SHUnicodeToUnicode function (shlwapi.h)

[This function is available through Windows XP and Windows Server 2003. It might be altered or unavailable in subsequent versions of Windows.]

Copies a Unicode string.


int SHUnicodeToUnicode(
  [in]  PCWSTR pwzSrc,
  [out] PWSTR  pwzDst,
        int    cwchBuf


[in] pwzSrc


A pointer to a null-terminated Unicode string to be copied to the output buffer.

[out] pwzDst


A pointer to an output buffer to receive the copied characters. The buffer must be large enough to contain the number of WCHAR characters specified by cwchBuf, including room for a terminating null character.


Type: int

The number of WCHAR characters that can be contained by the buffer pointed to by pwzDst parameter. This parameter must be greater than zero.

Return value

Type: int

Returns the number of WCHAR characters written to the output buffer, including the terminating null character. Returns 0 if unsuccessful.


Security Warning:  Using this function incorrectly can compromise the security of your application. For example, if pwzDst buffer is not large enough to contain the number of characters specified by cwchBuf, a buffer overrun can occur. Buffer overruns can cause a denial of service attack against an application if an access violation occurs. In the worst case, a buffer overrun might allow an attacker to inject executable code into your process, especially if pwzDst is a stack-based buffer. When copying an entire string, note that sizeof returns the number of bytes, which is not the correct value to use for the cwchBuf parameter. Instead, use sizeof(pwzDst)/sizeof(WCHAR). Note that this technique assumes that pwzDst is an array, not a pointer. Note also that the function silently truncates the output string if the buffer is not large enough. This can result in canonicalization or other security vulnerabilities.

If the pwzDst buffer is not large enough to contain the entire converted output string, the string is truncated to fit the buffer. There is no way to detect that the return string has been truncated. The string will always be null-terminated, even if it has been truncated. This ensures that no more than cwchBuf characters are copied to pwzDst. No attempt is made to avoid truncating the string in the middle of a Unicode surrogate pair.

If the pwzSrc and pwzDst buffers overlap, the function's behavior is undefined.

Note  Do not assume that the function has not changed any of the characters in the output buffer that follow the string's terminating null character. The contents of the output buffer following the string's terminating null character are undefined, up to and including the last character in the buffer.
SHTCharToUnicode is defined to be the same as SHUnicodeToUnicode.

SHUnicodeToTChar is defined to be the same as SHUnicodeToUnicode.


Minimum supported client Windows 2000 Professional, Windows XP [desktop apps only]
Minimum supported server Windows 2000 Server, Windows Server 2003 [desktop apps only]
Target Platform Windows
Header shlwapi.h
DLL Shlwapi.dll (version 5.0 or later)

See also