RtlStringCchCopyW function (ntstrsafe.h)

Article
10/21/2021

The RtlStringCchCopyW and RtlStringCchCopyA functions copy a null-terminated source string into a destination buffer of specified length.

Syntax

NTSTRSAFEDDI RtlStringCchCopyW(
  [out] NTSTRSAFE_PWSTR  pszDest,
  [in]  size_t           cchDest,
  [in]  NTSTRSAFE_PCWSTR pszSrc
);

Parameters

[out] pszDest

A pointer to a caller-supplied buffer that receives the copied string. The string at pszSrc is copied to the buffer at pszDest and terminated with a null character.

[in] cchDest

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

[in] pszSrc

A pointer to a caller-supplied, null-terminated string.

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 string was copied without truncation, and the resultant destination buffer is null-terminated.
STATUS_BUFFER_OVERFLOW	This warning status means the copy 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. A NULL pointer was present. The destination buffer length was zero at entry.

Return code

Description

STATUS_SUCCESS

This success status means source data was present, the string was copied without truncation, and the resultant destination buffer is null-terminated.

STATUS_BUFFER_OVERFLOW

This warning status means the copy 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.
A NULL pointer was present.
The destination buffer length was zero at entry.

Remarks

RtlStringCchCopyW and RtlStringCchCopyA should be used instead of the following functions:

strcpy
wcscpy

These functions are not replacements for strncpy. Use RtlStringCchCopyN or RtlStringCchCopyNEx to replace strncpy.

The size, in characters, of the destination buffer is provided to RtlStringCchCopyW and RtlStringCchCopyA to ensure that they do not write past the end of the buffer.

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

String data type	String literal	Function
WCHAR	L"string"	RtlStringCchCopyW
char	"string"	RtlStringCchCopyA

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 RtlStringCchCopyEx.

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	PASSIVE_LEVEL