MBRLEN(3) Library Functions Manual MBRLEN(3)
mbrlen -- get number of bytes in a multibyte character (restartable)
Standard C Library (libc, -lc)
mbrlen(const char * restrict s, size_t n, mbstate_t * restrict ps);
The mbrlen() 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.
mbrlen() is equivalent to the following call (except ps is evaluated only
mbrtowc(NULL, s, n, (ps != NULL) ? ps : &internal);
Here, internal is an internal state object.
In state-dependent encodings, s may point to the special sequence bytes
to change the shift-state. Although such sequence bytes corresponds to
no individual wide-character code, these affect the conversion state
object pointed to by ps, and the mbrlen() treats the special sequence
bytes as if these are a part of the subsequent multibyte character.
Unlike mblen(3), mbrlen() may accept the byte sequence when it is not a
complete character but possibly contains part of a valid character. In
this case, this function will accept all such bytes and save them into
the conversion state object pointed to by ps. They will be used on
subsequent calls of this function to restart the conversion suspended.
The behaviour of mbrlen() is affected by the LC_CTYPE category of the
These are the special cases:
s == NULL mbrlen() sets the conversion state object pointed to by ps to
an initial state and always returns 0. Unlike mblen(3), the
value returned does not indicate whether the current encoding
of the locale is state-dependent.
In this case, mbrlen() ignores n.
n == 0 In this case, the first n bytes of the array pointed to by s
never form a complete character. Thus, mbrlen() always
ps == NULL mbrlen() uses its own internal state object to keep the
conversion state, instead of ps mentioned in this manual
Calling any other functions in Standard C Library (libc, -lc)
never changes the internal state of mbrlen(), except for
calling setlocale(3) with a changing LC_CTYPE category of the
current locale. Such setlocale(3) calls cause the internal
state of this function to be indeterminate. This internal
state is initialized at startup time of the program.
The mbrlen() 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
(size_t)-2 s points to the byte sequence which possibly contains part of
a valid multibyte character, but which is incomplete. When n
is at least MB_CUR_MAX, this case can only occur if the array
pointed to by s contains a redundant shift sequence.
(size_t)-1 s points to an illegal byte sequence which does not form a
valid multibyte character. In this case, mbrtowc() sets
errno to indicate the error.
mbrlen() may cause an error in the following case:
[EILSEQ] s points to an invalid multibyte character.
[EINVAL] ps points to an invalid or uninitialized mbstate_t
mblen(3), mbrtowc(3), setlocale(3)
The mbrlen() function conforms to ISO/IEC 9899/AMD1:1995 (``ISO C90,
Amendment 1''). The restrict qualifier is added at ISO/IEC 9899:1999
NetBSD 6.1.5 February 3, 2002 NetBSD 6.1.5