The WideCharToMultiByte function maps a wide-character string to a new character string. The new character string is not necessarily from a multibyte character set.
int WideCharToMultiByte(
UINT CodePage, // code page
DWORD dwFlags, // performance and mapping flags
LPCWSTR lpWideCharStr, // address of wide-character string
int cchWideChar, // number of characters in string
LPSTR lpMultiByteStr, // address of buffer for new string
int cchMultiByte, // size of buffer
LPCSTR lpDefaultChar, // address of default for unmappable
// characters
LPBOOL lpUsedDefaultChar // address of flag set when default
// char. used
);
Value | Meaning |
---|---|
CP_ACP | ANSI code page |
CP_MACCP | Macintosh code page |
CP_OEMCP | OEM code page |
CP_SYMBOL | Symbol code page (42) |
CP_THREAD_ACP | Current thread's ANSI code page |
CP_UTF7 | Translate using UTF-7 |
CP_UTF8 | Translate using UTF-8 |
Value | Meaning |
---|---|
WC_NO_BEST_FIT_CHARS | Any Unicode characters that do not translate directly to multibyte equivalents will be translated to the default character (see lpDefaultChar parameter). In other words, if translating from Unicode to multibyte and back to Unicode again does not yield the exact same Unicode character, the default character is used. This flag may be used by itself or in combination with the other dwFlag options. |
WC_COMPOSITECHECK | Convert composite characters to precomposed characters. |
WC_DISCARDNS | Discard nonspacing characters during conversion. |
WC_SEPCHARS | Generate separate characters during conversion. This is the default conversion behavior. |
WC_DEFAULTCHAR | Replace exceptions with the default character during conversion. |
When WC_COMPOSITECHECK is specified, the function converts composite characters to precomposed 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.
When an application specifies WC_COMPOSITECHECK, it can use the last 3 flags in this list (WC_DISCARDNS, WC_SEPCHARS, and WC_DEFAULTCHAR) to customize the conversion to precomposed characters. These flags determine the function's behavior when there is no precomposed mapping for a base/nonspace character combination in a wide-character string. These last 3 flags can only be used if the WC_COMPOSITECHECK flag is set.
The function's default behavior is to generate separate characters (WC_SEPCHARS) for unmapped composite characters.
If the function succeeds, and cchMultiByte is nonzero, the return value is the number of bytes written to the buffer pointed to by lpMultiByteStr.
If the function succeeds, and cchMultiByte is zero, the return value is the required size, in bytes, 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
The lpMultiByteStr and lpWideCharStr pointers must not be the same. If they are the same, the function fails, and GetLastError returns ERROR_INVALID_PARAMETER.
An application can use the lpDefaultChar parameter to change the default character used for the conversion.
As noted earlier, the WideCharToMultiByte function operates most efficiently when both lpDefaultChar and lpUsedDefaultChar are NULL. The following table shows the behavior of WideCharToMultiByte for the four combinations of lpDefaultChar and lpUsedDefaultChar :
lpDefaultChar | lpUsedDefaultChar | Result |
---|---|---|
NULL | NULL | No default checking. This is the most efficient, quick way to use this function. |
non-NULL | NULL | Uses the specified default character, but does not set lpUsedDefaultChar. |
NULL | non-NULL | Uses the system default character and sets lpUsedDefaultChar if necessary. |
non-NULL | non-NULL | Uses the specified default character and sets lpUsedDefaultChar if necessary. |
Windows CE: Windows CE does not support the CP_UTF7 and CP_UTF8 values for the CodePage parameter and the WC_NO_BEST_FIT_CHARS value for the dwFlags parameter.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Requires version 1.0 or later.
Header: Declared in winnls.h.
Import Library: Use kernel32.lib.
Unicode and Character Sets Overview, Unicode and Character Set Functions, MultiByteToWideChar