Add template class SingleStateQueue

Change-Id: If7e2bc9b2a216524ee9cbb68682e2634933b4973

2 files changed, 132 insertions, 0 deletions

diff --git a/include/media/SingleStateQueue.h b/include/media/SingleStateQueue.h
new file mode 100644
index 0000000..04c5fd0
--- /dev/null
+++ b/include/media/SingleStateQueue.h
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef SINGLE_STATE_QUEUE_H
+#define SINGLE_STATE_QUEUE_H
+
+// Non-blocking single element state queue, or
+// Non-blocking single-reader / single-writer multi-word atomic load / store
+
+#include <stdint.h>
+
+namespace android {
+
+template<typename T> class SingleStateQueue {
+
+public:
+
+    class Mutator;
+    class Observer;
+
+    struct Shared {
+        // needs to be part of a union so don't define constructor or destructor
+
+        friend class Mutator;
+        friend class Observer;
+
+private:
+        void                init() { mAck = 0; mSequence = 0; }
+
+        volatile int32_t    mAck;
+#if 0
+        int                 mPad[7];
+        // cache line boundary
+#endif
+        volatile int32_t    mSequence;
+        T                   mValue;
+    };
+
+    class Mutator {
+    public:
+        Mutator(Shared *shared);
+        /*virtual*/ ~Mutator() { }
+
+        // push new value onto state queue, overwriting previous value;
+        // returns a sequence number which can be used with ack()
+        int32_t push(const T& value);
+
+        // return true if most recent push has been observed
+        bool ack();
+
+        // return true if a push with specified sequence number or later has been observed
+        bool ack(int32_t sequence);
+
+    private:
+        int32_t     mSequence;
+        Shared * const mShared;
+    };
+
+    class Observer {
+    public:
+        Observer(Shared *shared);
+        /*virtual*/ ~Observer() { }
+
+        // return true if value has changed
+        bool poll(T& value);
+
+    private:
+        int32_t     mSequence;
+        int         mSeed;  // for PRNG
+        Shared * const mShared;
+    };
+
+#if 0
+    SingleStateQueue(void /*Shared*/ *shared);
+    /*virtual*/ ~SingleStateQueue() { }
+
+    static size_t size() { return sizeof(Shared); }
+#endif
+
+};
+
+}   // namespace android
+
+#endif  // SINGLE_STATE_QUEUE_H
diff --git a/include/private/media/StaticAudioTrackState.h b/include/private/media/StaticAudioTrackState.h
new file mode 100644
index 0000000..46a5946
--- /dev/null
+++ b/include/private/media/StaticAudioTrackState.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef STATIC_AUDIO_TRACK_STATE_H
+#define STATIC_AUDIO_TRACK_STATE_H
+
+namespace android {
+
+// Represents a single state of an AudioTrack that was created in static mode (shared memory buffer
+// supplied by the client).  This state needs to be communicated from the client to server.  As this
+// state is too large to be updated atomically without a mutex, and mutexes aren't allowed here, the
+// state is wrapped by a SingleStateQueue.
+struct StaticAudioTrackState {
+    // do not define constructors, destructors, or virtual methods
+    size_t  mLoopStart;
+    size_t  mLoopEnd;
+    int     mLoopCount;
+};
+
+}   // namespace android
+
+#endif  // STATIC_AUDIO_TRACK_STATE_H