RtlStringCbCopyNExA - 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
RtlStringCbCopyNEx(
_Out_writes_bytes_(cbDest) LPTSTR pszDest OPTIONAL,
_In_ size_t cbDest,
_In_ LPCTSTR pszSrc OPTIONAL,
_In_ size_t cbToCopy,
_Outptr_opt_result_bytebuffer_(*pcbRemaining) LPTSTR* ppszDestEnd OPTIONAL,
_Out_opt_ size_t* pcbRemaining OPTIONAL,
_In_ DWORD dwFlags
);
Routine Description:
This routine is a safer version of the C built-in function 'strncpy' with
some additional parameters. In addition to functionality provided by
RtlStringCbCopyN, this routine also returns a pointer to the end of the
destination string and the number of bytes left in the destination string
including the null terminator. The flags parameter allows additional controls.
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.
Arguments:
pszDest - destination string
cbDest - size of destination buffer in bytes.
length must be ((_tcslen(pszSrc) + 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
ppszDestEnd - if ppszDestEnd is non-null, the function will return a
pointer to the end of the destination string. If the
function copied any data, the result will point to the
null termination character
pcbRemaining - pcbRemaining is non-null,the function will return the
number of bytes left in the destination string,
including the null terminator
dwFlags - controls some details of the string copy:
STRSAFE_FILL_BEHIND_NULL
if the function succeeds, the low byte of dwFlags will be
used to fill the uninitialize part of destination buffer
behind the null terminator
STRSAFE_IGNORE_NULLS
treat NULL string pointers like empty strings (TEXT("")).
this flag is useful for emulating functions like lstrcpy
STRSAFE_FILL_ON_FAILURE
if the function fails, the low byte of dwFlags will be
used to fill all of the destination buffer, and it will
be null terminated. This will overwrite any truncated
string returned when the failure is
STATUS_BUFFER_OVERFLOW
STRSAFE_NO_TRUNCATION /
STRSAFE_NULL_ON_FAILURE
if the function fails, the destination buffer will be set
to the empty string. This will overwrite any truncated string
returned when the failure is STATUS_BUFFER_OVERFLOW.
Notes:
Behavior is undefined if source and destination strings overlap.
pszDest and pszSrc should not be NULL unless the STRSAFE_IGNORE_NULLS flag
is specified. If STRSAFE_IGNORE_NULLS is passed, both pszDest and pszSrc
may be NULL. An error may still be returned even though NULLS are ignored
due to insufficient space.
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
RtlStringCbCopyNExA(
_Out_writes_bytes_(cbDest) NTSTRSAFE_PSTR pszDest,
_In_ size_t cbDest,
_In_reads_bytes_(cbToCopy) STRSAFE_PCNZCH pszSrc,
_In_ size_t cbToCopy,
_Outptr_opt_result_bytebuffer_(*pcbRemaining) NTSTRSAFE_PSTR* ppszDestEnd,
_Out_opt_ size_t* pcbRemaining,
_In_ DWORD dwFlags)
{
NTSTATUS status;
size_t cchDest = cbDest / sizeof(char);
status = RtlStringExValidateDestA(pszDest, cchDest, NTSTRSAFE_MAX_CCH, dwFlags);
if (NT_SUCCESS(status))
{
NTSTRSAFE_PSTR pszDestEnd = pszDest;
size_t cchRemaining = cchDest;
size_t cchToCopy = cbToCopy / sizeof(char);
status = RtlStringExValidateSrcA(&pszSrc, &cchToCopy, NTSTRSAFE_MAX_CCH, dwFlags);
if (NT_SUCCESS(status))
{
if (dwFlags & (~STRSAFE_VALID_FLAGS))
{
status = STATUS_INVALID_PARAMETER;
if (cchDest != 0)
{
*pszDest = '\0';
}
}
else if (cchDest == 0)
{
// only fail if there was actually src data to copy
if ((cchToCopy != 0) && (*pszSrc != '\0'))
{
if (pszDest == NULL)
{
status = STATUS_INVALID_PARAMETER;
}
else
{
status = STATUS_BUFFER_OVERFLOW;
}
}
else
{
// for consistency with other use in this case...
__analysis_assume_nullterminated(pszDest);
}
}
else
{
size_t cchCopied = 0;
status = RtlStringCopyWorkerA(pszDest,
cchDest,
&cchCopied,
pszSrc,
cchToCopy);
pszDestEnd = pszDest + cchCopied;
cchRemaining = cchDest - cchCopied;
if (NT_SUCCESS(status) &&
(dwFlags & STRSAFE_FILL_BEHIND_NULL) &&
(cchRemaining > 1))
{
size_t cbRemaining;
// safe to multiply cchRemaining * sizeof(char) since cchRemaining < NTSTRSAFE_MAX_CCH and sizeof(char) is 1
cbRemaining = (cchRemaining * sizeof(char)) + (cbDest % sizeof(char));
// handle the STRSAFE_FILL_BEHIND_NULL flag
RtlStringExHandleFillBehindNullA(pszDestEnd, cbRemaining, dwFlags);
}
}
}
else
{
if (cchDest != 0)
{
*pszDest = '\0';
}
}
if (!NT_SUCCESS(status) &&
(dwFlags & (STRSAFE_NO_TRUNCATION | STRSAFE_FILL_ON_FAILURE | STRSAFE_NULL_ON_FAILURE)) &&
(cbDest != 0))
{
// handle the STRSAFE_FILL_ON_FAILURE, STRSAFE_NULL_ON_FAILURE, and STRSAFE_NO_TRUNCATION flags
RtlStringExHandleOtherFlagsA(pszDest,
cbDest,
0,
&pszDestEnd,
&cchRemaining,
dwFlags);
}
if (NT_SUCCESS(status) || (status == STATUS_BUFFER_OVERFLOW))
{
if (ppszDestEnd)
{
*ppszDestEnd = pszDestEnd;
}
if (pcbRemaining)
{
// safe to multiply cchRemaining * sizeof(char) since cchRemaining < NTSTRSAFE_MAX_CCH and sizeof(char) is 1
*pcbRemaining = (cchRemaining * sizeof(char)) + (cbDest % sizeof(char));
}
}
}
return status;
}
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