cpal 0.14.0

Low-level cross-platform audio I/O library in pure Rust.
Documentation 
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use std::sync::Arc;

extern crate jni;

use self::jni::Executor;
use self::jni::{errors::Result as JResult, JNIEnv, JavaVM};

// constants from android.media.AudioFormat
pub const ENCODING_PCM_16BIT: i32 = 2;
pub const ENCODING_PCM_FLOAT: i32 = 4;
pub const CHANNEL_OUT_MONO: i32 = 4;
pub const CHANNEL_OUT_STEREO: i32 = 12;

fn with_attached<F, R>(closure: F) -> JResult<R>
where
    F: FnOnce(&JNIEnv) -> JResult<R>,
{
    let android_context = ndk_context::android_context();
    let vm = Arc::new(unsafe { JavaVM::from_raw(android_context.vm().cast())? });
    Executor::new(vm).with_attached(|env| closure(env))
}

fn get_min_buffer_size(
    class: &'static str,
    sample_rate: i32,
    channel_mask: i32,
    format: i32,
) -> i32 {
    // Unwrapping everything because these operations are not expected to fail
    // or throw exceptions. Android returns negative values for invalid parameters,
    // which is what we expect.
    with_attached(|env| {
        let class = env.find_class(class).unwrap();
        env.call_static_method(
            class,
            "getMinBufferSize",
            "(III)I",
            &[sample_rate.into(), channel_mask.into(), format.into()],
        )
        .unwrap()
        .i()
    })
    .unwrap()
}

pub fn get_audio_track_min_buffer_size(sample_rate: i32, channel_mask: i32, format: i32) -> i32 {
    get_min_buffer_size(
        "android/media/AudioTrack",
        sample_rate,
        channel_mask,
        format,
    )
}

pub fn get_audio_record_min_buffer_size(sample_rate: i32, channel_mask: i32, format: i32) -> i32 {
    get_min_buffer_size(
        "android/media/AudioRecord",
        sample_rate,
        channel_mask,
        format,
    )
}