mblen
[minimal multibyte length function]

SYNOPSIS
#include<stdlib.h>
int mblen(const char *s, size_t n);

DESCRIPTION
When MB_CAPABLE is not defined, this is a minimal ANSI-conforming implementation of mblen. In this case, the only multibyte character sequences recognized are single bytes, and thus 1 is returned unless s is the null pointer, has a length of 0, or is the empty string.

When MB_CAPABLE is defined, this routine calls _mbtowc_r to perform the conversion, passing a state variable to allow state dependent decoding. The result is based on the locale setting which may be restricted to a defined set of locales.

RETURNS
This implementation of mblen returns 0 if s is NULL or the empty string; it returns 1 if not MB_CAPABLE or the character is a single-byte character; it returns -1 if the multibyte character is invalid; otherwise, it returns the number of bytes in the multibyte character.

COMPLIANCE
mblen is required in the ANSI C standard. However, the precise effects vary with the locale.

mblen requires no supporting OS subroutines.