SHAnsiToUnicode function (shlwapi.h)

Article
10/13/2021

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

Converts a string from the ANSI code page to the Unicode code page.

Syntax

int SHAnsiToUnicode(
  [in]  PCSTR pszSrc,
  [out] PWSTR pwszDst,
        int   cwchBuf
);

Parameters

[in] pszSrc

Type: PCSTR

A pointer to a null-terminated ANSI string to be converted to Unicode.

[out] pwszDst

Type: PWSTR

A pointer to a buffer that, when this function returns successfully, receives the string specified by pszSrc, after the ANSI characters have been converted to Unicode (WCHAR). The buffer must be large enough to contain the number of Unicode characters specified by the cwchBuf parameter, including a terminating null character.

cwchBuf

Type: int

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

Return value

Type: int

Returns the number of Unicode characters written to pwszDst, including the terminating null character. Returns 0 if unsuccessful.

Remarks

Security Warning: Using this function incorrectly can compromise the security of your application. For example, if pwszDst 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 pwszDst 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(pwszDst)/sizeof(WCHAR). Note that this technique assumes that pwszDst is an array, not a pointer.

If the pwszDst 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 is always null-terminated, even if it has been truncated. This ensures that no more than cwchBuf characters are copied to pwszDst. No attempt is made to avoid truncating the string in the middle of a Unicode surrogate pair.

If the pszSrc and pwszDst 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.

SHAnsiToTChar is defined to be the same as SHAnsiToUnicode.

Requirements

Requirement	Value
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)