Merge pull request #235 from ArtemGr/master

Switching the headset on and off

src/wasapi/device.rs

@@ -20,6 +20,7 @@ use COMMON_SAMPLE_RATES;
 use super::check_result;
 use super::com;
 use super::winapi::Interface;
+use super::winapi::ctypes::c_void;
 use super::winapi::shared::devpkey;
 use super::winapi::shared::ksmedia;
 use super::winapi::shared::guiddef::{
@@ -31,6 +32,9 @@ use super::winapi::shared::minwindef::{
 };
 use super::winapi::shared::mmreg;
 use super::winapi::shared::wtypes;
+// https://msdn.microsoft.com/en-us/library/cc230355.aspx
+use super::winapi::um::winnt::LPWSTR;
+use super::winapi::um::winnt::WCHAR;
 use super::winapi::um::coml2api;
 use super::winapi::um::audioclient::{
     IAudioClient,
@@ -532,7 +536,41 @@ impl Device {
 impl PartialEq for Device {
     #[inline]
     fn eq(&self, other: &Device) -> bool {
-        self.device == other.device
+        // Use case: In oder to check whether the default device has changed
+        // the client code might need to compare the previous default device with the current one.
+        // The pointer comparison (`self.device == other.device`) don't work there,
+        // because the pointers are different even when the default device stays the same.
+        //
+        // In this code section we're trying to use the GetId method for the device comparison, cf.
+        // https://docs.microsoft.com/en-us/windows/desktop/api/mmdeviceapi/nf-mmdeviceapi-immdevice-getid
+        unsafe {
+            struct IdRAII (LPWSTR);
+            /// RAII for device IDs.
+            impl Drop for IdRAII {
+                fn drop(&mut self) {
+                    unsafe {CoTaskMemFree(self.0 as *mut c_void)}
+                }
+            }
+            let mut id1: LPWSTR = ptr::null_mut();
+            let rc1 = (*self.device).GetId(&mut id1);
+            // GetId only fails with E_OUTOFMEMORY and if it does, we're probably dead already.
+            // Plus it won't do to change the device comparison logic unexpectedly.
+            if rc1 != winerror::S_OK {panic! ("cpal: GetId failure: {}", rc1)}
+            let id1 = IdRAII(id1);
+            let mut id2: LPWSTR = ptr::null_mut();
+            let rc2 = (*other.device).GetId(&mut id2);
+            if rc2 != winerror::S_OK {panic! ("cpal: GetId failure: {}", rc1)}
+            let id2 = IdRAII(id2);
+            // 16-bit null-terminated comparison.
+            let mut offset = 0;
+            loop {
+                let w1: WCHAR = *id1.0.offset(offset);
+                let w2: WCHAR = *id2.0.offset(offset);
+                if w1 == 0 && w2 == 0 {return true}
+                if w1 != w2 {return false}
+                offset += 1;
+            }
+        }
     }
 }
 

src/wasapi/stream.rs

@@ -500,6 +500,13 @@ impl EventLoop {
                     let mut frames_available = {
                         let mut padding = mem::uninitialized();
                         let hresult = (*stream.audio_client).GetCurrentPadding(&mut padding);
+                        // Happens when a bluetooth headset was turned off, for example.
+                        if hresult == AUDCLNT_E_DEVICE_INVALIDATED {
+                            // The client code should switch to a different device eventually.
+                            // For now let's just skip the invalidated device.
+                            // Would be nice to inform the client code about the invalidation,
+                            // but throwing a panic isn't the most ergonomic way to do so.
+                            continue}
                         check_result(hresult).unwrap();
                         stream.max_frames_in_buffer - padding
                     };