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Commit 58c1e6d0 authored by Phil Burk's avatar Phil Burk
Browse files

aaudio: protect MonotonicCounter from overflow 

Use __builtin_sub_overflow.

Bug: 214726263
Test: atest test_monotonic_counter
Test: Run OboeTester with Legacy output for 13 hours.
Change-Id: Ie3cbf155c3059f50c17a32361c203265d63dc31b
parent b4f42a9b

media/libaaudio/src/legacy/AudioStreamRecord.cpp

+1 −1
Original line number Diff line number Diff line
@@ -557,7 +557,7 @@ int64_t AudioStreamRecord::getFramesWritten() { 
        case AAUDIO_STREAM_STATE_STARTED:

            result = mAudioRecord->getPosition(&position);

            if (result == OK) {

                mFramesWritten.update32(position);

                mFramesWritten.update32((int32_t)position);

            }

            break;

        case AAUDIO_STREAM_STATE_STOPPING:

media/libaaudio/src/legacy/AudioStreamTrack.cpp

+1 −1
Original line number Diff line number Diff line
@@ -508,7 +508,7 @@ int64_t AudioStreamTrack::getFramesRead() { 
    case AAUDIO_STREAM_STATE_PAUSED:

        result = mAudioTrack->getPosition(&position);

        if (result == OK) {

            mFramesRead.update32(position);

            mFramesRead.update32((int32_t)position);

        }

        break;

    default:

media/libaaudio/src/utility/MonotonicCounter.h

+8 −3
Original line number Diff line number Diff line
@@ -41,7 +41,12 @@ public: 
    }



    /**

     * advance the current value to match the counter

     * Advance the current value to match the counter.

     *

     * Note that it will take several million years for the 64-bit

     * counters to wrap around.

     * So we do not use __builtin_sub_overflow.

     * We want to know if overflow happens because of a bug.

     */

    void catchUpTo(int64_t counter) {

        if ((counter - mCounter64) > 0) {
@@ -74,7 +79,8 @@ public: 
     * @return current value of the 64-bit counter

     */

    int64_t update32(int32_t counter32) {

        int32_t delta = counter32 - mCounter32;

        int32_t delta;

        __builtin_sub_overflow(counter32, mCounter32, &delta);

        // protect against the mCounter64 going backwards

        if (delta > 0) {

            mCounter64 += delta;
@@ -108,5 +114,4 @@ private: 
    int32_t mCounter32 = 0;

};





#endif //UTILITY_MONOTONIC_COUNTER_H