oboe: add openSharedStream

To prevent race conditions with the onError callbacks
that were resulting in the use of a deleted stream.

For bug #820

2 files changed, 22 insertions, 2 deletions

diff --git a/include/oboe/AudioStream.h b/include/oboe/AudioStream.h
index d9b2046a..f2452585 100644
--- a/include/oboe/AudioStream.h
+++ b/include/oboe/AudioStream.h
@@ -418,6 +418,22 @@ public:
     ResultWithValue<int32_t> waitForAvailableFrames(int32_t numFrames,
                                                     int64_t timeoutNanoseconds);
 
+    /*
+     * INTERNAL USE ONLY
+     * Set a weak_ptr to this stream from the shared_ptr so that we can
+     * later use a shared_ptr in the error callback.
+     */
+    void setWeakThis(std::shared_ptr<oboe::AudioStream> &sharedStream) {
+        mWeakThis = sharedStream;
+    }
+
+    /*
+     * Make a shared_ptr that will prevent this stream from being deleted.
+     */
+    std::shared_ptr<oboe::AudioStream> lockWeakThis() {
+        return mWeakThis.lock();
+    }
+
 protected:
 
     /**
@@ -497,17 +513,18 @@ protected:
 
     std::mutex           mLock; // for synchronizing start/stop/close
 
+
 private:
     int                  mPreviousScheduler = -1;
 
     std::atomic<bool>    mDataCallbackEnabled{false};
     std::atomic<bool>    mErrorCallbackCalled{false};
 
-
+    std::weak_ptr<AudioStream> mWeakThis;
 };
 
 /**
- * This struct is a stateless functor which closes a audiostream prior to its deletion.
+ * This struct is a stateless functor which closes an AudioStream prior to its deletion.
  * This means it can be used to safely delete a smart pointer referring to an open stream.
  */
     struct StreamDeleterFunctor {
diff --git a/include/oboe/AudioStreamBuilder.h b/include/oboe/AudioStreamBuilder.h
index b0f7de8e..636803a7 100644
--- a/include/oboe/AudioStreamBuilder.h
+++ b/include/oboe/AudioStreamBuilder.h
@@ -25,6 +25,7 @@ namespace oboe {
     // This depends on AudioStream, so we use forward declaration, it will close and delete the stream
     struct StreamDeleterFunctor;
     using ManagedStream = std::unique_ptr<AudioStream, StreamDeleterFunctor>;
+
 /**
  * Factory class for an audio Stream.
  */
@@ -399,6 +400,8 @@ public:
      */
     Result openManagedStream(ManagedStream &stream);
 
+    Result openSharedStream(std::shared_ptr<oboe::AudioStream> &sharedStream);
+
 private:
 
     /**