core/src/main/java/com/twitter/elephantbird/mapreduce/io/BinaryBlockReader.java
public boolean readNext(BinaryWritable<M> writable) throws IOException {
    byte[] blob = readNextProtoBytes();
    if (blob != null) {
      writable.set(protoConverter_.fromBytes(blob));
      return true;
    }
    return false;
  }
public boolean readNext(BinaryWritable<M> writable) throws IOException {
    byte[] blob = readNextProtoBytes();
    if (blob != null) {
      writable.set(protoConverter_.fromBytes(blob));
      return true;
    }
    return false;
  }
Returns true if new proto object was read into writable, false other wise.