RtlUnicodeStringCbCatNEx - 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_UNICODE_STRING_FUNCTIONS
#ifndef NTSTRSAFE_NO_CB_FUNCTIONS
/*++
NTSTATUS
RtlUnicodeStringCbCatNEx(
_Inout_ PUNICODE_STRING DestinationString OPTIONAL,
_In_ PCUNICODE_STRING SourceString OPTIONAL,
_In_ size_t cbToAppend,
_Out_opt_ PUNICODE_STRING RemainingString OPTIONAL,
_In_ DWORD dwFlags
);
Routine Description:
This routine is a safer version of the C built-in function 'strncat', with
some additional parameters and for PUNICODE_STRINGs. In addition to the
functionality provided by RtlUnicodeStringCbCatN, this routine
also returns a PUNICODE_STRING which points to the end of the destination
string. The flags parameter allows additional controls.
Arguments:
DestinationString - pointer to the counted unicode destination string
SourceString - pointer to the counted unicode source string
cbToAppend - maximum number of bytes to append
RemainingString - if RemainingString is non-null, the function will format
the pointer with the remaining buffer and number of
bytes left in the destination string
dwFlags - controls some details of the string copy:
STRSAFE_FILL_BEHIND
if the function succeeds, the low byte of dwFlags will be
used to fill the uninitialize part of destination buffer
STRSAFE_IGNORE_NULLS
do not fault if DestinationString is null and treat NULL SourceString like
empty strings (L""). 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. This will
overwrite any truncated string returned when the failure is
STATUS_BUFFER_OVERFLOW
STRSAFE_ZERO_LENGTH_ON_FAILURE
if the function fails, the destination Length will be set
to zero. This will overwrite any truncated string
returned when the failure is STATUS_BUFFER_OVERFLOW.
STRSAFE_NO_TRUNCATION
if the function returns STATUS_BUFFER_OVERFLOW, pszDest
will not contain a truncated string, it will remain unchanged.
Notes:
Behavior is undefined if source and destination strings overlap.
DestinationString and SourceString should not be NULL unless the STRSAFE_IGNORE_NULLS flag
is specified. If STRSAFE_IGNORE_NULLS is passed, both DestinationString and SourceString
may be NULL. An error may still be returned even though NULLS are ignored
due to insufficient space.
Return Value:
STATUS_SUCCESS - if all of SourceString or the first cbToAppend bytes were
concatenated to DestinationString
failure - the operation did not succeed
STATUS_BUFFER_OVERFLOW
Note: This status has the severity class Warning - IRPs completed with this
status do have their data copied back to user mode
- this return value is an indication that the
operation failed due to insufficient space. When this
error occurs, the destination buffer is modified to
contain a truncated version of the ideal result.
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
RtlUnicodeStringCbCatNEx(
_Inout_ PUNICODE_STRING DestinationString,
_In_ PCUNICODE_STRING SourceString,
_In_ size_t cbToAppend,
_Out_opt_ PUNICODE_STRING RemainingString,
_In_ DWORD dwFlags)
{
NTSTATUS status;
wchar_t* pszDest;
size_t cchDest;
size_t cchDestLength;
status = RtlUnicodeStringValidateDestWorker(DestinationString,
&pszDest,
&cchDest,
&cchDestLength,
NTSTRSAFE_UNICODE_STRING_MAX_CCH,
dwFlags);
if (NT_SUCCESS(status))
{
wchar_t* pszSrc;
size_t cchSrcLength;
wchar_t* pszDestEnd = pszDest + cchDestLength;
size_t cchRemaining = cchDest - cchDestLength;
size_t cchNewDestLength = cchDestLength;
status = RtlUnicodeStringValidateSrcWorker(SourceString,
&pszSrc,
&cchSrcLength,
NTSTRSAFE_UNICODE_STRING_MAX_CCH,
dwFlags);
if (NT_SUCCESS(status))
{
size_t cchToAppend = cbToAppend / sizeof(wchar_t);
if (cchToAppend > NTSTRSAFE_UNICODE_STRING_MAX_CCH)
{
status = STATUS_INVALID_PARAMETER;
}
else
{
if (cchSrcLength < cchToAppend)
{
cchToAppend = cchSrcLength;
}
if (dwFlags & (~STRSAFE_UNICODE_STRING_VALID_FLAGS))
{
status = STATUS_INVALID_PARAMETER;
}
else if (cchRemaining == 0)
{
// only fail if there was actually src data to append
if (cchToAppend != 0)
{
if (pszDest == NULL)
{
status = STATUS_INVALID_PARAMETER;
}
else
{
status = STATUS_BUFFER_OVERFLOW;
}
}
}
else
{
size_t cchCopied = 0;
status = RtlWideCharArrayCopyWorker(pszDestEnd,
cchRemaining,
&cchCopied,
pszSrc,
cchToAppend);
pszDestEnd = pszDestEnd + cchCopied;
cchRemaining = cchRemaining - cchCopied;
cchNewDestLength = cchDestLength + cchCopied;
if (NT_SUCCESS(status) &&
(dwFlags & STRSAFE_FILL_BEHIND) &&
(cchRemaining != 0))
{
// handle the STRSAFE_FILL_BEHIND flag
RtlUnicodeStringExHandleFill(pszDestEnd, cchRemaining, dwFlags);
}
}
}
}
if (!NT_SUCCESS(status) &&
(dwFlags & (STRSAFE_NO_TRUNCATION | STRSAFE_FILL_ON_FAILURE | STRSAFE_ZERO_LENGTH_ON_FAILURE)) &&
(cchDest != 0))
{
// handle the STRSAFE_NO_TRUNCATION, STRSAFE_FILL_ON_FAILURE, and STRSAFE_ZERO_LENGTH_ON_FAILURE flags
RtlUnicodeStringExHandleOtherFlags(pszDest,
cchDest,
cchDestLength,
&cchNewDestLength,
&pszDestEnd,
&cchRemaining,
dwFlags);
}
if (DestinationString)
{
// safe to multiply cchNewDestLength * sizeof(wchar_t) since cchDest < NTSTRSAFE_UNICODE_STRING_MAX_CCH and sizeof(wchar_t) is 2
DestinationString->Length = (USHORT)(cchNewDestLength * sizeof(wchar_t));
}
if (NT_SUCCESS(status) || (status == STATUS_BUFFER_OVERFLOW))
{
if (RemainingString)
{
RemainingString->Length = 0;
// safe to multiply cchRemaining * sizeof(wchar_t) since cchRemaining < NTSTRSAFE_UNICODE_STRING_MAX_CCH and sizeof(wchar_t) is 2
RemainingString->MaximumLength = (USHORT)(cchRemaining * sizeof(wchar_t));
RemainingString->Buffer = pszDestEnd;
}
}
}
return status;
}
View code on GitHub// ntstrsafe.h
NTSTRSAFEDDI RtlUnicodeStringCbCatNEx(
[in, out] PUNICODE_STRING DestinationString,
[in] PCUNICODE_STRING SourceString,
[in] size_t cbToAppend,
[out, optional] PUNICODE_STRING RemainingString,
[in] DWORD dwFlags
);
View the official Windows Driver Kit DDI referenceNo description available.
The RtlUnicodeStringCbCatNEx function concatenates two strings that are contained in UNICODE_STRING structures while limiting the size of the copied string.
DestinationString [in, out]Optional. A pointer to a UNICODE_STRING structure. This structure includes a buffer that, on input, contains a destination string to which the source string will be concatenated. On output, this buffer is the destination buffer that contains the entire resultant string. The source string is added to the end of the destination string. The maximum number of bytes in the structure's string buffer is NTSTRSAFE_UNICODE_STRING_MAX_CCH * sizeof(WCHAR). DestinationString can be NULL, but only if STRSAFE_IGNORE_NULLS is set in dwFlags.
SourceString [in]Optional. A pointer to a UNICODE_STRING structure. This structure includes a buffer that contains the source string. This string will be added to the end of the destination string. The maximum number of bytes in the structure's string buffer is NTSTRSAFE_UNICODE_STRING_MAX_CCH * sizeof(WCHAR). SourceString can be NULL, but only if STRSAFE_IGNORE_NULLS is set in dwFlags.
cbToAppend [in]The maximum number of bytes to append to the string that the DestinationString parameter describes.
RemainingString [out, optional]Optional. If the caller supplies a non-NULL pointer to a UNICODE_STRING structure, the function sets this structure's Buffer member to the end of the concatenated string, sets the structure's Length member to zero, and sets the structure's MaximumLength member to the number of bytes that are remaining in the destination buffer. RemainingString can be NULL, but only if STRSAFE_IGNORE_NULLS is set in dwFlags.
dwFlags [in]One or more flags and, optionally, a fill byte. The flags are defined as follows:
| Value | Meaning |
|---|---|
| STRSAFE_FILL_BEHIND | 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 last character in the string. |
| STRSAFE_IGNORE_NULLS | If this flag is set, the source or destination pointer, or both, can be NULL. RtlUnicodeStringCbCatNEx treats NULL source buffer pointers like empty strings (TEXT("")), which can be copied. NULL destination buffer 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. 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: * If STRSAFE_FILL_ON_FAILURE is also specified, STRSAFE_NO_TRUNCATION fills the destination buffer accordingly. * Otherwise, the destination buffer will be unmodified. |
| STRSAFE_ZERO_LENGTH_ON_FAILURE | If this flag is set and the function returns STATUS_BUFFER_OVERFLOW, the destination string length is set to zero bytes. |
RtlUnicodeStringCbCatNEx returns one of the following NTSTATUS values.
| Return code | Description |
|---|---|
| STATUS_SUCCESS | This success status means source data was present, and the strings were concatenated without truncation. |
| STATUS_BUFFER_OVERFLOW | This warning status means that the concatenation operation did not complete because of 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 that the function received an invalid input parameter. For more information, see the following list. |
RtlUnicodeStringCbCatNEx returns the STATUS_INVALID_PARAMETER value when one of the following occurs:
NTSTRSAFE_UNICODE_STRING_MAX_CCH * sizeof(WCHAR).For information about how to test NTSTATUS values, see Using NTSTATUS Values.
The RtlUnicodeStringCbCatNEx function uses the destination buffer's size to ensure that the concatenation operation does not write past the end of the buffer. By default, the function does not terminate the resultant string with a null character value (that is, with zero). As an option, the caller can use the STRSAFE_FILL_BEHIND flag and a fill byte value of zero to null-terminate a resultant string that does not occupy the entire destination buffer.
RtlUnicodeStringCbCatNEx adds to the functionality of the RtlUnicodeStringCbCatN function by returning a UNICODE_STRING structure that identifies the end of the destination string and the number of bytes that are left unused in that string. You can pass flags to RtlUnicodeStringCbCatNEx for additional control.
If the source and destination strings overlap, the behavior of the function is undefined.
The SourceString and DestinationString pointers cannot be NULL unless the STRSAFE_IGNORE_NULLS flag is set in dwFlags. If STRSAFE_IGNORE_NULLS is set, one or both of these pointers can be NULL. If the DestinationString pointer is NULL, the SourceString pointer must be NULL or the UNICODE_STRING structure must specify an empty string.
For more information about the safe string functions, see Using safe string functions.