WideCharToMultiByte

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This 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
,
DWORD
dwFlags
,
LPCWSTR
lpWideCharStr
,
int
cchWideChar
,
LPSTR
lpMultiByteStr
,
int
cbMultiByte
,
LPCSTR
lpDefaultChar
,
LPBOOL
lpUsedDefaultChar
);

Parameters

CodePage

[in] Specifies the code page 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 following values:

Value	Description
CP_ACP	ANSI code page
CP_MACCP	Not supported
CP_OEMCP	OEM code page
CP_SYMBOL	Not supported
CP_THREAD_ACP	Not supported

dwFlags

[in] Specifies the handling of unmapped characters. The function performs more quickly when none of these flags is set. The following flag constants are defined:

Value	Description
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 ï¿½, the eis the base character, and the accent grave mark is the nonspacing character.

When an application specifies WC_COMPOSITECHECK, it can use the last three 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 three 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.

lpWideCharStr

[in] Pointer to the wide-character string to be converted.

cchWideChar

[in] Specifies the number of Unicode (16-bit) characters in the string pointed to by the lpWideCharStrparameter. If this value is –1, the string is assumed to be null-terminated and the length is calculated automatically.

lpMultiByteStr

[out] Pointer to the buffer to receive the translated string.

cbMultiByte

[in] Specifies the size in bytes of the buffer pointed to by the lpMultiByteStrparameter. If this value is zero, the function returns the number of bytes required for the buffer. (In this case, the lpMultiByteStrbuffer is not used.)

lpDefaultChar

[in] Pointer to the character used if a wide character cannot be represented in the specified code page. If this parameter is NULL, a system default value is used. The function is faster when both lpDefaultCharand lpUsedDefaultCharare NULL.

lpUsedDefaultChar

[in/out] Pointer to a flag that indicates whether a default character was used. The flag is set to TRUE if one or more wide characters in the source string cannot be represented in the specified code page. Otherwise, the flag is set to FALSE. This parameter may be NULL. The function is faster when both lpDefaultCharand lpUsedDefaultCharare NULL.

Return Values

If cbMultiByteis nonzero, the number of bytes written to the buffer pointed to by lpMultiByteStrindicates success. If cbMultiByteis zero, the required size, in bytes, for a buffer that can receive the translated string indicates success. Zero indicates failure. To get extended error information, call GetLastError. Possible values for GetLastErrorinclude the following:

ERROR_INSUFFICIENT_BUFFER
ERROR_INVALID_FLAGS

ERROR_INVALID_PARAMETER

Remarks

The lpMultiByteStrand lpWideCharStrpointers must not be the same. If they are the same, the function fails, and GetLastErrorreturns ERROR_INVALID_PARAMETER.

An application can use the lpDefaultCharparameter to change the default character used for the conversion.

As noted earlier, the WideCharToMultiBytefunction operates most efficiently when both lpDefaultCharand lpUsedDefaultCharare NULL. The following table shows the behavior of WideCharToMultiBytefor the four combinations of lpDefaultCharand 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 lpUsedDefaultCharif necessary.
non-NULL	non-NULL	Uses the specified default character and sets lpUsedDefaultCharif necessary.

Requirements

Runs on	Versions	Defined in	Include	Link to
Windows CE OS	1.01 and later	Winnls.h

Note This API is part of the complete Windows CE OS package as provided by Microsoft. The functionality of a particular platform is determined by the original equipment manufacturer (OEM) and some devices may not support this API.

See Also

GetLastError, MultiByteToWideChar