Update the `emscripten` backend for the removal of the `EventLoop`
For the most part, behaviour should be largely unchanged, however each individual stream now has its own `set_timeout` callback loop, rather than using one for processing all streams at once. Many TODOs remain within the `emscripten` backend. These were left untouched for the most part in favour of addressing this in a more web-focused, future PR.
This commit is contained in:
mitchmindtree
parent
70dcf2390a
commit
37d80b98cf
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@ -1,7 +1,6 @@
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use std::mem;
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use std::os::raw::c_void;
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use std::slice::from_raw_parts;
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use std::sync::Mutex;
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use stdweb;
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use stdweb::Reference;
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use stdweb::unstable::TryInto;
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@ -17,25 +16,102 @@ use PauseStreamError;
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use PlayStreamError;
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use SupportedFormatsError;
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use StreamData;
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use StreamDataResult;
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use StreamError;
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use SupportedFormat;
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use UnknownTypeOutputBuffer;
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use traits::{DeviceTrait, EventLoopTrait, HostTrait, StreamIdTrait};
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use traits::{DeviceTrait, HostTrait, StreamTrait};
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// The emscripten backend currently works by instantiating an `AudioContext` object per `Stream`.
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// Creating a stream creates a new `AudioContext`. Destroying a stream destroys it. Creation of a
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// `Host` instance initializes the `stdweb` context.
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/// The default emscripten host type.
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#[derive(Debug)]
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pub struct Host;
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/// Content is false if the iterator is empty.
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pub struct Devices(bool);
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#[derive(Clone, Debug, PartialEq, Eq)]
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pub struct Device;
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pub struct Stream {
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// A reference to an `AudioContext` object.
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audio_ctxt_ref: Reference,
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}
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// Index within the `streams` array of the events loop.
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#[derive(Debug, Clone, PartialEq, Eq, Hash)]
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pub struct StreamId(usize);
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pub type SupportedInputFormats = ::std::vec::IntoIter<SupportedFormat>;
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pub type SupportedOutputFormats = ::std::vec::IntoIter<SupportedFormat>;
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impl Host {
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pub fn new() -> Result<Self, crate::HostUnavailable> {
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stdweb::initialize();
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Ok(Host)
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}
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}
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impl Devices {
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fn new() -> Result<Self, DevicesError> {
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Ok(Self::default())
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}
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}
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impl Device {
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#[inline]
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fn name(&self) -> Result<String, DeviceNameError> {
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Ok("Default Device".to_owned())
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}
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#[inline]
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fn supported_input_formats(&self) -> Result<SupportedInputFormats, SupportedFormatsError> {
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unimplemented!();
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}
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#[inline]
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fn supported_output_formats(&self) -> Result<SupportedOutputFormats, SupportedFormatsError> {
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// TODO: right now cpal's API doesn't allow flexibility here
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// "44100" and "2" (channels) have also been hard-coded in the rest of the code ; if
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// this ever becomes more flexible, don't forget to change that
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// According to https://developer.mozilla.org/en-US/docs/Web/API/BaseAudioContext/createBuffer
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// browsers must support 1 to 32 channels at leats and 8,000 Hz to 96,000 Hz.
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//
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// UPDATE: We can do this now. Might be best to use `crate::COMMON_SAMPLE_RATES` and
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// filter out those that lay outside the range specified above.
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Ok(
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vec![
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SupportedFormat {
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channels: 2,
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min_sample_rate: ::SampleRate(44100),
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max_sample_rate: ::SampleRate(44100),
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data_type: ::SampleFormat::F32,
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},
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].into_iter(),
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)
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}
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fn default_input_format(&self) -> Result<Format, DefaultFormatError> {
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unimplemented!();
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}
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fn default_output_format(&self) -> Result<Format, DefaultFormatError> {
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// TODO: because it is hard coded, see supported_output_formats.
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Ok(
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Format {
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channels: 2,
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sample_rate: ::SampleRate(44100),
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data_type: ::SampleFormat::F32,
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},
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)
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}
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}
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impl HostTrait for Host {
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type Devices = Devices;
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type Device = Device;
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type EventLoop = EventLoop;
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fn is_available() -> bool {
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// Assume this host is always available on emscripten.
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@ -53,15 +129,12 @@ impl HostTrait for Host {
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fn default_output_device(&self) -> Option<Self::Device> {
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default_output_device()
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}
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fn event_loop(&self) -> Self::EventLoop {
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EventLoop::new()
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}
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}
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impl DeviceTrait for Device {
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type SupportedInputFormats = SupportedInputFormats;
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type SupportedOutputFormats = SupportedOutputFormats;
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type Stream = Stream;
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fn name(&self) -> Result<String, DeviceNameError> {
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Device::name(self)
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@ -82,224 +155,124 @@ impl DeviceTrait for Device {
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fn default_output_format(&self) -> Result<Format, DefaultFormatError> {
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Device::default_output_format(self)
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}
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}
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impl EventLoopTrait for EventLoop {
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type Device = Device;
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type StreamId = StreamId;
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fn build_input_stream(
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fn build_input_stream<D, E>(
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&self,
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device: &Self::Device,
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format: &Format,
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) -> Result<Self::StreamId, BuildStreamError> {
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EventLoop::build_input_stream(self, device, format)
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}
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fn build_output_stream(
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&self,
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device: &Self::Device,
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format: &Format,
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) -> Result<Self::StreamId, BuildStreamError> {
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EventLoop::build_output_stream(self, device, format)
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}
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fn play_stream(&self, stream: Self::StreamId) -> Result<(), PlayStreamError> {
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EventLoop::play_stream(self, stream)
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}
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fn pause_stream(&self, stream: Self::StreamId) -> Result<(), PauseStreamError> {
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EventLoop::pause_stream(self, stream)
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}
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fn destroy_stream(&self, stream: Self::StreamId) {
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EventLoop::destroy_stream(self, stream)
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}
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fn run<F>(&self, callback: F) -> !
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_format: &Format,
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_data_callback: D,
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_error_callback: E,
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) -> Result<Self::Stream, BuildStreamError>
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where
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F: FnMut(Self::StreamId, StreamDataResult) + Send,
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D: FnMut(StreamData) + Send + 'static,
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E: FnMut(StreamError) + Send + 'static,
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{
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EventLoop::run(self, callback)
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unimplemented!()
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}
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fn build_output_stream<D, E>(
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&self,
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_format: &Format,
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data_callback: D,
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error_callback: E,
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) -> Result<Self::Stream, BuildStreamError>
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where
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D: FnMut(StreamData) + Send + 'static,
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E: FnMut(StreamError) + Send + 'static,
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{
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// Create the stream.
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let audio_ctxt_ref = js!(return new AudioContext()).into_reference().unwrap();
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let stream = Stream { audio_ctxt_ref };
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// Specify the callback.
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let mut user_data = (self, data_callback, error_callback);
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let user_data_ptr = &mut user_data as *mut (_, _, _);
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// Use `set_timeout` to invoke a Rust callback repeatedly.
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//
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// The job of this callback is to fill the content of the audio buffers.
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//
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// See also: The call to `set_timeout` at the end of the `audio_callback_fn` which creates
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// the loop.
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set_timeout(|| audio_callback_fn::<D, E>(user_data_ptr as *mut c_void), 10);
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Ok(stream)
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}
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}
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impl StreamIdTrait for StreamId {}
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// The emscripten backend works by having a global variable named `_cpal_audio_contexts`, which
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// is an array of `AudioContext` objects. A stream ID corresponds to an entry in this array.
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//
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// Creating a stream creates a new `AudioContext`. Destroying a stream destroys it.
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// TODO: handle latency better ; right now we just use setInterval with the amount of sound data
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// that is in each buffer ; this is obviously bad, and also the schedule is too tight and there may
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// be underflows
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pub struct EventLoop {
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streams: Mutex<Vec<Option<Reference>>>,
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}
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impl EventLoop {
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#[inline]
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pub fn new() -> EventLoop {
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stdweb::initialize();
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EventLoop {
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streams: Mutex::new(Vec::new()),
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}
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impl StreamTrait for Stream {
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fn play(&self) -> Result<(), PlayStreamError> {
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let audio_ctxt = &self.audio_ctxt_ref;
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js!(@{audio_ctxt}.resume());
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Ok(())
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}
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#[inline]
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fn run<F>(&self, callback: F) -> !
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where F: FnMut(StreamId, StreamDataResult),
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{
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// The `run` function uses `set_timeout` to invoke a Rust callback repeatidely. The job
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// of this callback is to fill the content of the audio buffers.
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fn pause(&self) -> Result<(), PauseStreamError> {
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let audio_ctxt = &self.audio_ctxt_ref;
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js!(@{audio_ctxt}.suspend());
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Ok(())
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}
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}
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// The first argument of the callback function (a `void*`) is a casted pointer to `self`
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// and to the `callback` parameter that was passed to `run`.
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// The first argument of the callback function (a `void*`) is a casted pointer to `self`
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// and to the `callback` parameter that was passed to `run`.
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fn audio_callback_fn<D, E>(user_data_ptr: *mut c_void)
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where
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D: FnMut(StreamData) + Send + 'static,
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E: FnMut(StreamError) + Send + 'static,
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{
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unsafe {
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let user_data_ptr2 = user_data_ptr as *mut (&Stream, D, E);
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let user_data = &mut *user_data_ptr2;
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let (ref stream, ref mut data_cb, ref mut _err_cb) = user_data;
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let audio_ctxt = &stream.audio_ctxt_ref;
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// TODO: We should be re-using a buffer.
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let mut temporary_buffer = vec![0.0; 44100 * 2 / 3];
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fn callback_fn<F>(user_data_ptr: *mut c_void)
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where F: FnMut(StreamId, StreamDataResult)
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{
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unsafe {
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let user_data_ptr2 = user_data_ptr as *mut (&EventLoop, F);
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let user_data = &mut *user_data_ptr2;
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let user_cb = &mut user_data.1;
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let streams = user_data.0.streams.lock().unwrap().clone();
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for (stream_id, stream) in streams.iter().enumerate() {
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let stream = match stream.as_ref() {
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Some(v) => v,
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None => continue,
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};
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let mut temporary_buffer = vec![0.0; 44100 * 2 / 3];
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{
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let buffer = UnknownTypeOutputBuffer::F32(::OutputBuffer { buffer: &mut temporary_buffer });
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let data = StreamData::Output { buffer: buffer };
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user_cb(StreamId(stream_id), Ok(data));
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// TODO: directly use a TypedArray<f32> once this is supported by stdweb
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}
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let typed_array = {
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let f32_slice = temporary_buffer.as_slice();
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let u8_slice: &[u8] = from_raw_parts(
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f32_slice.as_ptr() as *const _,
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f32_slice.len() * mem::size_of::<f32>(),
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);
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let typed_array: TypedArray<u8> = u8_slice.into();
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typed_array
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};
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let num_channels = 2u32; // TODO: correct value
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debug_assert_eq!(temporary_buffer.len() % num_channels as usize, 0);
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js!(
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var src_buffer = new Float32Array(@{typed_array}.buffer);
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var context = @{stream};
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var buf_len = @{temporary_buffer.len() as u32};
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var num_channels = @{num_channels};
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var buffer = context.createBuffer(num_channels, buf_len / num_channels, 44100);
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for (var channel = 0; channel < num_channels; ++channel) {
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var buffer_content = buffer.getChannelData(channel);
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for (var i = 0; i < buf_len / num_channels; ++i) {
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buffer_content[i] = src_buffer[i * num_channels + channel];
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}
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}
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var node = context.createBufferSource();
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node.buffer = buffer;
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node.connect(context.destination);
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node.start();
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);
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}
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set_timeout(|| callback_fn::<F>(user_data_ptr), 330);
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}
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let buffer = UnknownTypeOutputBuffer::F32(::OutputBuffer { buffer: &mut temporary_buffer });
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let data = StreamData::Output { buffer: buffer };
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data_cb(data);
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}
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let mut user_data = (self, callback);
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let user_data_ptr = &mut user_data as *mut (_, _);
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set_timeout(|| callback_fn::<F>(user_data_ptr as *mut _), 10);
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stdweb::event_loop();
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}
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#[inline]
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fn build_input_stream(&self, _: &Device, _format: &Format) -> Result<StreamId, BuildStreamError> {
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unimplemented!();
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}
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#[inline]
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fn build_output_stream(&self, _: &Device, _format: &Format) -> Result<StreamId, BuildStreamError> {
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let stream = js!(return new AudioContext()).into_reference().unwrap();
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let mut streams = self.streams.lock().unwrap();
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let stream_id = if let Some(pos) = streams.iter().position(|v| v.is_none()) {
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streams[pos] = Some(stream);
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pos
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} else {
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let l = streams.len();
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streams.push(Some(stream));
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l
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// TODO: directly use a TypedArray<f32> once this is supported by stdweb
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let typed_array = {
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let f32_slice = temporary_buffer.as_slice();
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let u8_slice: &[u8] = from_raw_parts(
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f32_slice.as_ptr() as *const _,
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f32_slice.len() * mem::size_of::<f32>(),
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);
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let typed_array: TypedArray<u8> = u8_slice.into();
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typed_array
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};
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Ok(StreamId(stream_id))
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}
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let num_channels = 2u32; // TODO: correct value
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debug_assert_eq!(temporary_buffer.len() % num_channels as usize, 0);
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#[inline]
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fn destroy_stream(&self, stream_id: StreamId) {
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self.streams.lock().unwrap()[stream_id.0] = None;
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}
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js!(
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var src_buffer = new Float32Array(@{typed_array}.buffer);
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var context = @{audio_ctxt};
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var buf_len = @{temporary_buffer.len() as u32};
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var num_channels = @{num_channels};
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#[inline]
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fn play_stream(&self, stream_id: StreamId) -> Result<(), PlayStreamError> {
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let streams = self.streams.lock().unwrap();
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let stream = streams
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.get(stream_id.0)
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.and_then(|v| v.as_ref())
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.expect("invalid stream ID");
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js!(@{stream}.resume());
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Ok(())
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}
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var buffer = context.createBuffer(num_channels, buf_len / num_channels, 44100);
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for (var channel = 0; channel < num_channels; ++channel) {
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var buffer_content = buffer.getChannelData(channel);
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for (var i = 0; i < buf_len / num_channels; ++i) {
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buffer_content[i] = src_buffer[i * num_channels + channel];
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}
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}
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#[inline]
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fn pause_stream(&self, stream_id: StreamId) -> Result<(), PauseStreamError> {
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let streams = self.streams.lock().unwrap();
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let stream = streams
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.get(stream_id.0)
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.and_then(|v| v.as_ref())
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.expect("invalid stream ID");
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js!(@{stream}.suspend());
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Ok(())
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}
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}
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var node = context.createBufferSource();
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node.buffer = buffer;
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node.connect(context.destination);
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node.start();
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);
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// Index within the `streams` array of the events loop.
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#[derive(Debug, Clone, PartialEq, Eq, Hash)]
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pub struct StreamId(usize);
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// Detects whether the `AudioContext` global variable is available.
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fn is_webaudio_available() -> bool {
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stdweb::initialize();
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|
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js!(if (!AudioContext) {
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return false;
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} else {
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return true;
|
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}).try_into()
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.unwrap()
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}
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|
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// Content is false if the iterator is empty.
|
||||
pub struct Devices(bool);
|
||||
|
||||
impl Devices {
|
||||
fn new() -> Result<Self, DevicesError> {
|
||||
Ok(Self::default())
|
||||
// TODO: handle latency better ; right now we just use setInterval with the amount of sound
|
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// data that is in each buffer ; this is obviously bad, and also the schedule is too tight
|
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// and there may be underflows
|
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set_timeout(|| audio_callback_fn::<D, E>(user_data_ptr), 330);
|
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}
|
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}
|
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|
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|
|
@ -336,54 +309,13 @@ fn default_output_device() -> Option<Device> {
|
|||
}
|
||||
}
|
||||
|
||||
#[derive(Clone, Debug, PartialEq, Eq)]
|
||||
pub struct Device;
|
||||
|
||||
impl Device {
|
||||
#[inline]
|
||||
fn name(&self) -> Result<String, DeviceNameError> {
|
||||
Ok("Default Device".to_owned())
|
||||
}
|
||||
|
||||
#[inline]
|
||||
fn supported_input_formats(&self) -> Result<SupportedInputFormats, SupportedFormatsError> {
|
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unimplemented!();
|
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}
|
||||
|
||||
#[inline]
|
||||
fn supported_output_formats(&self) -> Result<SupportedOutputFormats, SupportedFormatsError> {
|
||||
// TODO: right now cpal's API doesn't allow flexibility here
|
||||
// "44100" and "2" (channels) have also been hard-coded in the rest of the code ; if
|
||||
// this ever becomes more flexible, don't forget to change that
|
||||
// According to https://developer.mozilla.org/en-US/docs/Web/API/BaseAudioContext/createBuffer
|
||||
// browsers must support 1 to 32 channels at leats and 8,000 Hz to 96,000 Hz.
|
||||
Ok(
|
||||
vec![
|
||||
SupportedFormat {
|
||||
channels: 2,
|
||||
min_sample_rate: ::SampleRate(44100),
|
||||
max_sample_rate: ::SampleRate(44100),
|
||||
data_type: ::SampleFormat::F32,
|
||||
},
|
||||
].into_iter(),
|
||||
)
|
||||
}
|
||||
|
||||
fn default_input_format(&self) -> Result<Format, DefaultFormatError> {
|
||||
unimplemented!();
|
||||
}
|
||||
|
||||
fn default_output_format(&self) -> Result<Format, DefaultFormatError> {
|
||||
// TODO: because it is hard coded, see supported_output_formats.
|
||||
Ok(
|
||||
Format {
|
||||
channels: 2,
|
||||
sample_rate: ::SampleRate(44100),
|
||||
data_type: ::SampleFormat::F32,
|
||||
},
|
||||
)
|
||||
}
|
||||
// Detects whether the `AudioContext` global variable is available.
|
||||
fn is_webaudio_available() -> bool {
|
||||
stdweb::initialize();
|
||||
js!(if (!AudioContext) {
|
||||
return false;
|
||||
} else {
|
||||
return true;
|
||||
}).try_into()
|
||||
.unwrap()
|
||||
}
|
||||
|
||||
pub type SupportedInputFormats = ::std::vec::IntoIter<SupportedFormat>;
|
||||
pub type SupportedOutputFormats = ::std::vec::IntoIter<SupportedFormat>;
|
||||
|
|
|
|||
|
|
@ -435,9 +435,8 @@ mod platform_impl {
|
|||
pub use crate::host::emscripten::{
|
||||
Device as EmscriptenDevice,
|
||||
Devices as EmscriptenDevices,
|
||||
EventLoop as EmscriptenEventLoop,
|
||||
Host as EmscriptenHost,
|
||||
StreamId as EmscriptenStreamId,
|
||||
Stream as EmscriptenStream,
|
||||
SupportedInputFormats as EmscriptenSupportedInputFormats,
|
||||
SupportedOutputFormats as EmscriptenSupportedOutputFormats,
|
||||
};
|
||||
|
|
|
|||
Loading…
Reference in New Issue