/*  sxmshift.cpp  by K.Tsuru  */
// function ID = 506    BRADIX
/********************
SDecimal class
bit shift x --> x*2^p
*********************/
#ifndef SN_H
#include "sn.h"
#endif
SDecimal& SDecimal::BitShift(long p){
    if(!p || !Sign()) return *this;
    long  r, top, f0, shift;
    int   err = 0;
    fType mult, div;
    if(p > 0){
        shift = p/(long)BRADIX_BITS;
        r = p - shift*(long)BRADIX_BITS;// r >= 0
        mult = 1 << (int)r;
        top = (long)aTail - shift;      // top figure position after shift.
        if(top < 0) err = 1;
        else if( top == 0 ){
            f0 = (long)figure(0)*mult;
            if(f0 >= BRADIX) err = 1;   // first figure >= BRADIX
        }
        if(err) SetError(OVERFLOW_ERR, "SX BitShift", 506);
        if(shift) ShiftArray(-(int)shift);
        if(r) XsMult(*this, mult, *this);   // mult > 1
        return *this;
    }
// p < 0
    shift = -p/(long)BRADIX_BITS;
    r = -(BRADIX_BITS*shift + p);
    div = 1 << (int)r;

    if( shift + (long)aTail >= (long)CurrentMaxSize() ) SetZero();
    else {
        if(shift) ShiftArray((int)shift);
        if(r) XsDiv(*this, div, *this);
    }
    return *this;
}