chromeos: Add CPU temperature reader

chromeos/system/cpu_temp_reader.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/system/cpu_temp_reader.h"
+
+#include "base/files/file_enumerator.h"
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
+
+namespace chromeos {
+namespace system {
+
+namespace {
+
+// The location we read our CPU temperature and channel label from.
+const char kHwmonDir[] = "/sys/class/hwmon/";
+const char kDeviceDir[] = "device";
+const char kHwmonDirectoryPattern[] = "hwmon*";
+const char kCPUTempFilePattern[] = "temp*_input";
+
+}  // namespace
+
+std::vector<CPUTemperatureInfo> GetCPUTemperatures() {
+  std::vector<CPUTemperatureInfo> result;
+
+  // Get directories /sys/class/hwmon/hwmon*
+  base::FileEnumerator hwmon_enumerator(base::FilePath(kHwmonDir), false,
+                                        base::FileEnumerator::DIRECTORIES,
+                                        kHwmonDirectoryPattern);
+  for (base::FilePath hwmon_path = hwmon_enumerator.Next(); !hwmon_path.empty();
+       hwmon_path = hwmon_enumerator.Next()) {
+    // Get temp*_input files in hwmon*/ and hwmon*/device/
+    if (base::PathExists(hwmon_path.Append(kDeviceDir))) {
+      hwmon_path = hwmon_path.Append(kDeviceDir);
+    }
+    base::FileEnumerator enumerator(
+        hwmon_path, false, base::FileEnumerator::FILES, kCPUTempFilePattern);
+    for (base::FilePath temperature_path = enumerator.Next();
+         !temperature_path.empty(); temperature_path = enumerator.Next()) {
+      // Get appropriate temp*_label file.
+      std::string label_path = temperature_path.MaybeAsASCII();
+      if (label_path.empty()) {
+        LOG(WARNING) << "Unable to parse a path to temp*_input file as ASCII";
+        continue;
+      }

[stevenjb, 2017/04/14 15:44:04]

This would be a bit more readable if some or all of the code below was moved to
a local helper function.

[Simon Que, 2017/04/17 16:41:07]

Done.

+      base::ReplaceSubstringsAfterOffset(&label_path, 0, "input", "label");
+      base::FilePath name_path = hwmon_path.Append("name");
+
+      // Get the label describing this temperature. Use temp*_label
+      // if present, fall back on name file or blank.
+      std::string label;
+      if (base::PathExists(base::FilePath(label_path))) {
+        base::ReadFileToString(base::FilePath(label_path), &label);
+      } else if (base::PathExists(base::FilePath(name_path))) {
+        base::ReadFileToString(name_path, &label);
+      } else {
+        label = std::string();
+      }
+
+      // Read temperature in millidegree Celsius.
+      std::string temperature_string;
+      uint32_t temperature = 0;
+      if (base::ReadFileToString(temperature_path, &temperature_string) &&
+          base::StringToUint(temperature_string, &temperature)) {
+        CPUTemperatureInfo info;
+        info.temp_celsius = static_cast<double>(temperature) / 1000;
+        info.label = label;
+        result.push_back(info);

[Daniel Erat, 2017/04/14 18:53:32]

i think, but am not certain, that you might just be able to do this:

result.emplace_back(static_cast<double>(temperature) / 1000, label);

[Simon Que, 2017/04/17 16:41:07]

No longer applicable due to refactoring.

+      } else {
+        LOG(WARNING) << "Unable to read CPU temp from "
+                     << temperature_path.MaybeAsASCII();
+      }
+    }
+  }
+  return result;
+}
+
+}  // namespace system
+}  // namespace chromeos