/*-
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * the Systems Programming Group of the University of Utah Computer
 * Science Department.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)atof.c	5.2 (Berkeley) 4/12/91";
#endif /* LIBC_SCCS and not lint */

/*
 * simple atof() for IEEE 754 architectures
 */

#include <machine/endian.h>
#include <stdlib.h>
#include <math.h>
#include <ctype.h>

static double twoemax = 9007199254740992.;	/*2^53*/

/* attempt to be as exact as possible */
static struct {
	long low_word;
	long high_word;
} exp5[] = {
#if	BYTE_ORDER == BIG_ENDIAN
	{ 0x40140000, 0x00000000 },	/* 5 */
	{ 0x40390000, 0x00000000 },	/* 25 */
	{ 0x40838800, 0x00000000 },	/* 625 */
	{ 0x4117d784, 0x00000000 },	/* 390625 */
	{ 0x4241c379, 0x37e08000 },	/* 152587890625 */
	{ 0x4493b8b5, 0xb5056e17 },	/* 2.3283064365387e+022 */
	{ 0x49384f03, 0xe93ff9f5 },     /* 5.42101086242753e+044 */
	{ 0x52827748, 0xf9301d32 },     /* 2.93873587705572e+089 */
	{ 0x65154fdd, 0x7f73bf3b }      /* 8.63616855509445e+178 */
#else	/* BYTE_ORDER == LITTLE_ENDIAN */
	{ 0x00000000, 0x40140000 },	/* 5 */
	{ 0x00000000, 0x40390000 },	/* 25 */
	{ 0x00000000, 0x40838800 },	/* 625 */
	{ 0x00000000, 0x4117d784 },	/* 390625 */
	{ 0x37e08000, 0x4241c379 },	/* 152587890625 */
	{ 0xb5056e17, 0x4493b8b5 },	/* 2.3283064365387e+022 */
	{ 0xe93ff9f5, 0x49384f03 },	/* 5.42101086242753e+044 */
	{ 0xf9301d32, 0x52827748 },	/* 2.93873587705572e+089 */
	{ 0x7f73bf3b, 0x65154fdd }	/* 8.63616855509445e+178 */
#endif
};

double
atof(p)
	register const char *p;
{
	register int c;
	register int exp = 0;
	register int eexp = 0;
	double fl = 0;
	double flexp = 1.0;
	int bexp;
	int neg = 1;
	int negexp = 1;

	while (isspace(*p))
		++p;

	if ((c = *p++) == '-')
		neg = -1;
	else if (c == '+')
		/* skip it */;
	else
		--p;

	while ((c = *p++) && isdigit(c))
		if (fl < twoemax)
			fl = 10 * fl + (c-'0');
		else
			++exp;

	if (c == '.')
		while ((c = *p++) && isdigit(c))
			if (fl < twoemax) {
				fl = 10 * fl + (c-'0');
				--exp;
			}

	if (c == 'E' || c == 'e') {
		if ((c = *p++) == '-')
			negexp = -1;
		else if (c == '+')
			/* skip it */;
		else
			--p;
		while ((c = *p++) && isdigit(c))
			eexp = 10 * eexp + (c-'0');
		if (negexp < 0)
			eexp = -eexp;
		exp += eexp;
	}

	bexp = exp;
	if (exp < 0)
		exp = -exp;

	for (c = 0; exp && c < sizeof exp5 / sizeof exp5[0]; ++c) {
		if (exp & 1)
			flexp *= *(double *)&exp5[c];
		exp >>= 1;
	}

	if (bexp < 0)
		fl /= flexp;
	else
		fl *= flexp;

	fl = ldexp(fl, bexp);

	return neg < 0 ? -fl : fl;
}
