Merge pull request #58 from tomaka/enumeration

Global cleanup

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 
 name = "cpal"
-version = "0.1.2"
+version = "0.2.0"
 authors = ["Pierre Krieger <pierre.krieger1708@gmail.com>"]
 description = "Cross-platform audio playing library in pure Rust."
 repository = "https://github.com/tomaka/cpal"
@@ -11,6 +11,7 @@ keywords = ["audio", "sound"]
 
 [dependencies]
 libc = "*"
+lazy_static = "0.1"
 
 [target.i686-pc-windows-gnu.dependencies]
 winapi = "0.2.1"

examples/beep.rs

@@ -1,7 +1,9 @@
 extern crate cpal;
 
 fn main() {
-    let mut channel = cpal::Voice::new();
+    let endpoint = cpal::get_default_endpoint().unwrap();
+    let format = endpoint.get_supported_formats_list().unwrap().next().unwrap();
+    let mut channel = cpal::Voice::new(&endpoint, &format).unwrap();
 
     // Produce a sinusoid of maximum amplitude.
     let mut data_source = (0u64..).map(|t| t as f32 * 0.03)

src/alsa/enumerate.rs

@@ -0,0 +1,78 @@
+use super::alsa;
+use super::check_errors;
+use super::Endpoint;
+
+use std::ffi::CStr;
+use std::mem;
+
+/// ALSA implementation for `EndpointsIterator`.
+pub struct EndpointsIterator {
+    // we keep the original list so that we can pass it to the free function
+    global_list: *const *const u8,
+
+    // pointer to the next string ; contained within `global_list`
+    next_str: *const *const u8,
+}
+
+unsafe impl Send for EndpointsIterator {}
+unsafe impl Sync for EndpointsIterator {}
+
+impl Drop for EndpointsIterator {
+    fn drop(&mut self) {
+        unsafe {
+            alsa::snd_device_name_free_hint(self.global_list as *mut _);
+        }
+    }
+}
+
+impl Default for EndpointsIterator {
+    fn default() -> EndpointsIterator {
+        unsafe {
+            let mut hints = mem::uninitialized();
+            // TODO: check in which situation this can fail
+            check_errors(alsa::snd_device_name_hint(-1, b"pcm\0".as_ptr() as *const _,
+                                                    &mut hints)).unwrap();
+
+            let hints = hints as *const *const u8;
+
+            EndpointsIterator {
+                global_list: hints,
+                next_str: hints,
+            }
+        }
+    }
+}
+
+impl Iterator for EndpointsIterator {
+    type Item = Endpoint;
+
+    fn next(&mut self) -> Option<Endpoint> {
+        loop {
+            unsafe {
+                if (*self.next_str).is_null() {
+                    return None;
+                }
+
+                let name = alsa::snd_device_name_get_hint(*self.next_str as *const _,
+                                                          b"NAME".as_ptr() as *const _);
+                self.next_str = self.next_str.offset(1);
+
+                if name.is_null() {
+                    continue;
+                }
+
+                let name = CStr::from_ptr(name).to_bytes().to_vec();
+                let name = String::from_utf8(name).unwrap();
+
+                if name != "null" {
+                    return Some(Endpoint(name));
+                }
+            }
+        }
+    }
+}
+
+pub fn get_default_endpoint() -> Option<Endpoint> {
+    // TODO: do in a different way?
+    Some(Endpoint("default".to_owned()))
+}

src/alsa/mod.rs

@@ -1,9 +1,39 @@
 extern crate alsa_sys as alsa;
 extern crate libc;
 
+pub use self::enumerate::{EndpointsIterator, get_default_endpoint};
+
+use CreationError;
+use Format;
+use FormatsEnumerationError;
+use SampleFormat;
+use SamplesRate;
+
 use std::{ffi, iter, mem};
+use std::option::IntoIter as OptionIntoIter;
 use std::sync::Mutex;
 
+pub type SupportedFormatsIterator = OptionIntoIter<Format>;
+
+mod enumerate;
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Endpoint(String);
+
+impl Endpoint {
+    pub fn get_supported_formats_list(&self)
+            -> Result<SupportedFormatsIterator, FormatsEnumerationError>
+    {
+        let format = Format {
+            channels: 2,
+            samples_rate: SamplesRate(44100),
+            data_type: SampleFormat::I16,
+        };
+
+        Ok(Some(format).into_iter())
+    }
+}
+
 pub struct Voice {
     channel: Mutex<*mut alsa::snd_pcm_t>,
     num_channels: u16,
@@ -15,9 +45,9 @@ pub struct Buffer<'a, T> {
 }
 
 impl Voice {
-    pub fn new() -> Voice {
+    pub fn new(endpoint: &Endpoint, _format: &Format) -> Result<Voice, CreationError> {
         unsafe {
-            let name = ffi::CString::new(b"default".to_vec()).unwrap();
+            let name = ffi::CString::new(endpoint.0.clone()).unwrap();
 
             let mut playback_handle = mem::uninitialized();
             check_errors(alsa::snd_pcm_open(&mut playback_handle, name.as_ptr(), alsa::SND_PCM_STREAM_PLAYBACK, alsa::SND_PCM_NONBLOCK)).unwrap();
@@ -34,10 +64,10 @@ impl Voice {
 
             check_errors(alsa::snd_pcm_prepare(playback_handle)).unwrap();
 
-            Voice {
+            Ok(Voice {
                 channel: Mutex::new(playback_handle),
                 num_channels: 2,
-            }
+            })
         }
     }
 

src/lib.rs

@@ -4,7 +4,16 @@
 In order to play a sound, first you need to create a `Voice`.
 
 ```no_run
-let mut voice = cpal::Voice::new();
+// getting the default sound output of the system (can return `None` if nothing is supported)
+let endpoint = cpal::get_default_endpoint().unwrap();
+
+// note that the user can at any moment disconnect the device, therefore all operations return
+// a `Result` to handle this situation
+
+// getting a format for the PCM
+let format = endpoint.get_supported_formats_list().unwrap().next().unwrap();
+
+let mut voice = cpal::Voice::new(&endpoint, &format).unwrap();
 ```
 
 Then you must send raw samples to it by calling `append_data`. You must take the number of channels
@@ -19,7 +28,7 @@ this is not some obscure situation that can be ignored.
 After you have submitted data for the first time, call `play`:
 
 ```no_run
-# let mut voice = cpal::Voice::new();
+# let mut voice: cpal::Voice = unsafe { std::mem::uninitialized() };
 voice.play();
 ```
 
@@ -28,8 +37,13 @@ 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.
 
 */
+#[macro_use]
+extern crate lazy_static;
+
 pub use samples_formats::{SampleFormat, Sample};
 
+use std::fmt;
+use std::error::Error;
 use std::ops::{Deref, DerefMut};
 
 mod samples_formats;
@@ -50,6 +64,46 @@ mod cpal_impl;
 #[path="null/mod.rs"]
 mod cpal_impl;
 
+/// An iterator for the list of formats that are supported by the backend.
+pub struct EndpointsIterator(cpal_impl::EndpointsIterator);
+
+impl Iterator for EndpointsIterator {
+    type Item = Endpoint;
+
+    #[inline]
+    fn next(&mut self) -> Option<Endpoint> {
+        self.0.next().map(Endpoint)
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.0.size_hint()
+    }
+}
+
+/// Return an iterator to the list of formats that are supported by the system.
+pub fn get_endpoints_list() -> EndpointsIterator {
+    EndpointsIterator(Default::default())
+}
+
+/// Return the default endpoint, or `None` if no device is available.
+pub fn get_default_endpoint() -> Option<Endpoint> {
+    cpal_impl::get_default_endpoint().map(Endpoint)
+}
+
+/// An opaque type that identifies an end point.
+#[derive(Clone, PartialEq, Eq)]
+pub struct Endpoint(cpal_impl::Endpoint);
+
+impl Endpoint {
+    /// Returns an iterator that produces the list of formats that are supported by the backend.
+    pub fn get_supported_formats_list(&self) -> Result<SupportedFormatsIterator,
+                                                       FormatsEnumerationError>
+    {
+        Ok(SupportedFormatsIterator(try!(self.0.get_supported_formats_list())))
+    }
+}
+
 /// Number of channels.
 pub type ChannelsCount = u16;
 
@@ -57,6 +111,31 @@ pub type ChannelsCount = u16;
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
 pub struct SamplesRate(pub u32);
 
+/// Describes a format.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub struct Format {
+    pub channels: ChannelsCount,
+    pub samples_rate: SamplesRate,
+    pub data_type: SampleFormat,
+}
+
+/// An iterator that produces a list of formats supported by the endpoint.
+pub struct SupportedFormatsIterator(cpal_impl::SupportedFormatsIterator);
+
+impl Iterator for SupportedFormatsIterator {
+    type Item = Format;
+
+    #[inline]
+    fn next(&mut self) -> Option<Format> {
+        self.0.next()
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.0.size_hint()
+    }
+}
+
 /// 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
@@ -79,6 +158,61 @@ pub enum UnknownTypeBuffer<'a> {
     F32(Buffer<'a, f32>),
 }
 
+/// Error that can happen when enumerating the list of supported formats.
+#[derive(Debug)]
+pub enum FormatsEnumerationError {
+    /// The device no longer exists. This can happen if the device is disconnected while the
+    /// program is running.
+    DeviceNotAvailable,
+}
+
+impl fmt::Display for FormatsEnumerationError {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+        write!(fmt, "{}", self.description())
+    }
+}
+
+impl Error for FormatsEnumerationError {
+    fn description(&self) -> &str {
+        match self {
+            &FormatsEnumerationError::DeviceNotAvailable => {
+                "The requested device is no longer available (for example, it has been unplugged)."
+            },
+        }
+    }
+}
+
+/// Error that can happen when creating a `Voice`.
+#[derive(Debug)]
+pub enum CreationError {
+    /// The device no longer exists. This can happen if the device is disconnected while the
+    /// program is running.
+    DeviceNotAvailable,
+
+    /// The required format is not supported.
+    FormatNotSupported,
+}
+
+impl fmt::Display for CreationError {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+        write!(fmt, "{}", self.description())
+    }
+}
+
+impl Error for CreationError {
+    fn description(&self) -> &str {
+        match self {
+            &CreationError::DeviceNotAvailable => {
+                "The requested device is no longer available (for example, it has been unplugged)."
+            },
+
+            &CreationError::FormatNotSupported => {
+                "The requested samples format is not supported by the device."
+            },
+        }
+    }
+}
+
 /// Controls a sound output. A typical application has one `Voice` for each sound
 /// it wants to output.
 ///
@@ -95,15 +229,17 @@ pub struct Voice(cpal_impl::Voice);
 
 impl Voice {
     /// Builds a new channel.
-    pub fn new() -> Voice {
-        let channel = cpal_impl::Voice::new();
-        Voice(channel)
+    #[inline]
+    pub fn new(endpoint: &Endpoint, format: &Format) -> Result<Voice, CreationError> {
+        let channel = try!(cpal_impl::Voice::new(&endpoint.0, format));
+        Ok(Voice(channel))
     }
 
     /// Returns the number of channels.
     ///
     /// You can add data with any number of channels, but matching the voice's native format
     /// will lead to better performances.
+    #[inline]
     pub fn get_channels(&self) -> ChannelsCount {
         self.0.get_channels()
     }
@@ -112,6 +248,7 @@ impl Voice {
     ///
     /// You can add data with any samples rate, but matching the voice's native format
     /// will lead to better performances.
+    #[inline]
     pub fn get_samples_rate(&self) -> SamplesRate {
         self.0.get_samples_rate()
     }
@@ -120,6 +257,7 @@ impl Voice {
     ///
     /// You can add data of any format, but matching the voice's native format
     /// will lead to better performances.
+    #[inline]
     pub fn get_samples_format(&self) -> SampleFormat {
         self.0.get_samples_format()
     }
@@ -164,6 +302,7 @@ impl Voice {
     ///
     /// Only call this after you have submitted some data, otherwise you may hear
     /// some glitches.
+    #[inline]
     pub fn play(&mut self) {
         self.0.play()
     }
@@ -173,6 +312,7 @@ impl Voice {
     /// Has no effect is the voice was already paused.
     ///
     /// If you call `play` afterwards, the playback will resume exactly where it was.
+    #[inline]
     pub fn pause(&mut self) {
         self.0.pause()
     }
@@ -181,18 +321,21 @@ impl Voice {
 impl<'a, T> Deref for Buffer<'a, T> where T: Sample {
     type Target = [T];
 
+    #[inline]
     fn deref(&self) -> &[T] {
         panic!("It is forbidden to read from the audio buffer");
     }
 }
 
 impl<'a, T> DerefMut for Buffer<'a, 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 {
+    #[inline]
     fn drop(&mut self) {
         self.target.take().unwrap().finish();
     }

src/samples_formats.rs

@@ -13,6 +13,7 @@ pub enum SampleFormat {
 
 impl SampleFormat {
     /// Returns the size in bytes of a sample of this format.
+    #[inline]
     pub fn get_sample_size(&self) -> usize {
         match self {
             &SampleFormat::I16 => mem::size_of::<i16>(),
@@ -29,18 +30,21 @@ pub unsafe trait Sample: Copy + Clone {
 }
 
 unsafe impl Sample for u16 {
+    #[inline]
     fn get_format() -> SampleFormat {
         SampleFormat::U16
     }
 }
 
 unsafe impl Sample for i16 {
+    #[inline]
     fn get_format() -> SampleFormat {
         SampleFormat::I16
     }
 }
 
 unsafe impl Sample for f32 {
+    #[inline]
     fn get_format() -> SampleFormat {
         SampleFormat::F32
     }

src/wasapi/com.rs

@@ -0,0 +1,32 @@
+//! Handles COM initialization and cleanup.
+
+use std::ptr;
+use super::winapi;
+use super::ole32;
+use super::check_result;
+
+thread_local!(static COM_INITIALIZED: ComInitialized = {
+    unsafe {
+        // this call can fail if another library initialized COM in single-threaded mode
+        // handling this situation properly would make the API more annoying, so we just don't care
+        check_result(ole32::CoInitializeEx(ptr::null_mut(), winapi::COINIT_MULTITHREADED)).unwrap();
+        ComInitialized(ptr::null_mut())
+    }
+});
+
+/// RAII object that guards the fact that COM is initialized.
+///
+// We store a raw pointer because it's the only way at the moment to remove `Send`/`Sync` from the
+// object.
+struct ComInitialized(*mut ());
+
+impl Drop for ComInitialized {
+    fn drop(&mut self) {
+        unsafe { ole32::CoUninitialize() };
+    }
+}
+
+/// Ensures that COM is initialized in this thread.
+pub fn com_initialized() {
+    COM_INITIALIZED.with(|_| {});
+}

src/wasapi/enumerate.rs

@@ -0,0 +1,126 @@
+use super::winapi;
+use super::ole32;
+use super::com;
+use super::Endpoint;
+use super::check_result;
+
+use std::mem;
+use std::ptr;
+
+lazy_static! {
+    static ref ENUMERATOR: Enumerator = {
+        // COM initialization is thread local, but we only need to have COM initialized in the
+        // thread we create the objects in
+        com::com_initialized();
+
+        // building the devices enumerator object
+        unsafe {
+            let mut enumerator: *mut winapi::IMMDeviceEnumerator = mem::uninitialized();
+            
+            let hresult = ole32::CoCreateInstance(&winapi::CLSID_MMDeviceEnumerator,
+                                                  ptr::null_mut(), winapi::CLSCTX_ALL,
+                                                  &winapi::IID_IMMDeviceEnumerator,
+                                                  &mut enumerator
+                                                           as *mut *mut winapi::IMMDeviceEnumerator
+                                                           as *mut _);
+
+            check_result(hresult).unwrap();
+            Enumerator(enumerator)
+        }
+    };
+}
+
+/// RAII object around `winapi::IMMDeviceEnumerator`.
+struct Enumerator(*mut winapi::IMMDeviceEnumerator);
+
+unsafe impl Send for Enumerator {}
+unsafe impl Sync for Enumerator {}
+
+impl Drop for Enumerator {
+    fn drop(&mut self) {
+        unsafe {
+            (*self.0).Release();
+        }
+    }
+}
+
+/// WASAPI implementation for `EndpointsIterator`.
+pub struct EndpointsIterator {
+    collection: *mut winapi::IMMDeviceCollection,
+    total_count: u32,
+    next_item: u32,
+}
+
+unsafe impl Send for EndpointsIterator {}
+unsafe impl Sync for EndpointsIterator {}
+
+impl Drop for EndpointsIterator {
+    fn drop(&mut self) {
+        unsafe {
+            (*self.collection).Release();
+        }
+    }
+}
+
+impl Default for EndpointsIterator {
+    fn default() -> EndpointsIterator {
+        unsafe {
+            let mut collection: *mut winapi::IMMDeviceCollection = mem::uninitialized();
+            // can fail because of wrong parameters (should never happen) or out of memory
+            check_result((*ENUMERATOR.0).EnumAudioEndpoints(winapi::EDataFlow::eRender,
+                                                            winapi::DEVICE_STATE_ACTIVE,
+                                                            &mut collection))
+                                                            .unwrap();
+
+            let mut count = mem::uninitialized();
+            // can fail if the parameter is null, which should never happen
+            check_result((*collection).GetCount(&mut count)).unwrap();
+
+            EndpointsIterator {
+                collection: collection,
+                total_count: count,
+                next_item: 0,
+            }
+        }
+    }
+}
+
+impl Iterator for EndpointsIterator {
+    type Item = Endpoint;
+
+    fn next(&mut self) -> Option<Endpoint> {
+        if self.next_item >= self.total_count {
+            return None;
+        }
+
+        unsafe {
+            let mut device = mem::uninitialized();
+            // can fail if out of range, which we just checked above
+            check_result((*self.collection).Item(self.next_item, &mut device)).unwrap();
+
+            self.next_item += 1;
+            Some(Endpoint::from_immdevice(device))
+        }
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let num = self.total_count - self.next_item;
+        let num = num as usize;
+        (num, Some(num))
+    }
+}
+
+pub fn get_default_endpoint() -> Option<Endpoint> {
+    unsafe {
+        let mut device = mem::uninitialized();
+        let hres = (*ENUMERATOR.0).GetDefaultAudioEndpoint(winapi::EDataFlow::eRender,
+                                                           winapi::ERole::eConsole, &mut device);
+
+        if let Err(_err) = check_result(hres) {
+            return None;        // TODO: check specifically for `E_NOTFOUND`, and panic otherwise
+        }
+
+        Some(Endpoint::from_immdevice(device))
+    }
+}

src/wasapi/mod.rs

@@ -2,255 +2,175 @@ extern crate libc;
 extern crate winapi;
 extern crate ole32;
 
-use std::{cmp, slice, mem, ptr};
-use std::marker::PhantomData;
+use std::io::Error as IoError;
+use std::sync::{Arc, Mutex, MutexGuard};
+use std::ptr;
+use std::mem;
 
-// TODO: determine if should be NoSend or not
-pub struct Voice {
-    audio_client: *mut winapi::IAudioClient,
-    render_client: *mut winapi::IAudioRenderClient,
-    max_frames_in_buffer: winapi::UINT32,
-    num_channels: winapi::WORD,
-    bytes_per_frame: winapi::WORD,
-    samples_per_second: winapi::DWORD,
-    bits_per_sample: winapi::WORD,
-    playing: bool,
-}
+use Format;
+use FormatsEnumerationError;
+use SamplesRate;
+use SampleFormat;
 
-pub struct Buffer<'a, T: 'a> {
-    render_client: *mut winapi::IAudioRenderClient,
-    buffer_data: *mut T,
-    buffer_len: usize,
-    frames: winapi::UINT32,
-    marker: PhantomData<&'a mut T>,
-}
+pub use std::option::IntoIter as OptionIntoIter;
+pub use self::enumerate::{EndpointsIterator, get_default_endpoint};
+pub use self::voice::{Voice, Buffer};
 
-impl Voice {
-    pub fn new() -> Voice {
-        init().unwrap()
-    }
+pub type SupportedFormatsIterator = OptionIntoIter<Format>;
 
-    pub fn get_channels(&self) -> ::ChannelsCount {
-        self.num_channels as ::ChannelsCount
-    }
+mod com;
+mod enumerate;
+mod voice;
 
-    pub fn get_samples_rate(&self) -> ::SamplesRate {
-        ::SamplesRate(self.samples_per_second as u32)
-    }
-
-    pub fn get_samples_format(&self) -> ::SampleFormat {
-        match self.bits_per_sample {
-            16 => ::SampleFormat::I16,
-            _ => panic!("{}-bit format not yet supported", self.bits_per_sample),
-        }
-    }
-
-    pub fn append_data<'a, T>(&'a mut self, max_elements: usize) -> Buffer<'a, T> {
-        unsafe {
-            loop {
-                // 
-                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
-                };
-
-                if frames_available == 0 {
-                    // TODO: 
-                    ::std::thread::sleep_ms(1);
-                    continue;
-                }
-
-                let frames_available = cmp::min(frames_available,
-                                                max_elements as u32 * mem::size_of::<T>() as u32 /
-                                                self.bytes_per_frame as u32);
-                assert!(frames_available != 0);
-
-                // loading 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 libc::c_uchar);
-                    check_result(hresult).unwrap();
-                    assert!(!buffer.is_null());
-
-                    (buffer as *mut T,
-                     frames_available as usize * self.bytes_per_frame as usize
-                          / mem::size_of::<T>())
-                };
-
-                let buffer = Buffer {
-                    render_client: self.render_client,
-                    buffer_data: buffer_data,
-                    buffer_len: buffer_len,
-                    frames: frames_available,
-                    marker: PhantomData,
-                };
-
-                return buffer;
-            }
-        }
-    }
-
-    pub fn play(&mut self) {
-        if !self.playing {
-            unsafe {
-                let hresult = (*self.audio_client).Start();
-                check_result(hresult).unwrap();
-            }
-        }
-
-        self.playing = true;
-    }
-
-    pub fn pause(&mut self) {
-        if self.playing {
-            unsafe {
-                let hresult = (*self.audio_client).Stop();
-                check_result(hresult).unwrap();
-            }
-        }
-
-        self.playing = false;
-    }
-}
-
-unsafe impl Send for Voice {}
-unsafe impl Sync for Voice {}
-
-impl Drop for Voice {
-    fn drop(&mut self) {
-        unsafe {
-            (*self.render_client).Release();
-            (*self.audio_client).Release();
-        }
-    }
-}
-
-impl<'a, T> Buffer<'a, T> {
-    pub fn get_buffer<'b>(&'b mut self) -> &'b mut [T] {
-        unsafe {
-            slice::from_raw_parts_mut(self.buffer_data, self.buffer_len)
-        }
-    }
-
-    pub fn finish(self) {
-        // releasing buffer
-        unsafe {
-            let hresult = (*self.render_client).ReleaseBuffer(self.frames as u32, 0);
-            check_result(hresult).unwrap();
-        };
-    }
-}
-
-fn init() -> Result<Voice, String> {
-    // FIXME: release everything
-    unsafe {
-        try!(check_result(ole32::CoInitializeEx(ptr::null_mut(), 0)));
-
-        // building the devices enumerator object
-        let enumerator = {
-            let mut enumerator: *mut winapi::IMMDeviceEnumerator = mem::uninitialized();
-            
-            let hresult = ole32::CoCreateInstance(&winapi::CLSID_MMDeviceEnumerator,
-                                                   ptr::null_mut(), winapi::CLSCTX_ALL,
-                                                   &winapi::IID_IMMDeviceEnumerator,
-                                                   mem::transmute(&mut enumerator));
-
-            try!(check_result(hresult));
-            &mut *enumerator
-        };
-
-        // getting the default end-point
-        let device = {
-            let mut device: *mut winapi::IMMDevice = mem::uninitialized();
-            let hresult = enumerator.GetDefaultAudioEndpoint(winapi::EDataFlow::eRender, winapi::ERole::eConsole,
-                            mem::transmute(&mut device));
-            try!(check_result(hresult));
-            &mut *device
-        };
-
-        // activating in order to get a `IAudioClient`
-        let audio_client: &mut winapi::IAudioClient = {
-            let mut audio_client: *mut winapi::IAudioClient = mem::uninitialized();
-            let hresult = device.Activate(&winapi::IID_IAudioClient, winapi::CLSCTX_ALL,
-                            ptr::null_mut(), mem::transmute(&mut audio_client));
-            try!(check_result(hresult));
-            &mut *audio_client
-        };
-
-        // computing the format and initializing the device
-        let format = {
-            let format_attempt = winapi::WAVEFORMATEX {
-                wFormatTag: 1,      // WAVE_FORMAT_PCM ; TODO: replace by constant
-                nChannels: 2,
-                nSamplesPerSec: 44100,
-                nAvgBytesPerSec: 2 * 44100 * 2,
-                nBlockAlign: (2 * 16) / 8,
-                wBitsPerSample: 16,
-                cbSize: 0,
-            };
-
-            let mut format_ptr: *mut winapi::WAVEFORMATEX = mem::uninitialized();
-            let hresult = audio_client.IsFormatSupported(winapi::AUDCLNT_SHAREMODE::AUDCLNT_SHAREMODE_SHARED,
-                            &format_attempt, &mut format_ptr);
-            try!(check_result(hresult));
-
-            let format = if format_ptr.is_null() {
-                &format_attempt
-            } else {
-                &*format_ptr
-            };
-
-            let format_copy = ptr::read(format);
-
-            let hresult = audio_client.Initialize(winapi::AUDCLNT_SHAREMODE::AUDCLNT_SHAREMODE_SHARED,
-                            0, 10000000, 0, format, ptr::null());
-
-            if !format_ptr.is_null() {
-                ole32::CoTaskMemFree(format_ptr as *mut _);
-            }
-
-            try!(check_result(hresult));
-
-            format_copy
-        };
-
-        // 
-        let max_frames_in_buffer = {
-            let mut max_frames_in_buffer = mem::uninitialized();
-            let hresult = audio_client.GetBufferSize(&mut max_frames_in_buffer);
-            try!(check_result(hresult));
-            max_frames_in_buffer
-        };
-
-        // 
-        let render_client = {
-            let mut render_client: *mut winapi::IAudioRenderClient = mem::uninitialized();
-            let hresult = audio_client.GetService(&winapi::IID_IAudioRenderClient,
-                            mem::transmute(&mut render_client));
-            try!(check_result(hresult));
-            &mut *render_client
-        };
-
-        Ok(Voice {
-            audio_client: audio_client,
-            render_client: render_client,
-            max_frames_in_buffer: max_frames_in_buffer,
-            num_channels: format.nChannels,
-            bytes_per_frame: format.nBlockAlign,
-            samples_per_second: format.nSamplesPerSec,
-            bits_per_sample: format.wBitsPerSample,
-            playing: false,
-        })
-    }
-}
-
-fn check_result(result: winapi::HRESULT) -> Result<(), String> {
+fn check_result(result: winapi::HRESULT) -> Result<(), IoError> {
     if result < 0 {
-        return Err(format!("Error in winapi call"));        // TODO: 
-    }
-
+        Err(IoError::from_raw_os_error(result))
+    } else {
         Ok(())
     }
+}
+
+/// Wrapper because of that stupid decision to remove `Send` and `Sync` from raw pointers.
+#[derive(Copy, Clone)]
+#[allow(raw_pointer_derive)]
+struct IAudioClientWrapper(*mut winapi::IAudioClient);
+unsafe impl Send for IAudioClientWrapper {}
+unsafe impl Sync for IAudioClientWrapper {}
+
+/// An opaque type that identifies an end point.
+pub struct Endpoint {
+    device: *mut winapi::IMMDevice,
+
+    /// We cache an uninitialized `IAudioClient` so that we can call functions from it without
+    /// having to create/destroy audio clients all the time.
+    future_audio_client: Arc<Mutex<Option<IAudioClientWrapper>>>,      // TODO: add NonZero around the ptr
+}
+
+unsafe impl Send for Endpoint {}
+unsafe impl Sync for Endpoint {}
+
+impl Endpoint {
+    #[inline]
+    fn from_immdevice(device: *mut winapi::IMMDevice) -> Endpoint {
+        Endpoint {
+            device: device,
+            future_audio_client: Arc::new(Mutex::new(None)),
+        }
+    }
+
+    /// Ensures that `future_audio_client` contains a `Some` and returns a locked mutex to it.
+    fn ensure_future_audio_client(&self) -> Result<MutexGuard<Option<IAudioClientWrapper>>, IoError> {
+        let mut lock = self.future_audio_client.lock().unwrap();
+        if lock.is_some() {
+            return Ok(lock);
+        }
+
+        let audio_client: *mut winapi::IAudioClient = unsafe {
+            let mut audio_client = mem::uninitialized();
+            let hresult = (*self.device).Activate(&winapi::IID_IAudioClient, winapi::CLSCTX_ALL,
+                                                  ptr::null_mut(), &mut audio_client);
+
+            // can fail if the device has been disconnected since we enumerated it, or if
+            // the device doesn't support playback for some reason
+            try!(check_result(hresult));
+            assert!(!audio_client.is_null());
+            audio_client as *mut _
+        };
+
+        *lock = Some(IAudioClientWrapper(audio_client));
+        Ok(lock)
+    }
+
+    /// Returns an uninitialized `IAudioClient`.
+    fn build_audioclient(&self) -> Result<*mut winapi::IAudioClient, IoError> {
+        let mut lock = try!(self.ensure_future_audio_client());
+        let client = lock.unwrap().0;
+        *lock = None;
+        Ok(client)
+    }
+
+    pub fn get_supported_formats_list(&self)
+           -> Result<SupportedFormatsIterator, FormatsEnumerationError>
+    {
+        // We always create voices in shared mode, therefore all samples go through an audio
+        // processor to mix them together.
+        // However there is no way to query the list of all formats that are supported by the
+        // audio processor, but one format is guaranteed to be supported, the one returned by
+        // `GetMixFormat`.
+
+        // initializing COM because we call `CoTaskMemFree`
+        com::com_initialized();
+
+        let lock = match self.ensure_future_audio_client() {
+            Err(ref e) if e.raw_os_error() == Some(winapi::AUDCLNT_E_DEVICE_INVALIDATED) =>
+                return Err(FormatsEnumerationError::DeviceNotAvailable),
+            e => e.unwrap(),
+        };
+        let client = lock.unwrap().0;
+
+        unsafe {
+            let mut format_ptr = mem::uninitialized();
+            match check_result((*client).GetMixFormat(&mut format_ptr)) {
+                Err(ref e) if e.raw_os_error() == Some(winapi::AUDCLNT_E_DEVICE_INVALIDATED) => {
+                    return Err(FormatsEnumerationError::DeviceNotAvailable);
+                },
+                Err(e) => panic!("{:?}", e),
+                Ok(()) => (),
+            };
+
+            let format = {
+                let data_type = match (*format_ptr).wFormatTag {
+                    winapi::WAVE_FORMAT_PCM => SampleFormat::I16,
+                    winapi::WAVE_FORMAT_EXTENSIBLE => {
+                        let format_ptr = format_ptr as *const winapi::WAVEFORMATEXTENSIBLE;
+                        match (*format_ptr).SubFormat {
+                            winapi::KSDATAFORMAT_SUBTYPE_IEEE_FLOAT => SampleFormat::F32,
+                            winapi::KSDATAFORMAT_SUBTYPE_PCM => SampleFormat::I16,
+                            g => panic!("Unknown SubFormat GUID returned by GetMixFormat: {:?}", g)
+                        }
+                    },
+                    f => panic!("Unknown data format returned by GetMixFormat: {:?}", f)
+                };
+
+                Format {
+                    channels: (*format_ptr).nChannels,
+                    samples_rate: SamplesRate((*format_ptr).nSamplesPerSec),
+                    data_type: data_type,
+                }
+            };
+
+            ole32::CoTaskMemFree(format_ptr as *mut _);
+
+            Ok(Some(format).into_iter())
+        }
+    }
+}
+
+impl PartialEq for Endpoint {
+    fn eq(&self, other: &Endpoint) -> bool {
+        self.device == other.device
+    }
+}
+
+impl Eq for Endpoint {}
+
+impl Clone for Endpoint {
+    fn clone(&self) -> Endpoint {
+        unsafe { (*self.device).AddRef(); }
+
+        Endpoint {
+            device: self.device,
+            future_audio_client: self.future_audio_client.clone(),
+        }
+    }
+}
+
+impl Drop for Endpoint {
+    fn drop(&mut self) {
+        unsafe { (*self.device).Release(); }
+
+        if let Some(client) = self.future_audio_client.lock().unwrap().take() {
+            unsafe { (*client.0).Release(); }
+        }
+    }
+}

src/wasapi/voice.rs

@@ -0,0 +1,298 @@
+use super::com;
+use super::ole32;
+use super::winapi;
+use super::Endpoint;
+use super::check_result;
+
+use std::cmp;
+use std::slice;
+use std::mem;
+use std::ptr;
+use std::marker::PhantomData;
+
+use CreationError;
+use Format;
+use SampleFormat;
+
+pub struct Voice {
+    audio_client: *mut winapi::IAudioClient,
+    render_client: *mut winapi::IAudioRenderClient,
+    max_frames_in_buffer: winapi::UINT32,
+    num_channels: winapi::WORD,
+    bytes_per_frame: winapi::WORD,
+    samples_per_second: winapi::DWORD,
+    bits_per_sample: winapi::WORD,
+    playing: bool,
+}
+
+unsafe impl Send for Voice {}
+unsafe impl Sync for Voice {}
+
+impl Voice {
+    pub fn new(end_point: &Endpoint, format: &Format) -> Result<Voice, CreationError> {
+        // FIXME: release everything
+        unsafe {
+            // making sure that COM is initialized
+            // it's not actually sure that this is required, but when in doubt do it
+            com::com_initialized();
+
+            // obtaining a `IAudioClient`
+            let audio_client = match end_point.build_audioclient() {
+                Err(ref e) if e.raw_os_error() == Some(winapi::AUDCLNT_E_DEVICE_INVALIDATED) =>
+                    return Err(CreationError::DeviceNotAvailable),
+                e => e.unwrap(),
+            };
+
+            // computing the format and initializing the device
+            let format = {
+                let format_attempt = winapi::WAVEFORMATEXTENSIBLE {
+                    Format: winapi::WAVEFORMATEX {
+                        wFormatTag: match format.data_type {
+                            SampleFormat::I16 => winapi::WAVE_FORMAT_PCM,
+                            SampleFormat::F32 => winapi::WAVE_FORMAT_EXTENSIBLE,
+                            SampleFormat::U16 => return Err(CreationError::FormatNotSupported),
+                        },
+                        nChannels: format.channels as winapi::WORD,
+                        nSamplesPerSec: format.samples_rate.0 as winapi::DWORD,
+                        nAvgBytesPerSec: format.channels as winapi::DWORD *
+                                         format.samples_rate.0 as winapi::DWORD *
+                                         format.data_type.get_sample_size() as winapi::DWORD,
+                        nBlockAlign: format.channels as winapi::WORD *
+                                     format.data_type.get_sample_size() as winapi::WORD,
+                        wBitsPerSample: 8 * format.data_type.get_sample_size() as winapi::WORD,
+                        cbSize: match format.data_type {
+                            SampleFormat::I16 => 0,
+                            SampleFormat::F32 => (mem::size_of::<winapi::WAVEFORMATEXTENSIBLE>() -
+                                                  mem::size_of::<winapi::WAVEFORMATEX>()) as winapi::WORD,
+                            SampleFormat::U16 => return Err(CreationError::FormatNotSupported),
+                        },
+                    },
+                    Samples: 8 * format.data_type.get_sample_size() as winapi::WORD,
+                    dwChannelMask: 3,       // LEFT | RIGHT
+                    SubFormat: match format.data_type {
+                        SampleFormat::I16 => winapi::KSDATAFORMAT_SUBTYPE_PCM,
+                        SampleFormat::F32 => winapi::KSDATAFORMAT_SUBTYPE_IEEE_FLOAT,
+                        SampleFormat::U16 => return Err(CreationError::FormatNotSupported),
+                    },
+                };
+
+                let mut format_ptr: *mut winapi::WAVEFORMATEX = mem::uninitialized();
+                let hresult = (*audio_client).IsFormatSupported(winapi::AUDCLNT_SHAREMODE::AUDCLNT_SHAREMODE_SHARED,
+                                                                &format_attempt.Format, &mut format_ptr);
+
+                if !format_ptr.is_null() {
+                    ole32::CoTaskMemFree(format_ptr as *mut _);
+                }
+
+                if hresult == winapi::S_FALSE {
+                    return Err(CreationError::FormatNotSupported);
+                }
+
+                match check_result(hresult) {
+                    Err(ref e) if e.raw_os_error() == Some(winapi::AUDCLNT_E_DEVICE_INVALIDATED) =>
+                    {
+                        (*audio_client).Release();
+                        return Err(CreationError::DeviceNotAvailable);
+                    },
+                    Err(e) => {
+                        (*audio_client).Release();
+                        panic!("{:?}", e);
+                    },
+                    Ok(()) => (),
+                };
+
+                let hresult = (*audio_client).Initialize(winapi::AUDCLNT_SHAREMODE::AUDCLNT_SHAREMODE_SHARED,
+                                                         0, 10000000, 0, &format_attempt.Format, ptr::null());
+
+                match check_result(hresult) {
+                    Err(ref e) if e.raw_os_error() == Some(winapi::AUDCLNT_E_DEVICE_INVALIDATED) =>
+                    {
+                        (*audio_client).Release();
+                        return Err(CreationError::DeviceNotAvailable);
+                    },
+                    Err(e) => {
+                        (*audio_client).Release();
+                        panic!("{:?}", e);
+                    },
+                    Ok(()) => (),
+                };
+
+                format_attempt.Format
+            };
+
+            // 
+            let max_frames_in_buffer = {
+                let mut max_frames_in_buffer = mem::uninitialized();
+                let hresult = (*audio_client).GetBufferSize(&mut max_frames_in_buffer);
+
+                match check_result(hresult) {
+                    Err(ref e) if e.raw_os_error() == Some(winapi::AUDCLNT_E_DEVICE_INVALIDATED) =>
+                    {
+                        (*audio_client).Release();
+                        return Err(CreationError::DeviceNotAvailable);
+                    },
+                    Err(e) => {
+                        (*audio_client).Release();
+                        panic!("{:?}", e);
+                    },
+                    Ok(()) => (),
+                };
+
+                max_frames_in_buffer
+            };
+
+            // 
+            let render_client = {
+                let mut render_client: *mut winapi::IAudioRenderClient = mem::uninitialized();
+                let hresult = (*audio_client).GetService(&winapi::IID_IAudioRenderClient,
+                                                         &mut render_client as *mut *mut winapi::IAudioRenderClient
+                                                                            as *mut _);
+
+                match check_result(hresult) {
+                    Err(ref e) if e.raw_os_error() == Some(winapi::AUDCLNT_E_DEVICE_INVALIDATED) =>
+                    {
+                        (*audio_client).Release();
+                        return Err(CreationError::DeviceNotAvailable);
+                    },
+                    Err(e) => {
+                        (*audio_client).Release();
+                        panic!("{:?}", e);
+                    },
+                    Ok(()) => (),
+                };
+
+                &mut *render_client
+            };
+
+            Ok(Voice {
+                audio_client: audio_client,
+                render_client: render_client,
+                max_frames_in_buffer: max_frames_in_buffer,
+                num_channels: format.nChannels,
+                bytes_per_frame: format.nBlockAlign,
+                samples_per_second: format.nSamplesPerSec,
+                bits_per_sample: format.wBitsPerSample,
+                playing: false,
+            })
+        }
+    }
+
+    pub fn get_channels(&self) -> ::ChannelsCount {
+        self.num_channels as ::ChannelsCount
+    }
+
+    pub fn get_samples_rate(&self) -> ::SamplesRate {
+        ::SamplesRate(self.samples_per_second as u32)
+    }
+
+    pub fn get_samples_format(&self) -> ::SampleFormat {
+        match self.bits_per_sample {
+            16 => ::SampleFormat::I16,
+            32 => ::SampleFormat::F32,
+            _ => panic!("{}-bit format not yet supported", self.bits_per_sample),
+        }
+    }
+
+    pub fn append_data<'a, T>(&'a mut self, max_elements: usize) -> Buffer<'a, T> {
+        unsafe {
+            loop {
+                // 
+                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
+                };
+
+                if frames_available == 0 {
+                    // TODO: 
+                    ::std::thread::sleep_ms(1);
+                    continue;
+                }
+
+                let frames_available = cmp::min(frames_available,
+                                                max_elements as u32 * mem::size_of::<T>() as u32 /
+                                                self.bytes_per_frame as u32);
+                assert!(frames_available != 0);
+
+                // loading 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();
+                    assert!(!buffer.is_null());
+
+                    (buffer as *mut T,
+                     frames_available as usize * self.bytes_per_frame as usize
+                          / mem::size_of::<T>())
+                };
+
+                let buffer = Buffer {
+                    render_client: self.render_client,
+                    buffer_data: buffer_data,
+                    buffer_len: buffer_len,
+                    frames: frames_available,
+                    marker: PhantomData,
+                };
+
+                return buffer;
+            }
+        }
+    }
+
+    pub fn play(&mut self) {
+        if !self.playing {
+            unsafe {
+                let hresult = (*self.audio_client).Start();
+                check_result(hresult).unwrap();
+            }
+        }
+
+        self.playing = true;
+    }
+
+    pub fn pause(&mut self) {
+        if self.playing {
+            unsafe {
+                let hresult = (*self.audio_client).Stop();
+                check_result(hresult).unwrap();
+            }
+        }
+
+        self.playing = false;
+    }
+}
+
+impl Drop for Voice {
+    fn drop(&mut self) {
+        unsafe {
+            (*self.render_client).Release();
+            (*self.audio_client).Release();
+        }
+    }
+}
+
+pub struct Buffer<'a, T: 'a> {
+    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> {
+    pub fn get_buffer<'b>(&'b mut self) -> &'b mut [T] {
+        unsafe {
+            slice::from_raw_parts_mut(self.buffer_data, self.buffer_len)
+        }
+    }
+
+    pub fn finish(self) {
+        // releasing buffer
+        unsafe {
+            let hresult = (*self.render_client).ReleaseBuffer(self.frames as u32, 0);
+            check_result(hresult).unwrap();
+        };
+    }
+}