RtlUnicodeStringCbCopyNEx - 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
RtlUnicodeStringCbCopyNEx(
_Inout_ PUNICODE_STRING DestinationString OPTIONAL,
_In_ PCUNICODE_STRING SourceString OPTIONAL,
_In_ size_t cbToCopy,
_Out_opt_ PUNICODE_STRING RemainingString OPTIONAL,
_In_ DWORD dwFlags
);
Routine Description:
This routine is a safer version of the C built-in function 'strncpy' with
some additional parameters and for PUNICODE_STRINGs. In addition to the
functionality provided by RtlUnicodeStringCbCopyN, 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
cbToCopy - maximum number of bytes to copy from source string
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_NO_TRUNCATION /
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.
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 there was source data and it was all copied
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 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.
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
RtlUnicodeStringCbCopyNEx(
_Inout_ PUNICODE_STRING DestinationString,
_In_ PCUNICODE_STRING SourceString,
_In_ size_t cbToCopy,
_Out_opt_ PUNICODE_STRING RemainingString,
_In_ DWORD dwFlags)
{
NTSTATUS status;
wchar_t* pszDest;
size_t cchDest;
status = RtlUnicodeStringValidateDestWorker(DestinationString,
&pszDest,
&cchDest,
NULL,
NTSTRSAFE_UNICODE_STRING_MAX_CCH,
dwFlags);
if (NT_SUCCESS(status))
{
wchar_t* pszSrc;
size_t cchSrcLength;
wchar_t* pszDestEnd = pszDest;
size_t cchRemaining = cchDest;
size_t cchNewDestLength = 0;
status = RtlUnicodeStringValidateSrcWorker(SourceString,
&pszSrc,
&cchSrcLength,
NTSTRSAFE_UNICODE_STRING_MAX_CCH,
dwFlags);
if (NT_SUCCESS(status))
{
size_t cchToCopy = cbToCopy / sizeof(wchar_t);
if (cchToCopy > NTSTRSAFE_UNICODE_STRING_MAX_CCH)
{
status = STATUS_INVALID_PARAMETER;
}
else
{
if (cchSrcLength < cchToCopy)
{
cchToCopy = cchSrcLength;
}
if (dwFlags & (~STRSAFE_UNICODE_STRING_VALID_FLAGS))
{
status = STATUS_INVALID_PARAMETER;
}
else if (cchDest == 0)
{
// only fail if there was actually src data to copy
if (cchToCopy != 0)
{
if (pszDest == NULL)
{
status = STATUS_INVALID_PARAMETER;
}
else
{
status = STATUS_BUFFER_OVERFLOW;
}
}
}
else
{
status = RtlWideCharArrayCopyWorker(pszDest,
cchDest,
&cchNewDestLength,
pszSrc,
cchToCopy);
pszDestEnd = pszDest + cchNewDestLength;
cchRemaining = cchDest - cchNewDestLength;
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,
0,
&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;
}
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