_mbclen, mblen, _mblen_l, _mbclen_l

Gets the length and determines the validity of a multibyte character.

Важно

This API cannot be used in applications that execute in the Windows Runtime. For more information, see CRT functions not supported in Universal Windows Platform apps.

Syntax

C

size_t _mbclen(
   const unsigned char *c
);
size_t _mbclen_l(
   unsigned char const* c,
   _locale_t locale
);
int mblen(
   const char *mbstr,
   size_t count
);
int _mblen_l(
   const char *mbstr,
   size_t count,
   _locale_t locale
);

Parameters

c
Multibyte character.

mbstr
Address of a multibyte-character byte sequence.

count
Number of bytes to check.

locale
Locale to use.

Return value

_mbclen and _mbclen_l return 1 or 2, according to the length of the multibyte character c. The functions always return 1 for UTF-8, whether c is multibyte or not. There's no error return for _mbclen.

If mbstr isn't NULL, mblen and _mblen_l return the length, in bytes, of the multibyte character. The mblen and _mblen_l functions work correctly on UTF-8, and may return a value between 1 and 3. When mbstr is NULL (or it points to the wide-character null character), mblen and _mblen_l return 0. The object that mbstr points to must form a valid multibyte character within the first count characters, or mblen and _mblen_l return -1.

Remarks

The _mbclen function returns the length, in bytes, of the multibyte character c. If c doesn't 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's a valid multibyte character. It also determines multibyte-character validity associated with the code page. mblen examines count or fewer bytes contained in mbstr, but not more than MB_CUR_MAX bytes.

The output value is affected by the LC_CTYPE category setting of the locale. The versions of these functions without the _l suffix use the current locale for this locale-dependent behavior. The _l suffixed versions behave the same, but they use the locale parameter passed in instead. For more information, see setlocale and Locale.

_mbclen, _mblen_l, and _mbclen_l are Microsoft-specific, not part of the Standard C library. We don't recommend you use them where you want portable code. For Standard C compatibility, use mblen or mbrlen instead.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Generic-text routine mappings

Tchar.h routine	_UNICODE and _MBCS not defined	_MBCS defined	_UNICODE defined
_tclen	Maps to macro or inline function	_mbclen	Maps to macro or inline function

Requirements

Routine	Required header
_mbclen	<mbstring.h>
mblen	<stdlib.h>
_mblen_l	<stdlib.h>

For more compatibility information, see Compatibility.

Example

C

// crt_mblen.c
/* illustrates the behavior of the mblen function
*/

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

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

    printf( "Convert wide character to multibyte character:\n" );
    wctomb_s( &i, pmbc, sizeof(char), wc );
    printf( "   Characters converted: %u\n", i );
    printf( "   Multibyte 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 );
}

Output

Convert wide character to multibyte character:
   Characters converted: 1
   Multibyte character: 61

Length in bytes of multibyte character 61: 1
Length in bytes of NULL multibyte character 0: 0

See also

Character classification
Locale
Interpretation of multibyte-character sequences
_mbccpy, _mbccpy_l
mbrlen
strlen, wcslen, _mbslen, _mbslen_l, _mbstrlen, _mbstrlen_l