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PdhGetDefaultPerfObjectA function (pdh.h)

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Retrieves the name of the default object. This name can be used to set the initial object selection in the Browse Counter dialog box.

To use handles to data sources, use the PdhGetDefaultPerfObjectH function.

Syntax

PDH_FUNCTION PdhGetDefaultPerfObjectA(
  [in]      LPCSTR  szDataSource,
  [in]      LPCSTR  szMachineName,
  [out]     LPSTR   szDefaultObjectName,
  [in, out] LPDWORD pcchBufferSize
);

Parameters

[in] szDataSource

Should be NULL.

If you specify a log file, the szDefaultObjectName parameter will be a null string.

[in] szMachineName

Null-terminated string that specifies the name of the computer used to verify the object name. If NULL, the local computer is used to verify the name.

[out] szDefaultObjectName

Caller-allocated buffer that receives the null-terminated default object name. Set to NULL if the pcchBufferSize parameter is zero.

Note that PDH always returns Processor for the default object name.

[in, out] pcchBufferSize

Size of the szDefaultObjectName buffer, in TCHARs. If zero on input, the function returns PDH_MORE_DATA and sets this parameter to the required buffer size. If the buffer is larger than the required size, the function sets this parameter to the actual size of the buffer that was used. If the specified size on input is greater than zero but less than the required size, you should not rely on the returned size to reallocate the buffer.

Return value

If the function succeeds, it returns ERROR_SUCCESS.

If the function fails, the return value is a system error code or a PDH error code. The following are possible values.

Return code Description
PDH_MORE_DATA
 The szDefaultObjectName buffer is too small to contain the object name. This return value is expected if pcchBufferSize is zero on input. If the specified size on input is greater than zero but less than the required size, you should not rely on the returned size to reallocate the buffer.
PDH_INVALID_ARGUMENT
 A required parameter is not valid. For example, on some releases you could receive this error if the specified size on input is greater than zero but less than the required size.
PDH_MEMORY_ALLOCATION_FAILURE
 Unable to allocate memory in order to complete the function.
PDH_CSTATUS_NO_MACHINE
 The specified computer is offline or unavailable.

Remarks

You should call this function twice, the first time to get the required buffer size (set szDefaultObjectName to NULL and pcchBufferSize to 0), and the second time to get the data.

Note

The pdh.h header defines PdhGetDefaultPerfObject as an alias which 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 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 XP [desktop apps only]
Minimum supported server Windows Server 2003 [desktop apps only]
Target Platform Windows
Header pdh.h
Library Pdh.lib
DLL Pdh.dll

See also

PdhGetDefaultPerfCounter

PdhGetDefaultPerfObjectH