StringCchCatNW function (strsafe.h)
Concatenates the specified number of characters from one string to another string. The size of the destination buffer is provided to the function to ensure that it does not write past the end of this buffer.
StringCchCatN is a replacement for the following functions:
Syntax
STRSAFEAPI StringCchCatNW(
[in, out] STRSAFE_LPWSTR pszDest,
[in] size_t cchDest,
[in] STRSAFE_PCNZWCH pszSrc,
[in] size_t cchToAppend
);
Parameters
[in, out] pszDest
Type: LPTSTR
The destination buffer, which contains the string that is to be concatenated with pszSrc, and will receive the entire resultant string. The string at pszSrc, up to cchMaxAppend characters, is added to the end of the string at pszDest.
[in] cchDest
Type: size_t
The size of the destination buffer, in characters. This value must equal the length of pszSrc plus either the length of pszDest or cchMaxAppend (whichever is smaller). To this sum add 1 to account for the terminating null character. The maximum number of characters allowed is STRSAFE_MAX_CCH.
[in] pszSrc
Type: LPCTSTR
The source string that is concatenated to the end of pszDest. This string must be null-terminated.
[in] cchToAppend
Type: size_t
The maximum number of characters to be appended to pszDest.
Return value
Type: HRESULT
This function can return one of the following values. It is strongly recommended that you use the SUCCEEDED and FAILED macros to test the return value of this function.
| Return code | Description |
|---|---|
|
Source data was present, the strings were concatenated without truncation, and the resultant destination buffer is null-terminated. |
|
The value in cchDest is either larger than STRSAFE_MAX_CCH, or the destination buffer is already full. |
|
The concatenation operation failed due to insufficient buffer space. The destination buffer contains a truncated, null-terminated version of the intended result. In situations where truncation is acceptable, this may not necessarily be seen as a failure condition. |
Note that this function returns an HRESULT value, unlike the functions that it replaces.
Remarks
Compared to the functions it replaces, StringCchCatN provides additional processing for proper buffer handling in your code. Poor buffer handling is implicated in many security issues that involve buffer overruns. StringCchCatN always null-terminates and never overflows a valid destination buffer, even if the contents of the source string change during the operation.
Behavior is undefined if the strings pointed to by pszSrc and pszDest overlap.
Neither pszSrc nor pszDest should be NULL. See StringCchCatNEx if you require the handling of null string pointer values.
StringCchCatN can be used in its generic form, or in its more specific forms. The data type of the string determines the form of this function that you should use.
| String Data Type | String Literal | Function |
|---|---|---|
| char | "string" | StringCchCatNA |
| TCHAR | TEXT("string") | StringCchCatN |
| WCHAR | L"string" | StringCchCatNW |
Note
The strsafe.h header defines StringCchCatN as an alias that automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that is not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows XP with SP2 [desktop apps | UWP apps] |
| Minimum supported server | Windows Server 2003 with SP1 [desktop apps | UWP apps] |
| Target Platform | Windows |
| Header | strsafe.h |
See also
Reference