Support to get net speed

lib/data/model/server/net_speed.dart

@@ -0,0 +1,71 @@
+import 'dart:math';
+
+class NetSpeedPart {
+  String device;
+  int bytesIn;
+  int bytesOut;
+  int time;
+  NetSpeedPart(this.device, this.bytesIn, this.bytesOut, this.time);
+}
+
+class NetSpeed {
+  List<NetSpeedPart> old;
+  List<NetSpeedPart> now;
+  NetSpeed(this.old, this.now);
+
+  List<String> get devices {
+    final devices = <String>[];
+    for (var item in now) {
+      devices.add(item.device);
+    }
+    return devices;
+  }
+
+  NetSpeed update(List<NetSpeedPart> newOne) => NetSpeed(now, newOne);
+
+  int get timeDiff => now[0].time - old[0].time;
+
+  String speedIn({String? device}) {
+    if (old[0].device == '' || now[0].device == '') return '0kb/s';
+    int idx = 0;
+    if (device != null) {
+      for (var item in now) {
+        if (item.device == device) {
+          idx = now.indexOf(item);
+          break;
+        }
+      }
+    }
+    final speedInBytesPerSecond =
+        (now[idx].bytesIn - old[idx].bytesIn) / timeDiff;
+    int squareTimes = 0;
+    for (; speedInBytesPerSecond / pow(1024, squareTimes) > 1024;) {
+      if (squareTimes >= suffixs.length - 1) break;
+      squareTimes++;
+    }
+    return '${(speedInBytesPerSecond / pow(1024, squareTimes)).toStringAsFixed(1)} ${suffixs[squareTimes]}';
+  }
+
+  String speedOut({String? device}) {
+    if (old[0].device == '' || now[0].device == '') return '0kb/s';
+    int idx = 0;
+    if (device != null) {
+      for (var item in now) {
+        if (item.device == device) {
+          idx = now.indexOf(item);
+          break;
+        }
+      }
+    }
+    final speedInBytesPerSecond =
+        (now[idx].bytesOut - old[idx].bytesOut) / timeDiff;
+    int squareTimes = 0;
+    for (; speedInBytesPerSecond / pow(1024, squareTimes) > 1024;) {
+      if (squareTimes >= suffixs.length - 1) break;
+      squareTimes++;
+    }
+    return '${(speedInBytesPerSecond / pow(1024, squareTimes)).toStringAsFixed(1)} ${suffixs[squareTimes]}';
+  }
+}
+
+const suffixs = ['b/s', 'kb/s', 'mb/s', 'gb/s'];