RtlUnicodeStringCchCatN function (ntstrsafe.h)

Article
05/02/2024

The RtlUnicodeStringCchCatN function concatenates two strings that are contained in UNICODE_STRING structures while limiting the size of the copied string.

Syntax

NTSTRSAFEDDI RtlUnicodeStringCchCatN(
  [in, out] PUNICODE_STRING  DestinationString,
  [in]      PCUNICODE_STRING SourceString,
  [in]      size_t           cchToAppend
);

Parameters

[in, out] DestinationString

A pointer to a UNICODE_STRING structure. This structure includes a buffer that, on input, contains a destination string to which the source string will be concatenated. On output, this buffer is the destination buffer that contains the entire resultant string. The source string is added to the end of the destination string. The maximum number of characters in the structure's string buffer is NTSTRSAFE_UNICODE_STRING_MAX_CCH.

[in] SourceString

A pointer to a UNICODE_STRING structure. This structure includes a buffer that contains the source string. This string will be added to the end of the destination string. The maximum number of characters in the structure's string buffer is NTSTRSAFE_UNICODE_STRING_MAX_CCH.

[in] cchToAppend

The maximum number of characters to append to the string that the DestinationString parameter describes.

Return value

RtlUnicodeStringCchCatN returns one of the following NTSTATUS values.

Return code	Description
STATUS_SUCCESS	This success status means that source data was present, the strings were concatenated without truncation, and the resultant destination buffer is null-terminated.
STATUS_BUFFER_OVERFLOW	This warning status means that the concatenated operation did not complete because of insufficient buffer space. The destination buffer contains a truncated, null-terminated version of the intended result.
STATUS_INVALID_PARAMETER	This error status means that the function received an invalid input parameter. For more information, see the following list.

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

The contents of the UNICODE_STRING structure are invalid.
The destination buffer is already full.
A buffer pointer is NULL.
The destination buffer's length is zero, but a nonzero length source string is present.
The cchToAppend parameter's value is greater than NTSTRSAFE_UNICODE_STRING_MAX_CCH.

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

Remarks

The RtlUnicodeStringCchCatN function uses the destination buffer's size to ensure that the concatenation operation does not write past the end of the buffer. The function does not terminate the resultant string with a null character value (that is, with zero).

If the source and destination strings overlap, the behavior of the function is undefined.

The SourceString and DestinationString pointers cannot be NULL. If you need to handle NULL pointer values, use the RtlUnicodeStringCchCatNEx function.

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

Requirements

Requirement	Value
Minimum supported client	Available in Windows XP with Service Pack 1 (SP1) and later versions of Windows.
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