Add new API function: feedbackPrivate.readLogSource

chrome/browser/extensions/api/feedback_private/log_source_access_manager.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 "chrome/browser/extensions/api/feedback_private/log_source_access_manager.h"
+
+#include <algorithm>
+#include <utility>
+
+#include "base/bind.h"
+#include "base/time/default_tick_clock.h"
+
+namespace extensions {
+
+namespace {
+
+#if defined(OS_CHROMEOS)
+// The minimum time between consecutive reads of a log source by a particular
+// extension.
+const int kDefaultRateLimitingTimeoutMs = 1000;
+
+// If this is null, then |kDefaultRateLimitingTimeoutMs| is used as the timeout.
+const base::TimeDelta* g_rate_limiting_timeout = nullptr;
+#endif  // defined(OS_CHROMEOS)
+
+base::TimeDelta GetMinTimeBetweenReads() {
+  return g_rate_limiting_timeout
+             ? *g_rate_limiting_timeout
+             : base::TimeDelta::FromMilliseconds(kDefaultRateLimitingTimeoutMs);
+}
+
+}  // namespace
+
+LogSourceAccessManager::SourceAndExtension::SourceAndExtension(
+    api::feedback_private::LogSource source,
+    const std::string& extension_id)
+    : source(source), extension_id(extension_id) {}
+
+LogSourceAccessManager::LogSourceAccessManager()
+    : tick_clock_(new base::DefaultTickClock), weak_factory_(this) {}
+
+LogSourceAccessManager::~LogSourceAccessManager() {}
+
+// static
+void LogSourceAccessManager::SetRateLimitingTimeoutForTesting(
+    const base::TimeDelta* timeout) {
+  g_rate_limiting_timeout = timeout;
+}
+
+bool LogSourceAccessManager::AddExtension(const SourceAndExtension& key) {
+  // emplace() returns a pair where the second element is a flag indicating
+  // whether the entry was newly added.
+  return active_keys_.emplace(key).second;
+}
+
+bool LogSourceAccessManager::RemoveExtension(const SourceAndExtension& key) {
+  auto iter = active_keys_.find(key);

[tbarzic, 2017/06/01 19:23:46]

I'd prefer something like:

return active_keys_.erase(key) > 0;

or

if (active_keys_.count(key) == 0)
  return false;
active_keys_.erase(key);
return true;

[Simon Que, 2017/06/01 21:49:09]

Done.

+  if (iter == active_keys_.end())
+    return false;
+
+  active_keys_.erase(iter);
+  return true;
+}
+
+size_t LogSourceAccessManager::GetNumActiveExtensionsForSource(
+    api::feedback_private::LogSource source) const {
+  size_t count = 0;
+  // The stored entries are sorted first by source type, then by extension ID.
+  // We can take advantage of this fact to avoid iterating over all elements.
+  // Instead start from the first element that matches |source|, and end at the
+  // first element that does not match |source| anymore.
+  for (auto iter = active_keys_.lower_bound(SourceAndExtension(source, ""));
+       iter != active_keys_.end() && iter->source == source; ++iter) {
+    ++count;
+  }
+  return count;
+}
+
+bool LogSourceAccessManager::AccessSourceFromExtension(
+    const SourceAndExtension& key) {
+  base::TimeTicks last = GetLastExtensionAccessTime(key);
+  base::TimeTicks now = tick_clock_->NowTicks();
+  if (last.is_null() || now >= last + GetMinTimeBetweenReads()) {
+    last_access_times_[key] = now;
+    return true;
+  }
+  return false;

[tbarzic, 2017/06/01 19:23:46]

nit: I'd switch this as:
if (!last.is_null() && now < last + GetMinTimeBetweenReads())
  return false;

last_access_times_[key] = now;
return true;

[Simon Que, 2017/06/01 21:49:09]

Done.

+}
+
+base::TimeTicks LogSourceAccessManager::GetLastExtensionAccessTime(
+    const SourceAndExtension& key) const {
+  auto iter = last_access_times_.find(key);
+  if (iter == last_access_times_.end())
+    return base::TimeTicks();
+
+  return iter->second;
+}
+
+base::Closure LogSourceAccessManager::GetUnregisterCallback(
+    const SourceAndExtension& key) {
+  return base::Bind(&LogSourceAccessManager::RemoveExtensionNoReturn,
+                    weak_factory_.GetWeakPtr(), key);
+}
+
+void LogSourceAccessManager::RemoveExtensionNoReturn(
+    const SourceAndExtension& key) {
+  RemoveExtension(key);
+}
+
+}  // namespace extensions