1 files changed, 131 insertions, 0 deletions
diff --git a/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/flac/FlacBinarySearchSeeker.java b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/flac/FlacBinarySearchSeeker.java
new file mode 100644
index 0000000000..d13b1f394d
--- /dev/null
+++ b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/flac/FlacBinarySearchSeeker.java
@@ -0,0 +1,131 @@
+/*
+ * 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 org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.flac;
+
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.BinarySearchSeeker;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.ExtractorInput;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.FlacFrameReader;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.FlacFrameReader.SampleNumberHolder;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.SeekMap;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.util.FlacConstants;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.util.FlacStreamMetadata;
+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= */ Math.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, InterruptedException {
+      long searchPosition = input.getPosition();
+
+      // Find left frame.
+      long leftFrameFirstSampleNumber = findNextFrame(input);
+      long leftFramePosition = input.getPeekPosition();
+
+      input.advancePeekPosition(
+          Math.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.
+     * @throws InterruptedException If interrupted while peeking from input. In this case, there is
+     *     no guarantee on the peek position.
+     */
+    private long findNextFrame(ExtractorInput input) throws IOException, InterruptedException {
+      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;
+    }
+  }
+}