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PdhEnumObjectItemsHA function (pdh.h)

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Returns the specified object's counter and instance names that exist on the specified computer or in the specified log file.

This function is identical to the PdhEnumObjectItems function, except that it supports the use of handles to data sources.

Syntax

PDH_FUNCTION PdhEnumObjectItemsHA(
  [in]      PDH_HLOG hDataSource,
  [in]      LPCSTR   szMachineName,
  [in]      LPCSTR   szObjectName,
  [out]     PZZSTR   mszCounterList,
  [in, out] LPDWORD  pcchCounterListLength,
  [out]     PZZSTR   mszInstanceList,
  [in, out] LPDWORD  pcchInstanceListLength,
  [in]      DWORD    dwDetailLevel,
  [in]      DWORD    dwFlags
);

Parameters

[in] hDataSource

Handle to a data source returned by the PdhBindInputDataSource function.

[in] szMachineName

Null-terminated string that specifies the name of the computer that contains the counter and instance names that you want to enumerate.

Include the leading slashes in the computer name, for example, \computername.

If the szDataSource parameter is NULL, you can set szMachineName to NULL to specify the local computer.

[in] szObjectName

Null-terminated string that specifies the name of the object whose counter and instance names you want to enumerate.

[out] mszCounterList

Caller-allocated buffer that receives a list of null-terminated counter names provided by the specified object. The list contains unique counter names. The list is terminated by two NULL characters. Set to NULL if the pcchCounterListLength parameter is zero.

[in, out] pcchCounterListLength

Size of the mszCounterList buffer, in TCHARs. If zero on input and the object exists, 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.

[out] mszInstanceList

Caller-allocated buffer that receives a list of null-terminated instance names provided by the specified object. The list contains unique instance names. The list is terminated by two NULL characters. Set to NULL if the pcchInstanceListLength parameter is zero.

[in, out] pcchInstanceListLength

Size of the mszInstanceList buffer, in TCHARs. If zero on input and the object exists, 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.

If the specified object does not support variable instances, then the returned value will be zero. If the specified object does support variable instances, but does not currently have any instances, then the value returned is 2, which is the size of an empty MULTI_SZ list string.

[in] dwDetailLevel

Detail level of the performance items to return. All items that are of the specified detail level or less will be returned (the levels are listed in increasing order). This parameter can be one of the following values.

Value Meaning
PERF_DETAIL_NOVICE
 Novice user level of detail.
PERF_DETAIL_ADVANCED
 Advanced user level of detail.
PERF_DETAIL_EXPERT
 Expert user level of detail.
PERF_DETAIL_WIZARD
 System designer level of detail.

[in] dwFlags

This parameter must be zero.

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
 One of the buffers is too small to contain the list of names. This return value is expected if pcchCounterListLength or pcchInstanceListLength 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 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 to support this function.
PDH_CSTATUS_NO_MACHINE
 The specified computer is offline or unavailable.
PDH_CSTATUS_NO_OBJECT
 The specified object could not be found on the specified computer or in the specified log file.

Remarks

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

Consecutive calls to this function will return identical lists of counters and instances, because PdhEnumObjectItemsH will always query the list of performance objects defined by the last call to PdhEnumObjectsH or PdhEnumObjectItemsH. To refresh the list of performance objects, call PdhEnumObjectsH with a bRefresh flag value of TRUE before calling PdhEnumObjectItemsH again.

The order of the instance and counter names is undetermined.

Note

The pdh.h header defines PdhEnumObjectItemsH 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 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

PdhBindInputDataSource

PdhEnumObjectsH