Add implementation of SwapMemory() for windows

internal/common/common_windows.go

@@ -48,7 +48,8 @@ var (
 	Modkernel32 = windows.NewLazyDLL("kernel32.dll")
 	ModNt       = windows.NewLazyDLL("ntdll.dll")
 	ModPdh      = windows.NewLazyDLL("pdh.dll")
-
+	ModPsapi    = windows.NewLazyDLL("psapi.dll")
+	
 	ProcGetSystemTimes           = Modkernel32.NewProc("GetSystemTimes")
 	ProcNtQuerySystemInformation = ModNt.NewProc("NtQuerySystemInformation")
 	PdhOpenQuery                 = ModPdh.NewProc("PdhOpenQuery")

mem/mem_windows.go

@@ -11,6 +11,7 @@ import (
 
 var (
 	procGlobalMemoryStatusEx = common.Modkernel32.NewProc("GlobalMemoryStatusEx")
+	procGetPerformanceInfo = common.ModPsapi.NewProc("GetPerformanceInfo")
 )
 
 type memoryStatusEx struct {
@@ -43,8 +44,40 @@ func VirtualMemory() (*VirtualMemoryStat, error) {
 	return ret, nil
 }
 
+type performanceInformation struct {
+	cb				uint32
+	commitTotal		uint64
+	commitLimit		uint64
+	commitPeak		uint64
+	physicalTotal	uint64
+	physicalAvailable uint64
+	systemCache uint64
+	kernelTotal uint64
+	kernelPaged uint64
+	kernelNonpaged uint64
+	pageSize uint64
+	handleCount uint32
+	processCount uint32
+	threadCount uint32
+}
+
 func SwapMemory() (*SwapMemoryStat, error) {
-	ret := &SwapMemoryStat{}
+	var perfInfo performanceInformation
+	perfInfo.cb = uint32(unsafe.Sizeof(perfInfo))
+	mem, _, _ := procGetPerformanceInfo.Call(uintptr(unsafe.Pointer(&perfInfo)), uintptr(perfInfo.cb))
+	if mem == 0 {
+		return nil, windows.GetLastError()
+	}
+	tot := perfInfo.commitLimit * perfInfo.pageSize
+	used := perfInfo.commitTotal * perfInfo.pageSize
+	free := tot - used
+	ret := &SwapMemoryStat{
+		Total: tot,
+		Used: used,
+		Free: free,
+		UsedPercent: float64(used/tot),
+	}
 
 	return ret, nil
 }
+