question: public static byte [ ] decode ( byte [ ] input , int offset , int len , int flags ) { Decoder decoder = new Decoder ( flags , new byte [ len * 3 / 4 ] ) ; if ( ! decoder . process ( input , offset , len , true ) ) { throw new IllegalArgumentException ( "bad base-64" ) ; } if ( decoder . op == decoder . output . length ) { return decoder . output ; } byte [ ] temp = new byte [ decoder . op ] ; System . arraycopy ( decoder . output , 0 , temp , 0 , decoder . op ) ; return temp ; }
target:  Decode the Base64-encoded data in input and return the data in a new byte array. <p> The padding '=' characters at the end are considered optional, but if any are present, there must be the correct number of them.