WdfRegistryQueryUnicodeString - NtDoc
Native API online documentation, based on the System Informer
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headers
// wdfregistry.h
NTSTATUS WdfRegistryQueryUnicodeString(
[in] WDFKEY Key,
[in] PCUNICODE_STRING ValueName,
[out, optional] PUSHORT ValueByteLength,
[in, out] PUNICODE_STRING Value
);
View the official Windows Driver Kit DDI referenceNo description available.
[Applies to KMDF and UMDF]
The WdfRegistryQueryUnicodeString method retrieves the string data that is currently assigned to a specified registry string value and copies the string to a specified UNICODE_STRING structure.
Key [in]A handle to a registry-key object that represents an opened registry key.
ValueName [in]A pointer to a UNICODE_STRING structure that contains a name for the registry value.
ValueByteLength [out, optional]A pointer to a location that receives the number of bytes that are contained in the Unicode string that Value points to, including the terminating NULL byte. This pointer is optional and can be NULL
Value [in, out]A pointer to a UNICODE_STRING structure that receives the data string for the key that Key specifies. If this parameter is NULL and ValueByteLength is non-NULL, WdfRegistryQueryUnicodeString returns only the size of the string.
WdfRegistryQueryUnicodeString returns STATUS_SUCCESS if the operation succeeds. Otherwise, the method might return one of the following values:
| Return code | Description |
|---|---|
| STATUS_INVALID_DEVICE_REQUEST | WdfRegistryQueryUnicodeString was not called at IRQL = PASSIVE_LEVEL. |
| STATUS_INVALID_PARAMETER | An invalid parameter was specified. |
| STATUS_INSUFFICIENT_RESOURCES | There was insufficient memory to complete the operation. |
| STATUS_ACCESS_DENIED | The driver did not open the registry key with KEY_QUERY_VALUE, KEY_READ, or KEY_ALL_ACCESS access. |
| STATUS_OBJECT_TYPE_MISMATCH | The data type of the registry value that the ValueName parameter specified was not REG_SZ. |
| STATUS_BUFFER_OVERFLOW | The buffer that the Value parameter points to was too small, and only partial data was written to the buffer. |
| STATUS_BUFFER_OVERFLOW | The buffer that the Value parameter points to was too small, and no data was written to the buffer. |
| STATUS_OBJECT_NAME_NOT_FOUND | The registry value was not available. |
This method also might return other NTSTATUS values.
A bug check occurs if the driver supplies an invalid object handle.
For more information about registry-key objects, see Using the Registry in Framework-Based Drivers.
The following code example, which is from the Serial sample driver, retrieves the Unicode string that represents the string data that is assigned to the PortName value under a device's hardware key.
NTSTATUS
SerialReadSymName(
IN WDFDEVICE Device,
__out PWCHAR RegName,
IN OUT PUSHORT LengthOfRegName // In characters
)
{
NTSTATUS status;
WDFKEY hKey;
UNICODE_STRING value;
UNICODE_STRING valueName;
USHORT requiredLength;
value.Buffer = RegName;
value.MaximumLength = *LengthOfRegName;
value.Length = 0;
status = WdfDeviceOpenRegistryKey(
Device,
PLUGPLAY_REGKEY_DEVICE,
STANDARD_RIGHTS_ALL,
WDF_NO_OBJECT_ATTRIBUTES,
&hKey
);
if (NT_SUCCESS (status)) {
RtlInitUnicodeString(
&valueName,
L"PortName"
);
status = WdfRegistryQueryUnicodeString (
hKey,
&valueName,
&requiredLength,
&value
);
WdfRegistryClose(hKey);
}
return status;
}