WideCharToMultiByte

A version of this page is also available for

Windows Embedded CE 6.0 R3

4/8/2010

This function maps a wide-character string to a new character string. The new character string is not necessarily from a multibyte character set.

Syntax

int WideCharToMultiByte(
  UINT CodePage,
  DWORD dwFlags,
  LPCWSTR lpWideCharStr,
  int cchWideChar,
  LPSTR lpMultiByteStr,
  int cbMultiByte,
  LPCSTR lpDefaultChar,
  LPBOOL lpUsedDefaultChar
);

Parameters

• CodePage
  [in] Code page used to perform the conversion.

  You can set this parameter to 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	Description
  CP_ACP	ANSI code page
  CP_MACCP	Not supported
  CP_OEMCP	OEM code page
  CP_SYMBOL	Not supported
  CP_THREAD_ACP	Not supported
  CP_UTF7	UTF-7 code page
  CP_UTF8	UTF-8 code page

  When SYSGEN_LOCUSA is set, only the 1252 and 437 code pages are supported.

  To create an image that has very limited locale support, specify the image with SYSGEN_CORELOC and put the necessary locales for the image into Public\Common\Oak\Files\Nlscfg.inf.

• dwFlags
  [in] Handling of unmapped characters. The function performs more quickly when none of these flags is set.

  The flag constants are described in the following table.

  Value	Description
  WC_COMPOSITECHECK	Convert composite characters to precomposed characters.
  WC_DEFAULTCHAR	Replace exceptions with the default character during conversion.
  WC_DISCARDNS	Discard nonspacing characters during conversion.
  WC_SEPCHARS	Generate separate characters during conversion. This is the default conversion behavior.

  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 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.

  Note

  For the code page 65001 (UTF-8), dwFlags must be set to 0. Otherwise, the function fails with ERROR_INVALID_FLAGS.

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

• cchWideChar
  [in] Number of Unicode (16-bit) characters in the string pointed to by the lpWideCharStr parameter. 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] Size, in bytes, of the buffer pointed to by the lpMultiByteStr parameter. If this value is zero, the function returns the number of bytes required for the buffer. (In this case, the lpMultiByteStr buffer 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 lpDefaultChar and lpUsedDefaultChar are 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 can be NULL.

  The function is faster when both lpDefaultChar and lpUsedDefaultChar are NULL.

Return Value

The number of bytes written to the buffer pointed to by lpMultiByteStr indicates success if cbMultiByte is nonzero,.

The required size, in bytes, for a buffer that can receive the translated string indicates success if cbMultiByte is zero,.

Zero indicates failure. To get extended error information, call GetLastError. Possible values for GetLastError include the following:

• ERROR_INSUFFICIENT_BUFFER
• ERROR_INVALID_FLAGS
• ERROR_INVALID_PARAMETER

Remarks

If the lpMultiByteStr and lpWideCharStr pointers 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.

WideCharToMultiByte operates most efficiently when both lpDefaultChar and lpUsedDefaultChar are NULL. The behavior of WideCharToMultiByte for the four combinations of lpDefaultChar and lpUsedDefaultChar is shown in the following table.

Requirements

See Also

Reference

Unicode Functions
MultiByteToWideChar