Add basic implementation for alsa

src/alsa/mod.rs

@@ -0,0 +1,107 @@
+extern crate "alsa-sys" as alsa;
+extern crate libc;
+
+use std::{mem, ptr};
+
+pub struct Channel {
+    channel: *mut alsa::snd_pcm_t,
+    num_channels: u16,
+}
+
+pub struct Buffer<'a, T> {
+    channel: &'a mut Channel,
+    buffer: Vec<T>,
+}
+
+impl Channel {
+    pub fn new() -> Channel {
+        unsafe {
+            let name = "default".to_c_str();
+
+            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();
+
+            let mut hw_params = mem::uninitialized();
+            check_errors(alsa::snd_pcm_hw_params_malloc(&mut hw_params)).unwrap();
+            check_errors(alsa::snd_pcm_hw_params_any(playback_handle, hw_params)).unwrap();
+            check_errors(alsa::snd_pcm_hw_params_set_access(playback_handle, hw_params, alsa::SND_PCM_ACCESS_RW_INTERLEAVED)).unwrap();
+            check_errors(alsa::snd_pcm_hw_params_set_format(playback_handle, hw_params, alsa::SND_PCM_FORMAT_S16_LE)).unwrap(); // TODO: check endianess
+            check_errors(alsa::snd_pcm_hw_params_set_rate(playback_handle, hw_params, 44100, 0)).unwrap();
+            check_errors(alsa::snd_pcm_hw_params_set_channels(playback_handle, hw_params, 2)).unwrap();
+            check_errors(alsa::snd_pcm_hw_params(playback_handle, hw_params)).unwrap();
+            alsa::snd_pcm_hw_params_free(hw_params);
+
+            check_errors(alsa::snd_pcm_prepare(playback_handle)).unwrap();
+
+            Channel {
+                channel: playback_handle,
+                num_channels: 2,
+            }
+        }
+    }
+
+    pub fn get_channels(&self) -> ::ChannelsCount {
+        self.num_channels
+    }
+
+    pub fn get_samples_rate(&self) -> ::SamplesRate {
+        ::SamplesRate(44100)
+    }
+
+    pub fn get_samples_format(&self) -> ::SampleFormat {
+        ::SampleFormat::U16
+    }
+
+    pub fn append_data<'a, T>(&'a mut self, max_elements: uint) -> Buffer<'a, T> where T: Clone {
+        let available = unsafe { alsa::snd_pcm_avail(self.channel) };
+        let available = available * self.num_channels as alsa::snd_pcm_sframes_t;
+
+        let elements = ::std::cmp::min(available as uint, max_elements);
+
+        Buffer {
+            channel: self,
+            buffer: Vec::from_elem(elements, unsafe { mem::uninitialized() })
+        }
+    }
+}
+
+impl Drop for Channel {
+    fn drop(&mut self) {
+        unsafe {
+            alsa::snd_pcm_close(self.channel);
+        }
+    }
+}
+
+impl<'a, T> Buffer<'a, T> {
+    pub fn get_buffer<'b>(&'b mut self) -> &'b mut [T] {
+        self.buffer.as_mut_slice()
+    }
+
+    pub fn finish(self) {
+        let written = (self.buffer.len() / self.channel.num_channels as uint) as alsa::snd_pcm_uframes_t;
+
+        unsafe {
+            let result = alsa::snd_pcm_writei(self.channel.channel,
+                                              self.buffer.as_ptr() as *const libc::c_void,
+                                              written);
+
+            if result < 0 {
+                check_errors(result as libc::c_int).unwrap();
+            }
+        }
+    }
+}
+
+fn check_errors(err: libc::c_int) -> Result<(), String> {
+    use std::c_str::CString;
+
+    if err < 0 {
+        unsafe {
+            let s = CString::new(alsa::snd_strerror(err), false);
+            return Err(s.to_string());
+        }
+    }
+
+    Ok(())
+}

src/lib.rs

@@ -1,10 +1,13 @@
 #![feature(unsafe_destructor)]
 
-#[cfg(all(not(windows)))]
+#[cfg(all(not(windows), not(unix)))]
 use this_platform_is_not_supported;
 
 mod conversions;
 
+#[cfg(unix)]
+#[path="alsa/mod.rs"]
+pub mod cpal_impl;
 #[cfg(windows)]
 #[path="wasapi/mod.rs"]
 pub mod cpal_impl;