ATSParser.cpp revision e332a9181cf6a3155ed1a0fd2afc212ccb1f2753 
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//#define LOG_NDEBUG 0
18#define LOG_TAG "ATSParser"
19#include <utils/Log.h>
20
21#include "ATSParser.h"
22
23#include "AnotherPacketSource.h"
24#include "ESQueue.h"
25#include "include/avc_utils.h"
26
27#include <media/stagefright/foundation/ABitReader.h>
28#include <media/stagefright/foundation/ABuffer.h>
29#include <media/stagefright/foundation/ADebug.h>
30#include <media/stagefright/foundation/AMessage.h>
31#include <media/stagefright/foundation/hexdump.h>
32#include <media/stagefright/MediaDefs.h>
33#include <media/stagefright/MediaErrors.h>
34#include <media/stagefright/MetaData.h>
35#include <utils/KeyedVector.h>
36
37namespace android {
38
39// I want the expression "y" evaluated even if verbose logging is off.
40#define MY_LOGV(x, y) \
41    do { unsigned tmp = y; LOGV(x, tmp); } while (0)
42
43static const size_t kTSPacketSize = 188;
44
45struct ATSParser::Program : public RefBase {
46    Program(unsigned programMapPID);
47
48    bool parsePID(
49            unsigned pid, unsigned payload_unit_start_indicator,
50            ABitReader *br);
51
52    void signalDiscontinuity(bool isASeek);
53
54    sp<MediaSource> getSource(SourceType type);
55
56    int64_t convertPTSToTimestamp(uint64_t PTS);
57
58private:
59    unsigned mProgramMapPID;
60    KeyedVector<unsigned, sp<Stream> > mStreams;
61    bool mFirstPTSValid;
62    uint64_t mFirstPTS;
63
64    void parseProgramMap(ABitReader *br);
65
66    DISALLOW_EVIL_CONSTRUCTORS(Program);
67};
68
69struct ATSParser::Stream : public RefBase {
70    Stream(Program *program, unsigned elementaryPID, unsigned streamType);
71
72    void parse(
73            unsigned payload_unit_start_indicator,
74            ABitReader *br);
75
76    void signalDiscontinuity(bool isASeek);
77
78    sp<MediaSource> getSource(SourceType type);
79
80protected:
81    virtual ~Stream();
82
83private:
84    Program *mProgram;
85    unsigned mElementaryPID;
86    unsigned mStreamType;
87
88    sp<ABuffer> mBuffer;
89    sp<AnotherPacketSource> mSource;
90    bool mPayloadStarted;
91
92    ElementaryStreamQueue mQueue;
93
94    void flush();
95    void parsePES(ABitReader *br);
96
97    void onPayloadData(
98            unsigned PTS_DTS_flags, uint64_t PTS, uint64_t DTS,
99            const uint8_t *data, size_t size);
100
101    void extractAACFrames(const sp<ABuffer> &buffer);
102
103    DISALLOW_EVIL_CONSTRUCTORS(Stream);
104};
105
106////////////////////////////////////////////////////////////////////////////////
107
108ATSParser::Program::Program(unsigned programMapPID)
109    : mProgramMapPID(programMapPID),
110      mFirstPTSValid(false),
111      mFirstPTS(0) {
112}
113
114bool ATSParser::Program::parsePID(
115        unsigned pid, unsigned payload_unit_start_indicator,
116        ABitReader *br) {
117    if (pid == mProgramMapPID) {
118        if (payload_unit_start_indicator) {
119            unsigned skip = br->getBits(8);
120            br->skipBits(skip * 8);
121        }
122
123        parseProgramMap(br);
124        return true;
125    }
126
127    ssize_t index = mStreams.indexOfKey(pid);
128    if (index < 0) {
129        return false;
130    }
131
132    mStreams.editValueAt(index)->parse(
133            payload_unit_start_indicator, br);
134
135    return true;
136}
137
138void ATSParser::Program::signalDiscontinuity(bool isASeek) {
139    for (size_t i = 0; i < mStreams.size(); ++i) {
140        mStreams.editValueAt(i)->signalDiscontinuity(isASeek);
141    }
142}
143
144void ATSParser::Program::parseProgramMap(ABitReader *br) {
145    unsigned table_id = br->getBits(8);
146    LOGV("  table_id = %u", table_id);
147    CHECK_EQ(table_id, 0x02u);
148
149    unsigned section_syntax_indicator = br->getBits(1);
150    LOGV("  section_syntax_indicator = %u", section_syntax_indicator);
151    CHECK_EQ(section_syntax_indicator, 1u);
152
153    CHECK_EQ(br->getBits(1), 0u);
154    MY_LOGV("  reserved = %u", br->getBits(2));
155
156    unsigned section_length = br->getBits(12);
157    LOGV("  section_length = %u", section_length);
158    CHECK((section_length & 0xc00) == 0);
159    CHECK_LE(section_length, 1021u);
160
161    MY_LOGV("  program_number = %u", br->getBits(16));
162    MY_LOGV("  reserved = %u", br->getBits(2));
163    MY_LOGV("  version_number = %u", br->getBits(5));
164    MY_LOGV("  current_next_indicator = %u", br->getBits(1));
165    MY_LOGV("  section_number = %u", br->getBits(8));
166    MY_LOGV("  last_section_number = %u", br->getBits(8));
167    MY_LOGV("  reserved = %u", br->getBits(3));
168    MY_LOGV("  PCR_PID = 0x%04x", br->getBits(13));
169    MY_LOGV("  reserved = %u", br->getBits(4));
170
171    unsigned program_info_length = br->getBits(12);
172    LOGV("  program_info_length = %u", program_info_length);
173    CHECK((program_info_length & 0xc00) == 0);
174
175    br->skipBits(program_info_length * 8);  // skip descriptors
176
177    // infoBytesRemaining is the number of bytes that make up the
178    // variable length section of ES_infos. It does not include the
179    // final CRC.
180    size_t infoBytesRemaining = section_length - 9 - program_info_length - 4;
181
182    while (infoBytesRemaining > 0) {
183        CHECK_GE(infoBytesRemaining, 5u);
184
185        unsigned streamType = br->getBits(8);
186        LOGV("    stream_type = 0x%02x", streamType);
187
188        MY_LOGV("    reserved = %u", br->getBits(3));
189
190        unsigned elementaryPID = br->getBits(13);
191        LOGV("    elementary_PID = 0x%04x", elementaryPID);
192
193        MY_LOGV("    reserved = %u", br->getBits(4));
194
195        unsigned ES_info_length = br->getBits(12);
196        LOGV("    ES_info_length = %u", ES_info_length);
197        CHECK((ES_info_length & 0xc00) == 0);
198
199        CHECK_GE(infoBytesRemaining - 5, ES_info_length);
200
201#if 0
202        br->skipBits(ES_info_length * 8);  // skip descriptors
203#else
204        unsigned info_bytes_remaining = ES_info_length;
205        while (info_bytes_remaining >= 2) {
206            MY_LOGV("      tag = 0x%02x", br->getBits(8));
207
208            unsigned descLength = br->getBits(8);
209            LOGV("      len = %u", descLength);
210
211            CHECK_GE(info_bytes_remaining, 2 + descLength);
212
213            br->skipBits(descLength * 8);
214
215            info_bytes_remaining -= descLength + 2;
216        }
217        CHECK_EQ(info_bytes_remaining, 0u);
218#endif
219
220        ssize_t index = mStreams.indexOfKey(elementaryPID);
221#if 0  // XXX revisit
222        CHECK_LT(index, 0);
223        mStreams.add(elementaryPID,
224                     new Stream(this, elementaryPID, streamType));
225#else
226        if (index < 0) {
227            mStreams.add(elementaryPID,
228                         new Stream(this, elementaryPID, streamType));
229        }
230#endif
231
232        infoBytesRemaining -= 5 + ES_info_length;
233    }
234
235    CHECK_EQ(infoBytesRemaining, 0u);
236
237    MY_LOGV("  CRC = 0x%08x", br->getBits(32));
238}
239
240sp<MediaSource> ATSParser::Program::getSource(SourceType type) {
241    for (size_t i = 0; i < mStreams.size(); ++i) {
242        sp<MediaSource> source = mStreams.editValueAt(i)->getSource(type);
243        if (source != NULL) {
244            return source;
245        }
246    }
247
248    return NULL;
249}
250
251int64_t ATSParser::Program::convertPTSToTimestamp(uint64_t PTS) {
252    if (!mFirstPTSValid) {
253        mFirstPTSValid = true;
254        mFirstPTS = PTS;
255        PTS = 0;
256    } else if (PTS < mFirstPTS) {
257        PTS = 0;
258    } else {
259        PTS -= mFirstPTS;
260    }
261
262    return (PTS * 100) / 9;
263}
264
265////////////////////////////////////////////////////////////////////////////////
266
267ATSParser::Stream::Stream(
268        Program *program, unsigned elementaryPID, unsigned streamType)
269    : mProgram(program),
270      mElementaryPID(elementaryPID),
271      mStreamType(streamType),
272      mBuffer(new ABuffer(128 * 1024)),
273      mPayloadStarted(false),
274      mQueue(streamType == 0x1b
275              ? ElementaryStreamQueue::H264 : ElementaryStreamQueue::AAC) {
276    mBuffer->setRange(0, 0);
277
278    LOGV("new stream PID 0x%02x, type 0x%02x", elementaryPID, streamType);
279}
280
281ATSParser::Stream::~Stream() {
282}
283
284void ATSParser::Stream::parse(
285        unsigned payload_unit_start_indicator, ABitReader *br) {
286    if (payload_unit_start_indicator) {
287        if (mPayloadStarted) {
288            // Otherwise we run the danger of receiving the trailing bytes
289            // of a PES packet that we never saw the start of and assuming
290            // we have a a complete PES packet.
291
292            flush();
293        }
294
295        mPayloadStarted = true;
296    }
297
298    if (!mPayloadStarted) {
299        return;
300    }
301
302    size_t payloadSizeBits = br->numBitsLeft();
303    CHECK((payloadSizeBits % 8) == 0);
304
305    CHECK_LE(mBuffer->size() + payloadSizeBits / 8, mBuffer->capacity());
306
307    memcpy(mBuffer->data() + mBuffer->size(), br->data(), payloadSizeBits / 8);
308    mBuffer->setRange(0, mBuffer->size() + payloadSizeBits / 8);
309}
310
311void ATSParser::Stream::signalDiscontinuity(bool isASeek) {
312    isASeek = false;  // Always signal a "real" discontinuity
313
314    mPayloadStarted = false;
315    mBuffer->setRange(0, 0);
316
317    mQueue.clear();
318
319    if (isASeek) {
320        // This is only a "minor" discontinuity, we stay within the same
321        // bitstream.
322
323        if (mSource != NULL) {
324            mSource->clear();
325        }
326        return;
327    }
328
329    if (mStreamType == 0x1b && mSource != NULL) {
330        // Don't signal discontinuities on audio streams.
331        mSource->queueDiscontinuity();
332    }
333}
334
335void ATSParser::Stream::parsePES(ABitReader *br) {
336    unsigned packet_startcode_prefix = br->getBits(24);
337
338    LOGV("packet_startcode_prefix = 0x%08x", packet_startcode_prefix);
339
340    CHECK_EQ(packet_startcode_prefix, 0x000001u);
341
342    unsigned stream_id = br->getBits(8);
343    LOGV("stream_id = 0x%02x", stream_id);
344
345    unsigned PES_packet_length = br->getBits(16);
346    LOGV("PES_packet_length = %u", PES_packet_length);
347
348    if (stream_id != 0xbc  // program_stream_map
349            && stream_id != 0xbe  // padding_stream
350            && stream_id != 0xbf  // private_stream_2
351            && stream_id != 0xf0  // ECM
352            && stream_id != 0xf1  // EMM
353            && stream_id != 0xff  // program_stream_directory
354            && stream_id != 0xf2  // DSMCC
355            && stream_id != 0xf8) {  // H.222.1 type E
356        CHECK_EQ(br->getBits(2), 2u);
357
358        MY_LOGV("PES_scrambling_control = %u", br->getBits(2));
359        MY_LOGV("PES_priority = %u", br->getBits(1));
360        MY_LOGV("data_alignment_indicator = %u", br->getBits(1));
361        MY_LOGV("copyright = %u", br->getBits(1));
362        MY_LOGV("original_or_copy = %u", br->getBits(1));
363
364        unsigned PTS_DTS_flags = br->getBits(2);
365        LOGV("PTS_DTS_flags = %u", PTS_DTS_flags);
366
367        unsigned ESCR_flag = br->getBits(1);
368        LOGV("ESCR_flag = %u", ESCR_flag);
369
370        unsigned ES_rate_flag = br->getBits(1);
371        LOGV("ES_rate_flag = %u", ES_rate_flag);
372
373        unsigned DSM_trick_mode_flag = br->getBits(1);
374        LOGV("DSM_trick_mode_flag = %u", DSM_trick_mode_flag);
375
376        unsigned additional_copy_info_flag = br->getBits(1);
377        LOGV("additional_copy_info_flag = %u", additional_copy_info_flag);
378
379        MY_LOGV("PES_CRC_flag = %u", br->getBits(1));
380        MY_LOGV("PES_extension_flag = %u", br->getBits(1));
381
382        unsigned PES_header_data_length = br->getBits(8);
383        LOGV("PES_header_data_length = %u", PES_header_data_length);
384
385        unsigned optional_bytes_remaining = PES_header_data_length;
386
387        uint64_t PTS = 0, DTS = 0;
388
389        if (PTS_DTS_flags == 2 || PTS_DTS_flags == 3) {
390            CHECK_GE(optional_bytes_remaining, 5u);
391
392            CHECK_EQ(br->getBits(4), PTS_DTS_flags);
393
394            PTS = ((uint64_t)br->getBits(3)) << 30;
395            CHECK_EQ(br->getBits(1), 1u);
396            PTS |= ((uint64_t)br->getBits(15)) << 15;
397            CHECK_EQ(br->getBits(1), 1u);
398            PTS |= br->getBits(15);
399            CHECK_EQ(br->getBits(1), 1u);
400
401            LOGV("PTS = %llu", PTS);
402            // LOGI("PTS = %.2f secs", PTS / 90000.0f);
403
404            optional_bytes_remaining -= 5;
405
406            if (PTS_DTS_flags == 3) {
407                CHECK_GE(optional_bytes_remaining, 5u);
408
409                CHECK_EQ(br->getBits(4), 1u);
410
411                DTS = ((uint64_t)br->getBits(3)) << 30;
412                CHECK_EQ(br->getBits(1), 1u);
413                DTS |= ((uint64_t)br->getBits(15)) << 15;
414                CHECK_EQ(br->getBits(1), 1u);
415                DTS |= br->getBits(15);
416                CHECK_EQ(br->getBits(1), 1u);
417
418                LOGV("DTS = %llu", DTS);
419
420                optional_bytes_remaining -= 5;
421            }
422        }
423
424        if (ESCR_flag) {
425            CHECK_GE(optional_bytes_remaining, 6u);
426
427            br->getBits(2);
428
429            uint64_t ESCR = ((uint64_t)br->getBits(3)) << 30;
430            CHECK_EQ(br->getBits(1), 1u);
431            ESCR |= ((uint64_t)br->getBits(15)) << 15;
432            CHECK_EQ(br->getBits(1), 1u);
433            ESCR |= br->getBits(15);
434            CHECK_EQ(br->getBits(1), 1u);
435
436            LOGV("ESCR = %llu", ESCR);
437            MY_LOGV("ESCR_extension = %u", br->getBits(9));
438
439            CHECK_EQ(br->getBits(1), 1u);
440
441            optional_bytes_remaining -= 6;
442        }
443
444        if (ES_rate_flag) {
445            CHECK_GE(optional_bytes_remaining, 3u);
446
447            CHECK_EQ(br->getBits(1), 1u);
448            MY_LOGV("ES_rate = %u", br->getBits(22));
449            CHECK_EQ(br->getBits(1), 1u);
450
451            optional_bytes_remaining -= 3;
452        }
453
454        br->skipBits(optional_bytes_remaining * 8);
455
456        // ES data follows.
457
458        if (PES_packet_length != 0) {
459            CHECK_GE(PES_packet_length, PES_header_data_length + 3);
460
461            unsigned dataLength =
462                PES_packet_length - 3 - PES_header_data_length;
463
464            CHECK_GE(br->numBitsLeft(), dataLength * 8);
465
466            onPayloadData(
467                    PTS_DTS_flags, PTS, DTS, br->data(), dataLength);
468
469            br->skipBits(dataLength * 8);
470        } else {
471            onPayloadData(
472                    PTS_DTS_flags, PTS, DTS,
473                    br->data(), br->numBitsLeft() / 8);
474
475            size_t payloadSizeBits = br->numBitsLeft();
476            CHECK((payloadSizeBits % 8) == 0);
477
478            LOGV("There's %d bytes of payload.", payloadSizeBits / 8);
479        }
480    } else if (stream_id == 0xbe) {  // padding_stream
481        CHECK_NE(PES_packet_length, 0u);
482        br->skipBits(PES_packet_length * 8);
483    } else {
484        CHECK_NE(PES_packet_length, 0u);
485        br->skipBits(PES_packet_length * 8);
486    }
487}
488
489void ATSParser::Stream::flush() {
490    if (mBuffer->size() == 0) {
491        return;
492    }
493
494    LOGV("flushing stream 0x%04x size = %d", mElementaryPID, mBuffer->size());
495
496    ABitReader br(mBuffer->data(), mBuffer->size());
497    parsePES(&br);
498
499    mBuffer->setRange(0, 0);
500}
501
502void ATSParser::Stream::onPayloadData(
503        unsigned PTS_DTS_flags, uint64_t PTS, uint64_t DTS,
504        const uint8_t *data, size_t size) {
505    LOGV("onPayloadData mStreamType=0x%02x", mStreamType);
506
507    CHECK(PTS_DTS_flags == 2 || PTS_DTS_flags == 3);
508    int64_t timeUs = mProgram->convertPTSToTimestamp(PTS);
509
510    status_t err = mQueue.appendData(data, size, timeUs);
511    CHECK_EQ(err, (status_t)OK);
512
513    sp<ABuffer> accessUnit;
514    while ((accessUnit = mQueue.dequeueAccessUnit()) != NULL) {
515        if (mSource == NULL) {
516            sp<MetaData> meta = mQueue.getFormat();
517
518            if (meta != NULL) {
519                LOGV("created source!");
520                mSource = new AnotherPacketSource(meta);
521                mSource->queueAccessUnit(accessUnit);
522            }
523        } else if (mQueue.getFormat() != NULL) {
524            // After a discontinuity we invalidate the queue's format
525            // and won't enqueue any access units to the source until
526            // the queue has reestablished the new format.
527            mSource->queueAccessUnit(accessUnit);
528        }
529    }
530}
531
532sp<MediaSource> ATSParser::Stream::getSource(SourceType type) {
533    if ((type == AVC_VIDEO && mStreamType == 0x1b)
534        || (type == MPEG2ADTS_AUDIO && mStreamType == 0x0f)) {
535        return mSource;
536    }
537
538    return NULL;
539}
540
541////////////////////////////////////////////////////////////////////////////////
542
543ATSParser::ATSParser() {
544}
545
546ATSParser::~ATSParser() {
547}
548
549void ATSParser::feedTSPacket(const void *data, size_t size) {
550    CHECK_EQ(size, kTSPacketSize);
551
552    ABitReader br((const uint8_t *)data, kTSPacketSize);
553    parseTS(&br);
554}
555
556void ATSParser::signalDiscontinuity(bool isASeek) {
557    for (size_t i = 0; i < mPrograms.size(); ++i) {
558        mPrograms.editItemAt(i)->signalDiscontinuity(isASeek);
559    }
560}
561
562void ATSParser::parseProgramAssociationTable(ABitReader *br) {
563    unsigned table_id = br->getBits(8);
564    LOGV("  table_id = %u", table_id);
565    CHECK_EQ(table_id, 0x00u);
566
567    unsigned section_syntax_indictor = br->getBits(1);
568    LOGV("  section_syntax_indictor = %u", section_syntax_indictor);
569    CHECK_EQ(section_syntax_indictor, 1u);
570
571    CHECK_EQ(br->getBits(1), 0u);
572    MY_LOGV("  reserved = %u", br->getBits(2));
573
574    unsigned section_length = br->getBits(12);
575    LOGV("  section_length = %u", section_length);
576    CHECK((section_length & 0xc00) == 0);
577
578    MY_LOGV("  transport_stream_id = %u", br->getBits(16));
579    MY_LOGV("  reserved = %u", br->getBits(2));
580    MY_LOGV("  version_number = %u", br->getBits(5));
581    MY_LOGV("  current_next_indicator = %u", br->getBits(1));
582    MY_LOGV("  section_number = %u", br->getBits(8));
583    MY_LOGV("  last_section_number = %u", br->getBits(8));
584
585    size_t numProgramBytes = (section_length - 5 /* header */ - 4 /* crc */);
586    CHECK_EQ((numProgramBytes % 4), 0u);
587
588    for (size_t i = 0; i < numProgramBytes / 4; ++i) {
589        unsigned program_number = br->getBits(16);
590        LOGV("    program_number = %u", program_number);
591
592        MY_LOGV("    reserved = %u", br->getBits(3));
593
594        if (program_number == 0) {
595            MY_LOGV("    network_PID = 0x%04x", br->getBits(13));
596        } else {
597            unsigned programMapPID = br->getBits(13);
598
599            LOGV("    program_map_PID = 0x%04x", programMapPID);
600
601            mPrograms.push(new Program(programMapPID));
602        }
603    }
604
605    MY_LOGV("  CRC = 0x%08x", br->getBits(32));
606}
607
608void ATSParser::parsePID(
609        ABitReader *br, unsigned PID,
610        unsigned payload_unit_start_indicator) {
611    if (PID == 0) {
612        if (payload_unit_start_indicator) {
613            unsigned skip = br->getBits(8);
614            br->skipBits(skip * 8);
615        }
616        parseProgramAssociationTable(br);
617        return;
618    }
619
620    bool handled = false;
621    for (size_t i = 0; i < mPrograms.size(); ++i) {
622        if (mPrograms.editItemAt(i)->parsePID(
623                    PID, payload_unit_start_indicator, br)) {
624            handled = true;
625            break;
626        }
627    }
628
629    if (!handled) {
630        LOGV("PID 0x%04x not handled.", PID);
631    }
632}
633
634void ATSParser::parseAdaptationField(ABitReader *br) {
635    unsigned adaptation_field_length = br->getBits(8);
636    if (adaptation_field_length > 0) {
637        br->skipBits(adaptation_field_length * 8);  // XXX
638    }
639}
640
641void ATSParser::parseTS(ABitReader *br) {
642    LOGV("---");
643
644    unsigned sync_byte = br->getBits(8);
645    CHECK_EQ(sync_byte, 0x47u);
646
647    MY_LOGV("transport_error_indicator = %u", br->getBits(1));
648
649    unsigned payload_unit_start_indicator = br->getBits(1);
650    LOGV("payload_unit_start_indicator = %u", payload_unit_start_indicator);
651
652    MY_LOGV("transport_priority = %u", br->getBits(1));
653
654    unsigned PID = br->getBits(13);
655    LOGV("PID = 0x%04x", PID);
656
657    MY_LOGV("transport_scrambling_control = %u", br->getBits(2));
658
659    unsigned adaptation_field_control = br->getBits(2);
660    LOGV("adaptation_field_control = %u", adaptation_field_control);
661
662    unsigned continuity_counter = br->getBits(4);
663    LOGV("continuity_counter = %u", continuity_counter);
664
665    // LOGI("PID = 0x%04x, continuity_counter = %u", PID, continuity_counter);
666
667    if (adaptation_field_control == 2 || adaptation_field_control == 3) {
668        parseAdaptationField(br);
669    }
670
671    if (adaptation_field_control == 1 || adaptation_field_control == 3) {
672        parsePID(br, PID, payload_unit_start_indicator);
673    }
674}
675
676sp<MediaSource> ATSParser::getSource(SourceType type) {
677    for (size_t i = 0; i < mPrograms.size(); ++i) {
678        sp<MediaSource> source = mPrograms.editItemAt(i)->getSource(type);
679
680        if (source != NULL) {
681            return source;
682        }
683    }
684
685    return NULL;
686}
687
688}  // namespace android
689