RtlStringCbCopyNA - NtDoc
Native API online documentation, based on the System Informer
(formerly Process Hacker) phnt
headers
#ifndef _NTSTRSAFE_H_INCLUDED_
#ifndef NTSTRSAFE_LIB_IMPL
#ifndef NTSTRSAFE_NO_CB_FUNCTIONS
/*++
NTSTATUS
RtlStringCbCopyN(
_Out_writes_bytes_(cbDest) LPTSTR pszDest,
_In_ size_t cbDest,
_In_ LPCTSTR pszSrc,
_In_ size_t cbToCopy
);
Routine Description:
This routine is a safer version of the C built-in function 'strncpy'.
The size of the destination buffer (in bytes) is a parameter and this
function will not write past the end of this buffer and it will ALWAYS
null terminate the destination buffer (unless it is zero length).
This routine is meant as a replacement for strncpy, but it does behave
differently. This function will not pad the destination buffer with extra
null termination characters if cbToCopy is greater than the size of pszSrc.
This function returns an NTSTATUS value, and not a pointer. It returns
STATUS_SUCCESS if the entire string or the first cbToCopy characters were
copied without truncation and the resultant destination string was null
terminated, otherwise it will return a failure code. In failure cases as
much of pszSrc will be copied to pszDest as possible, and pszDest will be
null terminated.
Arguments:
pszDest - destination string
cbDest - size of destination buffer in bytes.
length must be = ((_tcslen(src) + 1) * sizeof(TCHAR)) to
hold all of the source including the null terminator
pszSrc - source string
cbToCopy - maximum number of bytes to copy from source string,
not including the null terminator.
Notes:
Behavior is undefined if source and destination strings overlap.
pszDest and pszSrc should not be NULL. See RtlStringCbCopyEx if you require
the handling of NULL values.
Return Value:
STATUS_SUCCESS - if there was source data and it was all copied and the
resultant dest string was null terminated
failure - you can use the macro NTSTATUS_CODE() to get a win32
error code for all hresult failure cases
STATUS_BUFFER_OVERFLOW /
NTSTATUS_CODE(status) == ERROR_INSUFFICIENT_BUFFER
- this return value is an indication that the copy
operation failed due to insufficient space. When this
error occurs, the destination buffer is modified to
contain a truncated version of the ideal result and is
null terminated. This is useful for situations where
truncation is ok
It is strongly recommended to use the NT_SUCCESS() macro to test the
return value of this function.
--*/
NTSTRSAFEDDI
RtlStringCbCopyNA(
_Out_writes_bytes_(cbDest) NTSTRSAFE_PSTR pszDest,
_In_ size_t cbDest,
_In_reads_bytes_(cbToCopy) STRSAFE_PCNZCH pszSrc,
_In_ size_t cbToCopy)
{
NTSTATUS status;
size_t cchDest = cbDest / sizeof(char);
status = RtlStringValidateDestA(pszDest, cchDest, NTSTRSAFE_MAX_CCH);
if (NT_SUCCESS(status))
{
size_t cchToCopy = cbToCopy / sizeof(char);
if (cchToCopy > NTSTRSAFE_MAX_LENGTH)
{
status = STATUS_INVALID_PARAMETER;
*pszDest = '\0';
}
else
{
status = RtlStringCopyWorkerA(pszDest,
cchDest,
NULL,
pszSrc,
cchToCopy);
}
}
return status;
}
View code on GitHub// ntstrsafe.h
NTSTRSAFEDDI RtlStringCbCopyNA(
[out] NTSTRSAFE_PSTR pszDest,
[in] size_t cbDest,
[in] STRSAFE_PCNZCH pszSrc,
size_t cbToCopy
);
View the official Windows Driver Kit DDI referenceNo description available.
The RtlStringCbCopyNW and RtlStringCbCopyNA functions copy a byte-counted string to a buffer while limiting the size of the copied string.
pszDest [out]A pointer to a caller-supplied buffer that receives the copied string. The string at pszSrc, up to cbSrc bytes, is copied to the buffer at pszDest and terminated with a null character.
cbDest [in]The size, in bytes, of the destination buffer. The buffer must be large enough for both 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).
pszSrc [in]A pointer to a caller-supplied, null-terminated string.
cbToCopyThe maximum number of bytes to copy from pszSrc to pszDest.
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. The destination buffer contains a truncated version of the copied string. |
| 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 cbDest is larger than the maximum buffer size. * The destination buffer was already full. * A NULL pointer was present. * The destination buffer's length was zero, but a nonzero length source string was present. |
RtlStringCbCopyNW and RtlStringCbCopyNA should be used instead of strncpy. However, these functions differ in behavior. If cbSrc is larger than the number of bytes in pszSrc, the RtlStringCbCopyN functions—unlike strncpy—do not fill pszDest with null characters until cbSrc bytes have been copied.
RtlStringCbCopyN copies a given number of bytes from a source string. The size, in bytes, of the destination buffer is provided to the function to ensure that RtlStringCbCopyN does not write past the end of this buffer.
Use RtlStringCbCopyNW to handle Unicode strings and RtlStringCbCopyNA 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" | RtlStringCbCopyNW |
| char | "string" | RtlStringCbCopyNA |
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, see RtlStringCbCopyNEx.
For more information about the safe string functions, see Using Safe String Functions.