Refactor collectors

Signed-off-by: Jan-Otto Kröpke <mail@jkroepke.de>

pkg/headers/psapi/psapi.go

@@ -0,0 +1,45 @@
+package psapi
+
+import (
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+// PerformanceInformation is a wrapper of the PERFORMANCE_INFORMATION struct.
+// https://docs.microsoft.com/en-us/windows/win32/api/psapi/ns-psapi-performance_information
+type PerformanceInformation struct {
+	cb                uint32
+	CommitTotal       uint
+	CommitLimit       uint
+	CommitPeak        uint
+	PhysicalTotal     uint
+	PhysicalAvailable uint
+	SystemCache       uint
+	KernelTotal       uint
+	KernelPaged       uint
+	KernelNonpaged    uint
+	PageSize          uint
+	HandleCount       uint32
+	ProcessCount      uint32
+	ThreadCount       uint32
+}
+
+var (
+	psapi                  = windows.NewLazySystemDLL("psapi.dll")
+	procGetPerformanceInfo = psapi.NewProc("GetPerformanceInfo")
+)
+
+// GetPerformanceInfo returns the dereferenced version of GetLPPerformanceInfo.
+func GetPerformanceInfo() (PerformanceInformation, error) {
+	var lppi PerformanceInformation
+	size := (uint32)(unsafe.Sizeof(lppi))
+	lppi.cb = size
+	r1, _, err := procGetPerformanceInfo.Call(uintptr(unsafe.Pointer(&lppi)), uintptr(size))
+
+	if ret := *(*bool)(unsafe.Pointer(&r1)); !ret {
+		return PerformanceInformation{}, err
+	}
+
+	return lppi, nil
+}