/* _WStopfx function */
#include <wctype.h>
#include "xmath.h"

int _WStopfx(const wchar_t **ps, wchar_t **endptr)
	{	/* parse prefix of floating-point field */
	const wchar_t *s = *ps;
	int code = 0;
	while (iswspace(*s))
		{
		++s;
		}

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

	if (*s == L'n' || *s == L'N')
		{	/* parse "nan" or fail */
		if ((*++s != L'a' && *s != L'A') || (*++s != L'n' && *s != L'N'))
			{	/* parse failed, roll back pointer */
			s = *ps;
			code = FL_ERR;
			}
		else
			{	/* parse optional (n-char-sequence) */
			const wchar_t *q = ++s;
			code = FL_NAN;
			if (*q == L'(')
				{	/* got L'(', skip through L')' */
				do
					{
					++q;
					}
				while (iswalnum(*q) || *q == L'_');

				if (*q == L')')
					{
					s = ++q;
					}
				}
			}

		if (endptr != 0)
			{
			*endptr = (wchar_t *)s;
			}
		}
	else if (*s == L'i' || *s == L'I')
		{	/* parse "inf" or fail */
		if ((*++s != L'n' && *s != L'N') || (*++s != L'f' && *s != L'F'))
			{	/* parse failed, roll back pointer */
			s = *ps;
			code = FL_ERR;
			}
		else
			{	/* parse optional rest of L"infinity" */
			const wchar_t *q = ++s;
			code |= FL_INF;
			if ((*q == L'i' || *q == L'I')
				&& (*++q == L'n' || *q == L'N')
				&& (*++q == L'i' || *q == L'I')
				&& (*++q == L't' || *q == L'T')
				&& (*++q == L'y' || *q == L'Y'))
				{
				s = ++q;
				}
			}

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

		if (iswxdigit(*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 */