/* _Stopfx function */
#include "xmath.h"
#include <ctype.h>

int _Stopfx(const char **ps, char **endptr)
	{	/* parse prefix of floating-point field */
	const char *s = *ps;
	int code = 0;

	while (isspace((unsigned char)*s))
		{
		++s;
		}

	if (*s == '-')
		{
		code = FL_NEG;
		++s;
		}
	else if (*s == '+')
		{
		++s;
		}

	if (*s == 'n' || *s == 'N')
		{	/* parse "nan" or fail */
		if ((*++s != 'a' && *s != 'A') || (*++s != 'n' && *s != 'N'))
			{	/* parse failed, roll back pointer */
			s = *ps;
			code = FL_ERR;
			}
		else
			{	/* parse optional (n-char-sequence) */
			const char *q = ++s;

			code = FL_NAN;
			if (*q == '(')
				{	/* got '(', skip through ')' */
				do
					{
					++q;
					}
				while (isalnum((unsigned char)*q) || *q == '_');

				if (*q == ')')
					{
					s = ++q;
					}
				}
			}
		if (endptr != 0)
			{
			*endptr = (char *)s;
			}
		}
	else if (*s == 'i' || *s == 'I')
		{	/* parse "inf" or fail */
		if ((*++s != 'n' && *s != 'N') || (*++s != 'f' && *s != 'F'))
			{	/* parse failed, roll back pointer */
			s = *ps;
			code = FL_ERR;
			}
		else
			{	/* parse optional rest of "infinity" */
			const char *q = ++s;
			code |= FL_INF;

			if ((*q == 'i' || *q == 'I')
				&& (*++q == 'n' || *q == 'N')
				&& (*++q == 'i' || *q == 'I')
				&& (*++q == 't' || *q == 'T')
				&& (*++q == 'y' || *q == 'Y'))
				{
				s = ++q;
				}
			}

		if (endptr != 0)
			{
			*endptr = (char *)s;
			}
		}
	else if (*s == '0' && (s[1] == 'x' || s[1] == 'X'))
		{	/* test for valid hex field following 0x or 0X */
		const char *s1 = s + 2;
		if (*s1 == '.')
			{
			++s1;
			}

		if (isxdigit((unsigned char)*s1))
			{
			s += 2;
			code |= FL_HEX;
			}
		else
			{
			code |= FL_DEC;
			}
		}
	else
		{
		code |= FL_DEC;
		}

	*ps = s;
	return (code);
	}

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