@Override
  public synchronized byte read(final int offset) {
    Preconditions.checkState(!isClosed());
    Preconditions.checkArgument(offset >= 0);
    Preconditions.checkArgument(offset < mSize);
    return nativeReadByte(mNativePtr + offset);
  }
flag indicating if this object was closed @GuardedBy("this")
memory-types/nativememory/src/main/java/com/facebook/imagepipeline/memory/NativeMemoryChunk.java