Fix CPU Algorithm

lib/data/model/cpu_2_status.dart

@@ -0,0 +1,17 @@
+import 'package:toolbox/data/model/cpu_status.dart';
+
+class Cpu2Status {
+  List<CpuStatus> pre;
+  List<CpuStatus> now;
+  Cpu2Status(this.pre, this.now);
+
+  double usedPercent({int coreIdx = 0}) {
+    final used = (now[coreIdx].idle - pre[coreIdx].idle) /
+        (now[coreIdx].total - pre[coreIdx].total);
+    return used.isNaN ? 0 : used;
+  }
+
+  Cpu2Status update(List<CpuStatus> newStatus) {
+    return Cpu2Status(now, newStatus);
+  }
+}