AudioTrack::flush() will no longer flush later data

void AudioTrackClientProxy::flush()

{

    mCblk->u.mStreaming.mFlush++;

    // This works for mFrameCountP2 <= 2^30

    size_t increment = mFrameCountP2 << 1;

    size_t mask = increment - 1;

    audio_track_cblk_t* cblk = mCblk;

    int32_t newFlush = (cblk->u.mStreaming.mRear & mask) |

                        ((cblk->u.mStreaming.mFlush & ~mask) + increment);

    android_atomic_release_store(newFlush, &cblk->u.mStreaming.mFlush);

}

bool AudioTrackClientProxy::clearStreamEndDone() {

        rear = android_atomic_acquire_load(&cblk->u.mStreaming.mRear);

        front = cblk->u.mStreaming.mFront;

        if (flush != mFlush) {

            mFlush = flush;

            // effectively obtain then release whatever is in the buffer

            android_atomic_release_store(rear, &cblk->u.mStreaming.mFront);

            if (front != rear) {

            size_t mask = (mFrameCountP2 << 1) - 1;

            int32_t newFront = (front & ~mask) | (flush & mask);

            ssize_t filled = rear - newFront;

            // Rather than shutting down on a corrupt flush, just treat it as a full flush

            if (!(0 <= filled && (size_t) filled <= mFrameCount)) {

                ALOGE("mFlush %#x -> %#x, front %#x, rear %#x, mask %#x, newFront %#x, filled %d=%#x",

                        mFlush, flush, front, rear, mask, newFront, filled, filled);

                newFront = rear;

            }

            mFlush = flush;

            android_atomic_release_store(newFront, &cblk->u.mStreaming.mFront);

            // There is no danger from a false positive, so err on the side of caution

            if (true /*front != newFront*/) {

                int32_t old = android_atomic_or(CBLK_FUTEX_WAKE, &cblk->mFutex);

                if (!(old & CBLK_FUTEX_WAKE)) {

                    (void) syscall(__NR_futex, &cblk->mFutex,

                            mClientInServer ? FUTEX_WAKE_PRIVATE : FUTEX_WAKE, 1);

                }

            }

            front = rear;

            front = newFront;

        }

    } else {

        front = android_atomic_acquire_load(&cblk->u.mStreaming.mFront);

    int32_t flush = cblk->u.mStreaming.mFlush;

    if (flush != mFlush) {

        // FIXME should return an accurate value, but over-estimate is better than under-estimate

        return mFrameCount;

    }

    // the acquire might not be necessary since not doing a subsequent read