SCardGetReaderDeviceInstanceIdA function (winscard.h)

Article
11/20/2024

The SCardGetReaderDeviceInstanceId function gets the device instance identifier of the card reader for the given reader name. This function does not affect the state of the reader.

Syntax

LONG SCardGetReaderDeviceInstanceIdA(
  [in]            SCARDCONTEXT hContext,
  [in]            LPCSTR       szReaderName,
  [out, optional] LPSTR        szDeviceInstanceId,
  [in, out]       LPDWORD      pcchDeviceInstanceId
);

Parameters

[in] hContext

Handle that identifies the resource manager context for the query. You can set the resource manager context by a previous call to the SCardEstablishContext function. This parameter cannot be NULL.

[in] szReaderName

Reader name. You can get this value by calling the SCardListReaders function.

[out, optional] szDeviceInstanceId

Buffer that receives the device instance ID of the reader. If this value is NULL, the function ignores the buffer length supplied in cchDeviceInstanceId parameter, writes the length of the buffer that would have been returned if this parameter had not been NULL to cchDeviceInstanceId, and returns a success code.

[in, out] pcchDeviceInstanceId

Length, in characters, of the szDeviceInstanceId buffer, including the NULL terminator. If the buffer length is specified as SCARD_AUTOALLOCATE, then the szDeviceInstanceId parameter is converted to a pointer to a byte pointer, and receives the address of a block of memory containing the instance id. This block of memory must be deallocated with the SCardFreeMemory function.

Return value

This function returns different values depending on whether it succeeds or fails.

Return code	Description
Success	SCARD_S_SUCCESS.
Failure	An error code. For more information, see Smart Card Return Values.

Remarks

This function is not redirected. Calling the SCardGetReaderDeviceInstanceId function when inside a Remote Desktop session fails with the SCARD_E_READER_UNAVAILABLE error code.

Examples


LONG     lReturn;
LPTSTR   szReaderName = "USB Smart Card Reader 0";
WCHAR    szDeviceInstanceId[256];
DWORD    cchDeviceInstanceId = 256;

// Retrieve the reader's device instance ID.
// hContext was set by a previous call to SCardEstablishContext.
lReturn = SCardGetReaderDeviceInstanceId (hContext,
                         szReaderName,
                         szDeviceInstanceId,
                         &cchDeviceInstanceId);

if ( SCARD_S_SUCCESS != lReturn )
{
    printf("Failed SCardGetReaderDeviceInstanceId - %x\n", lReturn);
    // Take appropriate action.
}

Note

The winscard.h header defines SCardGetReaderDeviceInstanceId as an alias that automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that is not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.

Requirements

Requirement	Value
Minimum supported client	Windows 8 [desktop apps only]
Minimum supported server	Windows Server 2012 [desktop apps only]
Target Platform	Windows
Header	winscard.h

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