//  ============================================================
//
//  shift.cpp
//
//  Copyright 2002, Dennis Meilicke and Rene Peralta
//
//  ============================================================
//
//  Description:
//
//  Function for bit shifting a number.
//
//  ============================================================
#include <lnv3/ln3impl.h>
#include <lnv3/ln3impl.h>


void
ShiftRightEqual( Base *Operand, size_t distance )
//
//  Shift 'distance' bits to the right, in place.
//
{
    if( ( distance == 0 )  ||  ( Operand->size == 0 ) )
        return;

    size_t d1 = distance % digitSizeInBits;
    size_t d2 = digitSizeInBits - d1;
    size_t digitDiff = distance / digitSizeInBits;

    digit_t *dest   = Operand->digit;
    digit_t *source = dest + digitDiff;
    digit_t *end    = dest + Operand->size;
    
    *end = 0;

    for( ; source < end ; source++, dest++ )
        if( d1 )
            *dest = 
                ( ( *source ) >> d1 ) | ( ( *(source + 1) ) << d2 ) ;
        else
            *dest = *source;

    if( Operand->size > digitDiff )
        Operand->size -= digitDiff;
    else
        Operand->size = 0;

    //
    //  We may have shifted so that the leading digit is zero...
    //
    if( Operand->size )
        if( Operand->digit[ Operand->size - 1 ] == 0 )
            Operand->size--;
    
    return;
}


//  ============================================================


void
ShiftLeftEqual( Base *Operand, size_t distance )
//
//  Shift 'distance' bits to the right, in place.
//
{
    if( ( distance == 0 )  ||  ( Operand->size == 0 ) )
        return;

    size_t d1 = distance % digitSizeInBits;
    size_t d2 = digitSizeInBits - d1;
    size_t digitDiff = distance / digitSizeInBits;

    digit_t *source = Operand->digit + Operand->size - 1;
    digit_t *dest   = source + digitDiff;
    
    if( d1 )
    {
        *(dest + 1) = ( *source ) >> d2;
        for( ; source>Operand->digit ; source--, dest-- )
        {
            *dest = ( ( *source ) << d1 ) 
                  | ( *( source - 1 ) >> d2 );
        }
        *dest = ( ( *source ) << d1 );
        for( dest-- ; dest>=Operand->digit ; dest-- )
            *dest = 0;
    }
    else
    {
        for( ; source>=Operand->digit ; source--, dest-- )
            *dest = *source;
        for( ; dest>=Operand->digit ; dest-- )
            *dest = 0;
    }

    Operand->size += digitDiff;
    if( d1 ) Operand->size++;

    //
    //  If we extended the LargeNumber, we may have extended it 
    //  with zero (unset) bits.  If this is the case, decrement
    //  the index.
    //
    if( Operand->digit[ Operand->size - 1 ] == 0 )
        Operand->size--;
}