StringCchVPrintfEx (Windows CE 5.0)
Developing an Application > Safe String Functions > Safe String Reference > StrSafe.h Character-Count Functions
This function is a replacement for vsprintf. It accepts a format string and its arguments, provided as a va_list, and returns a formatted string.
The size, in characters, of the destination buffer is provided to the function to ensure that StringCchVPrintfEx does not write past the end of this buffer.
StringCchVPrintfEx adds to the functionality of StringCchVPrintf by returning a pointer to the end of the destination string, and by returning the number of characters left unused in that string.
Flags can also be passed to the function for additional control.
HRESULT StringCchVPrintfEx( LPTSTR pszDest, size_t cchDest, LPTSTR *ppszDestEnd, size_t *pcchRemaining, DWORD dwFlags, LPCTSTR pszFormat, va_list argList);
Parameters
pszDest
[out] Pointer to a buffer that receives the formatted, null-terminated string created from pszFormat and argList.cchDest
[in] Size of the destination buffer, in characters.This value must be sufficiently large to accommodate the final formatted string plus 1 to account for the terminating null character.
The maximum number of characters allowed is STRSAFE_MAX_CCH.
ppszDestEnd
[out] Address of a pointer to the end of pszDest.If ppszDestEnd is non-NULL and data is copied into the destination buffer, this points to the terminating null character at the end of the string.
pcchRemaining
[out] Pointer to a variable that indicates the number of unused characters in pszDest, including the terminating null character.If pcchRemaining is NULL, the count is not kept or returned.
dwFlags
[in] One or more of the following values.Value Description STRSAFE_FILL_BEHIND_NULL If the function succeeds, the low byte of dwFlags (0) is used to fill the uninitialized portion of pszDest following the terminating null character. STRSAFE_IGNORE_NULLS Treat null string pointers like empty strings (TEXT("")). STRSAFE_FILL_ON_FAILURE 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 truncated string returned is overwritten.
STRSAFE_NULL_ON_FAILURE If the function fails, pszDest is set to an empty string (TEXT("")). In the case of a STRSAFE_E_INSUFFICIENT_BUFFER failure, any truncated string is overwritten.
STRSAFE_NO_TRUNCATION As in the case of STRSAFE_NULL_ON_FAILURE, if the function fails, pszDest is set to an empty string (TEXT("")). In the case of a STRSAFE_E_INSUFFICIENT_BUFFER failure, any truncated string is overwritten.
pszFormat
[in] Pointer to a buffer containing a printf-style format string. This string must be null-terminated.argList
[in] A va_list containing the arguments to be inserted into pszFormat.
Return Value
This function returns an HRESULT, as opposed to vsprintf, which returns the number of characters written.
It is strongly recommended that you use the SUCCEEDED and FAILED macros to test the return value of this function.
| Value | Description |
|---|---|
| S_OK | There was sufficient space for the result to be copied to pszDest without truncation, and the buffer is null-terminated. |
| STRSAFE_E_INVALID_PARAMETER | The value in cchDest is 0 or larger than STRSAFE_MAX_CCH, or the destination buffer is already full. |
| STRSAFE_E_INSUFFICIENT_BUFFER | The copy operation failed due to insufficient buffer space.
Depending on the value of dwFlags, the destination buffer might contain a truncated, null-terminated version of the intended result. Where truncation is acceptable, this is not necessarily a failure condition. |
Remarks
StringCchVPrintfEx provides additional processing for proper buffer handling in your code.
Poor buffer handling is implicated in many security issues that involve buffer overruns. StringCchVPrintfEx always null-terminates a nonzero-length destination buffer.
For more information on va_lists, see the conventions defined in Stdarg.h.
StringCchVPrintfEx can be used in its generic form, or specifically as StringCchVPrintfExA (for ANSI strings) or StringCchVPrintfExW (for Unicode strings). The form to use is determined by your data.
| String data type | String literal | Function |
|---|---|---|
| char | "string" | StringCchVPrintfExA |
| TCHAR | TEXT("string") | StringCchVPrintfEx |
| WCHAR | L"string" | StringCchVPrintfExW |
StringCchVPrintfEx and its ANSI and Unicode variants are replacements for these functions:
If the strings pointed to by pszDest, pszFormat, or argument strings overlap, behavior is undefined.
Neither pszFormat nor pszDest should be NULL unless the STRSAFE_IGNORE_NULLS flag is specified; in which case both might be NULL.
An error due to insufficient space might still be returned even though null values are ignored.
Requirements
OS Versions: Windows CE 5.0 and later.
Header: strsafe.h.
Link Library: strsafe.lib.
See Also
StringCbVPrintfEx | StringCchVPrintf | StringCchPrintfEx
Send Feedback on this topic to the authors