Locale-Sensitive C/C++ String Operation Function

size_t strspn(const char *string, const char *strCharSet);

size_t wcsspn(const wchar_t *string, const wchar_t *strCharSet);

size_t _mbsspn(const unsigned char *string, const unsigned char *strCharSet);

size_t _tcsspn(const _TXCHAR *string, const _TXCHAR *strCharSet);

Internationalization (I18n) Function Overview

The strspn function returns the index of the first character in string that does not belong to the set of characters in strCharSet. The search does not include terminating null characters.

wcsspn is the wide character equivalent; its parameters are wide-character strings and it returns a wide-character index value.

_mbsspn is supported on Windows platforms only and is the multibyte equivalent; its parameters are multibyte strings and it returns a byte index.

_tcsspn is the Windows-only Generic version of the function; with the _MBCS or _UNICODE compiler flags determining its mapping to either _mbsspn or wcsspn.

I18n Issues

The strspn function does not work if strCharSet contains multibyte UTF-8 characters. (In a string using a multibyte UTF-8 character encoding, characters consisting of more than one byte are not treated by strspn as an entity, each byte is treated separately.)

If strCharSet may possibly contain multibyte UTF-8 characters, the parameters (string and strCharSet) will have to be converted to wide characters (wchar_t) and then use the wide function wcsspn. Similarly, the return value will then need to be converted from wide characters back to UTF-8 characters.

For Windows MBCS platforms, ensure that the multibyte code page is set properly, as _mbsspn depends on it. By default, the multibyte code page is set to the system-default ANSI code page obtained from the operating system at program startup. Use _getmbcp and _setmbcp to query or change the current multibyte code page, respectively.

Recommended Replacements*

ANSI UTF-8	strspn
ANSI UTF-16	wcsspn
Microsoft Windows MBCS	_mbsspn
Microsoft Windows Unicode	wcsspn
Microsoft Windows Generic	_tcsspn

Locale-Sensitive C/C++ String Operation Functions