Allow calling BackendBase::open multiple times on playback devices

It will not be called while the device is running. If the first call succeeds,
a subsequent call that happens to fail must leave the existing device state as
it was so it can be resumed.

This is a rough first pass. It will fail when trying to re-open the same device
which can only be opened once (for instance, with direct hardware access, on
hardware that doesn't do its own mixing). Some backends won't guarantee the new
device is usable until the reset() or start() call.

1 files changed, 91 insertions, 47 deletions

diff --git a/alc/backends/dsound.cpp b/alc/backends/dsound.cpp
index aa3a92a0..34fe25f4 100644
--- a/alc/backends/dsound.cpp
+++ b/alc/backends/dsound.cpp
@@ -107,6 +107,69 @@ HRESULT (WINAPI *pDirectSoundCaptureEnumerateW)(LPDSENUMCALLBACKW pDSEnumCallbac
 #endif
 
 
+template<typename T>
+class ComPtr {
+    T *mPtr{nullptr};
+
+public:
+    ComPtr() noexcept = default;
+    ComPtr(const ComPtr &rhs) : mPtr{rhs.mPtr} { if(mPtr) mPtr->AddRef(); }
+    ComPtr(ComPtr&& rhs) noexcept : mPtr{rhs.mPtr} { rhs.mPtr = nullptr; }
+    ComPtr(std::nullptr_t) noexcept { }
+    explicit ComPtr(T *ptr) noexcept : mPtr{ptr} { }
+    ~ComPtr() { if(mPtr) mPtr->Release(); }
+
+    ComPtr& operator=(const ComPtr &rhs)
+    {
+        if(!rhs.mPtr)
+        {
+            if(mPtr)
+                mPtr->Release();
+            mPtr = nullptr;
+        }
+        else
+        {
+            rhs.mPtr->AddRef();
+            try {
+                if(mPtr)
+                    mPtr->Release();
+                mPtr = rhs.mPtr;
+            }
+            catch(...) {
+                rhs.mPtr->Release();
+                throw;
+            }
+        }
+        return *this;
+    }
+    ComPtr& operator=(ComPtr&& rhs)
+    {
+        if(mPtr)
+            mPtr->Release();
+        mPtr = rhs.mPtr;
+        rhs.mPtr = nullptr;
+        return *this;
+    }
+
+    operator bool() const noexcept { return mPtr != nullptr; }
+
+    T& operator*() const noexcept { return *mPtr; }
+    T* operator->() const noexcept { return mPtr; }
+    T* get() const noexcept { return mPtr; }
+    T** getPtr() noexcept { return &mPtr; }
+
+    T* release() noexcept
+    {
+        T *ret{mPtr};
+        mPtr = nullptr;
+        return ret;
+    }
+
+    void swap(ComPtr &rhs) noexcept { std::swap(mPtr, rhs.mPtr); }
+    void swap(ComPtr&& rhs) noexcept { std::swap(mPtr, rhs.mPtr); }
+};
+
+
 #define MONO SPEAKER_FRONT_CENTER
 #define STEREO (SPEAKER_FRONT_LEFT|SPEAKER_FRONT_RIGHT)
 #define QUAD (SPEAKER_FRONT_LEFT|SPEAKER_FRONT_RIGHT|SPEAKER_BACK_LEFT|SPEAKER_BACK_RIGHT)
@@ -179,11 +242,11 @@ struct DSoundPlayback final : public BackendBase {
     void start() override;
     void stop() override;
 
-    IDirectSound       *mDS{nullptr};
-    IDirectSoundBuffer *mPrimaryBuffer{nullptr};
-    IDirectSoundBuffer *mBuffer{nullptr};
-    IDirectSoundNotify *mNotifies{nullptr};
-    HANDLE             mNotifyEvent{nullptr};
+    ComPtr<IDirectSound>       mDS;
+    ComPtr<IDirectSoundBuffer> mPrimaryBuffer;
+    ComPtr<IDirectSoundBuffer> mBuffer;
+    ComPtr<IDirectSoundNotify> mNotifies;
+    HANDLE mNotifyEvent{nullptr};
 
     std::atomic<bool> mKillNow{true};
     std::thread mThread;
@@ -193,19 +256,11 @@ struct DSoundPlayback final : public BackendBase {
 
 DSoundPlayback::~DSoundPlayback()
 {
-    if(mNotifies)
-        mNotifies->Release();
     mNotifies = nullptr;
-    if(mBuffer)
-        mBuffer->Release();
     mBuffer = nullptr;
-    if(mPrimaryBuffer)
-        mPrimaryBuffer->Release();
     mPrimaryBuffer = nullptr;
-
-    if(mDS)
-        mDS->Release();
     mDS = nullptr;
+
     if(mNotifyEvent)
         CloseHandle(mNotifyEvent);
     mNotifyEvent = nullptr;
@@ -234,8 +289,8 @@ FORCE_ALIGN int DSoundPlayback::mixerProc()
     bool Playing{false};
     DWORD LastCursor{0u};
     mBuffer->GetCurrentPosition(&LastCursor, nullptr);
-    while(!mKillNow.load(std::memory_order_acquire) &&
-          mDevice->Connected.load(std::memory_order_acquire))
+    while(!mKillNow.load(std::memory_order_acquire)
+        && mDevice->Connected.load(std::memory_order_acquire))
     {
         // Get current play cursor
         DWORD PlayCursor;
@@ -344,31 +399,34 @@ void DSoundPlayback::open(const char *name)
     }
 
     hr = DS_OK;
-    mNotifyEvent = CreateEventW(nullptr, FALSE, FALSE, nullptr);
-    if(!mNotifyEvent) hr = E_FAIL;
+    if(!mNotifyEvent)
+    {
+        mNotifyEvent = CreateEventW(nullptr, FALSE, FALSE, nullptr);
+        if(!mNotifyEvent) hr = E_FAIL;
+    }
 
     //DirectSound Init code
+    ComPtr<IDirectSound> ds;
     if(SUCCEEDED(hr))
-        hr = DirectSoundCreate(guid, &mDS, nullptr);
+        hr = DirectSoundCreate(guid, ds.getPtr(), nullptr);
     if(SUCCEEDED(hr))
-        hr = mDS->SetCooperativeLevel(GetForegroundWindow(), DSSCL_PRIORITY);
+        hr = ds->SetCooperativeLevel(GetForegroundWindow(), DSSCL_PRIORITY);
     if(FAILED(hr))
         throw al::backend_exception{al::backend_error::DeviceError, "Device init failed: 0x%08lx",
             hr};
 
+    mNotifies = nullptr;
+    mBuffer = nullptr;
+    mPrimaryBuffer = nullptr;
+    mDS = std::move(ds);
+
     mDevice->DeviceName = name;
 }
 
 bool DSoundPlayback::reset()
 {
-    if(mNotifies)
-        mNotifies->Release();
     mNotifies = nullptr;
-    if(mBuffer)
-        mBuffer->Release();
     mBuffer = nullptr;
-    if(mPrimaryBuffer)
-        mPrimaryBuffer->Release();
     mPrimaryBuffer = nullptr;
 
     switch(mDevice->FmtType)
@@ -465,7 +523,7 @@ retry_open:
             DSBUFFERDESC DSBDescription{};
             DSBDescription.dwSize = sizeof(DSBDescription);
             DSBDescription.dwFlags = DSBCAPS_PRIMARYBUFFER;
-            hr = mDS->CreateSoundBuffer(&DSBDescription, &mPrimaryBuffer, nullptr);
+            hr = mDS->CreateSoundBuffer(&DSBDescription, mPrimaryBuffer.getPtr(), nullptr);
         }
         if(SUCCEEDED(hr))
             hr = mPrimaryBuffer->SetFormat(&OutputType.Format);
@@ -485,7 +543,7 @@ retry_open:
         DSBDescription.dwBufferBytes = mDevice->BufferSize * OutputType.Format.nBlockAlign;
         DSBDescription.lpwfxFormat = &OutputType.Format;
 
-        hr = mDS->CreateSoundBuffer(&DSBDescription, &mBuffer, nullptr);
+        hr = mDS->CreateSoundBuffer(&DSBDescription, mBuffer.getPtr(), nullptr);
         if(FAILED(hr) && mDevice->FmtType == DevFmtFloat)
         {
             mDevice->FmtType = DevFmtShort;
@@ -499,7 +557,7 @@ retry_open:
         hr = mBuffer->QueryInterface(IID_IDirectSoundNotify, &ptr);
         if(SUCCEEDED(hr))
         {
-            mNotifies = static_cast<IDirectSoundNotify*>(ptr);
+            mNotifies = ComPtr<IDirectSoundNotify>{static_cast<IDirectSoundNotify*>(ptr)};
 
             uint num_updates{mDevice->BufferSize / mDevice->UpdateSize};
             assert(num_updates <= MAX_UPDATES);
@@ -517,14 +575,8 @@ retry_open:
 
     if(FAILED(hr))
     {
-        if(mNotifies)
-            mNotifies->Release();
         mNotifies = nullptr;
-        if(mBuffer)
-            mBuffer->Release();
         mBuffer = nullptr;
-        if(mPrimaryBuffer)
-            mPrimaryBuffer->Release();
         mPrimaryBuffer = nullptr;
         return false;
     }
@@ -567,8 +619,8 @@ struct DSoundCapture final : public BackendBase {
     void captureSamples(al::byte *buffer, uint samples) override;
     uint availableSamples() override;
 
-    IDirectSoundCapture *mDSC{nullptr};
-    IDirectSoundCaptureBuffer *mDSCbuffer{nullptr};
+    ComPtr<IDirectSoundCapture> mDSC;
+    ComPtr<IDirectSoundCaptureBuffer> mDSCbuffer;
     DWORD mBufferBytes{0u};
     DWORD mCursor{0u};
 
@@ -582,12 +634,8 @@ DSoundCapture::~DSoundCapture()
     if(mDSCbuffer)
     {
         mDSCbuffer->Stop();
-        mDSCbuffer->Release();
         mDSCbuffer = nullptr;
     }
-
-    if(mDSC)
-        mDSC->Release();
     mDSC = nullptr;
 }
 
@@ -693,20 +741,16 @@ void DSoundCapture::open(const char *name)
     DSCBDescription.lpwfxFormat = &InputType.Format;
 
     //DirectSoundCapture Init code
-    hr = DirectSoundCaptureCreate(guid, &mDSC, nullptr);
+    hr = DirectSoundCaptureCreate(guid, mDSC.getPtr(), nullptr);
     if(SUCCEEDED(hr))
-        mDSC->CreateCaptureBuffer(&DSCBDescription, &mDSCbuffer, nullptr);
+        mDSC->CreateCaptureBuffer(&DSCBDescription, mDSCbuffer.getPtr(), nullptr);
     if(SUCCEEDED(hr))
          mRing = RingBuffer::Create(mDevice->BufferSize, InputType.Format.nBlockAlign, false);
 
     if(FAILED(hr))
     {
         mRing = nullptr;
-        if(mDSCbuffer)
-            mDSCbuffer->Release();
         mDSCbuffer = nullptr;
-        if(mDSC)
-            mDSC->Release();
         mDSC = nullptr;
 
         throw al::backend_exception{al::backend_error::DeviceError, "Device init failed: 0x%08lx",