RtlStringCchPrintfA function (ntstrsafe.h)

Article
10/21/2021

The RtlStringCchPrintfW and RtlStringCchPrintfA functions create a character-counted text string, with formatting that is based on supplied formatting information.

Syntax

NTSTRSAFEDDI RtlStringCchPrintfA(
  [out] NTSTRSAFE_PSTR  pszDest,
  [in]  size_t          cchDest,
  [in]  NTSTRSAFE_PCSTR pszFormat,
        ...             
);

Parameters

[out] pszDest

A pointer to a caller-supplied buffer that receives a formatted, null-terminated string. The function creates this string from both the formatting string that is supplied by pszFormat and the function's argument list.

[in] cchDest

The size of the destination buffer, in characters. The buffer must be large enough to contain the formatted string plus the terminating null character. The maximum number of characters allowed is NTSTRSAFE_MAX_CCH.

[in] pszFormat

A pointer to a null-terminated text string that contains printf-styled formatting directives.

...

A list of arguments that are interpreted by the function, based on formatting directives contained in the pszFormat string.

Return value

The function returns one of the NTSTATUS values that are listed in the following table. For information about how to test NTSTATUS values, see Using NTSTATUS Values.

Return code	Description
STATUS_SUCCESS	This success status means source data was present, the string was created without truncation, and the resultant destination buffer is null-terminated.
STATUS_BUFFER_OVERFLOW	This warning status means the operation did not complete due to insufficient space in the destination buffer. The destination buffer contains a truncated version of the output string.
STATUS_INVALID_PARAMETER	This error status means the function received an invalid input parameter. For more information, see the following paragraph. The function returns the STATUS_INVALID_PARAMETER value when: The value in cchDest is larger than the maximum buffer size. The destination buffer was already full. A NULL pointer was present. The destination buffer's length was zero, but a nonzero length source string was present.

Return code

Description

STATUS_SUCCESS

This success status means source data was present, the string was created without truncation, and the resultant destination buffer is null-terminated.

STATUS_BUFFER_OVERFLOW

This warning status means the operation did not complete due to insufficient space in the destination buffer. The destination buffer contains a truncated version of the output string.

STATUS_INVALID_PARAMETER

This error status means the function received an invalid input parameter. For more information, see the following paragraph.

The function returns the STATUS_INVALID_PARAMETER value when:

The value in cchDest is larger than the maximum buffer size.
The destination buffer was already full.
A NULL pointer was present.
The destination buffer's length was zero, but a nonzero length source string was present.

Remarks

RtlStringCchPrintfW and RtlStringCchPrintfA should be used instead of the following functions:

sprintf
swprintf
_snprintf
_snwprintf

All of these functions accept a format string and a list of arguments and return a formatted string. RtlStringCchPrintfW and RtlStringCchPrintfA accept the size, in characters, of the destination buffer to ensure that the functions do not write past the end of the buffer.

Use RtlStringCchPrintfW to handle Unicode strings and RtlStringCchPrintfA to handle ANSI strings. The form you use depends on your data.

String data type	String literal	Function
WCHAR	L"string"	RtlStringCchPrintfW
char	"string"	RtlStringCchPrintfA

If pszDest and pszFormat point to overlapping strings, or if any argument strings overlap, behavior of the function is undefined.

Neither pszFormat nor pszDest can be NULL. If you need to handle NULL string pointer values, use RtlStringCchPrintfEx.

Examples

The following example shows a simple use of RtlStringCchPrintfW using four arguments.

WCHAR pszDest[30]; 
size_t cchDest = 30;

LPCWSTR pszFormat = L"%s %d + %d = %d.";
WCHAR* pszTxt = L"The answer is";

NTSTATUS status = 
    RtlStringCchPrintfW(pszDest, cchDest, pszFormat, pszTxt, 1, 2, 3);

The resultant string is "The answer is 1 + 2 = 3." It is contained in the buffer at pszDest.

For more information about the safe string functions, see Using Safe String Functions.

Requirements

Requirement	Value
Minimum supported client	Available starting with Windows XP with Service Pack 1 (SP1).
Target Platform	Desktop
Header	ntstrsafe.h (include Ntstrsafe.h)
Library	Ntstrsafe.lib
IRQL	Any if strings being manipulated are always resident in memory, otherwise PASSIVE_LEVEL

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