#define MYPUSHMARK(p) \
    ( *PL_markstack_ptr = ( ++PL_markstack_ptr == PL_markstack_max ) \
    ? ( markstack_grow(), (p) - PL_stack_base ) \
    : ( (p) - PL_stack_base ) )

#define CMP( callback, aa, bb )  ( \
    ( GvSV( a ) = ( aa ) ), \
    ( GvSV( b ) = ( bb ) ), \
    ( MYPUSHMARK(SP) ), \
    ( call_sv( callback, G_SCALAR|G_NOARGS ) ), \
    ( SPAGAIN ), \
    ( POPi ) \
)

void topNbsAB( int n, SV *cmp, AV*data ) {                           
    int i, k;                                                    
    int left, right;                                                 
    int len = av_len( data );                                        
                                                                     
    GV* a = gv_fetchpv( "main::a", TRUE, SVt_PV );
    GV* b = gv_fetchpv( "main::b", TRUE, SVt_PV );                   
                                                                     
    dSP; dMARK; dAX;
    POPMARK;
    POPs; POPs; POPs;
    EXTEND( SP, n );
    PUSHMARK( SP );
        
    for( i = 0; i < n; i++ ) {
       PUSHs( newSViv( 0 ) );                                        
    }                                                                
    PUTBACK;
    
    for( i = 0; i <= len; i++ ) {                                    
        SV *val = *av_fetch( data, i, 0 );                           
        if( CMP( cmp, val, ST( n-1 ) ) < 0 ) continue;      
                                                                     
        left = 0;                                                    
        right = n;                                              
        while (left < right) {                                       
           int middle = ( left + right ) >> 1;                       
           if( CMP( cmp, val, ST( middle ) ) <= 0 ) {       
              left = middle + 1;                                     
           } else {                                                  
              right = middle;                                        
           }                                                         
        }                                                            
        for( k = n; k >= left; k-- ) ST( k ) = ST( k - 1 );      
        ST( left ) = val;                                            
    }
    XSRETURN( n );                                                   
}