/*  snfblksf.cpp  by K.Tsuru  */
// function ID = 101
/************************************************************
SNumber auxiliary function
Provides the shift to upper(n>0) or lower(n<0) of FigBlock.
It does not enlarge the size, i.e. cut off an oversize area.
If abs(n) >= a.size(), "a" is initialized by zero.
*************************************************************/
#ifndef SN_H
#include "sn.h"
#endif

int FigBlockShift(FigBlock& a, int n){
    if(!n) return 1;
    fType* ev = a.Elements();

    int mv = (int)a.size() - abs(n);
    if( mv <= 0 ){  a.clear(0);     return 0;   }

    if(n > 0){  //shift to upper ev[j+n] <-- ev[j] for 0<= j < a.size() -n = mv
        memmove(&ev[n], &ev[0], sizeof(fType)*mv);
        a.clear(0, n-1);    //clear lower part
    } else {    //shift to lower ev[j] <-- ev[j+|n|]
        n = -n;
        memmove(&ev[0], &ev[n], sizeof(fType)*mv);
        a.clear(mv);    //clear upper part
    }
    return 1;
}