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StringCbVPrintfEx function

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.

StringCbVPrintfEx adds to the functionality of StringCbVPrintf 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.

StringCbVPrintfEx is a replacement for the following functions:

Syntax


HRESULT StringCbVPrintfEx(
  _Out_      LPTSTR pszDest,
  _In_       size_t cbDest,
  _Out_opt_  LPTSTR *ppszDestEnd,
  _Out_opt_  size_t *pcbRemaining,
  _In_       DWORD dwFlags,
  _In_       LPCTSTR pszFormat,
  _In_       va_list argList
);

Parameters

pszDest [out]

Type: LPTSTR

The destination buffer, which receives the formatted, null-terminated string created from pszFormat and argList.

cbDest [in]

Type: size_t

The size of the destination buffer, in bytes. This value must be sufficiently large to accommodate the final formatted string plus the terminating null character. The maximum number of bytes allowed is STRSAFE_MAX_CCH * sizeof(TCHAR).

ppszDestEnd [out, optional]

Type: LPTSTR*

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.

pcbRemaining [out, optional]

Type: size_t*

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]

Type: DWORD

One or more of the following values.

ValueMeaning
STRSAFE_FILL_BEHIND_NULL
0x00000200

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
0x00000100

Treat NULL string pointers like empty strings (TEXT("")).

STRSAFE_FILL_ON_FAILURE
0x00000400

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
0x00000800

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
0x00001000

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]

Type: LPCTSTR

The format string. This string must be null-terminated.

argList [in]

Type: va_list

The arguments to be inserted into the pszFormat string.

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 codeDescription
S_OK

There is 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 cbDest is either 0 or larger than STRSAFE_MAX_CCH * sizeof(TCHAR), 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 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.

Remarks

StringCbVPrintfEx provides additional processing for proper buffer handling in your code. Poor buffer handling is implicated in many security issues that involve buffer overruns. StringCbVPrintfEx 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.

StringCbVPrintfEx 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 TypeString LiteralFunction
char"string"StringCbVPrintfExA
TCHARTEXT("string")StringCbVPrintfEx
WCHARL"string"StringCbVPrintfExW

 

Requirements

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]

Header

Strsafe.h

Unicode and ANSI names

StringCbVPrintfExW (Unicode) and StringCbVPrintfExA (ANSI)

See also

Reference
StringCchVPrintfEx
StringCbVPrintf
StringCbPrintfEx

 

 

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