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MBLEN(3)                   Library Functions Manual                   MBLEN(3)

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
     examines at most n bytes of the array beginning from s.

     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, the mblen() function changes its own
     state by them and treats them 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 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      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 the number of bytes for the valid
                 multibyte character pointed to by s.  The value returned is
                 at most n, and at most the value of the MB_CUR_MAX macro.

     -1          s points to an invalid or incomplete multibyte character.
                 The mblen() function also sets errno to indicate the error.

     When s is equal to NULL, the mblen() function 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").

NetBSD 11.99                   February 3, 2024                   NetBSD 11.99