_mbclen, mblen

Visual Studio 6.0

Get the length and determine the validity of a multibyte character.

size_t _mbclen( const unsigned char *c );

int mblen( const char *mbstr, size_t count );

Routine Required Header Compatibility
_mbclen <mbstring.h> Win 95, Win NT
mblen <stdlib.h> ANSI, Win 95, Win NT

For additional compatibility information, see Compatibility in the Introduction.


LIBC.LIB Single thread static library, retail version
LIBCMT.LIB Multithread static library, retail version
MSVCRT.LIB Import library for MSVCRT.DLL, retail version

Return Value

_mbclen returns 1 or 2, according to whether the multibyte character c is one or two bytes long. There is no error return for _mbclen. If mbstr is not NULL, mblen returns the length, in bytes, of the multibyte character. If mbstr is NULL, or if it points to the wide-character null character, mblen returns 0. If the object that mbstr points to does not form a valid multibyte character within the first count characters, mblen returns –1.



Multibyte character


Address of multibyte-character byte sequence


Number of bytes to check


The _mbclen function returns the length, in bytes, of the multibyte character c. If c does not point to the lead byte of a multibyte character as determined by an implicit call to _ismbblead, the result of _mbclen is unpredictable.

mblen returns the length in bytes of mbstr if it is a valid multibyte character. It examines count or fewer bytes contained in mbstr, but not more than MB_CUR_MAX bytes. mblen determines multibyte-character validity according to the LC_CTYPE category setting of the current locale. For more information on the LC_CTYPE category, see setlocale.

Generic-Text Routine Mappings

TCHAR.H Routine _UNICODE & _MBCS Not Defined _MBCS Defined _UNICODE Defined
_tclen Maps to macro or inline function _mbclen Maps to macro or inline function


/* MBLEN.C illustrates the behavior of the mblen function

#include <stdlib.h>
#include <stdio.h>

void main( void )
    int      i;
    char    *pmbc = (char *)malloc( sizeof( char ) );
    wchar_t  wc   = L'a';

    printf( "Convert wide character to multibyte character:\n" );
    i = wctomb( pmbc, wc );
    printf( "\tCharacters converted: %u\n", i );
    printf( "\tMultibyte character: %x\n\n", pmbc );

    i = mblen( pmbc, MB_CUR_MAX );
    printf( "Length in bytes of multibyte character %x: %u\n", pmbc, i );

    pmbc = NULL;
    i = mblen( pmbc, MB_CUR_MAX );
    printf( "Length in bytes of NULL multibyte character %x: %u\n", pmbc, i );


Convert wide character to multibyte character:
   Characters converted: 1
   Multibyte character: 2c02cc

Length in bytes of multibyte character 2c02cc: 1
Length in bytes of NULL multibyte character 0: 0

Character Classification RoutinesLocale RoutinesInterpretation of Multibyte-Character Sequences

See Also   _mbccpy, _mbslen