content: /*
   * Copyright (C) 2018 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package com.google.android.exoplayer2.ext.flac;
  
  import static java.lang.Math.max;
  
  import com.google.android.exoplayer2.extractor.BinarySearchSeeker;
  import com.google.android.exoplayer2.extractor.ExtractorInput;
  import com.google.android.exoplayer2.extractor.FlacStreamMetadata;
  import com.google.android.exoplayer2.extractor.SeekMap;
  import com.google.android.exoplayer2.util.Assertions;
  import java.io.IOException;
  import java.nio.ByteBuffer;
  
  /**
   * A {@link SeekMap} implementation for FLAC stream using binary search.
   *
   * <p>This seeker performs seeking by using binary search within the stream, until it finds the
   * frame that contains the target sample.
   */
  /* package */ final class FlacBinarySearchSeeker extends BinarySearchSeeker {
  
    /**
     * Holds a frame extracted from a stream, together with the time stamp of the frame in
     * microseconds.
     */
    public static final class OutputFrameHolder {
  
      public final ByteBuffer byteBuffer;
      public long timeUs;
  
      /** Constructs an instance, wrapping the given byte buffer. */
      public OutputFrameHolder(ByteBuffer outputByteBuffer) {
        this.timeUs = 0;
        this.byteBuffer = outputByteBuffer;
      }
    }
  
    private static final int MIN_FRAME_HEADER_SIZE = 6;
  
    private final FlacDecoderJni decoderJni;
  
    /**
     * Creates a {@link FlacBinarySearchSeeker}.
     *
     * @param streamMetadata The stream metadata.
     * @param firstFramePosition The byte offset of the first frame in the stream.
     * @param inputLength The length of the stream in bytes.
     * @param decoderJni The FLAC JNI decoder.
     * @param outputFrameHolder A holder used to retrieve the frame found by a seeking operation.
     */
    public FlacBinarySearchSeeker(
        FlacStreamMetadata streamMetadata,
        long firstFramePosition,
        long inputLength,
        FlacDecoderJni decoderJni,
        OutputFrameHolder outputFrameHolder) {
      super(
          /* seekTimestampConverter= */ streamMetadata::getSampleNumber,
          new FlacTimestampSeeker(decoderJni, outputFrameHolder),
          streamMetadata.getDurationUs(),
          /* floorTimePosition= */ 0,
          /* ceilingTimePosition= */ streamMetadata.totalSamples,
          /* floorBytePosition= */ firstFramePosition,
          /* ceilingBytePosition= */ inputLength,
          /* approxBytesPerFrame= */ streamMetadata.getApproxBytesPerFrame(),
          /* minimumSearchRange= */ max(MIN_FRAME_HEADER_SIZE, streamMetadata.minFrameSize));
      this.decoderJni = Assertions.checkNotNull(decoderJni);
    }
  
    @Override
    protected void onSeekOperationFinished(boolean foundTargetFrame, long resultPosition) {
      if (!foundTargetFrame) {
        // If we can't find the target frame (sample), we need to reset the decoder jni so that
        // it can continue from the result position.
        decoderJni.reset(resultPosition);
      }
    }
  
    private static final class FlacTimestampSeeker implements TimestampSeeker {
  
      private final FlacDecoderJni decoderJni;
      private final OutputFrameHolder outputFrameHolder;
  
      private FlacTimestampSeeker(FlacDecoderJni decoderJni, OutputFrameHolder outputFrameHolder) {
        this.decoderJni = decoderJni;
        this.outputFrameHolder = outputFrameHolder;
      }
  
      @Override
      public TimestampSearchResult searchForTimestamp(ExtractorInput input, long targetSampleIndex)
          throws IOException {
        ByteBuffer outputBuffer = outputFrameHolder.byteBuffer;
        long searchPosition = input.getPosition();
        decoderJni.reset(searchPosition);
        try {
          decoderJni.decodeSampleWithBacktrackPosition(
              outputBuffer, /* retryPosition= */ searchPosition);
        } catch (FlacDecoderJni.FlacFrameDecodeException e) {
          // For some reasons, the extractor can't find a frame mid-stream.
          // Stop the seeking and let it re-try playing at the last search position.
          return TimestampSearchResult.NO_TIMESTAMP_IN_RANGE_RESULT;
        }
        if (outputBuffer.limit() == 0) {
          return TimestampSearchResult.NO_TIMESTAMP_IN_RANGE_RESULT;
        }
  
        long lastFrameSampleIndex = decoderJni.getLastFrameFirstSampleIndex();
        long nextFrameSampleIndex = decoderJni.getNextFrameFirstSampleIndex();
        long nextFrameSamplePosition = decoderJni.getDecodePosition();
  
        boolean targetSampleInLastFrame =
            lastFrameSampleIndex <= targetSampleIndex && nextFrameSampleIndex > targetSampleIndex;
  
        if (targetSampleInLastFrame) {
          // We are holding the target frame in outputFrameHolder. Set its presentation time now.
          outputFrameHolder.timeUs = decoderJni.getLastFrameTimestamp();
          // The input position is passed even though it does not indicate the frame containing the
          // target sample because the extractor must continue to read from this position.
          return TimestampSearchResult.targetFoundResult(input.getPosition());
        } else if (nextFrameSampleIndex <= targetSampleIndex) {
          return TimestampSearchResult.underestimatedResult(
              nextFrameSampleIndex, nextFrameSamplePosition);
        } else {
          return TimestampSearchResult.overestimatedResult(lastFrameSampleIndex, searchPosition);
        }
      }
    }
  }
  