Implement ping_freshness for update_client.

components/update_client/persisted_data.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 "components/update_client/persisted_data.h"
 
 #include <string>
 #include <vector>
 
+#include "base/guid.h"
 #include "base/macros.h"
 #include "base/threading/thread_checker.h"
 #include "base/values.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
 #include "components/prefs/scoped_user_pref_update.h"
 
 const char kPersistedDataPreference[] = "updateclientdata";
 const int kDateLastRollCallUnknown = -2;
+const std::string kPingFreshnessUnknown = "";
 
 namespace update_client {
 
 PersistedData::PersistedData(PrefService* pref_service)
     : pref_service_(pref_service) {}
 
 PersistedData::~PersistedData() {
   DCHECK(thread_checker_.CalledOnValidThread());
 }
 
 int PersistedData::GetDateLastRollCall(const std::string& id) const {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (!pref_service_)
     return kDateLastRollCallUnknown;
   int dlrc = kDateLastRollCallUnknown;
   const base::DictionaryValue* dict =
       pref_service_->GetDictionary(kPersistedDataPreference);
   // We assume ids do not contain '.' characters.
   DCHECK_EQ(std::string::npos, id.find('.'));
   if (!dict->GetInteger("apps." + id + ".dlrc", &dlrc))
     return kDateLastRollCallUnknown;
   return dlrc;
 }
 
+std::string PersistedData::GetPingFreshness(const std::string& id) const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (!pref_service_)
+    return kPingFreshnessUnknown;
+  std::string freshness = kPingFreshnessUnknown;

[Sorin Jianu, 2016/04/15 20:26:53]

Is there a need to define kPingFreshnessUnknown at all? We could just return
std::string().

[waffles, 2016/04/15 21:54:20]

Done.

+  const base::DictionaryValue* dict =
+      pref_service_->GetDictionary(kPersistedDataPreference);
+  // We assume ids do not contain '.' characters.
+  DCHECK_EQ(std::string::npos, id.find('.'));
+  if (!dict->GetString("apps." + id + ".pf", &freshness))
+    return kPingFreshnessUnknown;
+  return "{" + freshness + "}";

[Sorin Jianu, 2016/04/15 20:26:53]

if we need to format I suggest stringprintf, since expressions like this may
result in temporary variables being created.

This pattern is uses in other places in this CL and previous CLs. It might be
worth reviewing its usage.

I have to do some science with C++11 and the current compilers, since I believe
in some cases, it may avoid creating some of the temporaries. I am not concerned
about time efficiency but it space efficiency due to additional code needed to
create and destroy the temporaries.

[waffles, 2016/04/15 21:54:20]

Done.

+}
+
 void PersistedData::SetDateLastRollCall(const std::vector<std::string>& ids,
                                         int datenum) const {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (!pref_service_ || datenum < 0)
     return;
   DictionaryPrefUpdate update(pref_service_, kPersistedDataPreference);
   for (auto id : ids) {
     // We assume ids do not contain '.' characters.
     DCHECK_EQ(std::string::npos, id.find('.'));
     update->SetInteger("apps." + id + ".dlrc", datenum);
+    update->SetString("apps." + id + ".pf", base::GenerateGUID());
   }
 }
 
 void PersistedData::RegisterPrefs(PrefRegistrySimple* registry) {
   registry->RegisterDictionaryPref(kPersistedDataPreference);
 }
 
 }  // namespace update_client