mblen(3) - NetBSD Manual Pages

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MBLEN(3)                NetBSD 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 multi-
     byte 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 charac-
     ter.

     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 inde-
     terminate.

     The behaviour of mblen() is affected by the LC_CTYPE category of the cur-
     rent 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 null byte (`\0').

     positive    The value returned is a number of bytes for the valid multi-
                 byte 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 charac-
                        ter.


SEE ALSO

     mbrlen(3), mbtowc(3), setlocale(3)


STANDARDS

     The mblen() function conforms to ANSI X3.159-1989 (``ANSI C'').

NetBSD 2.1                     February 3, 2002                     NetBSD 2.1