PIBIO_ENGINE_VERIFY_FEATURE_SET_FN callback function (winbio_adapter.h)
Called by the Windows Biometric Framework to compare the template in the current feature set with a specific template in the database. If the templates are equivalent, the engine adapter must set the Boolean value pointed to by the Match parameter to TRUE, return the matched template in the PayloadBlob parameter, and return a hash of the template in the HashValue parameter.
Syntax
PIBIO_ENGINE_VERIFY_FEATURE_SET_FN PibioEngineVerifyFeatureSetFn;
HRESULT PibioEngineVerifyFeatureSetFn(
[in, out] PWINBIO_PIPELINE Pipeline,
[in] PWINBIO_IDENTITY Identity,
[in] WINBIO_BIOMETRIC_SUBTYPE SubFactor,
[out] PBOOLEAN Match,
[out] PUCHAR *PayloadBlob,
[out] PSIZE_T PayloadBlobSize,
[out] PUCHAR *HashValue,
[out] PSIZE_T HashSize,
[out] PWINBIO_REJECT_DETAIL RejectDetail
)
{...}
Parameters
[in, out] Pipeline
Pointer to a WINBIO_PIPELINE structure associated with the biometric unit performing the operation.
[in] Identity
Pointer to a WINBIO_IDENTITY structure that contains a GUID or SID that is expected to match that of the template recovered from the database.
[in] SubFactor
A WINBIO_BIOMETRIC_SUBTYPE value that is expected to match that of the template recovered from the database. See the Remarks section for more details.
[out] Match
Pointer to a Boolean value that specifies whether the Identity and SubFactor parameters match those of the template recovered from the database. TRUE specifies that these values match.
[out] PayloadBlob
Address of a variable that receives a pointer to the payload data saved with the template. If there is no payload data, set this value to NULL.
[out] PayloadBlobSize
Pointer to a value that receives the size, in bytes, of the buffer specified in the PayloadBlob parameter. If there is no payload data stored with the template, set this value to zero.
[out] HashValue
Address of a variable that receives a pointer to the hash of the template. If the engine adapter does not support hash generation, set this value to NULL.
[out] HashSize
Pointer to a value that contains the size, in bytes, of the hash specified by the HashValue parameter. If the engine adapter does not support hash generation, set this value to zero.
[out] RejectDetail
Pointer to a WINBIO_REJECT_DETAIL value that receives additional information if a capture failure prevents the engine from performing a matching operation. If the most-recent capture succeeded, set this parameter to zero. The following values are defined for fingerprint capture
- WINBIO_FP_TOO_HIGH
- WINBIO_FP_TOO_LOW
- WINBIO_FP_TOO_LEFT
- WINBIO_FP_TOO_RIGHT
- WINBIO_FP_TOO_FAST
- WINBIO_FP_TOO_SLOW
- WINBIO_FP_POOR_QUALITY
- WINBIO_FP_TOO_SKEWED
- WINBIO_FP_TOO_SHORT
- WINBIO_FP_MERGE_FAILURE
Return value
If the function succeeds, it returns S_OK. If the function fails, it must return one of the following HRESULT values to indicate the error.
| Return code | Description |
|---|---|
|
A mandatory pointer parameter is NULL. |
|
The value specified in the SubFactor parameter is not correct. |
|
The feature set did not meet the internal requirements of the engine adapter for a verification operation. Further information about the failure is specified by the RejectDetail parameter. |
|
The feature set in the pipeline matches one stored in the database but it does not correspond to the combination of values passed in the Identity and SubFactor parameters. |
Remarks
The SubFactor parameter specifies the sub-factor associated with the biometric template. The Windows Biometric Framework supports only fingerprint capture and can use the following constants to represent sub-type information.
- WINBIO_ANSI_381_POS_RH_THUMB
- WINBIO_ANSI_381_POS_RH_INDEX_FINGER
- WINBIO_ANSI_381_POS_RH_MIDDLE_FINGER
- WINBIO_ANSI_381_POS_RH_RING_FINGER
- WINBIO_ANSI_381_POS_RH_LITTLE_FINGER
- WINBIO_ANSI_381_POS_LH_THUMB
- WINBIO_ANSI_381_POS_LH_INDEX_FINGER
- WINBIO_ANSI_381_POS_LH_MIDDLE_FINGER
- WINBIO_ANSI_381_POS_LH_RING_FINGER
- WINBIO_ANSI_381_POS_LH_LITTLE_FINGER
- WINBIO_SUBTYPE_ANY
Do not attempt to validate the value supplied for the SubFactor parameter. The Windows Biometrics Service will validate the supplied value before passing it through to your implementation. If the value is WINBIO_SUBTYPE_NO_INFORMATION or WINBIO_SUBTYPE_ANY, then validate where appropriate.
The hash value returned by this function, if any, is the hash of the enrollment template found in the database, not the matching template attached to the pipeline.
The PayloadBlob and HashValue buffers are owned and managed by the engine adapter after the EngineAdapterIdentifyFeatureSet function returns successfully. The engine adapter must keep the buffer address valid, for this pipeline, until the next call to EngineAdapterClearContext.
Examples
The following pseudocode shows one possible implementation of this function. The example does not compile. You must adapt it to suit your purpose.
//////////////////////////////////////////////////////////////////////////////////////////
//
// EngineAdapterVerifyFeatureSet
//
// Purpose:
// Compares the template in the current feature set with a specific
// template in the database.
//
// Parameters:
// Pipeline - Pointer to a WINBIO_PIPELINE structure associated
// with the biometric unit performing the operation
// Identity - GUID or SID that is expected to match that of the
// template recovered from the database
// SubFactor - A WINBIO_BIOMETRIC_SUBTYPE value that is expected
// to match that of the template recovered from the
// database
// Match - A Boolean value that specifies whether the Identity
// and SubFactor parameters match those of the template
// recovered from the database
// PayloadBlob - Payload data saved with the template
// PayloadBlobSize - Size, in bytes, of the buffer specified in the
// PayloadBlob parameter
// HashValue - Hash of the template
// HashSize - Size, in bytes, of the hash specified by the
// HashValue parameter
// RejectDetail - Receives additional information if a capture failure
// prevents the engine from performing a matching operation
//
static HRESULT
WINAPI
EngineAdapterVerifyFeatureSet(
__inout PWINBIO_PIPELINE Pipeline,
__in PWINBIO_IDENTITY Identity,
__in WINBIO_BIOMETRIC_SUBTYPE SubFactor,
__out PBOOLEAN Match,
__out PUCHAR *PayloadBlob,
__out PSIZE_T PayloadBlobSize,
__out PUCHAR *HashValue,
__out PSIZE_T HashSize,
__out PWINBIO_REJECT_DETAIL RejectDetail
)
{
HRESULT hr = S_OK;
WINBIO_STORAGE_RECORD thisRecord;
BOOLEAN match = FALSE;
WINBIO_REJECT_DETAIL rejectDetail = 0;
// Verify that pointer arguments are not NULL.
if (!ARGUMENT_PRESENT(Pipeline) ||
!ARGUMENT_PRESENT(Identity) ||
!ARGUMENT_PRESENT(Match) ||
!ARGUMENT_PRESENT(PayloadBlob) ||
!ARGUMENT_PRESENT(PayloadBlobSize) ||
!ARGUMENT_PRESENT(HashValue) ||
!ARGUMENT_PRESENT(HashSize) ||
!ARGUMENT_PRESENT(RejectDetail))
{
hr = E_POINTER;
goto cleanup;
}
// Retrieve the context from the pipeline.
PWINBIO_ENGINE_CONTEXT context =
(PWINBIO_ENGINE_CONTEXT)Pipeline->EngineContext;
// Initialize the return values.
*Match = FALSE;
*PayloadBlob = NULL;
*PayloadBlobSize = 0;
*HashValue = NULL;
*HashSize = 0;
*RejectDetail = 0;
// The biometric unit cannot perform verification or identification
// operations while it is performing an enrollment sequence.
if (context->Enrollment.InProgress == TRUE)
{
hr = WINBIO_E_ENROLLMENT_IN_PROGRESS;
goto cleanup;
}
// Query the storage adapter to determine whether the Identity and
// SubFactor combination specified on input are in the database. If
// they are not, there can be no match. WbioStorageQueryBySubject
// is a wrapper function defined in the Winbio_adapter.h header file.
hr = WbioStorageQueryBySubject( Pipeline, Identity, SubFactor);
if (FAILED(hr))
{
if (hr == WINBIO_E_DATABASE_NO_RESULTS)
{
hr = WINBIO_E_NO_MATCH;
}
goto cleanup;
}
// Position the cursor on the first record in the database.
// WbioStorageFirstRecord is a wrapper function defined in the
// Winbio_adapter.h header file.
hr = WbioStorageFirstRecord( Pipeline );
if (FAILED(hr))
{
goto cleanup;
}
// Retrieve the current template record for the Identity and SubFactor
// combination specified on input.
hr = WbioStorageGetCurrentRecord( Pipeline, &thisRecord );
if (FAILED(hr))
{
goto cleanup;
}
// Call a custom function (_AdapterCompareTemplateToCurrentFeatureSet)
// to compare the feature set attached to the pipeline with the template
// retrieved from the database.
// If the template and feature set do not match, return WINBIO_E_NO_MATCH
// and set the Match parameter to FALSE.
// If your custom function cannot process the feature set, return
// WINBIO_E_BAD_CAPTURE and set extended error information in the
// RejectDetail parameter.
hr = _AdapterCompareTemplateToCurrentFeatureSet(
context,
context->FeatureSet,
context->FeatureSetSize,
thisRecord.TemplateBlob,
thisRecord.TemplateBlobSize,
&match,
RejectDetail
);
if (FAILED(hr))
{
goto cleanup;
}
// If there is a match and if your engine adapter supports template
// hashing, call a custom function (_AdapterGenerateHashForTemplate)
// to calculate the hash. Save the hash value in the context area of
// the engine adapter.
// Skip this step if your adapter does not support template hashing.
hr = _AdapterGenerateHashForTemplate(
context,
thisRecord.TemplateBlob,
thisRecord.TemplateBlobSize,
context->HashBuffer,
&context->HashSize
);
if (FAILED(hr))
{
goto cleanup;
}
// Set the return values.
*Match = TRUE;
*PayloadBlob = thisRecord.PayloadBlob;
*PayloadBlobSize = thisRecord.PayloadBlobSize;
*HashValue = &context->HashBuffer;
*HashSize = context->HashSize;
cleanup:
if (hr == WINBIO_E_DATABASE_NO_RESULTS)
{
hr = WINBIO_E_NO_MATCH;
}
return hr;
}
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows 7 [desktop apps only] |
| Minimum supported server | Windows Server 2008 R2 [desktop apps only] |
| Target Platform | Windows |
| Header | winbio_adapter.h (include Winbio_adapter.h) |