/*

 * CDDL HEADER START

 *

 * The contents of this file are subject to the terms of the

 * Common Development and Distribution License, Version 1.0 only

 * (the "License").  You may not use this file except in compliance

 * with the License.

 *

 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE

 * or http://www.opensolaris.org/os/licensing.

 * See the License for the specific language governing permissions

 * and limitations under the License.

 *

 * When distributing Covered Code, include this CDDL HEADER in each

 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.

 * If applicable, add the following below this CDDL HEADER, with the

 * fields enclosed by brackets "[]" replaced with your own identifying

 * information: Portions Copyright [yyyy] [name of copyright owner]

 *

 * CDDL HEADER END

 */

/*

 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.

 * Use is subject to license terms.

 */

#pragma ident	"%Z%%M%	%I%	%E% SMI"

/*	Copyright (c) 1988 AT&T	*/

/*	  All Rights Reserved  	*/

/*

 *	ecvt converts to decimal

 *	the number of digits is specified by ndigit

 *	decpt is set to the position of the decimal point

 *	sign is set to 0 for positive, 1 for negative

 *

 */

#pragma weak ecvt = _ecvt

#pragma weak fcvt = _fcvt

#include "synonyms.h"

#include <sys/types.h>

#include <values.h>

#include <nan.h>

#include <string.h>

#include "tsd.h"

#define	NMAX	((DSIGNIF * 3 + 19)/10) /* restrict max precision */

#define	NDIG	80

static char *cvt(double, int, int *, int *, int);

char *

ecvt(double value, int ndigit, int *decpt, int *sign)

{

	return (cvt(value, ndigit, decpt, sign, 0));

}

char *

fcvt(double value, int ndigit, int *decpt, int *sign)

{

	return (cvt(value, ndigit, decpt, sign, 1));

}

static char *

cvt(double value, int ndigit, int *decpt, int *sign, int f_flag)

{

	char *buf = tsdalloc(_T_ECVT, NDIG, NULL);

	char *p = &buf[0], *p_last = &buf[ndigit];

	buf[0] = '\0';

	if (IsNANorINF(value)) {

		if (IsINF(value))  /* value is an INF, return "inf" */

			(void) strncpy(buf, "inf", NDIG);

		else /* value is a NaN, return "NaN" */

			(void) strncpy(buf, "nan", NDIG);

		return (buf);

	}

	if ((*sign = (value < 0.0)) != 0)

		value = -value;

	*decpt = 0;

	if (value != 0.0) {

/*

 * rescale to range [1.0, 10.0)

 * in binary for speed and to minimize error build-up

 * even for the IEEE standard with its high exponents,

 *  it's probably better for speed to just loop on them

 */

		static const struct s { double p10; int n; } s[] = {

			1e32,	32,

			1e16,	16,

			1e8,	8,

			1e4,	4,

			1e2,	2,

			1e1,	1,

		};

		const struct s *sp = s;

		++*decpt;

		if (value >= 2.0 * MAXPOWTWO) /* can't be precisely integral */

			do {

				for (; value >= sp->p10; *decpt += sp->n)

					value /= sp->p10;

			} while (sp++->n > 1);

		else if (value >= 10.0) { /* convert integer part separately */

			double pow10 = 10.0, powtemp;

			while ((powtemp = 10.0 * pow10) <= value)

				pow10 = powtemp;

			for (; ; pow10 /= 10.0) {

				int digit = value/pow10;

				*p++ = digit + '0';

				value -= digit * pow10;

				++*decpt;

				if (pow10 <= 10.0)

					break;

			}

		} else if (value < 1.0)

			do {

				for (; value * sp->p10 < 10.0; *decpt -= sp->n)

					value *= sp->p10;

			} while (sp++->n > 1);

	}

	if (f_flag)

		p_last += *decpt;

	if (p_last >= buf) {

		if (p_last > &buf[NDIG - 2])

			p_last = &buf[NDIG - 2];

		for (; ; ++p) {

			if (value == 0 || p >= &buf[NMAX])

				*p = '0';

			else {

				int intx; /* intx in [0, 9] */

				*p = (intx = (int)value) + '0';

				value = 10.0 * (value - (double)intx);

			}

			if (p >= p_last) {

				p = p_last;

				break;

			}

		}

		if (*p >= '5') /* check rounding in last place + 1 */

			do {

				if (p == buf) { /* rollover from 99999... */

					buf[0] = '1'; /* later digits are 0 */

					++*decpt;

					if (f_flag)

						++p_last;

					break;

				}

				*p = '0';

			} while (++*--p > '9'); /* propagate carries left */

		*p_last = '\0';

	}

	return (buf);

}