Draft for switching to futures

Cargo.toml

@@ -10,10 +10,12 @@ license = "Apache-2.0"
 keywords = ["audio", "sound"]
 
 [dependencies]
+futures = { git = "https://github.com/alexcrichton/futures-rs" }
 libc = "0.2"
 lazy_static = "0.2"
 winapi = "0.2.8"
 ole32-sys = "0.2"
+kernel32-sys = "0.2"
 
 [target.arm-unknown-linux-gnueabihf.dependencies.alsa-sys]
 version = "0"

examples/beep.rs

@@ -1,16 +1,25 @@
 extern crate cpal;
+extern crate futures;
+
+use futures::Future;
+use futures::stream::Stream;
 
 fn main() {
     let endpoint = cpal::get_default_endpoint().expect("Failed to get default endpoint");
     let format = endpoint.get_supported_formats_list().unwrap().next().expect("Failed to get endpoint format");
-    let mut channel = cpal::Voice::new(&endpoint, &format).expect("Failed to create a channel");
+
+    let event_loop = cpal::EventLoop::new();
+
+    let (mut voice, stream) = cpal::Voice::new(&endpoint, &format, &event_loop).expect("Failed to create a voice");
 
     // Produce a sinusoid of maximum amplitude.
-    let mut data_source = (0u64..).map(|t| t as f32 * 440.0 * 2.0 * 3.141592 / format.samples_rate.0 as f32)     // 440 Hz
+    let samples_rate = format.samples_rate.0 as f32;
-                                  .map(|t| t.sin());
+    let mut data_source = (0u64..).map(move |t| t as f32 * 440.0 * 2.0 * 3.141592 / samples_rate)     // 440 Hz
+                                  .map(move |t| t.sin());
 
-    loop {
+    voice.play();
-        match channel.append_data(32768) {
+    stream.for_each(move |buffer| -> Result<_, ()> {
+        match buffer {
             cpal::UnknownTypeBuffer::U16(mut buffer) => {
                 for (sample, value) in buffer.chunks_mut(format.channels.len()).zip(&mut data_source) {
                     let value = ((value * 0.5 + 0.5) * std::u16::MAX as f32) as u16;
@@ -30,8 +39,10 @@ fn main() {
                     for out in sample.iter_mut() { *out = value; }
                 }
             },
-        }
+        };
 
-        channel.play();
+        Ok(())
-    }
+    }).forget();
+
+    event_loop.run();
 }

src/lib.rs

@@ -37,6 +37,8 @@ reaches the end of the data, it will stop playing. You must continuously fill th
 calling `append_data` repeatedly if you don't want the audio to stop playing.
 
 */
+
+extern crate futures;
 #[macro_use]
 extern crate lazy_static;
 extern crate libc;
@@ -50,6 +52,10 @@ use std::fmt;
 use std::error::Error;
 use std::ops::{Deref, DerefMut};
 
+use futures::stream::Stream;
+use futures::Poll;
+use futures::Task;
+
 mod null;
 mod samples_formats;
 
@@ -169,29 +175,43 @@ impl Iterator for SupportedFormatsIterator {
     }
 }
 
+pub struct EventLoop(cpal_impl::EventLoop);
+
+impl EventLoop {
+    #[inline]
+    pub fn new() -> EventLoop {
+        EventLoop(cpal_impl::EventLoop::new())
+    }
+
+    #[inline]
+    pub fn run(&self) {
+        self.0.run()
+    }
+}
+
 /// Represents a buffer that must be filled with audio data.
 ///
 /// You should destroy this object as soon as possible. Data is only committed when it
 /// is destroyed.
 #[must_use]
-pub struct Buffer<'a, T: 'a> where T: Sample {
+pub struct Buffer<T> where T: Sample {
     // also contains something, taken by `Drop`
-    target: Option<cpal_impl::Buffer<'a, T>>,
+    target: Option<cpal_impl::Buffer<T>>,
 }
 
 /// This is the struct that is provided to you by cpal when you want to write samples to a buffer.
 ///
 /// Since the type of data is only known at runtime, you have to fill the right buffer.
-pub enum UnknownTypeBuffer<'a> {
+pub enum UnknownTypeBuffer {
     /// Samples whose format is `u16`.
-    U16(Buffer<'a, u16>),
+    U16(Buffer<u16>),
     /// Samples whose format is `i16`.
-    I16(Buffer<'a, i16>),
+    I16(Buffer<i16>),
     /// Samples whose format is `f32`.
-    F32(Buffer<'a, f32>),
+    F32(Buffer<f32>),
 }
 
-impl<'a> UnknownTypeBuffer<'a> {
+impl UnknownTypeBuffer {
     /// Returns the length of the buffer in number of samples.
     #[inline]
     pub fn len(&self) -> usize {
@@ -282,13 +302,19 @@ pub struct Voice {
 impl Voice {
     /// Builds a new channel.
     #[inline]
-    pub fn new(endpoint: &Endpoint, format: &Format) -> Result<Voice, CreationError> {
+    pub fn new(endpoint: &Endpoint, format: &Format, event_loop: &EventLoop)
-        let channel = try!(cpal_impl::Voice::new(&endpoint.0, format));
+               -> Result<(Voice, SamplesStream), CreationError>
+    {
+        let (voice, stream) = try!(cpal_impl::Voice::new(&endpoint.0, format, &event_loop.0));
 
-        Ok(Voice {
+        let voice = Voice {
-            voice: channel,
+            voice: voice,
             format: format.clone(),
-        })
+        };
+
+        let stream = SamplesStream(stream);
+
+        Ok((voice, stream))
     }
 
     /// Returns the format used by the voice.
@@ -324,51 +350,6 @@ impl Voice {
         self.format().data_type
     }
 
-    /// Returns the minimum number of samples that should be put in a buffer before it is
-    /// processable by the audio output.
-    ///
-    /// If you put less than this value in the buffer, the buffer will not be processed and you
-    /// risk an underrun.
-    #[inline]
-    pub fn get_period(&self) -> usize {
-        self.voice.get_period()
-    }
-
-    /// Adds some PCM data to the voice's buffer.
-    ///
-    /// This function indirectly returns a `Buffer` object that must be filled with the audio data.
-    /// The size of the buffer being returned depends on the current state of the backend
-    /// and can't be known in advance. However it is never greater than `max_samples`.
-    ///
-    /// You must fill the buffer *entirely*, so do not set `max_samples` to a value greater
-    /// than the amount of data available to you.
-    ///
-    /// Channels are interleaved. For example if you have two channels, you must write
-    /// the first sample of the first channel, then the first sample of the second channel,
-    /// then the second sample of the first channel, then the second sample of the second
-    /// channel, etc.
-    ///
-    /// ## Panic
-    ///
-    /// Panics if `max_samples` is 0.
-    ///
-    #[inline]
-    pub fn append_data(&mut self, max_samples: usize) -> UnknownTypeBuffer {
-        assert!(max_samples != 0);
-
-        match self.get_samples_format() {
-            SampleFormat::U16 => UnknownTypeBuffer::U16(Buffer {
-                target: Some(self.voice.append_data(max_samples))
-            }),
-            SampleFormat::I16 => UnknownTypeBuffer::I16(Buffer {
-                target: Some(self.voice.append_data(max_samples))
-            }),
-            SampleFormat::F32 => UnknownTypeBuffer::F32(Buffer {
-                target: Some(self.voice.append_data(max_samples))
-            }),
-        }
-    }
-
     /// Sends a command to the audio device that it should start playing.
     ///
     /// Has no effect is the voice was already playing.
@@ -389,25 +370,26 @@ impl Voice {
     pub fn pause(&mut self) {
         self.voice.pause()
     }
+}
+
+pub struct SamplesStream(cpal_impl::SamplesStream);
+
+impl Stream for SamplesStream {
+    type Item = UnknownTypeBuffer;
+    type Error = ();
 
-    /// Returns the number of samples in the buffer that are currently being processed by the
-    /// audio playback backend.
-    ///
-    /// This function is useful to determine how much time it will take to finish playing the
-    /// current sound.
     #[inline]
-    pub fn get_pending_samples(&self) -> usize {
+    fn poll(&mut self, task: &mut Task) -> Poll<Option<Self::Item>, Self::Error> {
-        self.voice.get_pending_samples()
+        self.0.poll(task)
     }
 
-    /// Returns true if the voice has finished reading all the data you sent to it.
     #[inline]
-    pub fn underflowed(&self) -> bool {
+    fn schedule(&mut self, task: &mut Task) {
-        self.voice.underflowed()
+        self.0.schedule(task)
     }
 }
 
-impl<'a, T> Deref for Buffer<'a, T> where T: Sample {
+impl<T> Deref for Buffer<T> where T: Sample {
     type Target = [T];
 
     #[inline]
@@ -416,14 +398,14 @@ impl<'a, T> Deref for Buffer<'a, T> where T: Sample {
     }
 }
 
-impl<'a, T> DerefMut for Buffer<'a, T> where T: Sample {
+impl<T> DerefMut for Buffer<T> where T: Sample {
     #[inline]
     fn deref_mut(&mut self) -> &mut [T] {
         self.target.as_mut().unwrap().get_buffer()
     }
 }
 
-impl<'a, T> Drop for Buffer<'a, T> where T: Sample {
+impl<T> Drop for Buffer<T> where T: Sample {
     #[inline]
     fn drop(&mut self) {
         self.target.take().unwrap().finish();

src/wasapi/mod.rs

@@ -1,5 +1,6 @@
 extern crate winapi;
 extern crate ole32;
+extern crate kernel32;
 
 use std::io::Error as IoError;
 use std::os::windows::ffi::OsStringExt;
@@ -17,7 +18,7 @@ use SampleFormat;
 
 pub use std::option::IntoIter as OptionIntoIter;
 pub use self::enumerate::{EndpointsIterator, get_default_endpoint};
-pub use self::voice::{Voice, Buffer};
+pub use self::voice::{Voice, Buffer, EventLoop, SamplesStream};
 
 pub type SupportedFormatsIterator = OptionIntoIter<Format>;
 

src/wasapi/voice.rs

@@ -1,4 +1,5 @@
 use super::com;
+use super::kernel32;
 use super::ole32;
 use super::winapi;
 use super::Endpoint;
@@ -9,25 +10,141 @@ use std::slice;
 use std::mem;
 use std::ptr;
 use std::marker::PhantomData;
+use std::sync::atomic::AtomicBool;
+use std::sync::atomic::Ordering;
+use std::sync::Arc;
+use std::sync::Mutex;
+
+use futures::Poll;
+use futures::Task;
+use futures::TaskHandle;
+use futures::stream::Stream;
 
 use CreationError;
 use ChannelPosition;
 use Format;
 use SampleFormat;
+use UnknownTypeBuffer;
+
+pub struct EventLoop {
+    inner: Arc<EventLoopInner>,
+}
+
+unsafe impl Send for EventLoop {}
+unsafe impl Sync for EventLoop {}
+
+struct EventLoopInner {
+    // This event is signalled after elements have been added to `pending_scheduled`.
+    pending_scheduled_event: winapi::HANDLE,
+    scheduled: Mutex<EventLoopScheduled>,
+    pending_scheduled: Mutex<EventLoopScheduled>,
+}
+
+struct EventLoopScheduled {
+    // List of handles that correspond to voices.
+    // They are linked to `task_handles`, but we store them separately in order to easily call
+    // `WaitForMultipleObjectsEx` on the array without having to perform any conversion.
+    handles: Vec<winapi::HANDLE>,
+
+    // List of task handles corresponding to `handles`.
+    task_handles: Vec<(TaskHandle, Arc<AtomicBool>)>,
+}
+
+impl EventLoop {
+    pub fn new() -> EventLoop {
+        let pending_scheduled_event = unsafe {
+            kernel32::CreateEventA(ptr::null_mut(), 0, 0, ptr::null())
+        };
+
+        EventLoop {
+            inner: Arc::new(EventLoopInner {
+                pending_scheduled_event: pending_scheduled_event,
+                scheduled: Mutex::new(EventLoopScheduled {
+                    handles: vec![pending_scheduled_event],
+                    task_handles: vec![],
+                }),
+                pending_scheduled: Mutex::new(EventLoopScheduled {
+                    handles: vec![],
+                    task_handles: vec![],
+                })
+            })
+        }
+    }
+
+    pub fn run(&self) {
+        unsafe {
+            let mut scheduled = self.inner.scheduled.lock().unwrap();
+
+            loop {
+                // Creating a voice checks for the MAXIMUM_WAIT_OBJECTS limit.
+                debug_assert!(scheduled.handles.len() <= winapi::MAXIMUM_WAIT_OBJECTS as usize);
+
+                // Wait for any of the handles to be signalled, which means that the corresponding
+                // sound needs a buffer.
+                let result = kernel32::WaitForMultipleObjectsEx(scheduled.handles.len() as u32,
+                                                                scheduled.handles.as_ptr(),
+                                                                winapi::FALSE, winapi::INFINITE, /* TODO: allow setting a timeout */
+                                                                winapi::FALSE /* irrelevant parameter here */);
+
+                // Notifying the corresponding task handler.
+                assert!(result >= winapi::WAIT_OBJECT_0);
+                let handle_id = (result - winapi::WAIT_OBJECT_0) as usize;
+
+                if handle_id == 0 {
+                    let mut pending = self.inner.pending_scheduled.lock().unwrap();
+                    scheduled.handles.append(&mut pending.handles);
+                    scheduled.task_handles.append(&mut pending.task_handles);
+
+                } else {
+                    scheduled.handles.remove(handle_id);
+                    let (task_handle, ready) = scheduled.task_handles.remove(handle_id - 1);
+                    ready.store(true, Ordering::Relaxed);
+                    task_handle.notify();
+                }
+            }
+        }
+    }
+}
+
+impl Drop for EventLoop {
+    #[inline]
+    fn drop(&mut self) {
+        unsafe {
+            kernel32::CloseHandle(self.inner.pending_scheduled_event);
+        }
+    }
+}
 
 pub struct Voice {
-    audio_client: *mut winapi::IAudioClient,
+    inner: Arc<Mutex<VoiceInner>>,
-    render_client: *mut winapi::IAudioRenderClient,
+    playing: bool,
+}
+
+pub struct SamplesStream {
+    event_loop: Arc<EventLoopInner>,
+    inner: Arc<Mutex<VoiceInner>>,
+    // The event that is signalled whenever a buffer is ready to be submitted to the voice.
+    event: winapi::HANDLE,      // TODO: not deleted
     max_frames_in_buffer: winapi::UINT32,
     bytes_per_frame: winapi::WORD,
-    playing: bool,
+    ready: Arc<AtomicBool>,
+}
+
+unsafe impl Send for SamplesStream {}
+unsafe impl Sync for SamplesStream {}
+
+struct VoiceInner {
+    audio_client: *mut winapi::IAudioClient,
+    render_client: *mut winapi::IAudioRenderClient,
 }
 
 unsafe impl Send for Voice {}
 unsafe impl Sync for Voice {}
 
 impl Voice {
-    pub fn new(end_point: &Endpoint, format: &Format) -> Result<Voice, CreationError> {
+    pub fn new(end_point: &Endpoint, format: &Format, event_loop: &EventLoop)
+               -> Result<(Voice, SamplesStream), CreationError>
+    {
         unsafe {
             // making sure that COM is initialized
             // it's not actually sure that this is required, but when in doubt do it
@@ -76,8 +193,9 @@ impl Voice {
                 };
 
                 // finally initializing the audio client
-                let hresult = (*audio_client).Initialize(share_mode, 0, 10000000, 0,
+                let hresult = (*audio_client).Initialize(share_mode,
-                                                         &format_attempt.Format, ptr::null());
+                                                         winapi::AUDCLNT_STREAMFLAGS_EVENTCALLBACK,
+                                                         0, 0, &format_attempt.Format, ptr::null());
                 match check_result(hresult) {
                     Err(ref e) if e.raw_os_error() == Some(winapi::AUDCLNT_E_DEVICE_INVALIDATED) =>
                     {
@@ -94,6 +212,25 @@ impl Voice {
                 format_attempt.Format
             };
 
+            // Creating the event that will be signalled whenever we need to submit some samples.
+            let event = {
+                let event = kernel32::CreateEventA(ptr::null_mut(), 0, 0, ptr::null());
+                if event == ptr::null_mut() {
+                    (*audio_client).Release();
+                    panic!("Failed to create event");
+                }
+
+                match check_result((*audio_client).SetEventHandle(event)) {
+                    Err(e) => {
+                        (*audio_client).Release();
+                        panic!("Failed to call SetEventHandle")
+                    },
+                    Ok(_) => ()
+                };
+
+                event
+            };
+
             // obtaining the size of the samples buffer in number of frames
             let max_frames_in_buffer = {
                 let mut max_frames_in_buffer = mem::uninitialized();
@@ -115,7 +252,7 @@ impl Voice {
                 max_frames_in_buffer
             };
 
-            // building a `IAudioRenderClient` that will be used to fill the samples buffer
+            // Building a `IAudioRenderClient` that will be used to fill the samples buffer.
             let render_client = {
                 let mut render_client: *mut winapi::IAudioRenderClient = mem::uninitialized();
                 let hresult = (*audio_client).GetService(&winapi::IID_IAudioRenderClient,
@@ -139,79 +276,37 @@ impl Voice {
                 &mut *render_client
             };
 
-            // everything went fine
+            // Everything went fine.
-            Ok(Voice {
+            let inner = Arc::new(Mutex::new(VoiceInner {
                 audio_client: audio_client,
                 render_client: render_client,
+            }));
+
+            let voice = Voice {
+                inner: inner.clone(),
+                playing: false,
+            };
+
+            let samples_stream = SamplesStream {
+                event_loop: event_loop.inner.clone(),
+                inner: inner,
+                event: event,
                 max_frames_in_buffer: max_frames_in_buffer,
                 bytes_per_frame: format.nBlockAlign,
-                playing: false,
+                ready: Arc::new(AtomicBool::new(false)),
-            })
-        }
-    }
-
-    pub fn append_data<'a, T>(&'a mut self, max_elements: usize) -> Buffer<'a, T> {
-        unsafe {
-            // obtaining the number of frames that are available to be written
-            let frames_available = {
-                let mut padding = mem::uninitialized();
-                let hresult = (*self.audio_client).GetCurrentPadding(&mut padding);
-                check_result(hresult).unwrap();
-                self.max_frames_in_buffer - padding
             };
 
-            // making sure `frames_available` is inferior to `max_elements`
+            Ok((voice, samples_stream))
-            let frames_available = cmp::min(frames_available,
-                                            max_elements as u32 * mem::size_of::<T>() as u32 /
-                                            self.bytes_per_frame as u32);
-
-            // the WASAPI has some weird behaviors when the buffer size is zero, so we handle this
-            // ourselves
-            if frames_available == 0 {
-                return Buffer::Empty;
-            }
-
-            // obtaining a pointer to the buffer
-            let (buffer_data, buffer_len) = {
-                let mut buffer: *mut winapi::BYTE = mem::uninitialized();
-                let hresult = (*self.render_client).GetBuffer(frames_available,
-                                                              &mut buffer as *mut *mut _);
-                check_result(hresult).unwrap();     // FIXME: can return `AUDCLNT_E_DEVICE_INVALIDATED`
-                debug_assert!(!buffer.is_null());
-
-                (buffer as *mut T,
-                 frames_available as usize * self.bytes_per_frame as usize / mem::size_of::<T>())
-            };
-
-            Buffer::Buffer {
-                render_client: self.render_client,
-                buffer_data: buffer_data,
-                buffer_len: buffer_len,
-                frames: frames_available,
-                marker: PhantomData,
-            }
-        }
-    }
-
-    #[inline]
-    pub fn get_period(&self) -> usize {
-        0
-    }
-
-    pub fn get_pending_samples(&self) -> usize {
-        unsafe {
-            let mut padding = mem::uninitialized();
-            let hresult = (*self.audio_client).GetCurrentPadding(&mut padding);
-            check_result(hresult).unwrap();
-            padding as usize
         }
     }
 
     #[inline]
     pub fn play(&mut self) {
         if !self.playing {
+            let mut inner = self.inner.lock().unwrap();
+
             unsafe {
-                let hresult = (*self.audio_client).Start();
+                let hresult = (*inner.audio_client).Start();
                 check_result(hresult).unwrap();
             }
         }
@@ -222,27 +317,82 @@ impl Voice {
     #[inline]
     pub fn pause(&mut self) {
         if self.playing {
+            let mut inner = self.inner.lock().unwrap();
+
             unsafe {
-                let hresult = (*self.audio_client).Stop();
+                let hresult = (*inner.audio_client).Stop();
                 check_result(hresult).unwrap();
             }
         }
 
         self.playing = false;
     }
+}
 
-    pub fn underflowed(&self) -> bool {
+impl Stream for SamplesStream {
+    type Item = UnknownTypeBuffer;
+    type Error = ();
+
+    fn poll(&mut self, task: &mut Task) -> Poll<Option<Self::Item>, Self::Error> {
         unsafe {
-            let mut padding = mem::uninitialized();
+            if self.ready.swap(false, Ordering::Relaxed) == false {
-            let hresult = (*self.audio_client).GetCurrentPadding(&mut padding);
+                let result = kernel32::WaitForSingleObject(self.event, 0);
-            check_result(hresult).unwrap();
 
-            padding == 0
+                // Returning if timeout.
+                match result {
+                    winapi::WAIT_OBJECT_0 => (),
+                    winapi::WAIT_TIMEOUT => return Poll::NotReady,
+                    _ => unreachable!()
+                };
             }
+
+            let mut inner = self.inner.lock().unwrap();
+
+            // Obtaining the number of frames that are available to be written.
+            let frames_available = {
+                let mut padding = mem::uninitialized();
+                let hresult = (*inner.audio_client).GetCurrentPadding(&mut padding);
+                check_result(hresult).unwrap();
+                self.max_frames_in_buffer - padding
+            };
+
+            assert!(frames_available >= 0);
+
+            // Obtaining a pointer to the buffer.
+            let (buffer_data, buffer_len) = {
+                let mut buffer: *mut winapi::BYTE = mem::uninitialized();
+                let hresult = (*inner.render_client).GetBuffer(frames_available,
+                                                              &mut buffer as *mut *mut _);
+                check_result(hresult).unwrap();     // FIXME: can return `AUDCLNT_E_DEVICE_INVALIDATED`
+                debug_assert!(!buffer.is_null());
+
+                (buffer as *mut _,
+                 frames_available as usize * self.bytes_per_frame as usize / mem::size_of::<f32>())     // FIXME: correct size
+            };
+
+            let buffer = Buffer {
+                voice: self.inner.clone(),
+                buffer_data: buffer_data,
+                buffer_len: buffer_len,
+                frames: frames_available,
+            };
+
+            Poll::Ok(Some(UnknownTypeBuffer::F32(::Buffer { target: Some(buffer) })))        // FIXME: not necessarily F32
+        }
+    }
+
+    fn schedule(&mut self, task: &mut Task) {
+        let mut pending = self.event_loop.pending_scheduled.lock().unwrap();
+        pending.handles.push(self.event);
+        pending.task_handles.push((task.handle().clone(), self.ready.clone()));
+        drop(pending);
+
+        let result = unsafe { kernel32::SetEvent(self.event_loop.pending_scheduled_event) };
+        assert!(result != 0);
     }
 }
 
-impl Drop for Voice {
+impl Drop for VoiceInner {
     #[inline]
     fn drop(&mut self) {
         unsafe {
@@ -252,41 +402,34 @@ impl Drop for Voice {
     }
 }
 
-pub enum Buffer<'a, T: 'a> {
+pub struct Buffer<T> {
-    Empty,
+    voice: Arc<Mutex<VoiceInner>>,
-    Buffer {
+
-        render_client: *mut winapi::IAudioRenderClient,
     buffer_data: *mut T,
     buffer_len: usize,
     frames: winapi::UINT32,
-        marker: PhantomData<&'a mut T>,
-    },
 }
 
-impl<'a, T> Buffer<'a, T> {
+unsafe impl<T> Send for Buffer<T> {}
+
+impl<T> Buffer<T> {
     #[inline]
-    pub fn get_buffer<'b>(&'b mut self) -> &'b mut [T] {
+    pub fn get_buffer(&mut self) -> &mut [T] {
-        match self {
+        unsafe {
-            &mut Buffer::Empty => &mut [],
+            slice::from_raw_parts_mut(self.buffer_data, self.buffer_len)
-            &mut Buffer::Buffer { buffer_data, buffer_len, .. } => unsafe {
-                slice::from_raw_parts_mut(buffer_data, buffer_len)
-            },
         }
     }
 
     #[inline]
     pub fn len(&self) -> usize {
-        match self {
+        self.buffer_len
-            &Buffer::Empty => 0,
-            &Buffer::Buffer { buffer_len, .. } => buffer_len,
-        }
     }
 
     #[inline]
     pub fn finish(self) {
-        if let Buffer::Buffer { render_client, frames, .. } = self {
         unsafe {
-                let hresult = (*render_client).ReleaseBuffer(frames as u32, 0);
+            let mut inner = self.voice.lock().unwrap();
+            let hresult = (*inner.render_client).ReleaseBuffer(self.frames as u32, 0);
             match check_result(hresult) {
                 // ignoring the error that is produced if the device has been disconnected
                 Err(ref e)
@@ -295,7 +438,6 @@ impl<'a, T> Buffer<'a, T> {
             };
         }
     }
-    }
 }
 
 fn format_to_waveformatextensible(format: &Format)