通过

PIBIO_SENSOR_CLEAR_CONTEXT_FN回调函数 (winbio_adapter.h)

  • 项目

由 Windows 生物识别框架调用，为新操作准备生物识别单元的处理管道。 此函数应从传感器上下文中刷新临时数据，并将传感器适配器置于定义完善的初始状态。

语法

PIBIO_SENSOR_CLEAR_CONTEXT_FN PibioSensorClearContextFn;

HRESULT PibioSensorClearContextFn(
  [in, out] PWINBIO_PIPELINE Pipeline
)
{...}

参数

[in, out] Pipeline

指向与执行操作的生物识别单元关联的 WINBIO_PIPELINE 结构的指针。

返回值

如果函数成功，则返回S_OK。 如果函数失败，则必须返回以下 HRESULT 值之一来指示错误。

返回代码 说明
E_POINTER
 Pipeline 参数不能为 NULL。

注解

SensorAdapterClearContext 函数的实现应清除示例缓冲区。

示例

以下伪代码显示了此函数的一种可能实现。 该示例不编译。 必须根据自己的目的调整它。

//////////////////////////////////////////////////////////////////////////////////////////
//
// SensorAdapterClearContext
//
// Purpose:
//      Prepare the processing pipeline for a new operation. This function 
//      should flush temporary data from the sensor context and place the 
//      sensor adapter into a well-defined initial state.
//      
// Parameters:
//      Pipeline -  Pointer to a WINBIO_PIPELINE structure associated with 
//                  the biometric unit.
//
static HRESULT
WINAPI
SensorAdapterClearContext(
    __inout PWINBIO_PIPELINE Pipeline
    )
{
    // Verify that the Pipeline parameter is not NULL.
    if (!ARGUMENT_PRESENT(Pipeline))
    {
        hr = E_POINTER;
        goto cleanup;
    }

    // Retrieve the context from the pipeline.
    PWINBIO_SENSOR_CONTEXT sensorContext = 
        (PWINBIO_SENSOR_CONTEXT)Pipeline->SensorContext;

    // Validate the current state of the sensor.
    if (sensorContext == NULL)
    {
        return WINBIO_E_INVALID_DEVICE_STATE;
    }

    // Change the sensor adapter state and discard any partially completed
    // operations. Depending on the adapter, this can involve changes to state 
    // variables or actions implemented in hardware. The following example
    // assumes that your sensor adapter context contains a ULONG data member 
    // and pointers to a capture buffer and an attributes buffer.

    sensorContext->SomeField = 0L;

    if (sensorContext->CaptureBuffer != NULL)
    {
        // Zero the capture buffer.
        SecureZeroMemory(
            sensorContext->CaptureBuffer,
            sensorContext->CaptureBufferSize);

        // Release the capture buffer.
        _AdapterRelease(sensorContext->CaptureBuffer);
        sensorContext->CaptureBuffer = NULL;
        sensorContext->CaptureBufferSize = 0;
    }

    if (sensorContext->AttributesBuffer != NULL)
    {
        // Zero the attributes buffer.
        SecureZeroMemory(
            sensorContext->AttributesBuffer,
            sensorContext->AttributesBufferSize);

        // Release the attributes buffer.
        _AdapterRelease(sensorContext->AttributesBuffer);
        sensorContext->AttributesBuffer = NULL;
        sensorContext->AttributesBufferSize = 0;
    }

    // TODO: Perform any other work required to clear the sensor context.

    return S_OK;
}

要求

要求 值
最低受支持的客户端 Windows 7 [仅限桌面应用]
最低受支持的服务器 Windows Server 2008 R2 [仅限桌面应用]
目标平台 Windows
标头 winbio_adapter.h (包括 Winbio_adapter.h)

另请参阅

EngineAdapterClearContext

插件函数

StorageAdapterClearContext