android_audio/src/lib.rs

// Copyright 2024 The ChromiumOS Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#[cfg(feature = "libaaudio_stub")]
mod libaaudio_stub;

use std::os::raw::c_void;
use std::time::Duration;
use std::time::Instant;

use async_trait::async_trait;
use audio_streams::capture::AsyncCaptureBuffer;
use audio_streams::capture::AsyncCaptureBufferStream;
use audio_streams::capture::CaptureBuffer;
use audio_streams::capture::CaptureBufferStream;
use audio_streams::AsyncBufferCommit;
use audio_streams::AsyncPlaybackBuffer;
use audio_streams::AsyncPlaybackBufferStream;
use audio_streams::AudioStreamsExecutor;
use audio_streams::BoxError;
use audio_streams::BufferCommit;
use audio_streams::NoopStreamControl;
use audio_streams::PlaybackBuffer;
use audio_streams::PlaybackBufferStream;
use audio_streams::SampleFormat;
use audio_streams::StreamControl;
use audio_streams::StreamEffect;
use audio_streams::StreamSource;
use audio_streams::StreamSourceGenerator;
use base::warn;
use thiserror::Error;

#[derive(Clone, Copy)]
enum AndroidAudioStreamDirection {
    Input = 1,
    Output = 0,
}

#[derive(Error, Debug)]
pub enum AAudioError {
    #[error("Failed to create stream builder")]
    StreamBuilderCreation,
    #[error("Failed to open stream")]
    StreamOpen,
    #[error("Failed to start stream")]
    StreamStart,
    #[error("Failed to delete stream builder")]
    StreamBuilderDelete,
}

// Opaque blob
#[repr(C)]
struct AAudioStream {
    _data: [u8; 0],
    _marker: core::marker::PhantomData<(*mut u8, core::marker::PhantomPinned)>,
}

// Opaque blob
#[repr(C)]
struct AAudioStreamBuilder {
    _data: [u8; 0],
    _marker: core::marker::PhantomData<(*mut u8, core::marker::PhantomPinned)>,
}

type AaudioFormatT = i32;
type AaudioResultT = i32;
const AAUDIO_OK: AaudioResultT = 0;

extern "C" {
    fn AAudio_createStreamBuilder(builder: *mut *mut AAudioStreamBuilder) -> AaudioResultT;
    fn AAudioStreamBuilder_delete(builder: *mut AAudioStreamBuilder) -> AaudioResultT;
    fn AAudioStreamBuilder_setBufferCapacityInFrames(
        builder: *mut AAudioStreamBuilder,
        num_frames: i32,
    );
    fn AAudioStreamBuilder_setDirection(builder: *mut AAudioStreamBuilder, direction: u32);
    fn AAudioStreamBuilder_setFormat(builder: *mut AAudioStreamBuilder, format: AaudioFormatT);
    fn AAudioStreamBuilder_setSampleRate(builder: *mut AAudioStreamBuilder, sample_rate: i32);
    fn AAudioStreamBuilder_setChannelCount(builder: *mut AAudioStreamBuilder, channel_count: i32);
    fn AAudioStreamBuilder_openStream(
        builder: *mut AAudioStreamBuilder,
        stream: *mut *mut AAudioStream,
    ) -> AaudioResultT;
    fn AAudioStream_getBufferSizeInFrames(stream: *mut AAudioStream) -> i32;
    fn AAudioStream_requestStart(stream: *mut AAudioStream) -> AaudioResultT;
    fn AAudioStream_read(
        stream: *mut AAudioStream,
        buffer: *mut c_void,
        num_frames: i32,
        timeout_nanoseconds: i64,
    ) -> AaudioResultT;
    fn AAudioStream_write(
        stream: *mut AAudioStream,
        buffer: *const c_void,
        num_frames: i32,
        timeout_nanoseconds: i64,
    ) -> AaudioResultT;
    fn AAudioStream_close(stream: *mut AAudioStream) -> AaudioResultT;
}

struct AAudioStreamPtr {
    // TODO: Use callback function to avoid possible thread preemption and glitches cause by
    // using AAudio APIs in different threads.
    stream_ptr: *mut AAudioStream,
}

// SAFETY:
// AudioStream.drop.buffer_ptr: *const u8 points to AudioStream.buffer, which would be alive
// whenever AudioStream.drop.buffer_ptr is alive.
unsafe impl Send for AndroidAudioStreamCommit {}

struct AudioStream {
    buffer: Box<[u8]>,
    frame_size: usize,
    frame_rate: u32,
    next_frame: Instant,
    start_time: Option<Instant>,
    total_frames: i32,
    buffer_drop: AndroidAudioStreamCommit,
    read_count: i32,
    aaudio_buffer_size: usize,
}

struct AndroidAudioStreamCommit {
    buffer_ptr: *const u8,
    stream: AAudioStreamPtr,
    direction: AndroidAudioStreamDirection,
}

impl BufferCommit for AndroidAudioStreamCommit {
    fn commit(&mut self, _nwritten: usize) {
        // This traits function is never called.
        unimplemented!();
    }
}

#[async_trait(?Send)]
impl AsyncBufferCommit for AndroidAudioStreamCommit {
    async fn commit(&mut self, nwritten: usize) {
        match self.direction {
            AndroidAudioStreamDirection::Input => {}
            AndroidAudioStreamDirection::Output => {
                // SAFETY:
                // The AAudioStream_write reads buffer for nwritten * frame_size bytes
                // It is safe since nwritten < buffer_size and the buffer.len() == buffer_size *
                // frame_size
                let frames_written: i32 = unsafe {
                    AAudioStream_write(
                        self.stream.stream_ptr,
                        self.buffer_ptr as *const c_void,
                        nwritten as i32,
                        0, // this call will not wait.
                    )
                };
                if frames_written < 0 {
                    warn!("AAudio stream write failed.");
                } else if (frames_written as usize) < nwritten {
                    // Currently, the frames unable to write by the AAudio API are dropped.
                    warn!(
                        "Android Audio Stream:  Drop {} frames",
                        nwritten - (frames_written as usize)
                    );
                }
            }
        }
    }
}

impl AudioStream {
    pub fn new(
        num_channels: usize,
        format: SampleFormat,
        frame_rate: u32,
        buffer_size: usize,
        direction: AndroidAudioStreamDirection,
    ) -> Result<Self, BoxError> {
        let frame_size = format.sample_bytes() * num_channels;

        let mut stream_ptr: *mut AAudioStream = std::ptr::null_mut();
        let mut builder: *mut AAudioStreamBuilder = std::ptr::null_mut();
        // SAFETY:
        // Interfacing with the AAudio C API. Assumes correct linking
        // and `builder` and `stream_ptr` pointers are valid and properly initialized.
        unsafe {
            if AAudio_createStreamBuilder(&mut builder) != AAUDIO_OK {
                return Err(Box::new(AAudioError::StreamBuilderCreation));
            }
            AAudioStreamBuilder_setDirection(builder, direction as u32);
            AAudioStreamBuilder_setBufferCapacityInFrames(builder, buffer_size as i32 * 2);
            AAudioStreamBuilder_setFormat(builder, format as AaudioFormatT);
            AAudioStreamBuilder_setSampleRate(builder, frame_rate as i32);
            AAudioStreamBuilder_setChannelCount(builder, num_channels as i32);
            if AAudioStreamBuilder_openStream(builder, &mut stream_ptr) != AAUDIO_OK {
                return Err(Box::new(AAudioError::StreamOpen));
            }
            if AAudioStreamBuilder_delete(builder) != AAUDIO_OK {
                return Err(Box::new(AAudioError::StreamBuilderDelete));
            }
            if AAudioStream_requestStart(stream_ptr) != AAUDIO_OK {
                return Err(Box::new(AAudioError::StreamStart));
            }
        }
        // SAFETY:
        // Interfacing with the AAudio C API. Assumes correct linking
        // and `stream_ptr` pointers are valid and properly initialized.
        let aaudio_buffer_size = unsafe { AAudioStream_getBufferSizeInFrames(stream_ptr) } as usize;
        let buffer = vec![0; buffer_size * frame_size].into_boxed_slice();
        let stream = AAudioStreamPtr { stream_ptr };
        let buffer_drop = AndroidAudioStreamCommit {
            stream,
            buffer_ptr: buffer.as_ptr(),
            direction,
        };
        Ok(AudioStream {
            buffer,
            frame_size,
            frame_rate,
            next_frame: Instant::now(),
            start_time: None,
            total_frames: 0,
            buffer_drop,
            read_count: 0,
            aaudio_buffer_size,
        })
    }
}

impl PlaybackBufferStream for AudioStream {
    fn next_playback_buffer<'b, 's: 'b>(&'s mut self) -> Result<PlaybackBuffer<'b>, BoxError> {
        // This traits function is never called.
        unimplemented!();
    }
}

#[async_trait(?Send)]
impl AsyncPlaybackBufferStream for AudioStream {
    async fn next_playback_buffer<'a>(
        &'a mut self,
        ex: &dyn AudioStreamsExecutor,
    ) -> Result<AsyncPlaybackBuffer<'a>, BoxError> {
        self.total_frames += (self.buffer.len() / self.frame_size) as i32;
        let start_time = match self.start_time {
            Some(time) => {
                ex.delay(self.next_frame.saturating_duration_since(Instant::now()))
                    .await?;
                time
            }
            None => {
                let now = Instant::now();
                self.start_time = Some(now);
                now
            }
        };
        self.next_frame = start_time
            + Duration::from_millis(self.total_frames as u64 * 1000 / self.frame_rate as u64);
        Ok(
            AsyncPlaybackBuffer::new(self.frame_size, self.buffer.as_mut(), &mut self.buffer_drop)
                .map_err(Box::new)?,
        )
    }
}

#[async_trait(?Send)]
impl CaptureBufferStream for AudioStream {
    fn next_capture_buffer<'b, 's: 'b>(&'s mut self) -> Result<CaptureBuffer<'b>, BoxError> {
        // This traits function is never called.
        unimplemented!()
    }
}

#[async_trait(?Send)]
impl AsyncCaptureBufferStream for AudioStream {
    async fn next_capture_buffer<'a>(
        &'a mut self,
        ex: &dyn AudioStreamsExecutor,
    ) -> Result<AsyncCaptureBuffer<'a>, BoxError> {
        let buffer_size = self.buffer.len() / self.frame_size;
        self.read_count += 1;
        self.total_frames += buffer_size as i32;
        let start_time = match self.start_time {
            Some(time) => {
                ex.delay(self.next_frame.saturating_duration_since(Instant::now()))
                    .await?;
                time
            }
            None => {
                let now = Instant::now();
                self.start_time = Some(now);
                now
            }
        };
        self.next_frame = start_time
            + Duration::from_millis(self.total_frames as u64 * 1000 / self.frame_rate as u64);

        // Skip for at least (1.5x aaudio buffer size - buffer_size) to ensure there is always a
        // aaudio buffer available for read.
        if self.read_count < (self.aaudio_buffer_size * 3 / 2 / buffer_size) as i32 + 1 {
            self.buffer.fill(0);
            return Ok(AsyncCaptureBuffer::new(
                buffer_size,
                self.buffer.as_mut(),
                &mut self.buffer_drop,
            )
            .map_err(Box::new)?);
        }

        // SAFETY:
        // The AAudioStream_read writes buffer for buffer.len() / frame_size * frame_size bytes
        let frames_read = unsafe {
            AAudioStream_read(
                self.buffer_drop.stream.stream_ptr,
                self.buffer.as_mut_ptr() as *mut c_void,
                (buffer_size) as i32,
                0,
            )
        };

        if frames_read < 0 {
            warn!("AAudio stream read failed: {frames_read}");
            self.buffer.fill(0);
        } else if (frames_read as usize) < buffer_size {
            warn!(
                "AAudio stream read data not enough. frames read: {frames_read}, buffer size: {buffer_size}",
            );
            self.buffer[frames_read as usize * self.frame_size..].fill(0);
        }

        Ok(
            AsyncCaptureBuffer::new(buffer_size, self.buffer.as_mut(), &mut self.buffer_drop)
                .map_err(Box::new)?,
        )
    }
}

impl Drop for AAudioStreamPtr {
    fn drop(&mut self) {
        // SAFETY:
        // Interfacing with the AAudio C API. Assumes correct linking
        // and `stream_ptr` are valid and properly initialized.
        if unsafe { AAudioStream_close(self.stream_ptr) } != AAUDIO_OK {
            warn!("AAudio stream close failed.");
        }
    }
}

#[derive(Default)]
struct AndroidAudioStreamSource;

impl StreamSource for AndroidAudioStreamSource {
    #[allow(clippy::type_complexity)]
    fn new_playback_stream(
        &mut self,
        _num_channels: usize,
        _format: SampleFormat,
        _frame_rate: u32,
        _buffer_size: usize,
    ) -> Result<(Box<dyn StreamControl>, Box<dyn PlaybackBufferStream>), BoxError> {
        // This traits function is never called.
        unimplemented!();
    }

    #[allow(clippy::type_complexity)]
    fn new_async_playback_stream(
        &mut self,
        num_channels: usize,
        format: SampleFormat,
        frame_rate: u32,
        buffer_size: usize,
        _ex: &dyn AudioStreamsExecutor,
    ) -> Result<(Box<dyn StreamControl>, Box<dyn AsyncPlaybackBufferStream>), BoxError> {
        let audio_stream = AudioStream::new(
            num_channels,
            format,
            frame_rate,
            buffer_size,
            AndroidAudioStreamDirection::Output,
        )?;
        Ok((Box::new(NoopStreamControl::new()), Box::new(audio_stream)))
    }

    #[allow(clippy::type_complexity)]
    fn new_capture_stream(
        &mut self,
        _num_channels: usize,
        _format: SampleFormat,
        _frame_rate: u32,
        _buffer_size: usize,
        _effects: &[StreamEffect],
    ) -> std::result::Result<(Box<dyn StreamControl>, Box<dyn CaptureBufferStream>), BoxError> {
        // This traits function is never called.
        unimplemented!();
    }

    #[allow(clippy::type_complexity)]
    fn new_async_capture_stream(
        &mut self,
        num_channels: usize,
        format: SampleFormat,
        frame_rate: u32,
        buffer_size: usize,
        _effects: &[StreamEffect],
        _ex: &dyn AudioStreamsExecutor,
    ) -> std::result::Result<(Box<dyn StreamControl>, Box<dyn AsyncCaptureBufferStream>), BoxError>
    {
        let audio_stream = AudioStream::new(
            num_channels,
            format,
            frame_rate,
            buffer_size,
            AndroidAudioStreamDirection::Input,
        )?;
        Ok((Box::new(NoopStreamControl::new()), Box::new(audio_stream)))
    }
}

#[derive(Default)]
pub struct AndroidAudioStreamSourceGenerator;

impl AndroidAudioStreamSourceGenerator {
    pub fn new() -> Self {
        AndroidAudioStreamSourceGenerator {}
    }
}

/// `AndroidAudioStreamSourceGenerator` is a struct that implements [`StreamSourceGenerator`]
/// for `AndroidAudioStreamSource`.
impl StreamSourceGenerator for AndroidAudioStreamSourceGenerator {
    fn generate(&self) -> Result<Box<dyn StreamSource>, BoxError> {
        Ok(Box::new(AndroidAudioStreamSource))
    }
}