code: function( cfg, out ){
      var ldat = this._dat,
          lset = this._set,
          sdat = cfg._dat,
          sset = cfg._set,
          odat = out._dat,
          oset = 0,
          sbit;
  
      for( var i = 0; i < (LEN|0); i++ )
      {
        sbit = DAT_MASKS[ i ];
        // data is marked as set
        if( 0 !== ( lset & sbit ) )
        {
          if( (0 === ( sset & sbit )) || (ldat[ i ] !== sdat[ i ]) ) {
            oset |= sbit;
          }
          sdat[ i ] = ldat[ i ];
        }
      }
      odat.set( sdat );
      cfg._set |= lset;
      out._set = _fixSet( oset );
    }
docs: /*
  patch
  ============
  Apply this config on top of cfg input.