1 files changed, 133 insertions, 0 deletions
diff --git a/services/audioflinger/StateQueue.cpp b/services/audioflinger/StateQueue.cpp
new file mode 100644
index 0000000..ae263f5
--- /dev/null
+++ b/services/audioflinger/StateQueue.cpp
@@ -0,0 +1,133 @@
+/*
+ * 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.
+ */
+
+#define LOG_TAG "StateQueue"
+//#define LOG_NDEBUG 0
+
+#include <time.h>
+#include <cutils/atomic.h>
+#include <utils/Log.h>
+#include "StateQueue.h"
+
+namespace android {
+
+// Constructor and destructor
+
+template<typename T> StateQueue<T>::StateQueue() :
+    mNext(NULL), mAck(NULL), mCurrent(NULL),
+    mMutating(&mStates[0]), mExpecting(NULL),
+    mInMutation(false), mIsDirty(false), mIsInitialized(false)
+{
+}
+
+template<typename T> StateQueue<T>::~StateQueue()
+{
+}
+
+// Observer APIs
+
+template<typename T> const T* StateQueue<T>::poll()
+{
+    const T *next = (const T *) android_atomic_acquire_load((volatile int32_t *) &mNext);
+    if (next != mCurrent) {
+        mAck = next;    // no additional barrier needed
+        mCurrent = next;
+    }
+    return next;
+}
+
+// Mutator APIs
+
+template<typename T> T* StateQueue<T>::begin()
+{
+    ALOG_ASSERT(!mInMutation, "begin() called when in a mutation");
+    mInMutation = true;
+    return mMutating;
+}
+
+template<typename T> void StateQueue<T>::end(bool didModify)
+{
+    ALOG_ASSERT(mInMutation, "end() called when not in a mutation");
+    ALOG_ASSERT(mIsInitialized || didModify, "first end() must modify for initialization");
+    if (didModify) {
+        mIsDirty = true;
+        mIsInitialized = true;
+    }
+    mInMutation = false;
+}
+
+template<typename T> bool StateQueue<T>::push(StateQueue<T>::block_t block)
+{
+#define PUSH_BLOCK_ACK_NS    3000000L   // 3 ms: time between checks for ack in push()
+                                        //       FIXME should be configurable
+    static const struct timespec req = {0, PUSH_BLOCK_ACK_NS};
+
+    ALOG_ASSERT(!mInMutation, "push() called when in a mutation");
+
+    if (mIsDirty) {
+
+        // wait for prior push to be acknowledged
+        if (mExpecting != NULL) {
+            for (;;) {
+                const T *ack = (const T *) mAck;    // no additional barrier needed
+                if (ack == mExpecting) {
+                    // unnecessary as we're about to rewrite
+                    //mExpecting = NULL;
+                    break;
+                }
+                if (block == BLOCK_NEVER) {
+                    return false;
+                }
+                nanosleep(&req, NULL);
+            }
+        }
+
+        // publish
+        android_atomic_release_store((int32_t) mMutating, (volatile int32_t *) &mNext);
+        mExpecting = mMutating;
+
+        // copy with circular wraparound
+        if (++mMutating >= &mStates[kN]) {
+            mMutating = &mStates[0];
+        }
+        *mMutating = *mExpecting;
+        mIsDirty = false;
+
+    }
+
+    // optionally wait for this push or a prior push to be acknowledged
+    if (block == BLOCK_UNTIL_ACKED) {
+        if (mExpecting != NULL) {
+            for (;;) {
+                const T *ack = (const T *) mAck;    // no additional barrier needed
+                if (ack == mExpecting) {
+                    mExpecting = NULL;
+                    break;
+                }
+                nanosleep(&req, NULL);
+            }
+        }
+    }
+
+    return true;
+}
+
+}   // namespace android
+
+// hack for gcc
+#ifdef STATE_QUEUE_INSTANTIATIONS
+#include STATE_QUEUE_INSTANTIATIONS
+#endif