1 files changed, 148 insertions, 0 deletions
diff --git a/chrome/browser/extensions/extensions_quota_service.cc b/chrome/browser/extensions/extensions_quota_service.cc
new file mode 100644
index 0000000..9005d8f
--- /dev/null
+++ b/chrome/browser/extensions/extensions_quota_service.cc
@@ -0,0 +1,148 @@
+// Copyright (c) 2009 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/extensions_quota_service.h"
+
+#include "base/message_loop.h"
+#include "base/stl_util-inl.h"
+#include "chrome/browser/extensions/extension_function.h"
+
+// If the browser stays open long enough, we reset state once a day.
+// Whatever this value is, it should be an order of magnitude longer than
+// the longest interval in any of the QuotaLimitHeuristics in use.
+static const int kPurgeIntervalInDays = 1;
+
+const char QuotaLimitHeuristic::kGenericOverQuotaError[] =
+    "This request exceeds available quota.";
+
+ExtensionsQuotaService::ExtensionsQuotaService() {
+  if (MessageLoop::current() != NULL) {  // Null in unit tests.
+    purge_timer_.Start(base::TimeDelta::FromDays(kPurgeIntervalInDays),
+                       this, &ExtensionsQuotaService::Purge);
+  }
+}
+
+ExtensionsQuotaService::~ExtensionsQuotaService() {
+  purge_timer_.Stop();
+  Purge();
+}
+
+bool ExtensionsQuotaService::Assess(const std::string& extension_id,
+    ExtensionFunction* function, const Value* args,
+    const base::TimeTicks& event_time) {
+  // Lookup function list for extension.
+  FunctionHeuristicsMap& functions = function_heuristics_[extension_id];
+
+  // Lookup heuristics for function, create if necessary.
+  QuotaLimitHeuristics& heuristics = functions[function->name()];
+  if (heuristics.empty())
+    function->GetQuotaLimitHeuristics(&heuristics);
+
+  if (heuristics.empty())
+    return true;  // No heuristic implies no limit.
+
+  if (violators_.find(extension_id) != violators_.end())
+    return false;  // Repeat offender.
+
+  bool global_decision = true;
+  for (QuotaLimitHeuristics::iterator heuristic = heuristics.begin();
+       heuristic != heuristics.end(); ++heuristic) {
+    // Apply heuristic to each item (bucket).
+    global_decision = (*heuristic)->ApplyToArgs(args, event_time) &&
+        global_decision;
+  }
+
+  if (!global_decision) {
+    PurgeFunctionHeuristicsMap(&functions);
+    function_heuristics_.erase(extension_id);
+    violators_.insert(extension_id);
+  }
+  return global_decision;
+}
+
+void ExtensionsQuotaService::PurgeFunctionHeuristicsMap(
+    FunctionHeuristicsMap* map) {
+  FunctionHeuristicsMap::iterator heuristics = map->begin();
+  while (heuristics != map->end()) {
+    STLDeleteElements(&heuristics->second);
+    map->erase(heuristics++);
+  }
+}
+
+void ExtensionsQuotaService::Purge() {
+  std::map<std::string, FunctionHeuristicsMap>::iterator it =
+      function_heuristics_.begin();
+  for (; it != function_heuristics_.end(); function_heuristics_.erase(it++))
+    PurgeFunctionHeuristicsMap(&it->second);
+}
+
+void QuotaLimitHeuristic::Bucket::Reset(const Config& config,
+    const base::TimeTicks& start) {
+  num_tokens_ = config.refill_token_count;
+  expiration_ = start + config.refill_interval;
+}
+
+bool QuotaLimitHeuristic::ApplyToArgs(const Value* args,
+    const base::TimeTicks& event_time) {
+  BucketList buckets;
+  bucket_mapper_->GetBucketsForArgs(args, &buckets);
+  for (BucketList::iterator i = buckets.begin(); i != buckets.end(); ++i) {
+    if ((*i)->expiration().is_null())  // A brand new bucket.
+      (*i)->Reset(config_, event_time);
+    if (!Apply(*i, event_time))
+      return false;  // It only takes one to spoil it for everyone.
+  }
+  return true;
+}
+
+ExtensionsQuotaService::SustainedLimit::SustainedLimit(
+    const base::TimeDelta& sustain, const Config& config, BucketMapper* map)
+    : QuotaLimitHeuristic(config, map),
+      repeat_exhaustion_allowance_(sustain.InSeconds() /
+                                   config.refill_interval.InSeconds()),
+      num_available_repeat_exhaustions_(repeat_exhaustion_allowance_) {
+}
+
+bool ExtensionsQuotaService::TimedLimit::Apply(Bucket* bucket,
+    const base::TimeTicks& event_time) {
+  if (event_time > bucket->expiration())
+    bucket->Reset(config(), event_time);
+
+  return bucket->DeductToken();
+}
+
+bool ExtensionsQuotaService::SustainedLimit::Apply(Bucket* bucket,
+    const base::TimeTicks& event_time) {
+  if (event_time > bucket->expiration()) {
+    // We reset state for this item and start over again if this request breaks
+    // the bad cycle that was previously being tracked.  This occurs if the
+    // state in the bucket expired recently (it has been long enough since the
+    // event that we don't care about the last event), but the bucket still has
+    // tokens (so pressure was not sustained over that time), OR we are more
+    // than 1 full refill interval away from the last event (so even if we used
+    // up all the tokens in the last bucket, nothing happened in the entire
+    // next refill interval, so it doesn't matter).
+    if (bucket->has_tokens() || event_time > bucket->expiration() +
+        config().refill_interval) {
+      bucket->Reset(config(), event_time);
+      num_available_repeat_exhaustions_ = repeat_exhaustion_allowance_;
+    } else if (--num_available_repeat_exhaustions_ > 0) {
+      // The last interval was saturated with requests, and this is the first
+      // event in the next interval. If this happens
+      // repeat_exhaustion_allowance_ times, it's a violation. Reset the bucket
+      // state to start timing from the end of the last interval (and we'll
+      // deduct the token below) so we can detect this each time it happens.
+      bucket->Reset(config(), bucket->expiration());
+    } else {
+      // No allowances left; this request is a violation.
+      return false;
+    }
+  }
+
+  // We can go negative since we check has_tokens when we get to *next* bucket,
+  // and for the small interval all that matters is whether we used up all the
+  // tokens (which is true if num_tokens_ <= 0).
+  bucket->DeductToken();
+  return true;
+}