1 files changed, 204 insertions, 0 deletions
diff --git a/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/upstream/cache/CachedRegionTracker.java b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/upstream/cache/CachedRegionTracker.java
new file mode 100644
index 0000000000..9b08301ab8
--- /dev/null
+++ b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/upstream/cache/CachedRegionTracker.java
@@ -0,0 +1,204 @@
+/*
+ * Copyright (C) 2016 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.upstream.cache;
+
+import androidx.annotation.NonNull;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.ChunkIndex;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.util.Log;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.util.Util;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.NavigableSet;
+import java.util.TreeSet;
+
+/**
+ * Utility class for efficiently tracking regions of data that are stored in a {@link Cache}
+ * for a given cache key.
+ */
+public final class CachedRegionTracker implements Cache.Listener {
+
+  private static final String TAG = "CachedRegionTracker";
+
+  public static final int NOT_CACHED = -1;
+  public static final int CACHED_TO_END = -2;
+
+  private final Cache cache;
+  private final String cacheKey;
+  private final ChunkIndex chunkIndex;
+
+  private final TreeSet<Region> regions;
+  private final Region lookupRegion;
+
+  public CachedRegionTracker(Cache cache, String cacheKey, ChunkIndex chunkIndex) {
+    this.cache = cache;
+    this.cacheKey = cacheKey;
+    this.chunkIndex = chunkIndex;
+    this.regions = new TreeSet<>();
+    this.lookupRegion = new Region(0, 0);
+
+    synchronized (this) {
+      NavigableSet<CacheSpan> cacheSpans = cache.addListener(cacheKey, this);
+      // Merge the spans into regions. mergeSpan is more efficient when merging from high to low,
+      // which is why a descending iterator is used here.
+      Iterator<CacheSpan> spanIterator = cacheSpans.descendingIterator();
+      while (spanIterator.hasNext()) {
+        CacheSpan span = spanIterator.next();
+        mergeSpan(span);
+      }
+    }
+  }
+
+  public void release() {
+    cache.removeListener(cacheKey, this);
+  }
+
+  /**
+   * When provided with a byte offset, this method locates the cached region within which the
+   * offset falls, and returns the approximate end position in milliseconds of that region. If the
+   * byte offset does not fall within a cached region then {@link #NOT_CACHED} is returned.
+   * If the cached region extends to the end of the stream, {@link #CACHED_TO_END} is returned.
+   *
+   * @param byteOffset The byte offset in the underlying stream.
+   * @return The end position of the corresponding cache region, {@link #NOT_CACHED}, or
+   *     {@link #CACHED_TO_END}.
+   */
+  public synchronized int getRegionEndTimeMs(long byteOffset) {
+    lookupRegion.startOffset = byteOffset;
+    Region floorRegion = regions.floor(lookupRegion);
+    if (floorRegion == null || byteOffset > floorRegion.endOffset
+        || floorRegion.endOffsetIndex == -1) {
+      return NOT_CACHED;
+    }
+    int index = floorRegion.endOffsetIndex;
+    if (index == chunkIndex.length - 1
+        && floorRegion.endOffset == (chunkIndex.offsets[index] + chunkIndex.sizes[index])) {
+      return CACHED_TO_END;
+    }
+    long segmentFractionUs = (chunkIndex.durationsUs[index]
+        * (floorRegion.endOffset - chunkIndex.offsets[index])) / chunkIndex.sizes[index];
+    return (int) ((chunkIndex.timesUs[index] + segmentFractionUs) / 1000);
+  }
+
+  @Override
+  public synchronized void onSpanAdded(Cache cache, CacheSpan span) {
+    mergeSpan(span);
+  }
+
+  @Override
+  public synchronized void onSpanRemoved(Cache cache, CacheSpan span) {
+    Region removedRegion = new Region(span.position, span.position + span.length);
+
+    // Look up a region this span falls into.
+    Region floorRegion = regions.floor(removedRegion);
+    if (floorRegion == null) {
+      Log.e(TAG, "Removed a span we were not aware of");
+      return;
+    }
+
+    // Remove it.
+    regions.remove(floorRegion);
+
+    // Add new floor and ceiling regions, if necessary.
+    if (floorRegion.startOffset < removedRegion.startOffset) {
+      Region newFloorRegion = new Region(floorRegion.startOffset, removedRegion.startOffset);
+
+      int index = Arrays.binarySearch(chunkIndex.offsets, newFloorRegion.endOffset);
+      newFloorRegion.endOffsetIndex = index < 0 ? -index - 2 : index;
+      regions.add(newFloorRegion);
+    }
+
+    if (floorRegion.endOffset > removedRegion.endOffset) {
+      Region newCeilingRegion = new Region(removedRegion.endOffset + 1, floorRegion.endOffset);
+      newCeilingRegion.endOffsetIndex = floorRegion.endOffsetIndex;
+      regions.add(newCeilingRegion);
+    }
+  }
+
+  @Override
+  public void onSpanTouched(Cache cache, CacheSpan oldSpan, CacheSpan newSpan) {
+    // Do nothing.
+  }
+
+  private void mergeSpan(CacheSpan span) {
+    Region newRegion = new Region(span.position, span.position + span.length);
+    Region floorRegion = regions.floor(newRegion);
+    Region ceilingRegion = regions.ceiling(newRegion);
+    boolean floorConnects = regionsConnect(floorRegion, newRegion);
+    boolean ceilingConnects = regionsConnect(newRegion, ceilingRegion);
+
+    if (ceilingConnects) {
+      if (floorConnects) {
+        // Extend floorRegion to cover both newRegion and ceilingRegion.
+        floorRegion.endOffset = ceilingRegion.endOffset;
+        floorRegion.endOffsetIndex = ceilingRegion.endOffsetIndex;
+      } else {
+        // Extend newRegion to cover ceilingRegion. Add it.
+        newRegion.endOffset = ceilingRegion.endOffset;
+        newRegion.endOffsetIndex = ceilingRegion.endOffsetIndex;
+        regions.add(newRegion);
+      }
+      regions.remove(ceilingRegion);
+    } else if (floorConnects) {
+      // Extend floorRegion to the right to cover newRegion.
+      floorRegion.endOffset = newRegion.endOffset;
+      int index = floorRegion.endOffsetIndex;
+      while (index < chunkIndex.length - 1
+          && (chunkIndex.offsets[index + 1] <= floorRegion.endOffset)) {
+        index++;
+      }
+      floorRegion.endOffsetIndex = index;
+    } else {
+      // This is a new region.
+      int index = Arrays.binarySearch(chunkIndex.offsets, newRegion.endOffset);
+      newRegion.endOffsetIndex = index < 0 ? -index - 2 : index;
+      regions.add(newRegion);
+    }
+  }
+
+  private boolean regionsConnect(Region lower, Region upper) {
+    return lower != null && upper != null && lower.endOffset == upper.startOffset;
+  }
+
+  private static class Region implements Comparable<Region> {
+
+    /**
+     * The first byte of the region (inclusive).
+     */
+    public long startOffset;
+    /**
+     * End offset of the region (exclusive).
+     */
+    public long endOffset;
+    /**
+     * The index in chunkIndex that contains the end offset. May be -1 if the end offset comes
+     * before the start of the first media chunk (i.e. if the end offset is within the stream
+     * header).
+     */
+    public int endOffsetIndex;
+
+    public Region(long position, long endOffset) {
+      this.startOffset = position;
+      this.endOffset = endOffset;
+    }
+
+    @Override
+    public int compareTo(@NonNull Region another) {
+      return Util.compareLong(startOffset, another.startOffset);
+    }
+
+  }
+
+}