/*	$OpenBSD: sfrem.c,v 1.4 2001/03/29 03:58:19 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/sgl_float.h"

/*
 *  Single Precision Floating-point Remainder
 */
int
sgl_frem(srcptr1,srcptr2,dstptr,status)

sgl_floating_point *srcptr1, *srcptr2, *dstptr;
unsigned int *status;
{
	register unsigned int opnd1, opnd2, result;
	register int opnd1_exponent, opnd2_exponent, dest_exponent, stepcount;
	register int roundup = FALSE;

	opnd1 = *srcptr1;
	opnd2 = *srcptr2;
	/*
	 * check first operand for NaN's or infinity
	 */
	if ((opnd1_exponent = Sgl_exponent(opnd1)) == SGL_INFINITY_EXPONENT) {
		if (Sgl_iszero_mantissa(opnd1)) {
			if (Sgl_isnotnan(opnd2)) {
				/* invalid since first operand is infinity */
				if (Is_invalidtrap_enabled())
					return(INVALIDEXCEPTION);
				Set_invalidflag();
				Sgl_makequietnan(result);
				*dstptr = result;
				return(NOEXCEPTION);
			}
		}
		else {
			/*
			 * is NaN; signaling or quiet?
			 */
			if (Sgl_isone_signaling(opnd1)) {
				/* trap if INVALIDTRAP enabled */
				if (Is_invalidtrap_enabled())
					return(INVALIDEXCEPTION);
				/* make NaN quiet */
				Set_invalidflag();
				Sgl_set_quiet(opnd1);
			}
			/*
			 * is second operand a signaling NaN?
			 */
			else if (Sgl_is_signalingnan(opnd2)) {
				/* trap if INVALIDTRAP enabled */
				if (Is_invalidtrap_enabled())
					return(INVALIDEXCEPTION);
				/* make NaN quiet */
				Set_invalidflag();
				Sgl_set_quiet(opnd2);
				*dstptr = opnd2;
				return(NOEXCEPTION);
			}
			/*
			 * return quiet NaN
			 */
			*dstptr = opnd1;
			return(NOEXCEPTION);
		}
	}
	/*
	 * check second operand for NaN's or infinity
	 */
	if ((opnd2_exponent = Sgl_exponent(opnd2)) == SGL_INFINITY_EXPONENT) {
		if (Sgl_iszero_mantissa(opnd2)) {
			/*
			 * return first operand
			 */
			*dstptr = opnd1;
			return(NOEXCEPTION);
		}
		/*
		 * is NaN; signaling or quiet?
		 */
		if (Sgl_isone_signaling(opnd2)) {
			/* trap if INVALIDTRAP enabled */
			if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
			/* make NaN quiet */
			Set_invalidflag();
			Sgl_set_quiet(opnd2);
		}
		/*
		 * return quiet NaN
		 */
		*dstptr = opnd2;
		return(NOEXCEPTION);
	}
	/*
	 * check second operand for zero
	 */
	if (Sgl_iszero_exponentmantissa(opnd2)) {
		/* invalid since second operand is zero */
		if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
		Set_invalidflag();
		Sgl_makequietnan(result);
		*dstptr = result;
		return(NOEXCEPTION);
	}

	/*
	 * get sign of result
	 */
	result = opnd1;

	/*
	 * check for denormalized operands
	 */
	if (opnd1_exponent == 0) {
		/* check for zero */
		if (Sgl_iszero_mantissa(opnd1)) {
			*dstptr = opnd1;
			return(NOEXCEPTION);
		}
		/* normalize, then continue */
		opnd1_exponent = 1;
		Sgl_normalize(opnd1,opnd1_exponent);
	}
	else {
		Sgl_clear_signexponent_set_hidden(opnd1);
	}
	if (opnd2_exponent == 0) {
		/* normalize, then continue */
		opnd2_exponent = 1;
		Sgl_normalize(opnd2,opnd2_exponent);
	}
	else {
		Sgl_clear_signexponent_set_hidden(opnd2);
	}

	/* 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 && Sgl_isgreaterthan(opnd1,opnd2)) {
			Sgl_all(result) = ~Sgl_all(result);   /* set sign */
			/* align opnd2 with opnd1 */
			Sgl_leftshiftby1(opnd2);
			Sgl_subtract(opnd2,opnd1,opnd2);
			/* now normalize */
			while (Sgl_iszero_hidden(opnd2)) {
				Sgl_leftshiftby1(opnd2);
				dest_exponent--;
			}
			Sgl_set_exponentmantissa(result,opnd2);
			goto testforunderflow;
		}
		/*
		 * opnd1/opnd2 <= 1/2
		 *
		 * In this case n will round to zero, so
		 *    r = opnd1
		 */
		Sgl_set_exponentmantissa(result,opnd1);
		dest_exponent = opnd1_exponent;
		goto testforunderflow;
	}

	/*
	 * Generate result
	 *
	 * Do iterative subtract until remainder is less than operand 2.
	 */
	while (stepcount-- > 0 && Sgl_all(opnd1)) {
		if (Sgl_isnotlessthan(opnd1,opnd2))
			Sgl_subtract(opnd1,opnd2,opnd1);
		Sgl_leftshiftby1(opnd1);
	}
	/*
	 * Do last subtract, then determine which way to round if remainder
	 * is exactly 1/2 of opnd2
	 */
	if (Sgl_isnotlessthan(opnd1,opnd2)) {
		Sgl_subtract(opnd1,opnd2,opnd1);
		roundup = TRUE;
	}
	if (stepcount > 0 || Sgl_iszero(opnd1)) {
		/* division is exact, remainder is zero */
		Sgl_setzero_exponentmantissa(result);
		*dstptr = result;
		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.
	 */
	Sgl_leftshiftby1(opnd1);
	if (Sgl_isgreaterthan(opnd1,opnd2)) {
		Sgl_invert_sign(result);
		Sgl_subtract((opnd2<<1),opnd1,opnd1);
	}
	/* check for remainder being exactly 1/2 of opnd2 */
	else if (Sgl_isequal(opnd1,opnd2) && roundup) {
		Sgl_invert_sign(result);
	}

	/* normalize result's mantissa */
	while (Sgl_iszero_hidden(opnd1)) {
		dest_exponent--;
		Sgl_leftshiftby1(opnd1);
	}
	Sgl_set_exponentmantissa(result,opnd1);

	/*
	 * Test for underflow
	 */
    testforunderflow:
	if (dest_exponent <= 0) {
		/* trap if UNDERFLOWTRAP enabled */
		if (Is_underflowtrap_enabled()) {
			/*
			 * Adjust bias of result
			 */
			Sgl_setwrapped_exponent(result,dest_exponent,unfl);
			*dstptr = result;
			/* frem is always exact */
			return(UNDERFLOWEXCEPTION);
		}
		/*
		 * denormalize result or set to signed zero
		 */
		if (dest_exponent >= (1 - SGL_P)) {
			Sgl_rightshift_exponentmantissa(result,1-dest_exponent);
		} else {
			Sgl_setzero_exponentmantissa(result);
		}
	}
	else Sgl_set_exponent(result,dest_exponent);
	*dstptr = result;
	return(NOEXCEPTION);
}