/*	$OpenBSD: dfrem.c,v 1.3 1998/07/02 19:05:03 mickey Exp $	*/

/*
 * Copyright 1996 1995 by Open Software Foundation, Inc.   
 *              All Rights Reserved 
 *  
 * Permission to use, copy, modify, and distribute this software and 
 * its documentation for any purpose and without fee is hereby granted, 
 * provided that the above copyright notice appears in all copies and 
 * that both the copyright notice and this permission notice appear in 
 * supporting documentation. 
 *  
 * OSF DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE 
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 
 * FOR A PARTICULAR PURPOSE. 
 *  
 * IN NO EVENT SHALL OSF BE LIABLE FOR ANY SPECIAL, INDIRECT, OR 
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM 
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT, 
 * NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION 
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 
 * 
 */
/*
 * pmk1.1
 */
/*
 * (c) Copyright 1986 HEWLETT-PACKARD COMPANY
 *
 * To anyone who acknowledges that this file is provided "AS IS" 
 * without any express or implied warranty:
 *     permission to use, copy, modify, and distribute this file 
 * for any purpose is hereby granted without fee, provided that 
 * the above copyright notice and this notice appears in all 
 * copies, and that the name of Hewlett-Packard Company not be 
 * used in advertising or publicity pertaining to distribution 
 * of the software without specific, written prior permission.  
 * Hewlett-Packard Company makes no representations about the 
 * suitability of this software for any purpose.
 */


#include "../spmath/float.h"
#include "../spmath/dbl_float.h"

/*
 *  Double Precision Floating-point Remainder
 */
int
dbl_frem(srcptr1,srcptr2,dstptr,status)

dbl_floating_point *srcptr1, *srcptr2, *dstptr;
unsigned int *status;
{
	register unsigned int opnd1p1, opnd1p2, opnd2p1, opnd2p2;
	register unsigned int resultp1, resultp2;
	register int opnd1_exponent, opnd2_exponent, dest_exponent, stepcount;
	register boolean roundup = FALSE;

	Dbl_copyfromptr(srcptr1,opnd1p1,opnd1p2);
	Dbl_copyfromptr(srcptr2,opnd2p1,opnd2p2);
	/*
	 * check first operand for NaN's or infinity
	 */
	if ((opnd1_exponent = Dbl_exponent(opnd1p1)) == DBL_INFINITY_EXPONENT) {
		if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
			if (Dbl_isnotnan(opnd2p1,opnd2p2)) {
				/* invalid since first operand is infinity */
				if (Is_invalidtrap_enabled()) 
                                	return(INVALIDEXCEPTION);
                                Set_invalidflag();
                                Dbl_makequietnan(resultp1,resultp2);
				Dbl_copytoptr(resultp1,resultp2,dstptr);
				return(NOEXCEPTION);
			}
		}
		else {
                	/*
                 	 * is NaN; signaling or quiet?
                 	 */
                	if (Dbl_isone_signaling(opnd1p1)) {
                        	/* trap if INVALIDTRAP enabled */
                        	if (Is_invalidtrap_enabled()) 
                            		return(INVALIDEXCEPTION);
                        	/* make NaN quiet */
                        	Set_invalidflag();
                        	Dbl_set_quiet(opnd1p1);
                	}
			/* 
			 * is second operand a signaling NaN? 
			 */
			else if (Dbl_is_signalingnan(opnd2p1)) {
                        	/* trap if INVALIDTRAP enabled */
                        	if (Is_invalidtrap_enabled()) 
                            		return(INVALIDEXCEPTION);
                        	/* make NaN quiet */
                        	Set_invalidflag();
                        	Dbl_set_quiet(opnd2p1);
				Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
                		return(NOEXCEPTION);
			}
                	/*
                 	 * return quiet NaN
                 	 */
			Dbl_copytoptr(opnd1p1,opnd1p2,dstptr);
                	return(NOEXCEPTION);
		}
	} 
	/*
	 * check second operand for NaN's or infinity
	 */
	if ((opnd2_exponent = Dbl_exponent(opnd2p1)) == DBL_INFINITY_EXPONENT) {
		if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {
			/*
			 * return first operand
			 */
			Dbl_copytoptr(opnd1p1,opnd1p2,dstptr);
			return(NOEXCEPTION);
		}
                /*
                 * is NaN; signaling or quiet?
                 */
                if (Dbl_isone_signaling(opnd2p1)) {
                        /* trap if INVALIDTRAP enabled */
                        if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
                        /* make NaN quiet */
                        Set_invalidflag();
                        Dbl_set_quiet(opnd2p1);
                }
                /*
                 * return quiet NaN
                 */
		Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
                return(NOEXCEPTION);
	}
	/*
	 * check second operand for zero
	 */
	if (Dbl_iszero_exponentmantissa(opnd2p1,opnd2p2)) {
		/* invalid since second operand is zero */
		if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
                Set_invalidflag();
                Dbl_makequietnan(resultp1,resultp2);
		Dbl_copytoptr(resultp1,resultp2,dstptr);
		return(NOEXCEPTION);
	}

	/* 
	 * get sign of result
	 */
	resultp1 = opnd1p1;  

	/* 
	 * check for denormalized operands
	 */
	if (opnd1_exponent == 0) {
		/* check for zero */
		if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
			Dbl_copytoptr(opnd1p1,opnd1p2,dstptr);
			return(NOEXCEPTION);
		}
		/* normalize, then continue */
		opnd1_exponent = 1;
		Dbl_normalize(opnd1p1,opnd1p2,opnd1_exponent);
	}
	else {
		Dbl_clear_signexponent_set_hidden(opnd1p1);
	}
	if (opnd2_exponent == 0) {
		/* normalize, then continue */
		opnd2_exponent = 1;
		Dbl_normalize(opnd2p1,opnd2p2,opnd2_exponent);
	}
	else {
		Dbl_clear_signexponent_set_hidden(opnd2p1);
	}

	/* find result exponent and divide step loop count */
	dest_exponent = opnd2_exponent - 1;
	stepcount = opnd1_exponent - opnd2_exponent;

	/*
	 * check for opnd1/opnd2 < 1
	 */
	if (stepcount < 0) {
		/*
		 * check for opnd1/opnd2 > 1/2
		 *
		 * In this case n will round to 1, so 
		 *    r = opnd1 - opnd2 
		 */
		if (stepcount == -1 && 
		    Dbl_isgreaterthan(opnd1p1,opnd1p2,opnd2p1,opnd2p2)) {
			/* set sign */
			Dbl_allp1(resultp1) = ~Dbl_allp1(resultp1);
			/* align opnd2 with opnd1 */
			Dbl_leftshiftby1(opnd2p1,opnd2p2); 
			Dbl_subtract(opnd2p1,opnd2p2,opnd1p1,opnd1p2,
			 opnd2p1,opnd2p2);
			/* now normalize */
                	while (Dbl_iszero_hidden(opnd2p1)) {
                        	Dbl_leftshiftby1(opnd2p1,opnd2p2);
                        	dest_exponent--;
			}
			Dbl_set_exponentmantissa(resultp1,resultp2,opnd2p1,opnd2p2);
			goto testforunderflow;
		}
		/*
		 * opnd1/opnd2 <= 1/2
		 *
		 * In this case n will round to zero, so 
		 *    r = opnd1
		 */
		Dbl_set_exponentmantissa(resultp1,resultp2,opnd1p1,opnd1p2);
		dest_exponent = opnd1_exponent;
		goto testforunderflow;
	}

	/*
	 * Generate result
	 *
	 * Do iterative subtract until remainder is less than operand 2.
	 */
	while (stepcount-- > 0 && (Dbl_allp1(opnd1p1) || Dbl_allp2(opnd1p2))) {
		if (Dbl_isnotlessthan(opnd1p1,opnd1p2,opnd2p1,opnd2p2)) {
			Dbl_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2,opnd1p1,opnd1p2);
		}
		Dbl_leftshiftby1(opnd1p1,opnd1p2);
	}
	/*
	 * Do last subtract, then determine which way to round if remainder 
	 * is exactly 1/2 of opnd2 
	 */
	if (Dbl_isnotlessthan(opnd1p1,opnd1p2,opnd2p1,opnd2p2)) {
		Dbl_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2,opnd1p1,opnd1p2);
		roundup = TRUE;
	}
	if (stepcount > 0 || Dbl_iszero(opnd1p1,opnd1p2)) {
		/* division is exact, remainder is zero */
		Dbl_setzero_exponentmantissa(resultp1,resultp2);
		Dbl_copytoptr(resultp1,resultp2,dstptr);
		return(NOEXCEPTION);
	}

	/* 
	 * Check for cases where opnd1/opnd2 < n 
	 *
	 * In this case the result's sign will be opposite that of
	 * opnd1.  The mantissa also needs some correction.
	 */
	Dbl_leftshiftby1(opnd1p1,opnd1p2);
	if (Dbl_isgreaterthan(opnd1p1,opnd1p2,opnd2p1,opnd2p2)) {
		Dbl_invert_sign(resultp1);
		Dbl_leftshiftby1(opnd2p1,opnd2p2);
		Dbl_subtract(opnd2p1,opnd2p2,opnd1p1,opnd1p2,opnd1p1,opnd1p2);
	}
	/* check for remainder being exactly 1/2 of opnd2 */
	else if (Dbl_isequal(opnd1p1,opnd1p2,opnd2p1,opnd2p2) && roundup) { 
		Dbl_invert_sign(resultp1);
	}

	/* normalize result's mantissa */
        while (Dbl_iszero_hidden(opnd1p1)) {
                dest_exponent--;
                Dbl_leftshiftby1(opnd1p1,opnd1p2);
        }
	Dbl_set_exponentmantissa(resultp1,resultp2,opnd1p1,opnd1p2);

        /* 
         * Test for underflow
         */
    testforunderflow:
	if (dest_exponent <= 0) {
                /* trap if UNDERFLOWTRAP enabled */
                if (Is_underflowtrap_enabled()) {
                        /*
                         * Adjust bias of result
                         */
                        Dbl_setwrapped_exponent(resultp1,dest_exponent,unfl);
			/* frem is always exact */
			Dbl_copytoptr(resultp1,resultp2,dstptr);
			return(UNDERFLOWEXCEPTION);
                }
                /*
                 * denormalize result or set to signed zero
                 */
                if (dest_exponent >= (1 - DBL_P)) {
			Dbl_rightshift_exponentmantissa(resultp1,resultp2,
			 1-dest_exponent);
                }
                else {
			Dbl_setzero_exponentmantissa(resultp1,resultp2);
		}
	}
	else Dbl_set_exponent(resultp1,dest_exponent);
	Dbl_copytoptr(resultp1,resultp2,dstptr);
	return(NOEXCEPTION);
}