NAME
mblen —
get number of bytes in a
multibyte character
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <stdlib.h>
int
mblen(
const char
*s,
size_t n);
DESCRIPTION
The
mblen() function usually determines the number of bytes in
a multibyte character pointed to by
s and returns it.
This function shall only examine max n bytes of the array beginning from
s.
In state-dependent encodings,
s may point the special
sequence bytes to change the shift-state. Although such sequence bytes
corresponds to no individual wide-character code, the
mblen() changes the own state by them and treats them as if
they are a 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:
Calling any other functions in
Standard C Library (libc,
-lc) never changes the internal state of
mblen(),
except for calling
setlocale(3) with the
LC_CTYPE
category changed to that of the current
locale. Such
setlocale(3)
calls cause the internal state of this function to be indeterminate.
The behaviour of
mblen() is affected by the
LC_CTYPE
category of the current locale.
These are the 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
Normally,
mblen() returns:
-
-
- 0
- s points to a nul byte
(‘\0’).
-
-
- positive
- The value returned is a number of bytes for the valid
multibyte character pointed to by s. There are no
cases that this value is greater than n or the value
of the
MB_CUR_MAX
macro.
-
-
- -1
- s points to an invalid or incomplete
multibyte character. The mblen() also sets
errno to indicate the error.
When
s is equal to
NULL
, the
mblen() returns:
-
-
- 0
- The current encoding is state-independent.
-
-
- non-zero
- The current encoding is state-dependent.
ERRORS
mblen() may cause an error in the following case:
-
-
- [
EILSEQ
]
- s points to an invalid or incomplete
multibyte character.
SEE ALSO
mbrlen(3),
mbtowc(3),
setlocale(3)
STANDARDS
The
mblen() function conforms to
ANSI
X3.159-1989 (“ANSI C89”).