AVCSTRM_GET_STATE
The AVCSTRM_GET_STATE function code obtains the current stream state of the specified stream.
I/O Status Block
If successful, avcstrm.sys sets Irp->IoStatus.Status to STATUS_SUCCESS.
If successful, a STATUS_SUCCESS is returned. The StreamState member of the CommandData union has the current stream state. It can be KSSTATE_STOP, KSTATE_PAUSE, or KSSTATE_RUN.
Possible error return values include:
| Error Status | Description |
|---|---|
| STATUS_DEVICE_REMOVED | The device corresponding to the AVCSTRM_READ operation no longer exists. |
| STATUS_CANCELLED | The request was unable to be completed. |
| STATUS_INVALID_PARAMETER | A parameter specified in the IRP is incorrect, |
| STATUS_INSUFFICIENT_RESOURCES | There were not sufficient system resources to complete the request. |
| STATUS_PENDING | The request has been received but requires further processing. The I/O completion routine will handle the final response. |
AVC_STREAM_REQUEST_BLOCK Input
SizeOfThisBlock, Version and Function
Use the INIT_AVCSTRM_HEADER macro to initialize these members. Pass AVCSTRM_GET_STATE in the Request argument of the macro.
AVCStreamContext
Specifies the stream context (handle) returned by an earlier AVCSTRM_OPEN call to obtain the stream state from.
StreamState
If AVCSTRM_GET_STATE returns successfully, this member contains the current stream state.
A subunit driver must first allocate an IRP and an AVC_STREAM_REQUEST_BLOCK structure. Next, it should use the INIT_AVCSTRM_HEADER macro to initialize the AVC_STREAM_REQUEST_BLOCK structure, passing AVCSTRM_GET_STATE as the Request argument to the macro. Next, the subunit driver sets the AVCStreamContext member to the stream context (handle) of the stream to obtain the stream state from.
To send this request, a subunit submits an IRP_MJ_INTERNAL_DEVICE_CONTROL IRP with the IoControlCode member of the IRP set to IOCTL_AVCSTRM_CLASS and the Argument1 member of the IRP set to the AVC_STREAM_REQUEST_BLOCK structure that describes the stream to obtain the stream state from.
A subunit driver can expect this command to be completed synchronously. The result returns immediately without pending operation in avcstrm.sys.
This function code must be called at IRQL = PASSIVE_LEVEL.
Comments
This function uses the StreamState member of the CommandData union in the AVC_STREAM_REQUEST_BLOCK structure as shown below.
typedef struct _AVC_STREAM_REQUEST_BLOCK {
ULONG SizeOfThisBlock;
ULONG Version;
AVCSTRM_FUNCTION Function;
.
.
PVOID AVCStreamContext;
.
.
union _tagCommandData {
.
.
KSSTATE StreamState;
.
.
} CommandData;
} AVC_STREAM_REQUEST_BLOCK, *PAVC_STREAM_REQUEST_BLOCK;
Requirements
Headers: Declared in avcstrm.h. Include avcstrm.h.