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RtlStringCchLength function

The RtlStringCchLengthW and RtlStringCchLengthA functions determine the length, in characters, of a supplied string.

Syntax

C++


NTSTATUS RtlStringCchLength(
  _In_       LPCTSTR psz,
  _In_       size_t cchMax,
  _Out_opt_  size_t *pcch
);

Parameters

psz [in]: A pointer to a buffer that contains a null-terminated string, the length of which will be checked.
cchMax [in]: The maximum number of characters allowed in the buffer pointed to by psz, including the terminating null character. This value cannot exceed NTSTRSAFE_MAX_CCH.
pcch [out, optional]: If the caller supplies a non-NULL address pointer, the function loads the address with the length, in characters, of the string that is contained in the buffer. The length does not include the string's terminating null character.

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 the string at psz was not NULL, and the length of the string (including the terminating null character) is less than or equal to cchMax characters.
STATUS_INVALID_PARAMETER	This error status means the value in psz is NULL, cchMax is larger than NTSTRSAFE_MAX_CCH, or psz is longer than cchMax.

Remarks

RtlStringCchLengthW and RtlStringCchLengthA should be used instead of strlen. They are used to ensure that a string is not larger than a given length, in characters. If that condition is met, RtlStringCchLengthW and RtlStringCchLengthA return the current length of the string in characters, not including the terminating null character.

Use RtlStringCchLengthW to handle Unicode strings and RtlStringCchLengthA 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"	RtlStringCchLengthW
char	"string"	RtlStringCchLengthA

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

Requirements