RtlUnicodeStringCbCatStringNEx function (ntstrsafe.h)

The RtlUnicodeStringCbCatStringNEx function concatenates two strings when the destination string is contained in a UNICODE_STRING structure, while limiting the size of the appended string.

Syntax

NTSTRSAFEDDI RtlUnicodeStringCbCatStringNEx(
  [in, out]       PUNICODE_STRING  DestinationString,
  [in]            NTSTRSAFE_PCWSTR pszSrc,
  [in]            size_t           cbToAppend,
  [out, optional] PUNICODE_STRING  RemainingString,
  [in]            DWORD            dwFlags
);

Parameters

[in, out] DestinationString

Optional. 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 (excluding the terminating null) is added to the end of the destination string. The maximum number of bytes in the structure's string buffer is NTSTRSAFE_UNICODE_STRING_MAX_CCH * sizeof(WCHAR). DestinationString can be NULL, but only if STRSAFE_IGNORE_NULLS is set in dwFlags.

[in] pszSrc

A caller-supplied pointer to a null-terminated string. This string will be concatenated to the end of the string that is contained in the UNICODE_STRING structure that DestinationString points to. pszSrc can be NULL, but only if STRSAFE_IGNORE_NULLS is set in dwFlags.

[in] cbToAppend

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

[out, optional] RemainingString

Optional. If the caller supplies a non-NULL pointer to a UNICODE_STRING structure, the function sets this structure's Buffer member to the end of the concatenated 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:

Return value

RtlUnicodeStringCbCatStringNEx returns one of the following NTSTATUS values.

RtlUnicodeStringCbCatStringNEx 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.
• 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.
• The cbToAppend parameter's value is greater than NTSTRSAFE_UNICODE_STRING_MAX_CCH * sizeof(WCHAR).

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

Remarks

The **RtlUnicodeStringCbCatStringNEx **function uses the destination buffer's size to ensure that the concatenation 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.

RtlUnicodeStringCbCatStringNEx adds to the functionality of the RtlUnicodeStringCbCatStringN 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 RtlUnicodeStringCbCatStringNEx for additional control.

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

The pszSrc 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 pszSrc pointer must be NULL or point to an empty string.

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

Requirements

See also

• RtlUnicodeStringCbCatStringN
• RtlUnicodeStringCchCatStringNEx
• UNICODE_STRING