MultiByteToWideChar

The MultiByteToWideChar function maps a character string to a wide-character (Unicode) string. The character string mapped by this function is not necessarily from a multibyte character set.

int MultiByteToWideChar(
  UINT CodePage,         // code page
  DWORD dwFlags,         // character-type options
  LPCSTR lpMultiByteStr, // string to map
  int cbMultiByte,       // number of bytes in string
  LPWSTR lpWideCharStr,  // wide-character buffer
  int cchWideChar        // size of buffer
);

Parameters

CodePage

[in] Specifies the code page to be used to perform the conversion. This parameter can be given the value of any code page that is installed or available in the system. You can also specify one of the values shown in the following table.

Value	Meaning
CP_ACP	ANSI code page
CP_MACCP	Macintosh code page
CP_OEMCP	OEM code page
CP_SYMBOL	Windows 2000: Symbol code page (42)
CP_THREAD_ACP	The current thread's ANSI code page
CP_UTF7	Windows NT 4.0 and Windows 2000: Translate using UTF-7
CP_UTF8	Windows NT 4.0 and Windows 2000: Translate using UTF-8. When this is set, dwFlags must be zero.

dwFlags

[in] Indicates whether to translate to precomposed or composite-wide characters (if a composite form exists), whether to use glyph characters in place of control characters, and how to deal with invalid characters. You can specify a combination of the following flag constants.

Value	Meaning
MB_PRECOMPOSED	Always use precomposed characters—that is, characters in which a base character and a nonspacing character have a single character value. This is the default translation option. Cannot be used with MB_COMPOSITE.
MB_COMPOSITE	Always use composite characters—that is, characters in which a base character and a nonspacing character have different character values. Cannot be used with MB_PRECOMPOSED.
MB_ERR_INVALID_CHARS	If the function encounters an invalid input character, it fails and GetLastError returns ERROR_NO_UNICODE_TRANSLATION.
MB_USEGLYPHCHARS	Use glyph characters instead of control characters.

A composite character consists of a base character and a nonspacing character, each having different character values. A precomposed character has a single character value for a base/nonspacing character combination. In the character è, the e is the base character and the accent grave mark is the nonspacing character.

The function's default behavior is to translate to the precomposed form. If a precomposed form does not exist, the function attempts to translate to a composite form.

The flags MB_PRECOMPOSED and MB_COMPOSITE are mutually exclusive. The MB_USEGLYPHCHARS flag and the MB_ERR_INVALID_CHARS can be set regardless of the state of the other flags.

lpMultiByteStr

[in] Points to the character string to be converted.

cbMultiByte

[in] Specifies the size in bytes of the string pointed to by the lpMultiByteStr parameter, or it can be -1 if the string is null terminated.

If this parameter is -1, the function processes the entire input string including the null terminator. The resulting wide character string therefore has a null terminator, and the returned length includes the null terminator.

If this parameter is a positive integer, the function processes exactly the specified number of bytes. If the given length does not include a null terminator then the resulting wide character string will not be null terminated, and the returned length does not include a null terminator.

lpWideCharStr

[out] Points to a buffer that receives the translated string.

cchWideChar

[in] Specifies the size, in wide characters, of the buffer pointed to by the lpWideCharStr parameter. If this value is zero, the function returns the required buffer size, in wide characters, and makes no use of the lpWideCharStr buffer.

Return Values

If the function succeeds, and cchWideChar is nonzero, the return value is the number of wide characters written to the buffer pointed to by lpWideCharStr.

If the function succeeds, and cchWideChar is zero, the return value is the required size, in wide characters, for a buffer that can receive the translated string.

If the function fails, the return value is zero. To get extended error information, call GetLastError. GetLastError may return one of the following error codes:

ERROR_INSUFFICIENT_BUFFER
ERROR_INVALID_FLAGS
ERROR_INVALID_PARAMETER
ERROR_NO_UNICODE_TRANSLATION

Remarks

The lpMultiByteStr and lpWideCharStr pointers must not be the same. If they are the same, the function fails, and GetLastError returns the value ERROR_INVALID_PARAMETER.

The function fails if MB_ERR_INVALID_CHARS is set and encounters an invalid character in the source string. An invalid character is either, a) a character that is not the default character in the source string but translates to the default character when MB_ERR_INVALID_CHARS is not set, or b) for DBCS strings, a character which has a lead byte but no valid trailing byte. When an invalid character is found, and MB_ERR_INVALID_CHARS is set, the function returns 0 and sets GetLastError with the error ERROR_NO_UNICODE_TRANSLATION.

MAPI: For more information, see Syntax and Limitations for Win32 Functions Useful in MAPI Development.

Requirements

  Windows NT/2000: Requires Windows NT 3.1 or later.
  Windows 95/98: Requires Windows 95 or later.
  Header: Declared in Winnls.h; include Windows.h.
  Library: Use Kernel32.lib.

See Also

Unicode and Character Sets Overview, Unicode and Character Set Functions, WideCharToMultiByte