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      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 "components/metrics/cloned_install_detector.h"
      6 
      7 #include "base/bind.h"
      8 #include "base/location.h"
      9 #include "base/metrics/histogram.h"
     10 #include "base/prefs/pref_registry_simple.h"
     11 #include "base/prefs/pref_service.h"
     12 #include "base/single_thread_task_runner.h"
     13 #include "base/task_runner_util.h"
     14 #include "components/metrics/cloned_install_detector.h"
     15 #include "components/metrics/machine_id_provider.h"
     16 #include "components/metrics/metrics_hashes.h"
     17 #include "components/metrics/metrics_pref_names.h"
     18 
     19 namespace metrics {
     20 
     21 namespace {
     22 
     23 uint32 HashRawId(const std::string& value) {
     24   uint64 hash = metrics::HashMetricName(value);
     25 
     26   // Only use 24 bits from the 64-bit hash.
     27   return hash & ((1 << 24) - 1);
     28 }
     29 
     30 // State of the generated machine id in relation to the previously stored value.
     31 // Note: UMA histogram enum - don't re-order or remove entries
     32 enum MachineIdState {
     33   ID_GENERATION_FAILED,
     34   ID_NO_STORED_VALUE,
     35   ID_CHANGED,
     36   ID_UNCHANGED,
     37   ID_ENUM_SIZE
     38 };
     39 
     40 // Logs the state of generating a machine id and comparing it to a stored value.
     41 void LogMachineIdState(MachineIdState state) {
     42   UMA_HISTOGRAM_ENUMERATION("UMA.MachineIdState", state, ID_ENUM_SIZE);
     43 }
     44 
     45 }  // namespace
     46 
     47 ClonedInstallDetector::ClonedInstallDetector(MachineIdProvider* raw_id_provider)
     48     : raw_id_provider_(raw_id_provider), weak_ptr_factory_(this) {
     49 }
     50 
     51 ClonedInstallDetector::~ClonedInstallDetector() {
     52 }
     53 
     54 void ClonedInstallDetector::CheckForClonedInstall(
     55     PrefService* local_state,
     56     scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
     57   base::PostTaskAndReplyWithResult(
     58       task_runner.get(),
     59       FROM_HERE,
     60       base::Bind(&metrics::MachineIdProvider::GetMachineId, raw_id_provider_),
     61       base::Bind(&metrics::ClonedInstallDetector::SaveMachineId,
     62                  weak_ptr_factory_.GetWeakPtr(),
     63                  local_state));
     64 }
     65 
     66 void ClonedInstallDetector::SaveMachineId(PrefService* local_state,
     67                                           std::string raw_id) {
     68   if (raw_id.empty()) {
     69     LogMachineIdState(ID_GENERATION_FAILED);
     70     local_state->ClearPref(prefs::kMetricsMachineId);
     71     return;
     72   }
     73 
     74   int hashed_id = HashRawId(raw_id);
     75 
     76   MachineIdState id_state = ID_NO_STORED_VALUE;
     77   if (local_state->HasPrefPath(prefs::kMetricsMachineId)) {
     78     if (local_state->GetInteger(prefs::kMetricsMachineId) != hashed_id) {
     79       id_state = ID_CHANGED;
     80       // TODO(jwd): Use a callback to set the reset pref. That way
     81       // ClonedInstallDetector doesn't need to know about this pref.
     82       local_state->SetBoolean(prefs::kMetricsResetIds, true);
     83     } else {
     84       id_state = ID_UNCHANGED;
     85     }
     86   }
     87 
     88   LogMachineIdState(id_state);
     89 
     90   local_state->SetInteger(prefs::kMetricsMachineId, hashed_id);
     91 }
     92 
     93 // static
     94 void ClonedInstallDetector::RegisterPrefs(PrefRegistrySimple* registry) {
     95   registry->RegisterIntegerPref(prefs::kMetricsMachineId, 0);
     96 }
     97 
     98 }  // namespace metrics
     99