Move InputConsumer into separate files

This helps to keep track of things, and it also allows easier deletion
in the future.

Bug: 311142655
Test: none
Change-Id: Iece2bf6857ab05f86072031a4cf3a36f843b1634
diff --git a/libs/input/InputConsumer.cpp b/libs/input/InputConsumer.cpp
new file mode 100644
index 0000000..e0d874e
--- /dev/null
+++ b/libs/input/InputConsumer.cpp
@@ -0,0 +1,939 @@
+/**
+ * Copyright 2024 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 "InputTransport"
+#define ATRACE_TAG ATRACE_TAG_INPUT
+
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <math.h>
+#include <poll.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <android-base/logging.h>
+#include <android-base/properties.h>
+#include <android-base/stringprintf.h>
+#include <binder/Parcel.h>
+#include <cutils/properties.h>
+#include <ftl/enum.h>
+#include <log/log.h>
+#include <utils/Trace.h>
+
+#include <com_android_input_flags.h>
+#include <input/InputConsumer.h>
+#include <input/PrintTools.h>
+#include <input/TraceTools.h>
+
+namespace input_flags = com::android::input::flags;
+
+namespace android {
+
+namespace {
+
+/**
+ * Log debug messages relating to the consumer end of the transport channel.
+ * Enable this via "adb shell setprop log.tag.InputTransportConsumer DEBUG" (requires restart)
+ */
+
+const bool DEBUG_TRANSPORT_CONSUMER =
+        __android_log_is_loggable(ANDROID_LOG_DEBUG, LOG_TAG "Consumer", ANDROID_LOG_INFO);
+
+const bool IS_DEBUGGABLE_BUILD =
+#if defined(__ANDROID__)
+        android::base::GetBoolProperty("ro.debuggable", false);
+#else
+        true;
+#endif
+
+/**
+ * Log debug messages about touch event resampling.
+ *
+ * Enable this via "adb shell setprop log.tag.InputTransportResampling DEBUG".
+ * This requires a restart on non-debuggable (e.g. user) builds, but should take effect immediately
+ * on debuggable builds (e.g. userdebug).
+ */
+bool debugResampling() {
+    if (!IS_DEBUGGABLE_BUILD) {
+        static const bool DEBUG_TRANSPORT_RESAMPLING =
+                __android_log_is_loggable(ANDROID_LOG_DEBUG, LOG_TAG "Resampling",
+                                          ANDROID_LOG_INFO);
+        return DEBUG_TRANSPORT_RESAMPLING;
+    }
+    return __android_log_is_loggable(ANDROID_LOG_DEBUG, LOG_TAG "Resampling", ANDROID_LOG_INFO);
+}
+
+void initializeKeyEvent(KeyEvent& event, const InputMessage& msg) {
+    event.initialize(msg.body.key.eventId, msg.body.key.deviceId, msg.body.key.source,
+                     msg.body.key.displayId, msg.body.key.hmac, msg.body.key.action,
+                     msg.body.key.flags, msg.body.key.keyCode, msg.body.key.scanCode,
+                     msg.body.key.metaState, msg.body.key.repeatCount, msg.body.key.downTime,
+                     msg.body.key.eventTime);
+}
+
+void initializeFocusEvent(FocusEvent& event, const InputMessage& msg) {
+    event.initialize(msg.body.focus.eventId, msg.body.focus.hasFocus);
+}
+
+void initializeCaptureEvent(CaptureEvent& event, const InputMessage& msg) {
+    event.initialize(msg.body.capture.eventId, msg.body.capture.pointerCaptureEnabled);
+}
+
+void initializeDragEvent(DragEvent& event, const InputMessage& msg) {
+    event.initialize(msg.body.drag.eventId, msg.body.drag.x, msg.body.drag.y,
+                     msg.body.drag.isExiting);
+}
+
+void initializeMotionEvent(MotionEvent& event, const InputMessage& msg) {
+    uint32_t pointerCount = msg.body.motion.pointerCount;
+    PointerProperties pointerProperties[pointerCount];
+    PointerCoords pointerCoords[pointerCount];
+    for (uint32_t i = 0; i < pointerCount; i++) {
+        pointerProperties[i] = msg.body.motion.pointers[i].properties;
+        pointerCoords[i] = msg.body.motion.pointers[i].coords;
+    }
+
+    ui::Transform transform;
+    transform.set({msg.body.motion.dsdx, msg.body.motion.dtdx, msg.body.motion.tx,
+                   msg.body.motion.dtdy, msg.body.motion.dsdy, msg.body.motion.ty, 0, 0, 1});
+    ui::Transform displayTransform;
+    displayTransform.set({msg.body.motion.dsdxRaw, msg.body.motion.dtdxRaw, msg.body.motion.txRaw,
+                          msg.body.motion.dtdyRaw, msg.body.motion.dsdyRaw, msg.body.motion.tyRaw,
+                          0, 0, 1});
+    event.initialize(msg.body.motion.eventId, msg.body.motion.deviceId, msg.body.motion.source,
+                     msg.body.motion.displayId, msg.body.motion.hmac, msg.body.motion.action,
+                     msg.body.motion.actionButton, msg.body.motion.flags, msg.body.motion.edgeFlags,
+                     msg.body.motion.metaState, msg.body.motion.buttonState,
+                     msg.body.motion.classification, transform, msg.body.motion.xPrecision,
+                     msg.body.motion.yPrecision, msg.body.motion.xCursorPosition,
+                     msg.body.motion.yCursorPosition, displayTransform, msg.body.motion.downTime,
+                     msg.body.motion.eventTime, pointerCount, pointerProperties, pointerCoords);
+}
+
+void addSample(MotionEvent& event, const InputMessage& msg) {
+    uint32_t pointerCount = msg.body.motion.pointerCount;
+    PointerCoords pointerCoords[pointerCount];
+    for (uint32_t i = 0; i < pointerCount; i++) {
+        pointerCoords[i] = msg.body.motion.pointers[i].coords;
+    }
+
+    event.setMetaState(event.getMetaState() | msg.body.motion.metaState);
+    event.addSample(msg.body.motion.eventTime, pointerCoords);
+}
+
+void initializeTouchModeEvent(TouchModeEvent& event, const InputMessage& msg) {
+    event.initialize(msg.body.touchMode.eventId, msg.body.touchMode.isInTouchMode);
+}
+
+// Nanoseconds per milliseconds.
+constexpr nsecs_t NANOS_PER_MS = 1000000;
+
+// Latency added during resampling.  A few milliseconds doesn't hurt much but
+// reduces the impact of mispredicted touch positions.
+const std::chrono::duration RESAMPLE_LATENCY = 5ms;
+
+// Minimum time difference between consecutive samples before attempting to resample.
+const nsecs_t RESAMPLE_MIN_DELTA = 2 * NANOS_PER_MS;
+
+// Maximum time difference between consecutive samples before attempting to resample
+// by extrapolation.
+const nsecs_t RESAMPLE_MAX_DELTA = 20 * NANOS_PER_MS;
+
+// Maximum time to predict forward from the last known state, to avoid predicting too
+// far into the future.  This time is further bounded by 50% of the last time delta.
+const nsecs_t RESAMPLE_MAX_PREDICTION = 8 * NANOS_PER_MS;
+
+/**
+ * System property for enabling / disabling touch resampling.
+ * Resampling extrapolates / interpolates the reported touch event coordinates to better
+ * align them to the VSYNC signal, thus resulting in smoother scrolling performance.
+ * Resampling is not needed (and should be disabled) on hardware that already
+ * has touch events triggered by VSYNC.
+ * Set to "1" to enable resampling (default).
+ * Set to "0" to disable resampling.
+ * Resampling is enabled by default.
+ */
+const char* PROPERTY_RESAMPLING_ENABLED = "ro.input.resampling";
+
+inline float lerp(float a, float b, float alpha) {
+    return a + alpha * (b - a);
+}
+
+inline bool isPointerEvent(int32_t source) {
+    return (source & AINPUT_SOURCE_CLASS_POINTER) == AINPUT_SOURCE_CLASS_POINTER;
+}
+
+bool shouldResampleTool(ToolType toolType) {
+    return toolType == ToolType::FINGER || toolType == ToolType::UNKNOWN;
+}
+
+} // namespace
+
+using android::base::Result;
+using android::base::StringPrintf;
+
+// --- InputConsumer ---
+
+InputConsumer::InputConsumer(const std::shared_ptr<InputChannel>& channel)
+      : InputConsumer(channel, isTouchResamplingEnabled()) {}
+
+InputConsumer::InputConsumer(const std::shared_ptr<InputChannel>& channel,
+                             bool enableTouchResampling)
+      : mResampleTouch(enableTouchResampling), mChannel(channel), mMsgDeferred(false) {}
+
+InputConsumer::~InputConsumer() {}
+
+bool InputConsumer::isTouchResamplingEnabled() {
+    return property_get_bool(PROPERTY_RESAMPLING_ENABLED, true);
+}
+
+status_t InputConsumer::consume(InputEventFactoryInterface* factory, bool consumeBatches,
+                                nsecs_t frameTime, uint32_t* outSeq, InputEvent** outEvent) {
+    ALOGD_IF(DEBUG_TRANSPORT_CONSUMER,
+             "channel '%s' consumer ~ consume: consumeBatches=%s, frameTime=%" PRId64,
+             mChannel->getName().c_str(), toString(consumeBatches), frameTime);
+
+    *outSeq = 0;
+    *outEvent = nullptr;
+
+    // Fetch the next input message.
+    // Loop until an event can be returned or no additional events are received.
+    while (!*outEvent) {
+        if (mMsgDeferred) {
+            // mMsg contains a valid input message from the previous call to consume
+            // that has not yet been processed.
+            mMsgDeferred = false;
+        } else {
+            // Receive a fresh message.
+            status_t result = mChannel->receiveMessage(&mMsg);
+            if (result == OK) {
+                const auto [_, inserted] =
+                        mConsumeTimes.emplace(mMsg.header.seq, systemTime(SYSTEM_TIME_MONOTONIC));
+                LOG_ALWAYS_FATAL_IF(!inserted, "Already have a consume time for seq=%" PRIu32,
+                                    mMsg.header.seq);
+
+                // Trace the event processing timeline - event was just read from the socket
+                ATRACE_ASYNC_BEGIN("InputConsumer processing", /*cookie=*/mMsg.header.seq);
+            }
+            if (result) {
+                // Consume the next batched event unless batches are being held for later.
+                if (consumeBatches || result != WOULD_BLOCK) {
+                    result = consumeBatch(factory, frameTime, outSeq, outEvent);
+                    if (*outEvent) {
+                        ALOGD_IF(DEBUG_TRANSPORT_CONSUMER,
+                                 "channel '%s' consumer ~ consumed batch event, seq=%u",
+                                 mChannel->getName().c_str(), *outSeq);
+                        break;
+                    }
+                }
+                return result;
+            }
+        }
+
+        switch (mMsg.header.type) {
+            case InputMessage::Type::KEY: {
+                KeyEvent* keyEvent = factory->createKeyEvent();
+                if (!keyEvent) return NO_MEMORY;
+
+                initializeKeyEvent(*keyEvent, mMsg);
+                *outSeq = mMsg.header.seq;
+                *outEvent = keyEvent;
+                ALOGD_IF(DEBUG_TRANSPORT_CONSUMER,
+                         "channel '%s' consumer ~ consumed key event, seq=%u",
+                         mChannel->getName().c_str(), *outSeq);
+                break;
+            }
+
+            case InputMessage::Type::MOTION: {
+                ssize_t batchIndex = findBatch(mMsg.body.motion.deviceId, mMsg.body.motion.source);
+                if (batchIndex >= 0) {
+                    Batch& batch = mBatches[batchIndex];
+                    if (canAddSample(batch, &mMsg)) {
+                        batch.samples.push_back(mMsg);
+                        ALOGD_IF(DEBUG_TRANSPORT_CONSUMER,
+                                 "channel '%s' consumer ~ appended to batch event",
+                                 mChannel->getName().c_str());
+                        break;
+                    } else if (isPointerEvent(mMsg.body.motion.source) &&
+                               mMsg.body.motion.action == AMOTION_EVENT_ACTION_CANCEL) {
+                        // No need to process events that we are going to cancel anyways
+                        const size_t count = batch.samples.size();
+                        for (size_t i = 0; i < count; i++) {
+                            const InputMessage& msg = batch.samples[i];
+                            sendFinishedSignal(msg.header.seq, false);
+                        }
+                        batch.samples.erase(batch.samples.begin(), batch.samples.begin() + count);
+                        mBatches.erase(mBatches.begin() + batchIndex);
+                    } else {
+                        // We cannot append to the batch in progress, so we need to consume
+                        // the previous batch right now and defer the new message until later.
+                        mMsgDeferred = true;
+                        status_t result = consumeSamples(factory, batch, batch.samples.size(),
+                                                         outSeq, outEvent);
+                        mBatches.erase(mBatches.begin() + batchIndex);
+                        if (result) {
+                            return result;
+                        }
+                        ALOGD_IF(DEBUG_TRANSPORT_CONSUMER,
+                                 "channel '%s' consumer ~ consumed batch event and "
+                                 "deferred current event, seq=%u",
+                                 mChannel->getName().c_str(), *outSeq);
+                        break;
+                    }
+                }
+
+                // Start a new batch if needed.
+                if (mMsg.body.motion.action == AMOTION_EVENT_ACTION_MOVE ||
+                    mMsg.body.motion.action == AMOTION_EVENT_ACTION_HOVER_MOVE) {
+                    Batch batch;
+                    batch.samples.push_back(mMsg);
+                    mBatches.push_back(batch);
+                    ALOGD_IF(DEBUG_TRANSPORT_CONSUMER,
+                             "channel '%s' consumer ~ started batch event",
+                             mChannel->getName().c_str());
+                    break;
+                }
+
+                MotionEvent* motionEvent = factory->createMotionEvent();
+                if (!motionEvent) return NO_MEMORY;
+
+                updateTouchState(mMsg);
+                initializeMotionEvent(*motionEvent, mMsg);
+                *outSeq = mMsg.header.seq;
+                *outEvent = motionEvent;
+
+                ALOGD_IF(DEBUG_TRANSPORT_CONSUMER,
+                         "channel '%s' consumer ~ consumed motion event, seq=%u",
+                         mChannel->getName().c_str(), *outSeq);
+                break;
+            }
+
+            case InputMessage::Type::FINISHED:
+            case InputMessage::Type::TIMELINE: {
+                LOG_ALWAYS_FATAL("Consumed a %s message, which should never be seen by "
+                                 "InputConsumer!",
+                                 ftl::enum_string(mMsg.header.type).c_str());
+                break;
+            }
+
+            case InputMessage::Type::FOCUS: {
+                FocusEvent* focusEvent = factory->createFocusEvent();
+                if (!focusEvent) return NO_MEMORY;
+
+                initializeFocusEvent(*focusEvent, mMsg);
+                *outSeq = mMsg.header.seq;
+                *outEvent = focusEvent;
+                break;
+            }
+
+            case InputMessage::Type::CAPTURE: {
+                CaptureEvent* captureEvent = factory->createCaptureEvent();
+                if (!captureEvent) return NO_MEMORY;
+
+                initializeCaptureEvent(*captureEvent, mMsg);
+                *outSeq = mMsg.header.seq;
+                *outEvent = captureEvent;
+                break;
+            }
+
+            case InputMessage::Type::DRAG: {
+                DragEvent* dragEvent = factory->createDragEvent();
+                if (!dragEvent) return NO_MEMORY;
+
+                initializeDragEvent(*dragEvent, mMsg);
+                *outSeq = mMsg.header.seq;
+                *outEvent = dragEvent;
+                break;
+            }
+
+            case InputMessage::Type::TOUCH_MODE: {
+                TouchModeEvent* touchModeEvent = factory->createTouchModeEvent();
+                if (!touchModeEvent) return NO_MEMORY;
+
+                initializeTouchModeEvent(*touchModeEvent, mMsg);
+                *outSeq = mMsg.header.seq;
+                *outEvent = touchModeEvent;
+                break;
+            }
+        }
+    }
+    return OK;
+}
+
+status_t InputConsumer::consumeBatch(InputEventFactoryInterface* factory, nsecs_t frameTime,
+                                     uint32_t* outSeq, InputEvent** outEvent) {
+    status_t result;
+    for (size_t i = mBatches.size(); i > 0;) {
+        i--;
+        Batch& batch = mBatches[i];
+        if (frameTime < 0) {
+            result = consumeSamples(factory, batch, batch.samples.size(), outSeq, outEvent);
+            mBatches.erase(mBatches.begin() + i);
+            return result;
+        }
+
+        nsecs_t sampleTime = frameTime;
+        if (mResampleTouch) {
+            sampleTime -= std::chrono::nanoseconds(RESAMPLE_LATENCY).count();
+        }
+        ssize_t split = findSampleNoLaterThan(batch, sampleTime);
+        if (split < 0) {
+            continue;
+        }
+
+        result = consumeSamples(factory, batch, split + 1, outSeq, outEvent);
+        const InputMessage* next;
+        if (batch.samples.empty()) {
+            mBatches.erase(mBatches.begin() + i);
+            next = nullptr;
+        } else {
+            next = &batch.samples[0];
+        }
+        if (!result && mResampleTouch) {
+            resampleTouchState(sampleTime, static_cast<MotionEvent*>(*outEvent), next);
+        }
+        return result;
+    }
+
+    return WOULD_BLOCK;
+}
+
+status_t InputConsumer::consumeSamples(InputEventFactoryInterface* factory, Batch& batch,
+                                       size_t count, uint32_t* outSeq, InputEvent** outEvent) {
+    MotionEvent* motionEvent = factory->createMotionEvent();
+    if (!motionEvent) return NO_MEMORY;
+
+    uint32_t chain = 0;
+    for (size_t i = 0; i < count; i++) {
+        InputMessage& msg = batch.samples[i];
+        updateTouchState(msg);
+        if (i) {
+            SeqChain seqChain;
+            seqChain.seq = msg.header.seq;
+            seqChain.chain = chain;
+            mSeqChains.push_back(seqChain);
+            addSample(*motionEvent, msg);
+        } else {
+            initializeMotionEvent(*motionEvent, msg);
+        }
+        chain = msg.header.seq;
+    }
+    batch.samples.erase(batch.samples.begin(), batch.samples.begin() + count);
+
+    *outSeq = chain;
+    *outEvent = motionEvent;
+    return OK;
+}
+
+void InputConsumer::updateTouchState(InputMessage& msg) {
+    if (!mResampleTouch || !isPointerEvent(msg.body.motion.source)) {
+        return;
+    }
+
+    int32_t deviceId = msg.body.motion.deviceId;
+    int32_t source = msg.body.motion.source;
+
+    // Update the touch state history to incorporate the new input message.
+    // If the message is in the past relative to the most recently produced resampled
+    // touch, then use the resampled time and coordinates instead.
+    switch (msg.body.motion.action & AMOTION_EVENT_ACTION_MASK) {
+        case AMOTION_EVENT_ACTION_DOWN: {
+            ssize_t index = findTouchState(deviceId, source);
+            if (index < 0) {
+                mTouchStates.push_back({});
+                index = mTouchStates.size() - 1;
+            }
+            TouchState& touchState = mTouchStates[index];
+            touchState.initialize(deviceId, source);
+            touchState.addHistory(msg);
+            break;
+        }
+
+        case AMOTION_EVENT_ACTION_MOVE: {
+            ssize_t index = findTouchState(deviceId, source);
+            if (index >= 0) {
+                TouchState& touchState = mTouchStates[index];
+                touchState.addHistory(msg);
+                rewriteMessage(touchState, msg);
+            }
+            break;
+        }
+
+        case AMOTION_EVENT_ACTION_POINTER_DOWN: {
+            ssize_t index = findTouchState(deviceId, source);
+            if (index >= 0) {
+                TouchState& touchState = mTouchStates[index];
+                touchState.lastResample.idBits.clearBit(msg.body.motion.getActionId());
+                rewriteMessage(touchState, msg);
+            }
+            break;
+        }
+
+        case AMOTION_EVENT_ACTION_POINTER_UP: {
+            ssize_t index = findTouchState(deviceId, source);
+            if (index >= 0) {
+                TouchState& touchState = mTouchStates[index];
+                rewriteMessage(touchState, msg);
+                touchState.lastResample.idBits.clearBit(msg.body.motion.getActionId());
+            }
+            break;
+        }
+
+        case AMOTION_EVENT_ACTION_SCROLL: {
+            ssize_t index = findTouchState(deviceId, source);
+            if (index >= 0) {
+                TouchState& touchState = mTouchStates[index];
+                rewriteMessage(touchState, msg);
+            }
+            break;
+        }
+
+        case AMOTION_EVENT_ACTION_UP:
+        case AMOTION_EVENT_ACTION_CANCEL: {
+            ssize_t index = findTouchState(deviceId, source);
+            if (index >= 0) {
+                TouchState& touchState = mTouchStates[index];
+                rewriteMessage(touchState, msg);
+                mTouchStates.erase(mTouchStates.begin() + index);
+            }
+            break;
+        }
+    }
+}
+
+/**
+ * Replace the coordinates in msg with the coordinates in lastResample, if necessary.
+ *
+ * If lastResample is no longer valid for a specific pointer (i.e. the lastResample time
+ * is in the past relative to msg and the past two events do not contain identical coordinates),
+ * then invalidate the lastResample data for that pointer.
+ * If the two past events have identical coordinates, then lastResample data for that pointer will
+ * remain valid, and will be used to replace these coordinates. Thus, if a certain coordinate x0 is
+ * resampled to the new value x1, then x1 will always be used to replace x0 until some new value
+ * not equal to x0 is received.
+ */
+void InputConsumer::rewriteMessage(TouchState& state, InputMessage& msg) {
+    nsecs_t eventTime = msg.body.motion.eventTime;
+    for (uint32_t i = 0; i < msg.body.motion.pointerCount; i++) {
+        uint32_t id = msg.body.motion.pointers[i].properties.id;
+        if (state.lastResample.idBits.hasBit(id)) {
+            if (eventTime < state.lastResample.eventTime ||
+                state.recentCoordinatesAreIdentical(id)) {
+                PointerCoords& msgCoords = msg.body.motion.pointers[i].coords;
+                const PointerCoords& resampleCoords = state.lastResample.getPointerById(id);
+                ALOGD_IF(debugResampling(), "[%d] - rewrite (%0.3f, %0.3f), old (%0.3f, %0.3f)", id,
+                         resampleCoords.getX(), resampleCoords.getY(), msgCoords.getX(),
+                         msgCoords.getY());
+                msgCoords.setAxisValue(AMOTION_EVENT_AXIS_X, resampleCoords.getX());
+                msgCoords.setAxisValue(AMOTION_EVENT_AXIS_Y, resampleCoords.getY());
+                msgCoords.isResampled = true;
+            } else {
+                state.lastResample.idBits.clearBit(id);
+            }
+        }
+    }
+}
+
+void InputConsumer::resampleTouchState(nsecs_t sampleTime, MotionEvent* event,
+                                       const InputMessage* next) {
+    if (!mResampleTouch || !(isPointerEvent(event->getSource())) ||
+        event->getAction() != AMOTION_EVENT_ACTION_MOVE) {
+        return;
+    }
+
+    ssize_t index = findTouchState(event->getDeviceId(), event->getSource());
+    if (index < 0) {
+        ALOGD_IF(debugResampling(), "Not resampled, no touch state for device.");
+        return;
+    }
+
+    TouchState& touchState = mTouchStates[index];
+    if (touchState.historySize < 1) {
+        ALOGD_IF(debugResampling(), "Not resampled, no history for device.");
+        return;
+    }
+
+    // Ensure that the current sample has all of the pointers that need to be reported.
+    const History* current = touchState.getHistory(0);
+    size_t pointerCount = event->getPointerCount();
+    for (size_t i = 0; i < pointerCount; i++) {
+        uint32_t id = event->getPointerId(i);
+        if (!current->idBits.hasBit(id)) {
+            ALOGD_IF(debugResampling(), "Not resampled, missing id %d", id);
+            return;
+        }
+    }
+
+    // Find the data to use for resampling.
+    const History* other;
+    History future;
+    float alpha;
+    if (next) {
+        // Interpolate between current sample and future sample.
+        // So current->eventTime <= sampleTime <= future.eventTime.
+        future.initializeFrom(*next);
+        other = &future;
+        nsecs_t delta = future.eventTime - current->eventTime;
+        if (delta < RESAMPLE_MIN_DELTA) {
+            ALOGD_IF(debugResampling(), "Not resampled, delta time is too small: %" PRId64 " ns.",
+                     delta);
+            return;
+        }
+        alpha = float(sampleTime - current->eventTime) / delta;
+    } else if (touchState.historySize >= 2) {
+        // Extrapolate future sample using current sample and past sample.
+        // So other->eventTime <= current->eventTime <= sampleTime.
+        other = touchState.getHistory(1);
+        nsecs_t delta = current->eventTime - other->eventTime;
+        if (delta < RESAMPLE_MIN_DELTA) {
+            ALOGD_IF(debugResampling(), "Not resampled, delta time is too small: %" PRId64 " ns.",
+                     delta);
+            return;
+        } else if (delta > RESAMPLE_MAX_DELTA) {
+            ALOGD_IF(debugResampling(), "Not resampled, delta time is too large: %" PRId64 " ns.",
+                     delta);
+            return;
+        }
+        nsecs_t maxPredict = current->eventTime + std::min(delta / 2, RESAMPLE_MAX_PREDICTION);
+        if (sampleTime > maxPredict) {
+            ALOGD_IF(debugResampling(),
+                     "Sample time is too far in the future, adjusting prediction "
+                     "from %" PRId64 " to %" PRId64 " ns.",
+                     sampleTime - current->eventTime, maxPredict - current->eventTime);
+            sampleTime = maxPredict;
+        }
+        alpha = float(current->eventTime - sampleTime) / delta;
+    } else {
+        ALOGD_IF(debugResampling(), "Not resampled, insufficient data.");
+        return;
+    }
+
+    if (current->eventTime == sampleTime) {
+        // Prevents having 2 events with identical times and coordinates.
+        return;
+    }
+
+    // Resample touch coordinates.
+    History oldLastResample;
+    oldLastResample.initializeFrom(touchState.lastResample);
+    touchState.lastResample.eventTime = sampleTime;
+    touchState.lastResample.idBits.clear();
+    for (size_t i = 0; i < pointerCount; i++) {
+        uint32_t id = event->getPointerId(i);
+        touchState.lastResample.idToIndex[id] = i;
+        touchState.lastResample.idBits.markBit(id);
+        if (oldLastResample.hasPointerId(id) && touchState.recentCoordinatesAreIdentical(id)) {
+            // We maintain the previously resampled value for this pointer (stored in
+            // oldLastResample) when the coordinates for this pointer haven't changed since then.
+            // This way we don't introduce artificial jitter when pointers haven't actually moved.
+            // The isResampled flag isn't cleared as the values don't reflect what the device is
+            // actually reporting.
+
+            // We know here that the coordinates for the pointer haven't changed because we
+            // would've cleared the resampled bit in rewriteMessage if they had. We can't modify
+            // lastResample in place because the mapping from pointer ID to index may have changed.
+            touchState.lastResample.pointers[i] = oldLastResample.getPointerById(id);
+            continue;
+        }
+
+        PointerCoords& resampledCoords = touchState.lastResample.pointers[i];
+        const PointerCoords& currentCoords = current->getPointerById(id);
+        resampledCoords = currentCoords;
+        resampledCoords.isResampled = true;
+        if (other->idBits.hasBit(id) && shouldResampleTool(event->getToolType(i))) {
+            const PointerCoords& otherCoords = other->getPointerById(id);
+            resampledCoords.setAxisValue(AMOTION_EVENT_AXIS_X,
+                                         lerp(currentCoords.getX(), otherCoords.getX(), alpha));
+            resampledCoords.setAxisValue(AMOTION_EVENT_AXIS_Y,
+                                         lerp(currentCoords.getY(), otherCoords.getY(), alpha));
+            ALOGD_IF(debugResampling(),
+                     "[%d] - out (%0.3f, %0.3f), cur (%0.3f, %0.3f), "
+                     "other (%0.3f, %0.3f), alpha %0.3f",
+                     id, resampledCoords.getX(), resampledCoords.getY(), currentCoords.getX(),
+                     currentCoords.getY(), otherCoords.getX(), otherCoords.getY(), alpha);
+        } else {
+            ALOGD_IF(debugResampling(), "[%d] - out (%0.3f, %0.3f), cur (%0.3f, %0.3f)", id,
+                     resampledCoords.getX(), resampledCoords.getY(), currentCoords.getX(),
+                     currentCoords.getY());
+        }
+    }
+
+    event->addSample(sampleTime, touchState.lastResample.pointers);
+}
+
+status_t InputConsumer::sendFinishedSignal(uint32_t seq, bool handled) {
+    ALOGD_IF(DEBUG_TRANSPORT_CONSUMER,
+             "channel '%s' consumer ~ sendFinishedSignal: seq=%u, handled=%s",
+             mChannel->getName().c_str(), seq, toString(handled));
+
+    if (!seq) {
+        ALOGE("Attempted to send a finished signal with sequence number 0.");
+        return BAD_VALUE;
+    }
+
+    // Send finished signals for the batch sequence chain first.
+    size_t seqChainCount = mSeqChains.size();
+    if (seqChainCount) {
+        uint32_t currentSeq = seq;
+        uint32_t chainSeqs[seqChainCount];
+        size_t chainIndex = 0;
+        for (size_t i = seqChainCount; i > 0;) {
+            i--;
+            const SeqChain& seqChain = mSeqChains[i];
+            if (seqChain.seq == currentSeq) {
+                currentSeq = seqChain.chain;
+                chainSeqs[chainIndex++] = currentSeq;
+                mSeqChains.erase(mSeqChains.begin() + i);
+            }
+        }
+        status_t status = OK;
+        while (!status && chainIndex > 0) {
+            chainIndex--;
+            status = sendUnchainedFinishedSignal(chainSeqs[chainIndex], handled);
+        }
+        if (status) {
+            // An error occurred so at least one signal was not sent, reconstruct the chain.
+            for (;;) {
+                SeqChain seqChain;
+                seqChain.seq = chainIndex != 0 ? chainSeqs[chainIndex - 1] : seq;
+                seqChain.chain = chainSeqs[chainIndex];
+                mSeqChains.push_back(seqChain);
+                if (!chainIndex) break;
+                chainIndex--;
+            }
+            return status;
+        }
+    }
+
+    // Send finished signal for the last message in the batch.
+    return sendUnchainedFinishedSignal(seq, handled);
+}
+
+status_t InputConsumer::sendTimeline(int32_t inputEventId,
+                                     std::array<nsecs_t, GraphicsTimeline::SIZE> graphicsTimeline) {
+    ALOGD_IF(DEBUG_TRANSPORT_CONSUMER,
+             "channel '%s' consumer ~ sendTimeline: inputEventId=%" PRId32
+             ", gpuCompletedTime=%" PRId64 ", presentTime=%" PRId64,
+             mChannel->getName().c_str(), inputEventId,
+             graphicsTimeline[GraphicsTimeline::GPU_COMPLETED_TIME],
+             graphicsTimeline[GraphicsTimeline::PRESENT_TIME]);
+
+    InputMessage msg;
+    msg.header.type = InputMessage::Type::TIMELINE;
+    msg.header.seq = 0;
+    msg.body.timeline.eventId = inputEventId;
+    msg.body.timeline.graphicsTimeline = std::move(graphicsTimeline);
+    return mChannel->sendMessage(&msg);
+}
+
+nsecs_t InputConsumer::getConsumeTime(uint32_t seq) const {
+    auto it = mConsumeTimes.find(seq);
+    // Consume time will be missing if either 'finishInputEvent' is called twice, or if it was
+    // called for the wrong (synthetic?) input event. Either way, it is a bug that should be fixed.
+    LOG_ALWAYS_FATAL_IF(it == mConsumeTimes.end(), "Could not find consume time for seq=%" PRIu32,
+                        seq);
+    return it->second;
+}
+
+void InputConsumer::popConsumeTime(uint32_t seq) {
+    mConsumeTimes.erase(seq);
+}
+
+status_t InputConsumer::sendUnchainedFinishedSignal(uint32_t seq, bool handled) {
+    InputMessage msg;
+    msg.header.type = InputMessage::Type::FINISHED;
+    msg.header.seq = seq;
+    msg.body.finished.handled = handled;
+    msg.body.finished.consumeTime = getConsumeTime(seq);
+    status_t result = mChannel->sendMessage(&msg);
+    if (result == OK) {
+        // Remove the consume time if the socket write succeeded. We will not need to ack this
+        // message anymore. If the socket write did not succeed, we will try again and will still
+        // need consume time.
+        popConsumeTime(seq);
+
+        // Trace the event processing timeline - event was just finished
+        ATRACE_ASYNC_END("InputConsumer processing", /*cookie=*/seq);
+    }
+    return result;
+}
+
+bool InputConsumer::hasPendingBatch() const {
+    return !mBatches.empty();
+}
+
+int32_t InputConsumer::getPendingBatchSource() const {
+    if (mBatches.empty()) {
+        return AINPUT_SOURCE_CLASS_NONE;
+    }
+
+    const Batch& batch = mBatches[0];
+    const InputMessage& head = batch.samples[0];
+    return head.body.motion.source;
+}
+
+bool InputConsumer::probablyHasInput() const {
+    return hasPendingBatch() || mChannel->probablyHasInput();
+}
+
+ssize_t InputConsumer::findBatch(int32_t deviceId, int32_t source) const {
+    for (size_t i = 0; i < mBatches.size(); i++) {
+        const Batch& batch = mBatches[i];
+        const InputMessage& head = batch.samples[0];
+        if (head.body.motion.deviceId == deviceId && head.body.motion.source == source) {
+            return i;
+        }
+    }
+    return -1;
+}
+
+ssize_t InputConsumer::findTouchState(int32_t deviceId, int32_t source) const {
+    for (size_t i = 0; i < mTouchStates.size(); i++) {
+        const TouchState& touchState = mTouchStates[i];
+        if (touchState.deviceId == deviceId && touchState.source == source) {
+            return i;
+        }
+    }
+    return -1;
+}
+
+bool InputConsumer::canAddSample(const Batch& batch, const InputMessage* msg) {
+    const InputMessage& head = batch.samples[0];
+    uint32_t pointerCount = msg->body.motion.pointerCount;
+    if (head.body.motion.pointerCount != pointerCount ||
+        head.body.motion.action != msg->body.motion.action) {
+        return false;
+    }
+    for (size_t i = 0; i < pointerCount; i++) {
+        if (head.body.motion.pointers[i].properties != msg->body.motion.pointers[i].properties) {
+            return false;
+        }
+    }
+    return true;
+}
+
+ssize_t InputConsumer::findSampleNoLaterThan(const Batch& batch, nsecs_t time) {
+    size_t numSamples = batch.samples.size();
+    size_t index = 0;
+    while (index < numSamples && batch.samples[index].body.motion.eventTime <= time) {
+        index += 1;
+    }
+    return ssize_t(index) - 1;
+}
+
+std::string InputConsumer::dump() const {
+    std::string out;
+    out = out + "mResampleTouch = " + toString(mResampleTouch) + "\n";
+    out = out + "mChannel = " + mChannel->getName() + "\n";
+    out = out + "mMsgDeferred: " + toString(mMsgDeferred) + "\n";
+    if (mMsgDeferred) {
+        out = out + "mMsg : " + ftl::enum_string(mMsg.header.type) + "\n";
+    }
+    out += "Batches:\n";
+    for (const Batch& batch : mBatches) {
+        out += "    Batch:\n";
+        for (const InputMessage& msg : batch.samples) {
+            out += android::base::StringPrintf("        Message %" PRIu32 ": %s ", msg.header.seq,
+                                               ftl::enum_string(msg.header.type).c_str());
+            switch (msg.header.type) {
+                case InputMessage::Type::KEY: {
+                    out += android::base::StringPrintf("action=%s keycode=%" PRId32,
+                                                       KeyEvent::actionToString(
+                                                               msg.body.key.action),
+                                                       msg.body.key.keyCode);
+                    break;
+                }
+                case InputMessage::Type::MOTION: {
+                    out = out + "action=" + MotionEvent::actionToString(msg.body.motion.action);
+                    for (uint32_t i = 0; i < msg.body.motion.pointerCount; i++) {
+                        const float x = msg.body.motion.pointers[i].coords.getX();
+                        const float y = msg.body.motion.pointers[i].coords.getY();
+                        out += android::base::StringPrintf("\n            Pointer %" PRIu32
+                                                           " : x=%.1f y=%.1f",
+                                                           i, x, y);
+                    }
+                    break;
+                }
+                case InputMessage::Type::FINISHED: {
+                    out += android::base::StringPrintf("handled=%s, consumeTime=%" PRId64,
+                                                       toString(msg.body.finished.handled),
+                                                       msg.body.finished.consumeTime);
+                    break;
+                }
+                case InputMessage::Type::FOCUS: {
+                    out += android::base::StringPrintf("hasFocus=%s",
+                                                       toString(msg.body.focus.hasFocus));
+                    break;
+                }
+                case InputMessage::Type::CAPTURE: {
+                    out += android::base::StringPrintf("hasCapture=%s",
+                                                       toString(msg.body.capture
+                                                                        .pointerCaptureEnabled));
+                    break;
+                }
+                case InputMessage::Type::DRAG: {
+                    out += android::base::StringPrintf("x=%.1f y=%.1f, isExiting=%s",
+                                                       msg.body.drag.x, msg.body.drag.y,
+                                                       toString(msg.body.drag.isExiting));
+                    break;
+                }
+                case InputMessage::Type::TIMELINE: {
+                    const nsecs_t gpuCompletedTime =
+                            msg.body.timeline
+                                    .graphicsTimeline[GraphicsTimeline::GPU_COMPLETED_TIME];
+                    const nsecs_t presentTime =
+                            msg.body.timeline.graphicsTimeline[GraphicsTimeline::PRESENT_TIME];
+                    out += android::base::StringPrintf("inputEventId=%" PRId32
+                                                       ", gpuCompletedTime=%" PRId64
+                                                       ", presentTime=%" PRId64,
+                                                       msg.body.timeline.eventId, gpuCompletedTime,
+                                                       presentTime);
+                    break;
+                }
+                case InputMessage::Type::TOUCH_MODE: {
+                    out += android::base::StringPrintf("isInTouchMode=%s",
+                                                       toString(msg.body.touchMode.isInTouchMode));
+                    break;
+                }
+            }
+            out += "\n";
+        }
+    }
+    if (mBatches.empty()) {
+        out += "    <empty>\n";
+    }
+    out += "mSeqChains:\n";
+    for (const SeqChain& chain : mSeqChains) {
+        out += android::base::StringPrintf("    chain: seq = %" PRIu32 " chain=%" PRIu32, chain.seq,
+                                           chain.chain);
+    }
+    if (mSeqChains.empty()) {
+        out += "    <empty>\n";
+    }
+    out += "mConsumeTimes:\n";
+    for (const auto& [seq, consumeTime] : mConsumeTimes) {
+        out += android::base::StringPrintf("    seq = %" PRIu32 " consumeTime = %" PRId64, seq,
+                                           consumeTime);
+    }
+    if (mConsumeTimes.empty()) {
+        out += "    <empty>\n";
+    }
+    return out;
+}
+
+} // namespace android