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NF:ntstrsafe.RtlStringCbCopyExW |
RtlStringCbCopyExW function (ntstrsafe.h) |
Learn how the RtlStringCbCopyExW and RtlStringCbCopyExA functions copy a byte-counted string into a buffer. |
kernel\rtlstringcbcopyex.htm |
kernel |
08/26/2022 |
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RtlStringCbCopyEx, RtlStringCbCopyExA, RtlStringCbCopyExW, RtlStringCbCopyExW function [Kernel-Mode Driver Architecture], STRSAFE_FILL_BEHIND_NULL, STRSAFE_FILL_ON_FAILURE, STRSAFE_IGNORE_NULLS, STRSAFE_NO_TRUNCATION, STRSAFE_NULL_ON_FAILURE, kernel.rtlstringcbcopyex, ntstrsafe/RtlStringCbCopyExA, ntstrsafe/RtlStringCbCopyExW, safestrings_f0187c41-23b0-491b-9154-ff8778b06418.xml |
ntstrsafe.h |
Ntstrsafe.h |
Desktop |
Available in Windows XP with Service Pack 1 (SP1) and later versions of Windows. |
RtlStringCbCopyExW (Unicode) and RtlStringCbCopyExA (ANSI) |
Ntstrsafe.lib |
Any if strings being manipulated are always resident in memory, otherwise PASSIVE_LEVEL |
Windows |
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The RtlStringCbCopyExW and RtlStringCbCopyExA functions copy a byte-counted string into a buffer.
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. The pszDest pointer can be NULL, but only if STRSAFE_IGNORE_NULLS is set in dwFlags.
The size, in bytes, of the destination buffer. The buffer must be large enough for the string and the terminating null character.
For Unicode strings, the maximum number of bytes is NTSTRSAFE_MAX_CCH * sizeof(WCHAR)
For ANSI strings, the maximum number of bytes is NTSTRSAFE_MAX_CCH * sizeof(char)
If pszDest is NULL, cbDest must be zero.
A pointer to a caller-supplied, null-terminated string. The pszSrc pointer can be NULL, but only if STRSAFE_IGNORE_NULLS is set in dwFlags.
If the caller supplies a non-NULL address pointer, then after the copy operation completes, the function loads that address with a pointer to the destination buffer's resulting NULL string terminator.
If the caller supplies a non-NULL address pointer, the function loads the address with the number of unused bytes that are in the buffer pointed to by pszDest, including bytes used for the terminating null character.
One or more flags and, optionally, a fill byte. The flags are defined as follows:
| Value | Meaning |
|---|---|
| STRSAFE_FILL_BEHIND_NULL | If this flag is set and the function succeeds, the low byte of dwFlags is used to fill the portion of the destination buffer that follows the terminating null character. |
| STRSAFE_IGNORE_NULLS | If this flag is set, either pszDest or pszSrc, or both, can be NULL. NULL pszSrc pointers are treated like empty strings (TEXT("")), which can be copied. NULL pszDest pointers cannot receive nonempty strings. |
| STRSAFE_FILL_ON_FAILURE | If this flag is set and the function fails, the low byte of dwFlags is used to fill the entire destination buffer, and the buffer is null-terminated. This operation overwrites any preexisting buffer contents. |
| STRSAFE_NULL_ON_FAILURE | If this flag is set and the function fails, the destination buffer is set to an empty string (TEXT("")). This operation overwrites any preexisting buffer contents. |
| STRSAFE_NO_TRUNCATION |
If this flag is set and the function returns STATUS_BUFFER_OVERFLOW:
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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 space in the destination buffer. If STRSAFE_NO_TRUNCATION is set, see the dwFlags parameter for more information. |
| 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:
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RtlStringCbCopyExA and RtlStringCbCopyExW should be used instead of the following functions:
- strcpy
- wcscpy
The size, in bytes, of the destination buffer is provided to RtlStringCbCopyExA and RtlStringCbCopyExW to ensure that they do not write past the end of the buffer.
RtlStringCbCopyEx adds to the functionality of RtlStringCbCopy by returning a pointer to the end of the destination string as well as the number of bytes left unused in that string. Flags can be passed to the function for additional control.
Use RtlStringCbCopyExW to handle Unicode strings and RtlStringCbCopyExA 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" | RtlStringCbCopyExW |
| char | "string" | RtlStringCbCopyExA |
If pszSrc and pszDest point to overlapping strings, the behavior of the function is undefined.
Neither pszSrc nor pszDest can be NULL unless the STRSAFE_IGNORE_NULLS flag is set, in which case either or both can be NULL. If pszDest is NULL, pszSrc must either be NULL or point to an empty string.
For more information about the safe string functions, see Using safe string functions.