Concatenates 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.
StringCbCatEx adds to the functionality of StringCbCat by returning a pointer to the end of the destination string as well as the number of bytes left unused in that string. Flags may also be passed to the function for additional control.
StringCbCatEx is a replacement for the following functions:
HRESULT StringCbCatEx( _Inout_ LPTSTR pszDest, _In_ size_t cbDest, _In_ LPCTSTR pszSrc, _Out_opt_ LPTSTR *ppszDestEnd, _Out_opt_ size_t *pcbRemaining, _In_ DWORD dwFlags );
- pszDest [in, out]
The string to which pszSrc is to be concatenated, and that will receive the entire resultant string. The string at pszSrc is added to the end of the string at pszDest.
- cbDest [in]
The size of the destination buffer, in bytes. This value must consider the length of pszSrc plus the length of pszDest plus the terminating null character. The maximum number of bytes allowed is
STRSAFE_MAX_CCH * sizeof(TCHAR).
- pszSrc [in]
The source string that is concatenated to the end of pszDest. This string must be null-terminated.
- ppszDestEnd [out, optional]
The address of a pointer to the end of pszDest. If ppszDestEnd is non-NULL and any data is appended to the destination buffer, this points to the terminating null character at the end of the string.
- pcbRemaining [out, optional]
The number of unused bytes in pszDest, including those used for the terminating null character. If pcbRemaining is NULL, the count is not kept or returned.
- dwFlags [in]
One or more of the following values.
If the function succeeds, the low byte of dwFlags (0) is used to fill the uninitialized portion of pszDest following the terminating null character.
Treat NULL string pointers like empty strings (TEXT("")). This flag is useful for emulating functions such as lstrcpy.
If the function fails, the low byte of dwFlags (0) is used to fill the entire pszDest buffer, and the buffer is null-terminated. In the case of a STRSAFE_E_INSUFFICIENT_BUFFER failure, any pre-existing or truncated string in the destination buffer is overwritten.
If the function fails, pszDest is set to an empty string (TEXT("")). In the case of a STRSAFE_E_INSUFFICIENT_BUFFER failure, any pre-existing or truncated string in the destination buffer is overwritten.
If the function fails, pszDest is untouched. Nothing is added to the original contents.
Source data was present, the strings were fully concatenated without truncation, and the resultant destination buffer is null-terminated.
The value in cbDest is either less than
The copy operation failed due to insufficient buffer space. Depending on the value of dwFlags, the destination buffer may contain 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.
StringCbCatEx provides additional processing for proper buffer handling in your code. Poor buffer handling is implicated in many security issues that involve buffer overruns. StringCbCatEx 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 unless the STRSAFE_IGNORE_NULLS flag is specified, in which case both may be NULL. However, an error due to insufficient space may still be returned even though NULL values are ignored.
StringCbCatEx 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, as shown in the following table.
|String Data Type||String Literal||Function|
Minimum supported client
|Windows XP with SP2 [desktop apps | Windows Store apps]|
Minimum supported server
|Windows Server 2003 with SP1 [desktop apps | Windows Store apps]|
Unicode and ANSI names
|StringCbCatExW (Unicode) and StringCbCatExA (ANSI)|