PIBIO_STORAGE_GET_CURRENT_RECORD_FN回调函数 (winbio_adapter.h)

  • 项目

由 Windows 生物识别框架或引擎适配器调用，以检索管道结果集中当前记录的内容。

语法

PIBIO_STORAGE_GET_CURRENT_RECORD_FN PibioStorageGetCurrentRecordFn;

HRESULT PibioStorageGetCurrentRecordFn(
  [in, out] PWINBIO_PIPELINE Pipeline,
  [out]     PWINBIO_STORAGE_RECORD RecordContents
)
{...}

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。

[out] RecordContents

指向将接收记录内容的 WINBIO_STORAGE_RECORD 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_OUTOFMEMORY
 无法为记录分配内存。
E_POINTER
 强制指针参数为 NULL。
WINBIO_E_DATABASE_NO_RESULTS
 结果集中没有记录。
WINBIO_E_INVALID_DEVICE_STATE
 管道对象的 StorageContext 成员为 NULL 或 FileHandle 成员无效。

注解

在调用以下函数之一之前，此函数在 WINBIO_STORAGE_RECORD 结构中返回的任何地址必须保持有效：

调用 StorageAdapterGetCurrentRecord 函数不会更改结果集指针。 如果指针已位于集中的最后一条记录上，则重复调用此函数将返回相同的记录内容和 hrESULT 值S_OK。

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。

/////////////////////////////////////////////////////////////////////////////////////////
//
// StorageAdapterGetCurrentRecord
//
// Purpose:
//      Retrieves the contents of the current record in the pipeline result set.
//
// Parameters:
//      Pipeline       - Pointer to a WINBIO_PIPELINE structure associated with 
//                       the biometric unit performing the operation.
//      RecordContents - Pointer to a WINBIO_STORAGE_RECORD structure that will receive 
//                       the contents of the record.
//
static HRESULT
WINAPI
StorageAdapterGetCurrentRecord(
    __inout PWINBIO_PIPELINE Pipeline,
    __out PWINBIO_STORAGE_RECORD RecordContents
    )
{
    HRESULT hr = S_OK;
    struct _MY_ADAPTER_RECORD_HEADER *recordHeader = NULL;
    LARGE_INTEGER dataOffset = {0};
    SIZE_T allocationSize = 0;

    // Verify that pointer arguments are not NULL.
    if (!ARGUMENT_PRESENT(Pipeline) ||
        !ARGUMENT_PRESENT(RecordContents))
    {
        hr = E_POINTER;
        goto cleanup;
    }

    // Retrieve the context from the pipeline.
    PWINBIO_STORAGE_CONTEXT storageContext = (PWINBIO_STORAGE_CONTEXT)Pipeline->StorageContext;

    // Verify the pipeline state.
    if (storageContext == NULL || storageContext->FileHandle == INVALID_HANDLE_VALUE)
    {
        hr =  WINBIO_E_INVALID_DEVICE_STATE;
        goto cleanup;
    }

    // Call a custom function (_ResultSetGetCurrent) to retrieve the header
    // contents of the current record in the result set. This function should
    // also return the file offset of the template data in the record.
    hr = _ResultSetGetCurrent(
            &storageContext->ResultSet,
            &recordHeader,
            &dataOffset
            );
    if (FAILED(hr))
    {
        goto cleanup;
    }

    RecordContents->Identity = &recordHeader->Identity;
    RecordContents->SubFactor = recordHeader->SubFactor;
    RecordContents->IndexVector = _GetIndexVector(recordHeader);
    RecordContents->IndexElementCount = recordHeader->IndexElementCount;

    // Release any template data buffers created by previous calls to the
    // StorageAdapterGetCurrentRecord function. 
    if (storageContext->RawRecordData != NULL)
    {
        _AdapterRelease(storageContext->RawRecordData);
        storageContext->RawRecordData = NULL;
        storageContext->PayloadBlob = NULL;
    }

    if (storageContext->DecryptedTemplate != NULL)
    {
        // You must call SecureZeroMemory to clear any memory that contains
        // a plaintext version of the template data.
        SecureZeroMemory(
            storageContext->DecryptedTemplate, 
            storageContext->DecryptedTemplateSize
            );
        _AdapterRelease(storageContext->DecryptedTemplate);
        storageContext->DecryptedTemplate = NULL;
        storageContext->DecryptedTemplateSize = 0;
    }

    // Allocate a buffer for the template and payload portions of the record.
    allocationSize = 
        recordHeader->EncryptedTemplateBlobSize + 
        recordHeader->PayloadBlobSize;

    storageContext->RawRecordData = (PUCHAR)_AdapterAlloc(allocationSize);
    if (storageContext->RawRecordData == NULL)
    {
        hr = E_OUTOFMEMORY;
        goto cleanup;
    }

    // Call a custom function (_ReadRecordData) that reads the non-header
    // portion of the record.
    hr = _ReadRecordData(
            Pipeline->StorageHandle,
            dataOffset,
            storageContext->RawRecordData,
            (DWORD)allocationSize,
            (PDWORD)&storageContext->RawRecordDataSize
            );
    if (FAILED(hr))
    {
        goto cleanup;
    }

    // Call a custom function (_DecryptTemplate) that decrypts the template 
    // data and stores a pointer to the plaintext version in the storage context.
    hr = _DecryptTemplate(
            &storageContext->CryptoContext,
            storageContext->RawRecordData,
            recordHeader->EncryptedTemplateBlobSize,
            &storageContext->DecryptedTemplate,
            &storageContext->DecryptedTemplateSize
            );
    if (FAILED(hr))
    {
        goto cleanup;
    }

    // Set up return values for the caller. These values will remain valid until
    // the next query or get operation.
    RecordContents->TemplateBlob = storageContext->DecryptedTemplate;
    RecordContents->TemplateBlobSize = recordHeader->TemplateBlobSize;

    if (recordHeader->PayloadBlobSize != 0)
    {
        RecordContents->PayloadBlob = 
            storageContext->RawRecordData + 
            recordHeader->EncryptedTemplateBlobSize;

        RecordContents->PayloadBlobSize = recordHeader->PayloadBlobSize;
    }
    else
    {
        RecordContents->PayloadBlob = NULL;
        RecordContents->PayloadBlobSize = 0;
    }

cleanup:

    if (FAILED(hr))
    {
        if (storageContext->RawRecordData != NULL)
        {
            // Because the raw record data (including the payload blob) is
            // encrypted, it is not necessary to call SecureZeroMemory.
            _AdapterRelease(storageContext->RawRecordData);
            storageContext->RawRecordData = NULL;
            storageContext->PayloadBlob = NULL;
        }
        if (storageContext->DecryptedTemplate != NULL)
        {
            // You must call SecureZeroMemory to clear the plaintext version 
            // of the template before releasing it.
            SecureZeroMemory(
                storageContext->DecryptedTemplate, 
                storageContext->DecryptedTemplateSize
                );
            _AdapterRelease(storageContext->DecryptedTemplate);
            storageContext->DecryptedTemplate = NULL;
            storageContext->DecryptedTemplateSize = 0;
        }
    }

    return hr;
}

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

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