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diff --git a/include/ui/InputTransport.h b/include/ui/InputTransport.h
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+/*
+ * Copyright (C) 2010 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 _UI_INPUT_TRANSPORT_H
+#define _UI_INPUT_TRANSPORT_H
+
+/**
+ * Native input transport.
+ *
+ * Uses anonymous shared memory as a whiteboard for sending input events from an
+ * InputPublisher to an InputConsumer and ensuring appropriate synchronization.
+ * One interesting feature is that published events can be updated in place as long as they
+ * have not yet been consumed.
+ *
+ * The InputPublisher and InputConsumer only take care of transferring event data
+ * over an InputChannel and sending synchronization signals.  The InputDispatcher and InputQueue
+ * build on these abstractions to add multiplexing and queueing.
+ */
+
+#include <semaphore.h>
+#include <ui/Input.h>
+#include <utils/Errors.h>
+#include <utils/Timers.h>
+#include <utils/RefBase.h>
+#include <utils/String8.h>
+
+namespace android {
+
+/*
+ * An input channel consists of a shared memory buffer and a pair of pipes
+ * used to send input messages from an InputPublisher to an InputConsumer
+ * across processes.  Each channel has a descriptive name for debugging purposes.
+ *
+ * Each endpoint has its own InputChannel object that specifies its own file descriptors.
+ *
+ * The input channel is closed when all references to it are released.
+ */
+class InputChannel : public RefBase {
+protected:
+    virtual ~InputChannel();
+
+public:
+    InputChannel(const String8& name, int32_t ashmemFd, int32_t receivePipeFd,
+            int32_t sendPipeFd);
+
+    /* Creates a pair of input channels and their underlying shared memory buffers
+     * and pipes.
+     *
+     * Returns OK on success.
+     */
+    static status_t openInputChannelPair(const String8& name,
+            InputChannel** outServerChannel, InputChannel** outClientChannel);
+
+    inline String8 getName() const { return mName; }
+    inline int32_t getAshmemFd() const { return mAshmemFd; }
+    inline int32_t getReceivePipeFd() const { return mReceivePipeFd; }
+    inline int32_t getSendPipeFd() const { return mSendPipeFd; }
+
+    /* Sends a signal to the other endpoint.
+     *
+     * Returns OK on success.
+     * Errors probably indicate that the channel is broken.
+     */
+    status_t sendSignal(char signal);
+
+    /* Receives a signal send by the other endpoint.
+     * (Should only call this after poll() indicates that the receivePipeFd has available input.)
+     *
+     * Returns OK on success.
+     * Returns WOULD_BLOCK if there is no signal present.
+     * Other errors probably indicate that the channel is broken.
+     */
+    status_t receiveSignal(char* outSignal);
+
+private:
+    String8 mName;
+    int32_t mAshmemFd;
+    int32_t mReceivePipeFd;
+    int32_t mSendPipeFd;
+};
+
+/*
+ * Private intermediate representation of input events as messages written into an
+ * ashmem buffer.
+ */
+struct InputMessage {
+    /* Semaphore count is set to 1 when the message is published.
+     * It becomes 0 transiently while the publisher updates the message.
+     * It becomes 0 permanently when the consumer consumes the message.
+     */
+    sem_t semaphore;
+
+    /* Initialized to false by the publisher.
+     * Set to true by the consumer when it consumes the message.
+     */
+    bool consumed;
+
+    int32_t type;
+
+    struct SampleData {
+        nsecs_t eventTime;
+        PointerCoords coords[0]; // variable length
+    };
+
+    int32_t deviceId;
+    int32_t nature;
+
+    union {
+        struct {
+            int32_t action;
+            int32_t flags;
+            int32_t keyCode;
+            int32_t scanCode;
+            int32_t metaState;
+            int32_t repeatCount;
+            nsecs_t downTime;
+            nsecs_t eventTime;
+        } key;
+
+        struct {
+            int32_t action;
+            int32_t metaState;
+            int32_t edgeFlags;
+            nsecs_t downTime;
+            float xOffset;
+            float yOffset;
+            float xPrecision;
+            float yPrecision;
+            size_t pointerCount;
+            int32_t pointerIds[MAX_POINTERS];
+            size_t sampleCount;
+            SampleData sampleData[0]; // variable length
+        } motion;
+    };
+
+    /* Gets the number of bytes to add to step to the next SampleData object in a motion
+     * event message for a given number of pointers.
+     */
+    static inline size_t sampleDataStride(size_t pointerCount) {
+        return sizeof(InputMessage::SampleData) + pointerCount * sizeof(PointerCoords);
+    }
+
+    /* Adds the SampleData stride to the given pointer. */
+    static inline SampleData* sampleDataPtrIncrement(SampleData* ptr, size_t stride) {
+        return reinterpret_cast<InputMessage::SampleData*>(reinterpret_cast<char*>(ptr) + stride);
+    }
+};
+
+/*
+ * Publishes input events to an anonymous shared memory buffer.
+ * Uses atomic operations to coordinate shared access with a single concurrent consumer.
+ */
+class InputPublisher {
+public:
+    /* Creates a publisher associated with an input channel. */
+    explicit InputPublisher(const sp<InputChannel>& channel);
+
+    /* Destroys the publisher and releases its input channel. */
+    ~InputPublisher();
+
+    /* Gets the underlying input channel. */
+    inline sp<InputChannel> getChannel() { return mChannel; }
+
+    /* Prepares the publisher for use.  Must be called before it is used.
+     * Returns OK on success.
+     *
+     * This method implicitly calls reset(). */
+    status_t initialize();
+
+    /* Resets the publisher to its initial state and unpins its ashmem buffer.
+     * Returns OK on success.
+     *
+     * Should be called after an event has been consumed to release resources used by the
+     * publisher until the next event is ready to be published.
+     */
+    status_t reset();
+
+    /* Publishes a key event to the ashmem buffer.
+     *
+     * Returns OK on success.
+     * Returns INVALID_OPERATION if the publisher has not been reset.
+     */
+    status_t publishKeyEvent(
+            int32_t deviceId,
+            int32_t nature,
+            int32_t action,
+            int32_t flags,
+            int32_t keyCode,
+            int32_t scanCode,
+            int32_t metaState,
+            int32_t repeatCount,
+            nsecs_t downTime,
+            nsecs_t eventTime);
+
+    /* Publishes a motion event to the ashmem buffer.
+     *
+     * Returns OK on success.
+     * Returns INVALID_OPERATION if the publisher has not been reset.
+     * Returns BAD_VALUE if pointerCount is less than 1 or greater than MAX_POINTERS.
+     */
+    status_t publishMotionEvent(
+            int32_t deviceId,
+            int32_t nature,
+            int32_t action,
+            int32_t edgeFlags,
+            int32_t metaState,
+            float xOffset,
+            float yOffset,
+            float xPrecision,
+            float yPrecision,
+            nsecs_t downTime,
+            nsecs_t eventTime,
+            size_t pointerCount,
+            const int32_t* pointerIds,
+            const PointerCoords* pointerCoords);
+
+    /* Appends a motion sample to a motion event unless already consumed.
+     *
+     * Returns OK on success.
+     * Returns INVALID_OPERATION if the current event is not a MOTION_EVENT_ACTION_MOVE event.
+     * Returns FAILED_TRANSACTION if the current event has already been consumed.
+     * Returns NO_MEMORY if the buffer is full and no additional samples can be added.
+     */
+    status_t appendMotionSample(
+            nsecs_t eventTime,
+            const PointerCoords* pointerCoords);
+
+    /* Sends a dispatch signal to the consumer to inform it that a new message is available.
+     *
+     * Returns OK on success.
+     * Errors probably indicate that the channel is broken.
+     */
+    status_t sendDispatchSignal();
+
+    /* Receives the finished signal from the consumer in reply to the original dispatch signal.
+     *
+     * Returns OK on success.
+     * Returns WOULD_BLOCK if there is no signal present.
+     * Other errors probably indicate that the channel is broken.
+     */
+    status_t receiveFinishedSignal();
+
+private:
+    sp<InputChannel> mChannel;
+
+    size_t mAshmemSize;
+    InputMessage* mSharedMessage;
+    bool mPinned;
+    bool mSemaphoreInitialized;
+    bool mWasDispatched;
+
+    size_t mMotionEventPointerCount;
+    InputMessage::SampleData* mMotionEventSampleDataTail;
+    size_t mMotionEventSampleDataStride;
+
+    status_t publishInputEvent(
+            int32_t type,
+            int32_t deviceId,
+            int32_t nature);
+};
+
+/*
+ * Consumes input events from an anonymous shared memory buffer.
+ * Uses atomic operations to coordinate shared access with a single concurrent publisher.
+ */
+class InputConsumer {
+public:
+    /* Creates a consumer associated with an input channel. */
+    explicit InputConsumer(const sp<InputChannel>& channel);
+
+    /* Destroys the consumer and releases its input channel. */
+    ~InputConsumer();
+
+    /* Gets the underlying input channel. */
+    inline sp<InputChannel> getChannel() { return mChannel; }
+
+    /* Prepares the consumer for use.  Must be called before it is used. */
+    status_t initialize();
+
+    /* Consumes the input event in the buffer and copies its contents into
+     * an InputEvent object created using the specified factory.
+     * This operation will block if the publisher is updating the event.
+     *
+     * Returns OK on success.
+     * Returns INVALID_OPERATION if there is no currently published event.
+     * Returns NO_MEMORY if the event could not be created.
+     */
+    status_t consume(InputEventFactoryInterface* factory, InputEvent** event);
+
+    /* Sends a finished signal to the publisher to inform it that the current message is
+     * finished processing.
+     *
+     * Returns OK on success.
+     * Errors probably indicate that the channel is broken.
+     */
+    status_t sendFinishedSignal();
+
+    /* Receives the dispatched signal from the publisher.
+     *
+     * Returns OK on success.
+     * Returns WOULD_BLOCK if there is no signal present.
+     * Other errors probably indicate that the channel is broken.
+     */
+    status_t receiveDispatchSignal();
+
+private:
+    sp<InputChannel> mChannel;
+
+    size_t mAshmemSize;
+    InputMessage* mSharedMessage;
+
+    void populateKeyEvent(KeyEvent* keyEvent) const;
+    void populateMotionEvent(MotionEvent* motionEvent) const;
+};
+
+} // namespace android
+
+#endif // _UI_INPUT_TRANSPORT_H