NAME
mblen —
get number of bytes in a multibyte
character
SYNOPSIS
#include
<stdlib.h>
int
mblen(const
char *s, size_t
n);
DESCRIPTION
The
mblen()
function returns the number of bytes in the first multibyte character of the
multibyte string s. It examines at most the first
n bytes of s.
In state-dependent encodings, s
may point to special sequence bytes changing the shift state. Although such
sequence bytes correspond to no wide character, they affect the internal
conversion state of the
mblen()
function, and are treated as if they were part of the subsequent multibyte
character.
Unlike mbrlen(3), the first n bytes pointed to by s need to form an entire multibyte character. Otherwise, this function causes an error.
mblen()
is equivalent to the following call, except the internal state of the
mbtowc(3)
function is not affected:
mbtowc(NULL, s, n);
Calling any other function in
libc never changes
the internal state of
mblen(),
except for calling setlocale(3) with an LC_CTYPE that
differs from the current locale. Such
setlocale(3) calls cause the internal state of this function to
become indeterminate.
The behaviour of
mblen() is
affected by the LC_CTYPE category of the current
locale.
There are special cases:
- s == NULL
mblen() initializes its own internal state to an initial state, and determines whether the current encoding is state-dependent. This function returns 0 if the encoding is state-independent, otherwise non-zero.- n == 0
- In this case, the first n bytes of the array pointed
to by s never form a complete character. Thus,
mblen() always fails.
RETURN VALUES
The mblen() function returns:
- 0
- s points to a NUL byte (‘\0’).
- positive
- The value returned is the number of bytes in the valid multibyte character
pointed to by s. There are no cases when this value
is greater than n or the value of the
MB_CUR_MAXmacro. - -1
- s points an invalid or incomplete multibyte
character. The
mblen() function also sets errno to indicate the error.
When s is equal to
NULL, mblen() returns:
- 0
- The current encoding is state-independent.
- non-zero
- The current encoding is state-dependent.
ERRORS
The mblen() function may cause an error in
the following case:
- [
EILSEQ] - s points to an invalid or incomplete multibyte character.
SEE ALSO
STANDARDS
The mblen() function conforms to
ANSI X3.159-1989
(“ANSI C89”).