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      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 #include "include/ThrottledSource.h"
     18 
     19 #include <media/stagefright/foundation/ADebug.h>
     20 #include <media/stagefright/foundation/ALooper.h>
     21 
     22 namespace android {
     23 
     24 ThrottledSource::ThrottledSource(
     25         const sp<DataSource> &source,
     26         int32_t bandwidthLimitBytesPerSecond)
     27     : mSource(source),
     28       mBandwidthLimitBytesPerSecond(bandwidthLimitBytesPerSecond),
     29       mStartTimeUs(-1),
     30       mTotalTransferred(0) {
     31     CHECK(mBandwidthLimitBytesPerSecond > 0);
     32 }
     33 
     34 status_t ThrottledSource::initCheck() const {
     35     return mSource->initCheck();
     36 }
     37 
     38 ssize_t ThrottledSource::readAt(off64_t offset, void *data, size_t size) {
     39     Mutex::Autolock autoLock(mLock);
     40 
     41     ssize_t n = mSource->readAt(offset, data, size);
     42 
     43     if (n <= 0) {
     44         return n;
     45     }
     46 
     47     mTotalTransferred += n;
     48 
     49     int64_t nowUs = ALooper::GetNowUs();
     50 
     51     if (mStartTimeUs < 0) {
     52         mStartTimeUs = nowUs;
     53     }
     54 
     55     // How long would it have taken to transfer everything we ever
     56     // transferred given the limited bandwidth.
     57     int64_t durationUs =
     58         mTotalTransferred * 1000000ll / mBandwidthLimitBytesPerSecond;
     59 
     60     int64_t whenUs = mStartTimeUs + durationUs;
     61 
     62     if (whenUs > nowUs) {
     63         usleep(whenUs - nowUs);
     64     }
     65 
     66     return n;
     67 }
     68 
     69 status_t ThrottledSource::getSize(off64_t *size) {
     70     return mSource->getSize(size);
     71 }
     72 
     73 uint32_t ThrottledSource::flags() {
     74     return mSource->flags();
     75 }
     76 
     77 }  // namespace android
     78 
     79