src/net/android/cellular_signal_strength.cc

// Copyright 2016 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 "net/android/cellular_signal_strength.h"

#include "jni/AndroidCellularSignalStrength_jni.h"

namespace net {

namespace android {

namespace cellular_signal_strength {

namespace {

// GENERATED_JAVA_ENUM_PACKAGE: org.chromium.net
enum CellularSignalStrengthError {
  // Value returned by CellularSignalStrength APIs when a valid value is
  // unavailable. This value is same as INT32_MIN, but the following code uses
  // the explicit value of INT32_MIN so that the auto-generated Java enums work
  // correctly.
  ERROR_NOT_SUPPORTED = -2147483648,
};

static_assert(
    INT32_MIN == ERROR_NOT_SUPPORTED,
    "CellularSignalStrengthError.ERROR_NOT_SUPPORTED has unexpected value");

}  // namespace

base::Optional<int32_t> GetSignalStrengthLevel() {
  int32_t signal_strength_level =
      Java_AndroidCellularSignalStrength_getSignalStrengthLevel(
          base::android::AttachCurrentThread());
  if (signal_strength_level == ERROR_NOT_SUPPORTED)
    return base::nullopt;

  // |signal_strength_level| is expected to be between 0 and 4 (both inclusive).
  // See
  // https://developer.android.com/reference/android/telephony/SignalStrength.html#getLevel().
  // On some devices, |signal_strength_level| may have a value outside this
  // range (e.g., see https://crbug.com/835701). For such devices, cap the value
  // to be between 0 and 4.
  if (signal_strength_level < 0)
    return 0;
  if (signal_strength_level > 4)
    return 4;

  return signal_strength_level;
}

}  // namespace cellular_signal_strength

}  // namespace android

}  // namespace net