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diff --git a/include/ui/FenceTime.h b/include/ui/FenceTime.h
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+/*
+ * Copyright (C) 2016 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 ANDROID_FENCE_TIME_H
+#define ANDROID_FENCE_TIME_H
+
+#include <ui/Fence.h>
+#include <utils/Flattenable.h>
+#include <utils/Timers.h>
+
+#include <atomic>
+#include <mutex>
+#include <queue>
+
+namespace android {
+
+// A wrapper around fence that only implements isValid and getSignalTime.
+// It automatically closes the fence in a thread-safe manner once the signal
+// time is known.
+class FenceTime {
+public:
+    // An atomic snapshot of the FenceTime that is flattenable.
+    //
+    // This class is needed because the FenceTime class may not stay
+    // consistent for all steps of the flattening process.
+    //
+    // Not thread safe.
+    struct Snapshot : public Flattenable<Snapshot> {
+        enum class State {
+            EMPTY,
+            FENCE,
+            SIGNAL_TIME,
+        };
+
+        Snapshot() = default;  // Creates an empty snapshot.
+        explicit Snapshot(const sp<Fence>& fence);
+        explicit Snapshot(nsecs_t signalTime);
+
+        // Movable.
+        Snapshot(Snapshot&& src) = default;
+        Snapshot& operator=(Snapshot&& src) = default;
+        // Not copyable.
+        Snapshot(const Snapshot& src) = delete;
+        Snapshot& operator=(const Snapshot&& src) = delete;
+
+        // Flattenable implementation.
+        size_t getFlattenedSize() const;
+        size_t getFdCount() const;
+        status_t flatten(void*& buffer, size_t& size, int*& fds,
+                size_t& count) const;
+        status_t unflatten(void const*& buffer, size_t& size, int const*& fds,
+                size_t& count);
+
+        State state{State::EMPTY};
+        sp<Fence> fence{Fence::NO_FENCE};
+        nsecs_t signalTime{Fence::SIGNAL_TIME_INVALID};
+    };
+
+    static const std::shared_ptr<FenceTime> NO_FENCE;
+
+    explicit FenceTime(const sp<Fence>& fence);
+    explicit FenceTime(sp<Fence>&& fence);
+
+    // Passing in Fence::SIGNAL_TIME_PENDING is not allowed.
+    // Doing so will convert the signalTime to Fence::SIGNAL_TIME_INVALID.
+    explicit FenceTime(nsecs_t signalTime);
+
+    // Do not allow default construction. Share NO_FENCE or explicitly construct
+    // with Fence::SIGNAL_TIME_INVALID instead.
+    FenceTime() = delete;
+
+    // Do not allow copy, assign, or move. Use a shared_ptr to share the
+    // signalTime result. Or use getSnapshot() if a thread-safe copy is really
+    // needed.
+    FenceTime(const FenceTime&) = delete;
+    FenceTime(FenceTime&&) = delete;
+    FenceTime& operator=(const FenceTime&) = delete;
+    FenceTime& operator=(FenceTime&&) = delete;
+
+    // This method should only be called when replacing the fence with
+    // a signalTime. Since this is an indirect way of setting the signal time
+    // of a fence, the snapshot should come from a trusted source.
+    void applyTrustedSnapshot(const Snapshot& src);
+
+    bool isValid() const;
+
+    // Attempts to get the timestamp from the Fence if the timestamp isn't
+    // already cached. Otherwise, it returns the cached value.
+    nsecs_t getSignalTime();
+
+    // Gets the cached timestamp without attempting to query the Fence.
+    nsecs_t getCachedSignalTime() const;
+
+    // Returns a snapshot of the FenceTime in its current state.
+    Snapshot getSnapshot() const;
+
+    // Override new and delete since this needs 8-byte alignment, which
+    // is not guaranteed on x86.
+    static void* operator new(size_t nbytes) noexcept;
+    static void operator delete(void *p);
+
+private:
+    enum class State {
+        VALID,
+        INVALID,
+    };
+
+    const State mState{State::INVALID};
+
+    // mMutex guards mFence and mSignalTime.
+    // mSignalTime is also atomic since it is sometimes read outside the lock
+    // for quick checks.
+    mutable std::mutex mMutex;
+    sp<Fence> mFence{Fence::NO_FENCE};
+    std::atomic<nsecs_t> mSignalTime{Fence::SIGNAL_TIME_INVALID};
+};
+
+// A queue of FenceTimes that are expected to signal in FIFO order.
+// Only maintains a queue of weak pointers so it doesn't keep references
+// to Fences on its own.
+//
+// Can be used to get the signal time of a fence and close its file descriptor
+// without making a syscall for every fence later in the timeline.
+// Additionally, since the FenceTime caches the timestamp internally,
+// other timelines that reference the same FenceTime can avoid the syscall.
+//
+// FenceTimeline only keeps track of a limited number of entries to avoid
+// growing unbounded. Users of FenceTime must make sure they can work even
+// if FenceTimeline did nothing. i.e. they should eventually call
+// Fence::getSignalTime(), not only Fence::getCachedSignalTime().
+//
+// push() and updateSignalTimes() are safe to call simultaneously from
+// different threads.
+class FenceTimeline {
+public:
+    static constexpr size_t MAX_ENTRIES = 64;
+
+    void push(const std::shared_ptr<FenceTime>& fence);
+    void updateSignalTimes();
+
+private:
+    mutable std::mutex mMutex;
+    std::queue<std::weak_ptr<FenceTime>> mQueue;
+};
+
+}; // namespace android
+
+#endif // ANDROID_FENCE_TIME_H