Refactor CancelableTaskManager to use std::map.

src/cancelable-task.cc

 // Copyright 2015 the V8 project 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 "src/cancelable-task.h"
 
 #include "src/base/platform/platform.h"
 #include "src/isolate.h"
 
 namespace v8 {
 namespace internal {
 
 
 Cancelable::Cancelable(CancelableTaskManager* parent)
     : parent_(parent), status_(kWaiting), id_(0), cancel_counter_(0) {
   id_ = parent->Register(this);
-  CHECK(id_ != 0);
 }
 
 
 Cancelable::~Cancelable() {
   // The following check is needed to avoid calling an already terminated
   // manager object. This happens when the manager cancels all pending tasks
   // in {CancelAndWait} only before destroying the manager object.
   if (TryRun() || IsRunning()) {
     parent_->RemoveFinishedTask(id_);
   }
 }
 
-
-static bool ComparePointers(void* ptr1, void* ptr2) { return ptr1 == ptr2; }
-
-
-CancelableTaskManager::CancelableTaskManager()
-    : task_id_counter_(0), cancelable_tasks_(ComparePointers) {}
-
+CancelableTaskManager::CancelableTaskManager() : task_id_counter_(0) {}
 
 uint32_t CancelableTaskManager::Register(Cancelable* task) {
   base::LockGuard<base::Mutex> guard(&mutex_);
   uint32_t id = ++task_id_counter_;
   // The loop below is just used when task_id_counter_ overflows.
-  while ((id == 0) || (cancelable_tasks_.Lookup(reinterpret_cast<void*>(id),
-                                                id) != nullptr)) {
-    ++id;
-  }
-  HashMap::Entry* entry =
-      cancelable_tasks_.LookupOrInsert(reinterpret_cast<void*>(id), id);
-  entry->value = task;
+  while (cancelable_tasks_.count(id) > 0) ++id;
+  cancelable_tasks_[id] = task;
   return id;
 }
 
 
 void CancelableTaskManager::RemoveFinishedTask(uint32_t id) {
   base::LockGuard<base::Mutex> guard(&mutex_);
-  void* removed = cancelable_tasks_.Remove(reinterpret_cast<void*>(id), id);
+  size_t removed = cancelable_tasks_.erase(id);
   USE(removed);
-  DCHECK(removed != nullptr);
+  DCHECK_NE(0, removed);
   cancelable_tasks_barrier_.NotifyOne();
 }
 
 
 bool CancelableTaskManager::TryAbort(uint32_t id) {
   base::LockGuard<base::Mutex> guard(&mutex_);
-  HashMap::Entry* entry =
-      cancelable_tasks_.Lookup(reinterpret_cast<void*>(id), id);
-  if (entry != nullptr) {
-    Cancelable* value = reinterpret_cast<Cancelable*>(entry->value);
+  auto entry = cancelable_tasks_.find(id);
+  if (entry != cancelable_tasks_.end()) {
+    Cancelable* value = entry->second;
     if (value->Cancel()) {
       // Cannot call RemoveFinishedTask here because of recursive locking.
-      void* removed = cancelable_tasks_.Remove(reinterpret_cast<void*>(id), id);
-      USE(removed);
-      DCHECK(removed != nullptr);
+      cancelable_tasks_.erase(entry);
       cancelable_tasks_barrier_.NotifyOne();
       return true;
     }
   }
   return false;
 }
 
 
 void CancelableTaskManager::CancelAndWait() {
   // Clean up all cancelable fore- and background tasks. Tasks are canceled on
   // the way if possible, i.e., if they have not started yet.  After each round
   // of canceling we wait for the background tasks that have already been
   // started.
   base::LockGuard<base::Mutex> guard(&mutex_);
 
-  // HashMap does not support removing while iterating, hence keep a set of
-  // entries that are to be removed.
-  std::set<uint32_t> to_remove;
-
-  // Cancelable tasks could potentially register new tasks, requiring a loop
-  // here.
-  while (cancelable_tasks_.occupancy() > 0) {
-    for (HashMap::Entry* p = cancelable_tasks_.Start(); p != nullptr;
-         p = cancelable_tasks_.Next(p)) {
-      if (reinterpret_cast<Cancelable*>(p->value)->Cancel()) {
-        to_remove.insert(reinterpret_cast<Cancelable*>(p->value)->id());
+  // Cancelable tasks could be running or could potentially register new
+  // tasks, requiring a loop here.
+  while (!cancelable_tasks_.empty()) {
+    for (auto it = cancelable_tasks_.begin(); it != cancelable_tasks_.end();) {
+      auto current = it;
+      // We need to get to the next element before erasing the current.
+      ++it;
+      if (current->second->Cancel()) {
+        cancelable_tasks_.erase(current);
       }
     }
-    // Remove tasks that were successfully canceled.
-    for (auto id : to_remove) {
-      cancelable_tasks_.Remove(reinterpret_cast<void*>(id), id);
-    }
-    to_remove.clear();
-
-    // Finally, wait for already running background tasks.
-    if (cancelable_tasks_.occupancy() > 0) {
+    // Wait for already running background tasks.
+    if (!cancelable_tasks_.empty()) {
       cancelable_tasks_barrier_.Wait(&mutex_);
     }
   }
 }
 
 
 CancelableTask::CancelableTask(Isolate* isolate)
     : Cancelable(isolate->cancelable_task_manager()), isolate_(isolate) {}
 
 
 CancelableIdleTask::CancelableIdleTask(Isolate* isolate)
     : Cancelable(isolate->cancelable_task_manager()), isolate_(isolate) {}
 
 }  // namespace internal
 }  // namespace v8