How to add PdhParseCounterPath function

[jwenz723]

I am trying to add the PdhParseCounterPath function (as documented here https://msdn.microsoft.com/en-us/library/windows/desktop/aa372657(v=vs.85).aspx ) into pdh.go, but I am a bit unsure of how to do so. Wondering if any of the contributors could offer a little help? Here is what I've added:

type PDH_COUNTER_PATH_ELEMENTS struct {
	szMachineName string
	szObjectName string
	szInstanceName string
	szParentInstance string
	dwInstanceIndex uintptr
	szCounterName string
}

var (
	// Library
	libpdhDll *syscall.DLL

	// Functions
	pdh_AddCounterW               *syscall.Proc
	pdh_AddEnglishCounterW        *syscall.Proc
	pdh_CloseQuery                *syscall.Proc
	pdh_CollectQueryData          *syscall.Proc
	pdh_GetFormattedCounterValue  *syscall.Proc
	pdh_GetFormattedCounterArrayW *syscall.Proc
	pdh_OpenQuery                 *syscall.Proc
	pdh_ValidatePathW             *syscall.Proc
	pdh_ParseCounterPathW		  *syscall.Proc  // added this
)

func init() {
	// Library
	libpdhDll = syscall.MustLoadDLL("pdh.dll")

	// Functions
	pdh_AddCounterW = libpdhDll.MustFindProc("PdhAddCounterW")
	pdh_AddEnglishCounterW, _ = libpdhDll.FindProc("PdhAddEnglishCounterW") // XXX: only supported on versions > Vista.
	pdh_CloseQuery = libpdhDll.MustFindProc("PdhCloseQuery")
	pdh_CollectQueryData = libpdhDll.MustFindProc("PdhCollectQueryData")
	pdh_GetFormattedCounterValue = libpdhDll.MustFindProc("PdhGetFormattedCounterValue")
	pdh_GetFormattedCounterArrayW = libpdhDll.MustFindProc("PdhGetFormattedCounterArrayW")
	pdh_OpenQuery = libpdhDll.MustFindProc("PdhOpenQuery")
	pdh_ValidatePathW = libpdhDll.MustFindProc("PdhValidatePathW")
	pdh_ParseCounterPathW = libpdhDll.MustFindProc("PdhParseCounterPathW") // added this
}

func PdhParseCounterPath(szFullPathBuffer string, pCounterPathElements *PDH_COUNTER_PATH_ELEMENTS) uint32 {
	ptxt, _ := syscall.UTF16PtrFromString(szFullPathBuffer)

	var test uint32

	ret, _, _ := pdh_ParseCounterPathW.Call(
		uintptr(unsafe.Pointer(ptxt)), // I think this is correct
		uintptr(unsafe.Pointer(pCounterPathElements)), // not sure what to do here
		uintptr(unsafe.Pointer(&test)), // not sure what to do here
		0) // I think this is correct

	return uint32(ret)
}

[jwenz723]

Also, when I run it in this current condition I get the error code: PDH_INVALID_ARGUMENT, so I assume something is incorrect with the arguments I am passing into the function call.

[jwenz723]

Figured it out finally after many hours of trial and error...

func PdhParseCounterPath(szFullPathBuffer string, pCounterPathElements *PDH_COUNTER_PATH_ELEMENTS, pdwBufferSize *uint32) uint32 {
	ptxt, _ := syscall.UTF16PtrFromString(szFullPathBuffer)

	ret, _, _ := pdh_ParseCounterPathW.Call(
		uintptr(unsafe.Pointer(ptxt)),
		uintptr(unsafe.Pointer(pCounterPathElements)),
		uintptr(unsafe.Pointer(pdwBufferSize)),
		0)

	return uint32(ret)
}