core/src/main/java/com/twitter/elephantbird/mapreduce/io/BinaryBlockReader.java
public M readNext() throws IOException {
    byte[] blob = readNextProtoBytes();
    return blob == null ?
        null : protoConverter_.fromBytes(blob);
  }
public M readNext() throws IOException {
    byte[] blob = readNextProtoBytes();
    return blob == null ?
        null : protoConverter_.fromBytes(blob);
  }
Returns next deserialized object. null indicates end of stream or a
deserialization error. Use {@link #readNext(BinaryWritable)} to
distinguish betwen end of stream or deserialization error.