public static void writeByteArray(final DataOutput out, final byte[] b, final int offset,
    final int length) throws IOException {
    WritableUtils.writeVInt(out, length);
    out.write(b, offset, length);
  }
Write byte-array to out with a vint length prefix.
@param out    output stream
@param b      array
@param offset offset into array
@param length length past offset
@throws IOException e
hbase-common/src/main/java/org/apache/hadoop/hbase/util/Bytes.java