/* _Stoxflt function */
#include "xmath.h"
#include <ctype.h>
#include <locale.h>
#include <stdlib.h>
#include <string.h>

#define BASE	16	/* hexadecimal */
#define NDIG	7	/* hexadecimal digits per long element */
#define MAXSIG	(5 * NDIG)	/* maximum significant digits to keep */

int _Stoxflt(const char *s0, const char *s,
	char **endptr, long lo[], int maxsig)
	{	/* convert string to array of long plus exponent */
	char buf[MAXSIG + 1];	/* worst case, with room for rounding digit */
	int nsig = 0;	/* number of significant digits seen */
	int seen = 0;	/* any valid field characters seen */
	int word = 0;	/* current long word to fill */

	const char *pd;
	static const char digits[] = "0123456789abcdefABCDEF";
	static const char vals[] =
		{	/* values of hex digits */
		0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
		10, 11, 12, 13, 14, 15};

	maxsig *= NDIG;	/* convert word count to digit count */
	if (MAXSIG < maxsig)
		maxsig = MAXSIG;	/* protect against bad call */

	lo[0] = 0;	/* power of ten exponent */
	lo[1] = 0;	/* first NDIG-digit word of fraction */

	while (*s == '0')
		{	/* strip leading zeros */
		++s;
		seen = 1;
		}

	while ((pd = (char *)memchr(&digits[0], *s, 22)) != 0)
		{
		if (nsig <= maxsig)
			{
			buf[nsig++] = vals[pd - digits];	/* accumulate a digit */
			}
		else
			{
			++lo[0];	/* too many digits, just scale exponent */
			}

		++s;
		seen = 1;
		}

	if (*s == localeconv()->decimal_point[0])
		{
		++s;
		}

	if (nsig == 0)
		{
		for (; *s == '0'; ++s, seen = 1)
			{
			--lo[0];	/* strip zeros after point */
			}
		}

	for (; (pd = (char *)memchr(&digits[0], *s, 22)) != 0; ++s, seen = 1)
		{
		if (nsig <= maxsig)
			{	/* accumulate a fraction digit */
			buf[nsig++] = vals[pd - digits];
			--lo[0];
			}
		}

	if (maxsig < nsig)
		{	/* discard excess digit after rounding up */
		unsigned int ms = maxsig;	/* to quiet warnings */

		if (BASE / 2 <= buf[ms])
			{
			++buf[ms - 1];	/* okay if digit becomes BASE */
			}

		nsig = maxsig;
		++lo[0];
		}

	for (; 0 < nsig && buf[nsig - 1] == '\0'; --nsig)
		{
		++lo[0];	/* discard trailing zeros */
		}

	if (nsig == 0)
		{
		buf[nsig++] = '\0';	/* ensure at least one digit */
		}

	lo[0] <<= 2;	/* change hex exponent to binary exponent */
	if (seen)
		{	/* convert digit sequence to words */
		int bufidx = 0;	/* next digit in buffer */
		int wordidx = NDIG - nsig % NDIG;	/* next digit in word (% NDIG) */

		word = wordidx % NDIG == 0 ? 0 : 1;
		for (; bufidx < nsig; ++wordidx, ++bufidx)
			{
			if (wordidx % NDIG == 0)
				{
				lo[++word] = buf[bufidx];
				}
			else
				{
				lo[word] = lo[word] * BASE + buf[bufidx];
				}
			}

		if (*s == 'p' || *s == 'P')
			{	/* parse exponent */
			const char *ssav = s;
			const char esign = *++s == '+' || *s == '-' ? *s++ : '+';
			int eseen = 0;
			long lexp = 0;

			for (; isdigit((unsigned char)*s); ++s, eseen = 1)
				{
				if (lexp < 100000000)	/* else overflow */
					{
					lexp = lexp * 10 + (unsigned char)*s - '0';
					}
				}

			if (esign == '-')
				{
				lexp = -lexp;
				}

			lo[0] += lexp;
			if (!eseen)
				{
				s = ssav;	/* roll back if incomplete exponent */
				}
			}
		}

	if (!seen)
		{
		word = 0;	/* return zero if bad parse */
		}

	if (endptr)
		{
		*endptr = (char *)(seen ? s : s0);	/* roll back if bad parse */
		}

	return (word);
	}

/*
 * Copyright (c) by P.J. Plauger. All rights reserved.
 * Consult your license regarding permissions and restrictions.
V6.50:0009 */