StringCchVPrintfExA function (strsafe.h)
Writes formatted data to the specified string using a pointer to a list of arguments. The size of the destination buffer is provided to the function to ensure that it 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 as well as the number of characters left unused in that string. Flags may also be passed to the function for additional control.
StringCchVPrintfEx is a replacement for the following functions:
STRSAFEAPI StringCchVPrintfExA( [out] STRSAFE_LPSTR pszDest, [in] size_t cchDest, [out, optional] STRSAFE_LPSTR *ppszDestEnd, [out, optional] size_t *pcchRemaining, [in] DWORD dwFlags, [in] STRSAFE_LPCSTR pszFormat, [in] va_list argList );
The destination buffer, which receives the formatted, null-terminated string created from pszFormat and argList.
The 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.
[out, optional] ppszDestEnd
The address of a pointer to the end of pszDest. If ppszDestEnd is non-NULL and any data is copied into the destination buffer, this points to the terminating null character at the end of the string.
[out, optional] pcchRemaining
The number of unused characters in pszDest, including the terminating null character. If pcchRemaining is NULL, the count is not kept or returned.
One or more of the following values.
The format string. This string must be null-terminated. For more information, see Format Specification Syntax.
The arguments to be inserted into the pszFormat string.
||There was sufficient space for the result to be copied to pszDest without truncation and the buffer is null-terminated.|
||The value in cchDest is either 0 or larger than STRSAFE_MAX_CCH, or the destination buffer is already full.|
||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.
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.
Behavior is undefined if the strings pointed to by pszDest, pszFormat, or any argument strings overlap.
Neither pszFormat 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.
StringCchVPrintfEx 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|
The strsafe.h header defines StringCchVPrintfEx as an alias which 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 not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.
|Minimum supported client||Windows XP with SP2 [desktop apps | UWP apps]|
|Minimum supported server||Windows Server 2003 with SP1 [desktop apps | UWP apps]|