WDF_DECLARE_CONTEXT_TYPE macro

Article
03/01/2023

[Applies to KMDF and UMDF]

The WDF_DECLARE_CONTEXT_TYPE macro creates a name and an accessor method for a driver's object-specific context space.

Syntax

void WDF_DECLARE_CONTEXT_TYPE(
    _contexttype
);

Parameters

_contexttype
The structure type name of a driver-defined structure that describes the contents of an object's context space.

Return value

This macro does not return a value.

Remarks

For more information about using this macro, see Framework Object Context Space.

Examples

The following code example defines a context structure (MY_REQUEST_CONTEXT) for a request object, registers the structure, and then invokes the WDF_DECLARE_CONTEXT_TYPE macro. The macro creates an accessor method for the context structure and names the method WdfObjectGet_MY_REQUEST_CONTEXT.

typedef struct _MY_REQUEST_CONTEXT {
  LIST_ENTRY ListEntry;
  WDFMEMORY Memory;
} MY_REQUEST_CONTEXT, *PMY_REQUEST_CONTEXT;

WDF_DECLARE_CONTEXT_TYPE(MY_REQUEST_CONTEXT)

The following code example creates a request object, and then it uses the WdfObjectGet_MY_REQUEST_CONTEXT accessor method to obtain a pointer to the object's context space.

WDFREQUEST Request;
WDF_OBJECT_ATTRIBUTES MyRequestObjectAttributes;
PMY_REQUEST_CONTEXT pMyContext;

WDF_OBJECT_ATTRIBUTES_INIT(&MyRequestObjectAttributes);
WDF_OBJECT_ATTRIBUTES_SET_CONTEXT_TYPE(
                                       &MyRequestObjectAttributes,
                                       MY_REQUEST_CONTEXT
                                       );
status = WdfRequestCreate(
                          &MyRequestObjectAttributes
                          NULL,
                          &Request
                          );
if (!NT_SUCCESS(status)) {
    return status;
}
pMyContext = WdfObjectGet_MY_REQUEST_CONTEXT(Request);

Requirements

Target platform	Universal
Minimum KMDF version	1.0
Minimum UMDF version	2.0
Header	Wdfobject.h (include Wdf.h)

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