Windows Driver Kit: Kernel-Mode Driver Architecture
RtlUnicodeStringCchCatN
The RtlUnicodeStringCchCatN function concatenates two strings that are contained in UNICODE_STRING structures while limiting the size of the copied string.
NTSTATUS
RtlUnicodeStringCchCatN(
IN OUT PUNICODE_STRING DestinationString,
IN PCUNICODE_STRING SourceString,
IN size_t cchToAppend
);
Parameters
- 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.
- 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.
- 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 value | Meaning |
|---|
| 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.
Comments
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.
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
IRQL: PASSIVE_LEVEL
Headers: Declared in Ntstrsafe.h. Include Ntstrsafe.h. Link to Ntstrsafe.lib.
See Also
RtlUnicodeStringCbCatN, RtlUnicodeStringCchCatNEx, UNICODE_STRING