question: private int firstDoc ( int i4096 ) { long index = 0 ; while ( i4096 < indices . length ) { index = indices [ i4096 ] ; if ( index != 0 ) { final int i64 = Long . numberOfTrailingZeros ( index ) ; return ( i4096 << 12 ) | ( i64 << 6 ) | Long . numberOfTrailingZeros ( bits [ i4096 ] [ 0 ] ) ; } i4096 += 1 ; } return DocIdSetIterator . NO_MORE_DOCS ; }
target:  Return the first document that occurs on or after the provided block index. 