//  ============================================================
//
//  random.cc
//
//  Copyright 2002, Dennis Meilicke and Rene Peralta
//
//  ============================================================
//
//  Description:
//
//  Generate random numbers.
//
//  To do:
//
//  Re-implement the random sign stuff
//
//  This shouldn't be a member of ln, should it?
//  Shouldn't this be a Base function?
//
//  ============================================================


#include <lnv3/lnv3.h>

#include <sys/time.h>


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


static const digit_t mod_const = 32609;

static digit_t Xn_1 = 0;
static digit_t Xn_2 = 0;
static digit_t Xn_3 = 0;


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


static void
Initialize( void )
{
    struct timeval tv;

    if (Xn_1 == 0)
    {
        gettimeofday(&tv,0);
        Xn_1 = (tv.tv_usec + 1) % mod_const;
    }
        
    if (Xn_2 == 0) 
    {
        gettimeofday(&tv,0);
        Xn_2 = (tv.tv_usec + 1) % mod_const;
    }
        
    if (Xn_3 == 0)
    {
        gettimeofday(&tv,0);
        Xn_3 = (tv.tv_usec + 1) % mod_const;
    }
}


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


static inline digit_t
RandomBits( void )
{
    struct timeval tv;
    gettimeofday( &tv, 0 );
    Xn_1 = ( Xn_3 * Xn_2 + tv.tv_usec + 7 )  % mod_const;
    Xn_2 = ( Xn_3 * Xn_1 + tv.tv_usec + 3 )  % mod_const;
    Xn_3 = ( Xn_1 * Xn_2 + tv.tv_usec + 11 ) % mod_const;
    return Xn_1;
}


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


ln &
ln::Random( size_t digits ) 
//
//  Description
//
//  Generate a random LargeNumber
//
//  To Do:        This should not call the time of day system call for
//                every digit.  Once for each function call should be
//                enough.  Also, we should be generating random ln++
//                digits, not random decimal digits.  Then calcualte
//                the number of bits, and truncate the most
//                significant digit.  Note: if the most significant
//                bit of the truncated digit is zero, select another
//                random msd, and truncate again.  Continue until a 1
//                bit is generated.
//
//                This method is *slow*, and the above should speed it
//                up, considerably.
//
{
    if (digits <= 0)
        return ( *this = 0 );

    Initialize( );

    //
    //  The size of the buffer should really come from 
    //  the traits object...
    //
    char buffer[maxDigitsBase10];

    size_t i;
    for( i=0 ; i < digits ; i++ )
    {
        buffer[i] = (char)(RandomBits( ) % 10) + '0';    
    }
    buffer[i] = 0;

    return ( *this = buffer ); 
}


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


#ifdef UNDER_CONSTRUCTION


ln&
ln::RandomMod( const ln& mod )
{
    size_t numDigits = mod.GetSize( );

    size_t i;
    for( i=0 ; i<numDigits ; i++ )
    {
        digit_t temp = 0;
        for( size_t j=0 ; j<4 ; j++ )
        {
            temp <<= 8;
            temp &= ( RandomBits( ) & 0xff );
        }
        this->SetDigit( i, temp );
    }

    //
    //  At this point, what do we do?  Do we
    //  just take the mod of the new number?
    //  Or do we try to do something "smart"?
    //  
}


#endif


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