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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 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.

Note:
For the code page 65001 (UTF-8), dwFlagsmust 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 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] 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 can be NULL.

The function is faster when both lpDefaultCharand lpUsedDefaultCharare NULL.

Return Value

The number of bytes written to the buffer pointed to by lpMultiByteStrindicates success if cbMultiByteis nonzero,.

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

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

If the lpMultiByteStrand lpWideCharStrpointers 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.

WideCharToMultiByteoperates most efficiently when both lpDefaultCharand lpUsedDefaultCharare NULL. The behavior of WideCharToMultiBytefor the four combinations of lpDefaultCharand lpUsedDefaultCharis shown in the following table.

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

Header winnls.h
Library coredll.lib
Windows Embedded CE Windows CE 1.01 and later
Windows Mobile Windows Mobile Version 5.0 and later

See Also