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StringCchPrintfExW function (strsafe.h)

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Writes formatted data to the specified 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.

StringCchPrintfEx adds to the functionality of StringCchPrintf 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.

StringCchPrintfEx is a replacement for the following functions:

Syntax

STRSAFEAPI StringCchPrintfExW(
  [out]           STRSAFE_LPWSTR  pszDest,
  [in]            size_t          cchDest,
  [out, optional] STRSAFE_LPWSTR  *ppszDestEnd,
  [out, optional] size_t          *pcchRemaining,
  [in]            DWORD           dwFlags,
  [in]            STRSAFE_LPCWSTR pszFormat,
                  ...             
);

Parameters

[out] pszDest

Type: LPTSTR

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

[in] cchDest

Type: size_t

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

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.

[out, optional] pcchRemaining

Type: size_t*

The number of unused characters in pszDest, including the terminating null character. If pcchRemaining is NULL, the count is not kept or returned.

[in] dwFlags

Type: DWORD

One or more of the following values.

Value Meaning
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.

[in] pszFormat

Type: LPCTSTR

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.

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
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 either 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 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

Compared to the functions it replaces, StringCchPrintfEx provides additional processing for proper buffer handling in your code. Poor buffer handling is implicated in many security issues that involve buffer overruns. StringCchPrintfEx always null-terminates a nonzero-length destination buffer.

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.

StringCchPrintfEx 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" StringCchPrintfExA
TCHAR TEXT("string") StringCchPrintfEx
WCHAR L"string" StringCchPrintfExW
 

Note

The strsafe.h header defines StringCchPrintfEx 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

StringCbPrintfEx

StringCchPrintf

StringCchVPrintfEx