rpcfetch: implement Windows system stats fetching

Unfortunately I could not find any loadavg equivalent on Windows, so it returns a fixed value for now.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

fetch/apply_windows.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"log"
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+var (
+	kernel32             = syscall.NewLazyDLL("kernel32.dll")
+	globalMemoryStatusEx = kernel32.NewProc("GlobalMemoryStatusEx")
+)
+
+type globalMemoryStatusExT struct {
+	dwLength     uint32
+	dwMemoryLoad uint32
+	ullTotalPhys uint64
+	ullAvailPhys uint64
+	unused       [5]uint64
+}
+
+func init() {
+	if h, err := os.Hostname(); err != nil {
+		log.Fatalf("error reading hostname: %s", err)
+	} else {
+		hostname = h
+	}
+}
+
+func (s *applyState) populateLoadavg() {
+	if s.loadavg != nil {
+		return
+	}
+
+	// loadavg is unsupported on Windows
+	s.loadavg = &[3]string{"0.00", "0.00", "0.00"}
+}
+
+func (s *applyState) populateMem() {
+	if s.mem != nil {
+		return
+	}
+
+	// failure defaults
+	s.mem = &[2]int{-1, -1}
+
+	v := new(globalMemoryStatusExT)
+	v.dwLength = 64
+	r1, _, err := globalMemoryStatusEx.Call(uintptr(unsafe.Pointer(v)))
+	log.Printf("call to globalMemoryStatusEx, r1=%d, %s", r1, err)
+	s.mem[0] = int(v.ullAvailPhys / (1 << 10))
+	s.mem[1] = int(v.ullTotalPhys / (1 << 10))
+}