBlock<S> for AudioBlockSequentialView<'_, S> {
    type PlanarView = [S; 0];

    #[nonblocking]
    fn num_channels(&self) -> u16 {
        self.num_channels
    }

    #[nonblocking]
    fn num_frames(&self) -> usize {
        self.num_frames
    }

    #[nonblocking]
    fn num_channels_allocated(&self) -> u16 {
        self.num_channels_allocated
    }

    #[nonblocking]
    fn num_frames_allocated(&self) -> usize {
        self.num_frames_allocated
    }

    #[nonblocking]
    fn layout(&self) -> crate::BlockLayout {
        crate::BlockLayout::Sequential
    }

    #[nonblocking]
    fn sample(&self, channel: u16, frame: usize) -> S {
        assert!(channel < self.num_channels);
        assert!(frame < self.num_frames);
        unsafe {
            *self
                .data
                .get_unchecked(channel as usize * self.num_frames_allocated + frame)
        }
    }

    #[nonblocking]
    fn channel_iter(&self, channel: u16) -> impl Iterator<Item = &S> {
        assert!(channel < self.num_channels);
        self.data
            .iter()
            .skip(channel as usize * self.num_frames_allocated)
            .take(self.num_frames)
    }

    #[nonblocking]
    fn channels_iter(&self) -> impl Iterator<Item = impl Iterator<Item = &S> + '_> + '_ {
        let num_frames = self.num_frames; // Visible frames per channel
        let num_frames_allocated = self.num_frames_allocated; // Allocated frames per channel (chunk size)

        self.data
            .chunks(num_frames_allocated)
            .take(self.num_channels as usize)
            .map(move |channel_chunk| channel_chunk.iter().take(num_frames))
    }

    #[nonblocking]
    fn frame_iter(&self, frame: usize) -> impl Iterator<Item = &S> {
        assert!(frame < self.num_frames);
        self.data
            .iter()
            .skip(frame)
            .step_by(self.num_frames_allocated)
            .take(self.num_channels as usize)
    }

    #[nonblocking]
    fn frames_iter(&self) -> impl Iterator<Item = impl Iterator<Item = &S> + '_> + '_ {
        let num_channels = self.num_channels as usize;
        let num_frames = self.num_frames;
        let stride = self.num_frames_allocated;
        let data_ptr = self.data.as_ptr();

        (0..num_frames).map(move |frame_idx| {
            // Safety check: Ensure data isn't empty if we calculate a start_ptr.
            // If num_frames or num_channels is 0, remaining will be 0, iterator is safe.
            // If data is empty, ptr is dangling, but add(0) is okay. add(>0) is UB.
            // But if data is empty, num_channels or num_frames must be 0.
            let start_ptr = if self.data.is_empty() {
                NonNull::dangling().as_ptr() // Use dangling pointer if slice is empty
            } else {
                // Safety: channel_idx is < num_channels <= num_channels_allocated.
                // Adding it to a valid data_ptr is safe within slice bounds.
                unsafe { data_ptr.add(frame_idx) }
            };

            StridedSampleIter::<'_, S> {
                // Note: '_ lifetime from &self borrow
                // Safety: Pointer is either dangling (if empty) or valid start pointer.
                // NonNull::new is safe if start_ptr is non-null (i.e., data not empty).
                ptr: NonNull::new(start_ptr as *mut S).unwrap_or(NonNull::dangling()), // Use dangling on null/empty
                stride,
                remaining: num_channels, // If 0, iterator yields None immediately
                _marker: PhantomData,
            }
        })
    }

    #[nonblocking]
    fn as_view(&self) -> impl AudioBlock<S> {
        self.view()
    }

    #[nonblocking]
    fn as_sequential_view(&self) -> Option<AudioBlockSequentialView<'_, S>> {
        Some(self.view())
    }
}

impl<S: Sample + core::fmt::Debug> core::fmt::Debug for AudioBlockSequentialView<'_, S> {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        writeln!(f, "AudioBlockSequentialView {{")?;
        writeln!(f, "  num_channels: {}", self.num_channels)?;
        writeln!(f, "  num_frames: {}", self.num_frames)?;
        writeln!(
            f,
            "  num_channels_allocated: {}",
            self.num_channels_allocated
        )?;
        writeln!(f, "  num_frames_allocated: {}", self.num_frames_allocated)?;
        writeln!(f, "  channels:")?;

        for (i, channel) in self.channels().enumerate() {
            writeln!(f, "    {}: {:?}", i, channel)?;
        }

        writeln!(f, "  raw_data: {:?}", self.raw_data())?;
        writeln!(f, "}}")?;

        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use rtsan_standalone::no_sanitize_realtime;

    #[test]
    fn test_member_functions() {
        let block = AudioBlockSequentialView::from_slice_limited(
            &[0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 0.0, 0.0, 0.0, 0.0],
            2,
            3,
            3,
            4,
        );

        // single frame
        assert_eq!(block.channel(0), &[0.0, 1.0, 2.0]);
        assert_eq!(block.channel(1), &[4.0, 5.0, 6.0]);

        // all frames
        let mut channels = block.channels();
        assert_eq!(channels.next().unwrap(), &[0.0, 1.0, 2.0]);
        assert_eq!(channels.next().unwrap(), &[4.0, 5.0, 6.0]);
        assert_eq!(channels.next(), None);
        drop(channels);

        // raw data
        assert_eq!(
            block.raw_data(),
            &[0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 0.0, 0.0, 0.0, 0.0]
        );

        // views
        let view = block.view();
        assert_eq!(view.num_channels(), block.num_channels());
        assert_eq!(view.num_frames(), block.num_frames());
        assert_eq!(
            view.num_channels_allocated(),
            block.num_channels_allocated()
        );
        assert_eq!(view.num_frames_allocated(), block.num_frames_allocated());
        assert_eq!(view.raw_data(), block.raw_data());
    }

    #[test]
    fn test_samples() {
        let data = [0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0];
        let block = AudioBlockSequentialView::<f32>::from_slice(&data, 2);

        for ch in 0..block.num_channels() {
            for f in 0..block.num_frames() {
                assert_eq!(
                    block.sample(ch, f),
                    (ch as usize * block.num_frames() + f) as f32
                );
            }
        }
    }

    #[test]
    fn test_channel_iter() {
        let data = vec![0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0];
        let block = AudioBlockSequentialView::<f32>::from_slice(&data, 2);

        let channel = block.channel_iter(0).copied().collect::<Vec<_>>();
        assert_eq!(channel, vec![0.0, 1.0, 2.0, 3.0, 4.0]);
        let channel = block.channel_iter(1).copied().collect::<Vec<_>>();
        assert_eq!(channel, vec![5.0, 6.0, 7.0, 8.0, 9.0]);
    }

    #[test]
    fn test_channel_iters() {
        let data = vec![0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0];
        let block = AudioBlockSequentialView::<f32>::from_slice(&data, 2);

        let mut channels_iter = block.channels_iter();
        let channel = channels_iter.next().unwrap().copied().collect::<Vec<_>>();
        assert_eq!(channel, vec![0.0, 1.0, 2.0, 3.0, 4.0]);

        let channel = channels_iter.next().unwrap().copied().collect::<Vec<_>>();
        assert_eq!(channel, vec![5.0, 6.0, 7.0, 8.0, 9.0]);
        assert!(channels_iter.next().is_none());
    }

    #[test]
    fn test_frame_iter() {
        let data = vec![0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0];
        let block = AudioBlockSequentialView::<f32>::from_slice(&data, 2);

        let channel = block.frame_iter(0).copied().collect::<Vec<_>>();
        assert_eq!(channel, vec![0.0, 5.0]);
        let channel = block.frame_iter(1).copied().collect::<Vec<_>>();
        assert_eq!(channel, vec![1.0, 6.0]);
        let channel = block.frame_iter(2).copied().collect::<Vec<_>>();
        assert_eq!(channel, vec![2.0, 7.0]);
        let channel = block.frame_iter(3).copied().collect::<Vec<_>>();
        assert_eq!(channel, vec![3.0, 8.0]);
        let channel = block.frame_iter(4).copied().collect::<Vec<_>>();
        assert_eq!(channel, vec![4.0, 9.0]);
    }

    #[test]
    fn test_frame_iters() {
        let data = vec![0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0];
        let block = AudioBlockSequentialView::<f32>::from_slice(&data, 2);

        let mut frames_iter = block.frames_iter();
        let channel = frames_iter.next().unwrap().copied().collect::<Vec<_>>();
        assert_eq!(channel, vec![0.0, 5.0]);
        let channel = frames_iter.next().unwrap().copied().collect::<Vec<_>>();
        assert_eq!(channel, vec![1.0, 6.0]);
        let channel = frames_iter.next().unwrap().copied().collect::<Vec<_>>();
        assert_eq!(channel, vec![2.0, 7.0]);
        let channel = frames_iter.next().unwrap().copied().collect::<Vec<_>>();
        assert_eq!(channel, vec![3.0, 8.0]);
        let channel = frames_iter.next().unwrap().copied().collect::<Vec<_>>();
        assert_eq!(channel, vec![4.0, 9.0]);
        assert!(frames_iter.next().is_none());
    }

    #[test]
    fn test_from_slice() {
        let data = [0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0];
        let block = AudioBlockSequentialView::<f32>::from_slice(&data, 2);
        assert_eq!(block.num_channels(), 2);
        assert_eq!(block.num_channels_allocated, 2);
        assert_eq!(block.num_frames(), 5);
        assert_eq!(block.num_frames_allocated, 5);
        assert_eq!(
            block.channel_iter(0).copied().collect::<Vec<_>>(),
            vec![0.0, 1.0, 2.0, 3.0, 4.0]
        );
        assert_eq!(
            block.channel_iter(1).copied().collect::<Vec<_>>(),
            vec![5.0, 6.0, 7.0, 8.0, 9.0]
        );
        assert_eq!(
            block.frame_iter(0).copied().collect::<Vec<_>>(),
            vec![0.0, 5.0]
        );
        assert_eq!(
            block.frame_iter(1).copied().collect::<Vec<_>>(),
            vec![1.0, 6.0]
        );
        assert_eq!(
            block.frame_iter(2).copied().collect::<Vec<_>>(),
            vec![2.0, 7.0]
        );
        assert_eq!(
            block.frame_iter(3).copied().collect::<Vec<_>>(),
            vec![3.0, 8.0]
        );
        assert_eq!(
            block.frame_iter(4).copied().collect::<Vec<_>>(),
            vec![4.0, 9.0]
        );
    }

    #[test]
    fn test_view() {
        let data = [0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0];
        let block = AudioBlockSequentialView::<f32>::from_slice(&data, 2);
        assert!(block.as_interleaved_view().is_none());
        assert!(block.as_planar_view().is_none());
        assert!(block.as_sequential_view().is_some());
        let view = block.as_view();
        assert_eq!(
            view.channel_iter(0).copied().collect::<Vec<_>>(),
            vec![0.0, 1.0, 2.0, 3.0, 4.0]
        );
        assert_eq!(
            view.channel_iter(1).copied().collect::<Vec<_>>(),
            vec![5.0, 6.0, 7.0, 8.0, 9.0]
        );
    }

    #[test]
    fn test_limited() {
        let data = [1.0, 2.0, 0.0, 3.0, 4.0, 0.0, 5.0, 6.0, 0.0, 0.0, 0.0, 0.0];

        let block = AudioBlockSequentialView::from_slice_limited(&data, 2, 3, 3, 4);

        assert_eq!(block.num_channels(), 2);
        assert_eq!(block.num_frames(), 3);
        assert_eq!(block.num_channels_allocated, 3);
        assert_eq!(block.num_frames_allocated, 4);

        for i in 0..block.num_channels() {
            assert_eq!(block.channel_iter(i).count(), 3);
        }
        for i in 0..block.num_frames() {
            assert_eq!(block.frame_iter(i).count(), 2);
        }
    }

    #[test]
    fn test_from_ptr() {
        let mut data = [0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0];
        let block = unsafe { AudioBlockSequentialView::<f32>::from_ptr(data.as_mut_ptr(), 2, 5) };
        assert_eq!(block.num_channels(), 2);
        assert_eq!(block.num_channels_allocated, 2);
        assert_eq!(block.num_frames(), 5);
        assert_eq!(block.num_frames_allocated, 5);
        assert_eq!(
            block.channel_iter(0).copied().collect::<Vec<_>>(),
            vec![0.0, 1.0, 2.0, 3.0, 4.0]
        );
        assert_eq!(
            block.channel_iter(1).copied().collect::<Vec<_>>(),
            vec![5.0, 6.0, 7.0, 8.0, 9.0]
        );
        assert_eq!(
            block.frame_iter(0).copied().collect::<Vec<_>>(),
            vec![0.0, 5.0]
        );
        assert_eq!(
            block.frame_iter(1).copied().collect::<Vec<_>>(),
            vec![1.0, 6.0]
        );
        assert_eq!(
            block.frame_iter(2).copied().collect::<Vec<_>>(),
            vec![2.0, 7.0]
        );
        assert_eq!(
            block.frame_iter(3).copied().collect::<Vec<_>>(),
            vec![3.0, 8.0]
        );
        assert_eq!(
            block.frame_iter(4).copied().collect::<Vec<_>>(),
            vec![4.0, 9.0]
        );
    }

    #[test]
    fn test_from_ptr_limited() {
        let data = [1.0, 2.0, 0.0, 3.0, 4.0, 0.0, 5.0, 6.0, 0.0, 0.0, 0.0, 0.0];

        let block =
            unsafe { AudioBlockSequentialView::from_ptr_limited(data.as_ptr(), 2, 3, 3, 4) };

        assert_eq!(block.num_channels(), 2);
        assert_eq!(block.num_frames(), 3);
        assert_eq!(block.num_channels_allocated, 3);
        assert_eq!(block.num_frames_allocated, 4);

        for i in 0..block.num_channels() {
            assert_eq!(block.channel_iter(i).count(), 3);
        }
        for i in 0..block.num_frames() {
            assert_eq!(block.frame_iter(i).count(), 2);
        }
    }

    #[test]
    #[should_panic]
    #[no_sanitize_realtime]
    fn test_slice_out_of_bounds() {
        let data = [1.0, 1.0, 1.0, 0.0, 2.0, 2.0, 2.0, 0.0, 0.0, 0.0, 0.0, 0.0];
        let block = AudioBlockSequentialView::from_slice_limited(&data, 2, 3, 3, 4);

        block.channel(2);
    }
}