/*
    Copyright (C) 1995-1997 AROS - The Amiga Replacement OS
    $Id: umult64.c,v 1.7 1997/02/03 02:58:32 ldp Exp $

    Desc: Unsigned 64-bit product of two 32-bit numbers.
    Lang: english
*/
#include "utility_intern.h"

/*****************************************************************************

    NAME */
#include <proto/utility.h>

        AROS_LH2(UQUAD, UMult64,

/*  SYNOPSIS */
        AROS_LHA(ULONG, arg1, D0),
        AROS_LHA(ULONG, arg2, D1),

/*  LOCATION */
        struct UtilityBase *, UtilityBase, 34, Utility)

/*  FUNCTION
        Compute the unsigned 64-bit product of arg1 * arg2.

    INPUTS
        arg1, arg2  -   32 bit unsigned numbers.

    RESULT
        arg1 * arg2

    NOTES
        For m68k assembly programmers, UQUADs are returned in D0:D1 (with
        the high 32 bits in D0.

        This function is really only for people programming in
        assembly on real Amigas. Most compilers will be able to do this
        math for you inline.

    EXAMPLE

    BUGS

    SEE ALSO
        SMult32(), UMult32(), SMult64()

    INTERNALS
        This may or may not be handled by code in config/$(KERNEL),
        for m68k-native it is...

        This is essentially UMult32(), but with the code to calculate
        the product of the high 32 bits of the multiplicands.

    HISTORY
        29-10-95    digulla automatically created from
                            utility_lib.fd and clib/utility_protos.h
        18-08-96    iaint   Modified UMult32().

*****************************************************************************/
{
    AROS_LIBFUNC_INIT

    /* If we have native support for 32 * 32 -> 32, use that. */
    return arg1 * arg2;


#if 0
    /* This is partially the algoritm that is used, however for a
       more complete version see config/m68k-native/smult64.s

       This version has problems with:
        - adding the partial products together
        - setting the value of QUADs
    */

    UQUAD product;
    UWORD a0, a1, b0, b1;
    ULONG part_prod;

    a1 = (arg1 >> 16) & 0xffff;
    a0 = arg1 & 0xffff;
    b1 = (arg2 >> 16) & 0xffff;
    b0 = arg2 & 0xffff;

    part_prod = (a0 * b1) + (a1 * b0);

    SET_HIGH32OF64(product, (part_prod >> 16) + (a1 * b1));
    SET_LOW32OF64(product, ((part_prod & 0xFFFF) << 16) + (a0 * b0));

    return product;
#endif

    AROS_LIBFUNC_EXIT
} /* UMult64 */