diff --git a/services/surfaceflinger/TransactionState.h b/services/surfaceflinger/TransactionState.h
new file mode 100644
index 0000000..fe3f3fc
--- /dev/null
+++ b/services/surfaceflinger/TransactionState.h
@@ -0,0 +1,115 @@
+/*
+ * Copyright (C) 2021 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.
+ */
+
+#pragma once
+
+#include <gui/LayerState.h>
+
+namespace android {
+class CountDownLatch;
+
+struct TransactionState {
+    TransactionState(const FrameTimelineInfo& frameTimelineInfo,
+                     const Vector<ComposerState>& composerStates,
+                     const Vector<DisplayState>& displayStates, uint32_t transactionFlags,
+                     const sp<IBinder>& applyToken, const InputWindowCommands& inputWindowCommands,
+                     int64_t desiredPresentTime, bool isAutoTimestamp,
+                     const client_cache_t& uncacheBuffer, int64_t postTime, uint32_t permissions,
+                     bool hasListenerCallbacks, std::vector<ListenerCallbacks> listenerCallbacks,
+                     int originPid, int originUid, uint64_t transactionId)
+          : frameTimelineInfo(frameTimelineInfo),
+            states(composerStates),
+            displays(displayStates),
+            flags(transactionFlags),
+            applyToken(applyToken),
+            inputWindowCommands(inputWindowCommands),
+            desiredPresentTime(desiredPresentTime),
+            isAutoTimestamp(isAutoTimestamp),
+            buffer(uncacheBuffer),
+            postTime(postTime),
+            permissions(permissions),
+            hasListenerCallbacks(hasListenerCallbacks),
+            listenerCallbacks(listenerCallbacks),
+            originPid(originPid),
+            originUid(originUid),
+            id(transactionId) {}
+
+    TransactionState() {}
+
+    void traverseStatesWithBuffers(std::function<void(const layer_state_t&)> visitor);
+
+    FrameTimelineInfo frameTimelineInfo;
+    Vector<ComposerState> states;
+    Vector<DisplayState> displays;
+    uint32_t flags;
+    sp<IBinder> applyToken;
+    InputWindowCommands inputWindowCommands;
+    int64_t desiredPresentTime;
+    bool isAutoTimestamp;
+    client_cache_t buffer;
+    int64_t postTime;
+    uint32_t permissions;
+    bool hasListenerCallbacks;
+    std::vector<ListenerCallbacks> listenerCallbacks;
+    int originPid;
+    int originUid;
+    uint64_t id;
+    std::shared_ptr<CountDownLatch> transactionCommittedSignal;
+};
+
+class CountDownLatch {
+public:
+    enum {
+        eSyncTransaction = 1 << 0,
+        eSyncInputWindows = 1 << 1,
+    };
+    explicit CountDownLatch(uint32_t flags) : mFlags(flags) {}
+
+    // True if there is no waiting condition after count down.
+    bool countDown(uint32_t flag) {
+        std::unique_lock<std::mutex> lock(mMutex);
+        if (mFlags == 0) {
+            return true;
+        }
+        mFlags &= ~flag;
+        if (mFlags == 0) {
+            mCountDownComplete.notify_all();
+            return true;
+        }
+        return false;
+    }
+
+    // Return true if triggered.
+    bool wait_until(const std::chrono::seconds& timeout) const {
+        std::unique_lock<std::mutex> lock(mMutex);
+        const auto untilTime = std::chrono::system_clock::now() + timeout;
+        while (mFlags != 0) {
+            // Conditional variables can be woken up sporadically, so we check count
+            // to verify the wakeup was triggered by |countDown|.
+            if (std::cv_status::timeout == mCountDownComplete.wait_until(lock, untilTime)) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+private:
+    uint32_t mFlags;
+    mutable std::condition_variable mCountDownComplete;
+    mutable std::mutex mMutex;
+};
+
+} // namespace android