chrome/browser/metrics/cloned_install_detector.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chrome/browser/metrics/cloned_install_detector.h"
   6
   7 #include "base/bind.h"
   8 #include "base/metrics/histogram.h"
   9 #include "base/prefs/pref_registry_simple.h"
  10 #include "base/prefs/pref_service.h"
  11 #include "chrome/browser/metrics/cloned_install_detector.h"
  12 #include "chrome/browser/metrics/machine_id_provider.h"
  13 #include "chrome/common/pref_names.h"
  14 #include "components/metrics/metrics_hashes.h"
  15 #include "content/public/browser/browser_thread.h"
  16
  17 namespace metrics {
  18
  19 namespace {
  20
  21 uint32 HashRawId(const std::string& value) {
  22   uint64 hash = metrics::HashMetricName(value);
  23
  24   // Only use 24 bits from the 64-bit hash.
  25   return hash & ((1 << 24) - 1);
  26 }
  27
  28 // State of the generated machine id in relation to the previously stored value.
  29 // Note: UMA histogram enum - don't re-order or remove entries
  30 enum MachineIdState {
  31   ID_GENERATION_FAILED,
  32   ID_NO_STORED_VALUE,
  33   ID_CHANGED,
  34   ID_UNCHANGED,
  35   ID_ENUM_SIZE
  36 };
  37
  38 // Logs the state of generating a machine id and comparing it to a stored value.
  39 void LogMachineIdState(MachineIdState state) {
  40   UMA_HISTOGRAM_ENUMERATION("UMA.MachineIdState", state, ID_ENUM_SIZE);
  41 }
  42
  43 }  // namespace
  44
  45 ClonedInstallDetector::ClonedInstallDetector(MachineIdProvider* raw_id_provider)
  46     : raw_id_provider_(raw_id_provider),
  47       weak_ptr_factory_(this) {}
  48
  49 ClonedInstallDetector::~ClonedInstallDetector() {}
  50
  51 void ClonedInstallDetector::CheckForClonedInstall(PrefService* local_state) {
  52   content::BrowserThread::PostTaskAndReplyWithResult(
  53       content::BrowserThread::FILE,
  54       FROM_HERE,
  55       base::Bind(&metrics::MachineIdProvider::GetMachineId,
  56                  raw_id_provider_),
  57       base::Bind(&metrics::ClonedInstallDetector::SaveMachineId,
  58                  weak_ptr_factory_.GetWeakPtr(),
  59                  local_state));
  60 }
  61
  62 void ClonedInstallDetector::SaveMachineId(
  63     PrefService* local_state,
  64     std::string raw_id) {
  65   if (raw_id.empty()) {
  66     LogMachineIdState(ID_GENERATION_FAILED);
  67     local_state->ClearPref(prefs::kMetricsMachineId);
  68     return;
  69   }
  70
  71   int hashed_id = HashRawId(raw_id);
  72
  73   MachineIdState id_state = ID_NO_STORED_VALUE;
  74   if (local_state->HasPrefPath(prefs::kMetricsMachineId)) {
  75     if (local_state->GetInteger(prefs::kMetricsMachineId) != hashed_id) {
  76       id_state = ID_CHANGED;
  77       // TODO(jwd): Use a callback to set the reset pref. That way
  78       // ClonedInstallDetector doesn't need to know about this pref.
  79       local_state->SetBoolean(prefs::kMetricsResetIds, true);
  80     } else {
  81       id_state = ID_UNCHANGED;
  82     }
  83   }
  84
  85   LogMachineIdState(id_state);
  86
  87   local_state->SetInteger(prefs::kMetricsMachineId, hashed_id);
  88 }
  89
  90 // static
  91 void ClonedInstallDetector::RegisterPrefs(PrefRegistrySimple* registry) {
  92   registry->RegisterIntegerPref(prefs::kMetricsMachineId, 0);
  93 }
  94
  95 }  // namespace metrics