RtlUnicodeStringVPrintfEx function (ntstrsafe.h)

Article
05/02/2024

The RtlUnicodeStringVPrintfEx function creates a text string, with formatting that is based on supplied formatting information, and stores the string in a UNICODE_STRING structure.

Syntax

NTSTRSAFEDDI RtlUnicodeStringVPrintfEx(
  [out]           PUNICODE_STRING  DestinationString,
  [out, optional] PUNICODE_STRING  RemainingString,
  [in]            DWORD            dwFlags,
  [in]            NTSTRSAFE_PCWSTR pszFormat,
  [in]            va_list          argList
);

Parameters

[out] DestinationString

Optional. A pointer to a UNICODE_STRING structure that receives a formatted string. RtlUnicodeStringVPrintfEx creates this string from the formatting string that pszFormat supplies and the function's argument list. The maximum number of characters in the string is NTSTRSAFE_UNICODE_STRING_MAX_CCH. DestinationString can be NULL, but only if STRSAFE_IGNORE_NULLS is set in dwFlags.

[out, optional] RemainingString

Optional. If the caller supplies a non-NULL pointer to a UNICODE_STRING structure, RtlUnicodeStringVPrintfE sets this structure's Buffer member to the end of the formatted string, sets the structure's Length member to zero, and sets the structure's MaximumLength member to the number of bytes that are remaining in the destination buffer. RemainingString can be NULL, but only if STRSAFE_IGNORE_NULLS is set in dwFlags.

[in] dwFlags

One or more flags and, optionally, a fill byte. The flags are defined as follows:

STRSAFE_FILL_BEHIND

If this flag is set and the function succeeds, the low byte of dwFlags is used to fill the portion of the destination buffer that follows the last character in the string.

STRSAFE_IGNORE_NULLS

If this flag is set, the source or destination pointer, or both, can be NULL. RtlUnicodeStringVPrintfEx treats NULL source buffer pointers like empty strings (TEXT("")), which can be copied. NULL destination buffer pointers cannot receive nonempty strings.

STRSAFE_FILL_ON_FAILURE

If this flag is set and the function fails, the low byte of dwFlags is used to fill the entire destination buffer. This operation overwrites any preexisting buffer contents.

STRSAFE_NULL_ON_FAILURE

If this flag is set and the function fails, the destination buffer is set to an empty string (TEXT("")). This operation overwrites any preexisting buffer contents.

STRSAFE_NO_TRUNCATION

If this flag is set and the function returns STATUS_BUFFER_OVERFLOW, the contents of the destination buffer are not modified.

STRSAFE_ZERO_LENGTH_ON_FAILURE

If this flag is set and the function returns STATUS_BUFFER_OVERFLOW, the destination string length is set to zero bytes.

[in] pszFormat

A pointer to a null-terminated text string that contains printf-styled formatting directives. This pointer can be NULL, but only if STRSAFE_IGNORE_NULLS is set in dwFlags.

[in] argList

A va_list-typed argument list. Arguments in this argument list will be interpreted by the using formatting string that pszFormat supplies.

Return value

RtlUnicodeStringVPrintfEx returns one of the following NTSTATUS values.

Return code	Description
STATUS_SUCCESS	This success status means source data was present, and the strings were concatenated without truncation.
STATUS_BUFFER_OVERFLOW	This warning status means the copy operation did not complete due to insufficient space in the destination buffer. If STRSAFE_NO_TRUNCATION is set in dwFlags, the destination buffer is not modified. If the flag is not set, the destination buffer contains a truncated version of the copied string.
STATUS_INVALID_PARAMETER	This error status means the function received an invalid input parameter. For more information, see the following paragraph.

RtlUnicodeStringVPrintfEx returns the STATUS_INVALID_PARAMETER value when one of the following occurs:

The contents of a UNICODE_STRING structure are invalid.
An invalid flag is specified in dwFlags.
The destination buffer is already full.
A buffer pointer is NULL and the STRSAFE_IGNORE_NULLS flag is not specified in dwFlags.
The destination buffer pointer is NULL, but the buffer size is not zero.
The destination buffer pointer is NULL, or its length is zero, but a nonzero length source string is present.

For information about how to test NTSTATUS values, see Using NTSTATUS Values.

Remarks

The RtlUnicodeStringVPrintfEx function uses the destination buffer's size to ensure that the string formatting operation does not write past the end of the buffer. By default, the function does not terminate the resultant string with a null character value (that is, with zero). As an option, the caller can use the STRSAFE_FILL_BEHIND flag and a fill byte value of zero to null-terminate a resultant string that does not occupy the entire destination buffer.

RtlUnicodeStringVPrintfEx adds to the functionality of the RtlUnicodeStringVPrintf function by returning a UNICODE_STRING structure that identifies the end of the destination string and the number of bytes that are left unused in that string. You can pass flags to RtlUnicodeStringVPrintfEx for additional control.

If the format string and the destination string overlap, the behavior of the function is undefined.

The pszFormat and DestinationString pointers cannot be NULL unless the STRSAFE_IGNORE_NULLS flag is set in dwFlags. If STRSAFE_IGNORE_NULLS is set, one or both of these pointers can be NULL. If the DestinationString pointer is NULL, the pszFormat pointer must be NULL or point to an empty string.

For more information about va_list-typed argument lists, see the Microsoft Windows SDK documentation.

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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