question: public static byte [ ] readByteArray ( final DataInput in ) throws IOException { int len = WritableUtils . readVInt ( in ) ; if ( len < 0 ) { throw new NegativeArraySizeException ( Integer . toString ( len ) ) ; } byte [ ] result = new byte [ len ] ; in . readFully ( result , 0 , len ) ; return result ; }
target:  Read byte-array written with a WritableableUtils.vint prefix.