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RtlStringCchCatNW function (ntstrsafe.h)

  • Article

The RtlStringCchCatNW and RtlStringCchCatNA functions concatenate two character-counted strings while limiting the size of the appended string.

Syntax

NTSTRSAFEDDI RtlStringCchCatNW(
  [in, out] NTSTRSAFE_PWSTR pszDest,
  [in]      size_t          cchDest,
  [in]      STRSAFE_PCNZWCH pszSrc,
            size_t          cchToAppend
);

Parameters

[in, out] pszDest

A pointer to a buffer which, on input, contains a null-terminated string to which pszSrc will be concatenated. On output, this is the destination buffer that contains the entire resultant string. The string at pszSrc, up to cchMaxAppend characters, is added to the end of the string at pszDest and terminated with a null character.

[in] cchDest

The size of the destination buffer, in characters. The maximum number of characters allowed is NTSTRSAFE_MAX_CCH.

[in] pszSrc

A pointer to a null-terminated string. This string will be concatenated to the end of the string that is contained in the buffer at pszDest.

cchToAppend

The maximum number of characters to append to the string that is contained in the buffer at pszDest.

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 strings were concatenated without truncation, and the resultant destination buffer is null-terminated.
STATUS_BUFFER_OVERFLOW
 This warning status means the concatenation operation did not complete due to insufficient buffer space. The destination buffer contains a truncated, null-terminated version of the intended result.
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

RtlStringCchCatNW and RtlStringCchCatNA should be used instead of the following functions:

  • strncat
  • wcsncat
The size, in characters, of the destination buffer is provided to the function to ensure that RtlStringCchCatNW and RtlStringCchCatNA do not write past the end of the buffer.

Use RtlStringCchCatNW to handle Unicode strings and RtlStringCchCatNA to handle ANSI strings. The form you use depends on your data, as shown in the following table.

String data type String literal Function
WCHAR L"string" RtlStringCchCatNW
char "string" RtlStringCchCatNA
 

If pszSrc and pszDest point to overlapping strings, the behavior of the function is undefined.

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

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

See also

RtlStringCbCatN

RtlStringCchCat

RtlStringCchCatNEx