[mem][windows]: add ExWindows and implement VirualTotal/Avail

This commit fixes #1588. Thank you!

mem/ex_windows.go

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: BSD-3-Clause
+//go:build windows
+
+package mem
+
+import (
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+// ExVirtualMemory represents Windows specific information
+// https://learn.microsoft.com/en-us/windows/win32/api/sysinfoapi/ns-sysinfoapi-memorystatusex
+type ExVirtualMemory struct {
+	VirtualTotal uint64 `json:"virtualTotal"`
+	VirtualAvail uint64 `json:"virtualAvail"`
+}
+
+type ExWindows struct{}
+
+func NewExWindows() *ExWindows {
+	return &ExWindows{}
+}
+
+func (e *ExWindows) VirtualMemory() (*ExVirtualMemory, error) {
+	var memInfo memoryStatusEx
+	memInfo.cbSize = uint32(unsafe.Sizeof(memInfo))
+	mem, _, _ := procGlobalMemoryStatusEx.Call(uintptr(unsafe.Pointer(&memInfo)))
+	if mem == 0 {
+		return nil, windows.GetLastError()
+	}
+
+	ret := &ExVirtualMemory{
+		VirtualTotal: memInfo.ullTotalVirtual,
+		VirtualAvail: memInfo.ullAvailVirtual,
+	}
+
+	return ret, nil
+}