mbtowc, _mbtowc_l

發行項
06/05/2017

The new home for Visual Studio documentation is Visual Studio 2017 Documentation on docs.microsoft.com.

The latest version of this topic can be found at mbtowc, _mbtowc_l.

Convert a multibyte character to a corresponding wide character.

Syntax

int mbtowc(  
   wchar_t *wchar,  
   const char *mbchar,  
   size_t count   
);  
int _mbtowc_l(  
   wchar_t *wchar,  
   const char *mbchar,  
   size_t count,  
   _locale_t locale  
);

Parameters

wchar
Address of a wide character (type wchar_t).

mbchar
Address of a sequence of bytes (a multibyte character).

count
Number of bytes to check.

locale
The locale to use.

Return Value

If mbchar is not NULL and if the object that mbchar points to forms a valid multibyte character, mbtowc returns the length in bytes of the multibyte character. If mbchar is NULL or the object that it points to is a wide-character null character (L'\0'), the function returns 0. If the object that mbchar points to does not form a valid multibyte character within the first count characters, it returns –1.

Remarks

The mbtowc function converts count or fewer bytes pointed to by mbchar, if mbchar is not NULL, to a corresponding wide character. mbtowc stores the resulting wide character at wchar, if wchar is not NULL. mbtowc does not examine more than MB_CUR_MAX bytes. mbtowc uses the current locale for locale-dependent behavior; _mbtowc_l is identical except that it uses the locale passed in instead. For more information, see Locale.

Requirements

Routine	Required header
`mbtowc`	<stdlib.h>
_mbtowc_l	<stdlib.h>

For additional compatibility information, see Compatibility in the Introduction.

Libraries

All versions of the C run-time libraries.

Example

// crt_mbtowc.c  
/* Illustrates the behavior of the mbtowc function  
 */  
  
#include <stdlib.h>  
#include <stdio.h>  
  
int main( void )  
{  
    int      i;  
    char    *pmbc    = (char *)malloc( sizeof( char ) );  
    wchar_t  wc      = L'a';  
    wchar_t *pwcnull = NULL;  
    wchar_t *pwc     = (wchar_t *)malloc( sizeof( wchar_t ) );  
    printf( "Convert a 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 );  
  
    printf( "Convert multibyte character back to a wide "  
            "character:\n" );  
    i = mbtowc( pwc, pmbc, MB_CUR_MAX );  
    printf( "  Bytes converted: %u\n", i );  
    printf( "  Wide character: %x\n\n", *pwc );  
    printf( "Attempt to convert when target is NULL\n" );  
    printf( "  returns the length of the multibyte character:\n" );  
    i = mbtowc( pwcnull, pmbc, MB_CUR_MAX );  
    printf( "  Length of multibyte character: %u\n\n", i );  
  
    printf( "Attempt to convert a NULL pointer to a" );  
    printf( " wide character:\n" );  
    pmbc = NULL;  
    i = mbtowc( pwc, pmbc, MB_CUR_MAX );  
    printf( "  Bytes converted: %u\n", i );  
}

Output

Convert a wide character to multibyte character:  
  Characters converted: 1  
  Multibyte character: 61  
  
Convert multibyte character back to a wide character:  
  Bytes converted: 1  
  Wide character: 61  
  
Attempt to convert when target is NULL  
  returns the length of the multibyte character:  
  Length of multibyte character: 1  
  
Attempt to convert a NULL pointer to a wide character:  
  Bytes converted: 0

.NET Framework Equivalent

Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.

共用方式為