RtlStringCchCopyExA - 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_CCH_FUNCTIONS
/*++
NTSTATUS
RtlStringCchCopyEx(
_Out_writes_(cchDest) _Always_(_Post_z_) LPTSTR pszDest OPTIONAL,
_In_ size_t cchDest,
_In_ LPCTSTR pszSrc OPTIONAL,
_Outptr_opt_result_buffer_(*pcchRemaining) LPTSTR* ppszDestEnd OPTIONAL,
_Out_opt_ size_t* pcchRemaining OPTIONAL,
_In_ DWORD dwFlags
);
Routine Description:
This routine is a safer version of the C built-in function 'strcpy' with
some additional parameters. In addition to functionality provided by
RtlStringCchCopy, this routine also returns a pointer to the end of the
destination string and the number of characters left in the destination string
including the null terminator. The flags parameter allows additional controls.
Arguments:
pszDest - destination string
cchDest - size of destination buffer in characters.
length must be = (_tcslen(pszSrc) + 1) to hold all of
the source including the null terminator
pszSrc - source string which must be null terminated
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
pcchRemaining - if pcchRemaining is non-null, the function will return the
number of characters 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
RtlStringCchCopyExA(
_Out_writes_(cchDest) _Always_(_Post_z_) NTSTRSAFE_PSTR pszDest,
_In_ size_t cchDest,
_In_ NTSTRSAFE_PCSTR pszSrc,
_Outptr_opt_result_buffer_(*pcchRemaining) NTSTRSAFE_PSTR* ppszDestEnd,
_Out_opt_ size_t* pcchRemaining,
_In_ DWORD dwFlags)
{
NTSTATUS status;
status = RtlStringExValidateDestA(pszDest, cchDest, NTSTRSAFE_MAX_CCH, dwFlags);
if (NT_SUCCESS(status))
{
NTSTRSAFE_PSTR pszDestEnd = pszDest;
size_t cchRemaining = cchDest;
status = RtlStringExValidateSrcA(&pszSrc, NULL, 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 (*pszSrc != '\0')
{
if (pszDest == NULL)
{
status = STATUS_INVALID_PARAMETER;
}
else
{
status = STATUS_BUFFER_OVERFLOW;
}
}
}
else
{
size_t cchCopied = 0;
status = RtlStringCopyWorkerA(pszDest,
cchDest,
&cchCopied,
pszSrc,
NTSTRSAFE_MAX_LENGTH);
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);
// 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)) &&
(cchDest != 0))
{
size_t cbDest;
// safe to multiply cchDest * sizeof(char) since cchDest < NTSTRSAFE_MAX_CCH and sizeof(char) is 1
cbDest = cchDest * sizeof(char);
// 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 (pcchRemaining)
{
*pcchRemaining = cchRemaining;
}
}
}
else if (cchDest > 0)
{
*pszDest = '\0';
}
return status;
}
View code on GitHub// ntstrsafe.h
NTSTRSAFEDDI RtlStringCchCopyExA(
[out, optional] NTSTRSAFE_PSTR pszDest,
[in] size_t cchDest,
[in, optional] NTSTRSAFE_PCSTR pszSrc,
[out, optional] NTSTRSAFE_PSTR *ppszDestEnd,
[out, optional] size_t *pcchRemaining,
[in] DWORD dwFlags
);
View the official Windows Driver Kit DDI referenceNo description available.
The RtlStringCchCopyExW and RtlStringCchCopyExA functions copy a character-counted string into a buffer.
pszDest [out, optional]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.
cchDest [in]The size of the destination buffer, in characters. The maximum number of characters allowed is NTSTRSAFE_MAX_CCH. If pszDest is NULL, cchDest must be zero.
pszSrc [in, optional]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.
ppszDestEnd [out, optional]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.
pcchRemaining [out, optional]If the caller supplies a non-NULL address pointer, the function loads the address with the number of unused characters that are in the buffer pointed to by pszDest, including the terminating null character.
dwFlags [in]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: * If STRSAFE_FILL_ON_FAILURE is also specified, STRSAFE_NO_TRUNCATION fills the destination buffer accordingly. * Otherwise, the contents of the destination buffer will be set to an empty string, even if STRSAFE_NULL_ON_FAILURE is not set. STRSAFE_FILL_BEHIND_NULL is ignored. |
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 in dwFlags, 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: * An invalid flag was specified. * The value in cchDest is larger than the maximum buffer size. * The destination buffer was already full. * A NULL pointer was present without the STRSAFE_IGNORE_NULLS flag. * The destination buffer pointer was NULL, but the buffer size was not zero. * The destination buffer pointer was NULL, or its length was zero, but a nonzero length source string was present. |
RtlStringCchCopyExW and RtlStringCchCopyExA should be used instead of the following functions:
The size, in characters, of the destination buffer is provided to RtlStringCchCopyExW and RtlStringCchCopyExA to ensure that they do not write past the end of the buffer.
RtlStringCchCopyExW and RtlStringCchCopyExA add to the functionality of RtlStringCchCopy by returning a pointer to the end of the destination string, as well as the number of characters left unused in that string. Flags can be passed to the function for additional control. Use RtlStringCchCopyExW to handle Unicode strings and RtlStringCchCopyExA 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" | RtlStringCchCopyExW |
| char | "string" | RtlStringCchCopyExA |
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.