InputTransport.h revision d76b67c340d1564abf8d14d976fdaf83bf2b3320 
1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef _UI_INPUT_TRANSPORT_H
18#define _UI_INPUT_TRANSPORT_H
19
20/**
21 * Native input transport.
22 *
23 * Uses anonymous shared memory as a whiteboard for sending input events from an
24 * InputPublisher to an InputConsumer and ensuring appropriate synchronization.
25 * One interesting feature is that published events can be updated in place as long as they
26 * have not yet been consumed.
27 *
28 * The InputPublisher and InputConsumer only take care of transferring event data
29 * over an InputChannel and sending synchronization signals.  The InputDispatcher and InputQueue
30 * build on these abstractions to add multiplexing and queueing.
31 */
32
33#include <semaphore.h>
34#include <ui/Input.h>
35#include <utils/Errors.h>
36#include <utils/PollLoop.h>
37#include <utils/Timers.h>
38#include <utils/RefBase.h>
39#include <utils/String8.h>
40
41namespace android {
42
43/*
44 * An input channel consists of a shared memory buffer and a pair of pipes
45 * used to send input messages from an InputPublisher to an InputConsumer
46 * across processes.  Each channel has a descriptive name for debugging purposes.
47 *
48 * Each endpoint has its own InputChannel object that specifies its own file descriptors.
49 *
50 * The input channel is closed when all references to it are released.
51 */
52class InputChannel : public RefBase {
53protected:
54    virtual ~InputChannel();
55
56public:
57    InputChannel(const String8& name, int32_t ashmemFd, int32_t receivePipeFd,
58            int32_t sendPipeFd);
59
60    /* Creates a pair of input channels and their underlying shared memory buffers
61     * and pipes.
62     *
63     * Returns OK on success.
64     */
65    static status_t openInputChannelPair(const String8& name,
66            sp<InputChannel>& outServerChannel, sp<InputChannel>& outClientChannel);
67
68    inline String8 getName() const { return mName; }
69    inline int32_t getAshmemFd() const { return mAshmemFd; }
70    inline int32_t getReceivePipeFd() const { return mReceivePipeFd; }
71    inline int32_t getSendPipeFd() const { return mSendPipeFd; }
72
73    /* Sends a signal to the other endpoint.
74     *
75     * Returns OK on success.
76     * Returns DEAD_OBJECT if the channel's peer has been closed.
77     * Other errors probably indicate that the channel is broken.
78     */
79    status_t sendSignal(char signal);
80
81    /* Receives a signal send by the other endpoint.
82     * (Should only call this after poll() indicates that the receivePipeFd has available input.)
83     *
84     * Returns OK on success.
85     * Returns WOULD_BLOCK if there is no signal present.
86     * Returns DEAD_OBJECT if the channel's peer has been closed.
87     * Other errors probably indicate that the channel is broken.
88     */
89    status_t receiveSignal(char* outSignal);
90
91private:
92    String8 mName;
93    int32_t mAshmemFd;
94    int32_t mReceivePipeFd;
95    int32_t mSendPipeFd;
96};
97
98/*
99 * Private intermediate representation of input events as messages written into an
100 * ashmem buffer.
101 */
102struct InputMessage {
103    /* Semaphore count is set to 1 when the message is published.
104     * It becomes 0 transiently while the publisher updates the message.
105     * It becomes 0 permanently when the consumer consumes the message.
106     */
107    sem_t semaphore;
108
109    /* Initialized to false by the publisher.
110     * Set to true by the consumer when it consumes the message.
111     */
112    bool consumed;
113
114    int32_t type;
115
116    struct SampleData {
117        nsecs_t eventTime;
118        PointerCoords coords[0]; // variable length
119    };
120
121    int32_t deviceId;
122    int32_t nature;
123
124    union {
125        struct {
126            int32_t action;
127            int32_t flags;
128            int32_t keyCode;
129            int32_t scanCode;
130            int32_t metaState;
131            int32_t repeatCount;
132            nsecs_t downTime;
133            nsecs_t eventTime;
134        } key;
135
136        struct {
137            int32_t action;
138            int32_t metaState;
139            int32_t edgeFlags;
140            nsecs_t downTime;
141            float xOffset;
142            float yOffset;
143            float xPrecision;
144            float yPrecision;
145            size_t pointerCount;
146            int32_t pointerIds[MAX_POINTERS];
147            size_t sampleCount;
148            SampleData sampleData[0]; // variable length
149        } motion;
150    };
151
152    /* Gets the number of bytes to add to step to the next SampleData object in a motion
153     * event message for a given number of pointers.
154     */
155    static inline size_t sampleDataStride(size_t pointerCount) {
156        return sizeof(InputMessage::SampleData) + pointerCount * sizeof(PointerCoords);
157    }
158
159    /* Adds the SampleData stride to the given pointer. */
160    static inline SampleData* sampleDataPtrIncrement(SampleData* ptr, size_t stride) {
161        return reinterpret_cast<InputMessage::SampleData*>(reinterpret_cast<char*>(ptr) + stride);
162    }
163};
164
165/*
166 * Publishes input events to an anonymous shared memory buffer.
167 * Uses atomic operations to coordinate shared access with a single concurrent consumer.
168 */
169class InputPublisher {
170public:
171    /* Creates a publisher associated with an input channel. */
172    explicit InputPublisher(const sp<InputChannel>& channel);
173
174    /* Destroys the publisher and releases its input channel. */
175    ~InputPublisher();
176
177    /* Gets the underlying input channel. */
178    inline sp<InputChannel> getChannel() { return mChannel; }
179
180    /* Prepares the publisher for use.  Must be called before it is used.
181     * Returns OK on success.
182     *
183     * This method implicitly calls reset(). */
184    status_t initialize();
185
186    /* Resets the publisher to its initial state and unpins its ashmem buffer.
187     * Returns OK on success.
188     *
189     * Should be called after an event has been consumed to release resources used by the
190     * publisher until the next event is ready to be published.
191     */
192    status_t reset();
193
194    /* Publishes a key event to the ashmem buffer.
195     *
196     * Returns OK on success.
197     * Returns INVALID_OPERATION if the publisher has not been reset.
198     */
199    status_t publishKeyEvent(
200            int32_t deviceId,
201            int32_t nature,
202            int32_t action,
203            int32_t flags,
204            int32_t keyCode,
205            int32_t scanCode,
206            int32_t metaState,
207            int32_t repeatCount,
208            nsecs_t downTime,
209            nsecs_t eventTime);
210
211    /* Publishes a motion event to the ashmem buffer.
212     *
213     * Returns OK on success.
214     * Returns INVALID_OPERATION if the publisher has not been reset.
215     * Returns BAD_VALUE if pointerCount is less than 1 or greater than MAX_POINTERS.
216     */
217    status_t publishMotionEvent(
218            int32_t deviceId,
219            int32_t nature,
220            int32_t action,
221            int32_t edgeFlags,
222            int32_t metaState,
223            float xOffset,
224            float yOffset,
225            float xPrecision,
226            float yPrecision,
227            nsecs_t downTime,
228            nsecs_t eventTime,
229            size_t pointerCount,
230            const int32_t* pointerIds,
231            const PointerCoords* pointerCoords);
232
233    /* Appends a motion sample to a motion event unless already consumed.
234     *
235     * Returns OK on success.
236     * Returns INVALID_OPERATION if the current event is not a MOTION_EVENT_ACTION_MOVE event.
237     * Returns FAILED_TRANSACTION if the current event has already been consumed.
238     * Returns NO_MEMORY if the buffer is full and no additional samples can be added.
239     */
240    status_t appendMotionSample(
241            nsecs_t eventTime,
242            const PointerCoords* pointerCoords);
243
244    /* Sends a dispatch signal to the consumer to inform it that a new message is available.
245     *
246     * Returns OK on success.
247     * Errors probably indicate that the channel is broken.
248     */
249    status_t sendDispatchSignal();
250
251    /* Receives the finished signal from the consumer in reply to the original dispatch signal.
252     *
253     * Returns OK on success.
254     * Returns WOULD_BLOCK if there is no signal present.
255     * Other errors probably indicate that the channel is broken.
256     */
257    status_t receiveFinishedSignal();
258
259private:
260    sp<InputChannel> mChannel;
261
262    size_t mAshmemSize;
263    InputMessage* mSharedMessage;
264    bool mPinned;
265    bool mSemaphoreInitialized;
266    bool mWasDispatched;
267
268    size_t mMotionEventPointerCount;
269    InputMessage::SampleData* mMotionEventSampleDataTail;
270    size_t mMotionEventSampleDataStride;
271
272    status_t publishInputEvent(
273            int32_t type,
274            int32_t deviceId,
275            int32_t nature);
276};
277
278/*
279 * Consumes input events from an anonymous shared memory buffer.
280 * Uses atomic operations to coordinate shared access with a single concurrent publisher.
281 */
282class InputConsumer {
283public:
284    /* Creates a consumer associated with an input channel. */
285    explicit InputConsumer(const sp<InputChannel>& channel);
286
287    /* Destroys the consumer and releases its input channel. */
288    ~InputConsumer();
289
290    /* Gets the underlying input channel. */
291    inline sp<InputChannel> getChannel() { return mChannel; }
292
293    /* Prepares the consumer for use.  Must be called before it is used. */
294    status_t initialize();
295
296    /* Consumes the input event in the buffer and copies its contents into
297     * an InputEvent object created using the specified factory.
298     * This operation will block if the publisher is updating the event.
299     *
300     * Returns OK on success.
301     * Returns INVALID_OPERATION if there is no currently published event.
302     * Returns NO_MEMORY if the event could not be created.
303     */
304    status_t consume(InputEventFactoryInterface* factory, InputEvent** outEvent);
305
306    /* Sends a finished signal to the publisher to inform it that the current message is
307     * finished processing.
308     *
309     * Returns OK on success.
310     * Errors probably indicate that the channel is broken.
311     */
312    status_t sendFinishedSignal();
313
314    /* Receives the dispatched signal from the publisher.
315     *
316     * Returns OK on success.
317     * Returns WOULD_BLOCK if there is no signal present.
318     * Other errors probably indicate that the channel is broken.
319     */
320    status_t receiveDispatchSignal();
321
322private:
323    sp<InputChannel> mChannel;
324
325    size_t mAshmemSize;
326    InputMessage* mSharedMessage;
327
328    void populateKeyEvent(KeyEvent* keyEvent) const;
329    void populateMotionEvent(MotionEvent* motionEvent) const;
330};
331
332} // namespace android
333
334#endif // _UI_INPUT_TRANSPORT_H
335