content: /*
   * Copyright (C) 2019 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.extractor.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.FlacFrameReader;
  import com.google.android.exoplayer2.extractor.FlacFrameReader.SampleNumberHolder;
  import com.google.android.exoplayer2.extractor.FlacStreamMetadata;
  import com.google.android.exoplayer2.extractor.SeekMap;
  import java.io.IOException;
  
  /**
   * 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 {
  
    /**
     * Creates a {@link FlacBinarySearchSeeker}.
     *
     * @param flacStreamMetadata The stream metadata.
     * @param frameStartMarker The frame start marker, consisting of the 2 bytes by which every frame
     *     in the stream must start.
     * @param firstFramePosition The byte offset of the first frame in the stream.
     * @param inputLength The length of the stream in bytes.
     */
    public FlacBinarySearchSeeker(
        FlacStreamMetadata flacStreamMetadata,
        int frameStartMarker,
        long firstFramePosition,
        long inputLength) {
      super(
          /* seekTimestampConverter= */ flacStreamMetadata::getSampleNumber,
          new FlacTimestampSeeker(flacStreamMetadata, frameStartMarker),
          flacStreamMetadata.getDurationUs(),
          /* floorTimePosition= */ 0,
          /* ceilingTimePosition= */ flacStreamMetadata.totalSamples,
          /* floorBytePosition= */ firstFramePosition,
          /* ceilingBytePosition= */ inputLength,
          /* approxBytesPerFrame= */ flacStreamMetadata.getApproxBytesPerFrame(),
          /* minimumSearchRange= */ max(
              FlacConstants.MIN_FRAME_HEADER_SIZE, flacStreamMetadata.minFrameSize));
    }
  
    private static final class FlacTimestampSeeker implements TimestampSeeker {
  
      private final FlacStreamMetadata flacStreamMetadata;
      private final int frameStartMarker;
      private final SampleNumberHolder sampleNumberHolder;
  
      private FlacTimestampSeeker(FlacStreamMetadata flacStreamMetadata, int frameStartMarker) {
        this.flacStreamMetadata = flacStreamMetadata;
        this.frameStartMarker = frameStartMarker;
        sampleNumberHolder = new SampleNumberHolder();
      }
  
      @Override
      public TimestampSearchResult searchForTimestamp(ExtractorInput input, long targetSampleNumber)
          throws IOException {
        long searchPosition = input.getPosition();
  
        // Find left frame.
        long leftFrameFirstSampleNumber = findNextFrame(input);
        long leftFramePosition = input.getPeekPosition();
  
        input.advancePeekPosition(
            max(FlacConstants.MIN_FRAME_HEADER_SIZE, flacStreamMetadata.minFrameSize));
  
        // Find right frame.
        long rightFrameFirstSampleNumber = findNextFrame(input);
        long rightFramePosition = input.getPeekPosition();
  
        if (leftFrameFirstSampleNumber <= targetSampleNumber
            && rightFrameFirstSampleNumber > targetSampleNumber) {
          return TimestampSearchResult.targetFoundResult(leftFramePosition);
        } else if (rightFrameFirstSampleNumber <= targetSampleNumber) {
          return TimestampSearchResult.underestimatedResult(
              rightFrameFirstSampleNumber, rightFramePosition);
        } else {
          return TimestampSearchResult.overestimatedResult(
              leftFrameFirstSampleNumber, searchPosition);
        }
      }
  
      /**
       * Searches for the next frame in {@code input}.
       *
       * <p>The peek position is advanced to the start of the found frame, or at the end of the stream
       * if no frame was found.
       *
       * @param input The input from which to search (starting from the peek position).
       * @return The number of the first sample in the found frame, or the total number of samples in
       *     the stream if no frame was found.
       * @throws IOException If peeking from the input fails. In this case, there is no guarantee on
       *     the peek position.
       */
      private long findNextFrame(ExtractorInput input) throws IOException {
        while (input.getPeekPosition() < input.getLength() - FlacConstants.MIN_FRAME_HEADER_SIZE
            && !FlacFrameReader.checkFrameHeaderFromPeek(
                input, flacStreamMetadata, frameStartMarker, sampleNumberHolder)) {
          input.advancePeekPosition(1);
        }
  
        if (input.getPeekPosition() >= input.getLength() - FlacConstants.MIN_FRAME_HEADER_SIZE) {
          input.advancePeekPosition((int) (input.getLength() - input.getPeekPosition()));
          return flacStreamMetadata.totalSamples;
        }
  
        return sampleNumberHolder.sampleNumber;
      }
    }
  }
  