[CrOS Tether] Move the DeviceStatus normalizer code from HostScanner into its own file.

chromeos/components/tether/device_status_util.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chromeos/components/tether/device_status_util.h"
+
+namespace chromeos {
+
+namespace tether {
+
+namespace {
+
+const char kDefaultCellCarrierName[] = "unknown-carrier";
+
+// Android signal strength is measured between 0 and 4 (inclusive), but Chrome
+// OS signal strength is measured between 0 and 100 (inclusive). In order to
+// convert between Android signal strength to Chrome OS signal strength, the
+// value must be multiplied by the below value.
+const int32_t kAndroidTetherHostToChromeOSSignalStrengthMultiplier = 25;
+
+int32_t ForceBetweenZeroAndOneHundred(int32_t value) {
+  return std::min(std::max(value, 0), 100);
+}
+
+}  // namespace
+
+void NormalizeDeviceStatus(const DeviceStatus& status,
+                           std::string* carrier_out,
+                           int32_t* battery_percentage_out,
+                           int32_t* signal_strength_out) {
+  // Use a sentinel value if carrier information is not available. This value is
+  // special-cased and replaced with a localized string in the settings UI.
+  if (carrier_out) {
+    *carrier_out =
+        (!status.has_cell_provider() || status.cell_provider().empty())
+            ? kDefaultCellCarrierName
+            : status.cell_provider();
+  }
+
+  // If battery or signal strength are missing, assume they are 100. For
+  // battery percentage, force the value to be between 0 and 100. For signal
+  // strength, convert from Android signal strength to Chrome OS signal
+  // strength and force the value to be between 0 and 100.
+  if (battery_percentage_out) {
+    *battery_percentage_out =
+        status.has_battery_percentage()
+            ? ForceBetweenZeroAndOneHundred(status.battery_percentage())
+            : 100;
+  }
+  if (signal_strength_out) {
+    *signal_strength_out =
+        status.has_connection_strength()
+            ? ForceBetweenZeroAndOneHundred(
+                  kAndroidTetherHostToChromeOSSignalStrengthMultiplier *
+                  status.connection_strength())
+            : 100;
+  }
+}
+
+}  // namespace tether
+
+}  // namespace chromeos