simplificed monotonic time functions by using x/sys/unix

system.go

@@ -0,0 +1,32 @@
+package hodu
+
+import "syscall"
+import "unsafe"
+import "golang.org/x/sys/unix"
+
+
+// utilize the builtin runtime.nanotime()
+//go:noescape
+//go:linkname nanotime runtime.nanotime
+func nanotime() int64
+
+func monotonic_time() uint64 {
+	var n int64
+	var err error
+	var uts unix.Timespec
+
+	n = nanotime() // hopefully it's faster than a system call. say, vdso is utilized.
+	if (n >= 0) { return uint64(n) }
+
+	err = unix.ClockGettime(unix.CLOCK_MONOTONIC, &uts)
+	if err != nil {
+		//var errno syscall.Errno
+		var r uintptr
+		var sts syscall.Timespec
+		r, _, _/*errno*/ = syscall.Syscall(syscall.SYS_CLOCK_GETTIME, unix.CLOCK_MONOTONIC, uintptr(unsafe.Pointer(&sts)), 0)
+		if r == ^uintptr(0) { return uint64(n) } // may be negative cast to unsigned. no other fall-back
+		return uint64(sts.Nano())
+	}
+
+	return uint64(uts.Nano())
+}