| /* |
| * Copyright 2016 Google Inc. All Rights Reserved. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef NB_THREAD_LOCAL_OBJECT_H_ |
| #define NB_THREAD_LOCAL_OBJECT_H_ |
| |
| #include <set> |
| |
| #include "starboard/configuration.h" |
| #include "starboard/log.h" |
| #include "starboard/mutex.h" |
| #include "starboard/thread.h" |
| |
| namespace nb { |
| |
| // Like base::ThreadLocalPointer<T> but destroys objects. This is important |
| // for using ThreadLocalObjects that aren't tied to a singleton, or for |
| // access by threads which will call join(). |
| // |
| // FEATURE COMPARISON TABLE: |
| // | Thread Join | Container Destroyed |
| // ------------------------------------------------------------------ |
| // ThreadLocalPointer<T> | LEAKS | LEAKS |
| // ThreadLocalObject<T> | Object Destroyed | Objects Destroyed |
| // |
| // EXAMPLE: |
| // ThreadLocalObject<std::map<std::string, int> > map_tls; |
| // Map* map = map_tls->GetOrCreate(); |
| // (*map)["my string"] = 15; |
| // Thread t = new Thread(&map_tls); |
| // t->start(); |
| // // t creates it's own thread local map. |
| // t->join(); // Make sure that thread joins before map_tls is destroyed! |
| // |
| // OBJECT DESTRUCTION: |
| // There are two ways for an object to be destroyed by the ThreadLocalObject. |
| // The first way is via a thread join. In this case only the object |
| // associated with the thread is deleted. |
| // The second way an object is destroyed is by the ThreadLocalObject |
| // container to be destroyed, in this case ALL thread local objects are |
| // destroyed. |
| // |
| // PERFORMANCE: |
| // ThreadLocalObject is fast for the Get() function if the object has |
| // has already been created, requiring one extra pointer dereference |
| // over ThreadLocalPointer<T>. |
| template <typename Type> |
| class ThreadLocalObject { |
| public: |
| ThreadLocalObject() : slot_() { |
| slot_ = SbThreadCreateLocalKey(DeleteEntry); |
| SB_DCHECK(kSbThreadLocalKeyInvalid != slot_); |
| constructing_thread_id_ = SbThreadGetId(); |
| } |
| |
| // Enables destruction by any other thread. Otherwise, the class instance |
| // will warn when a different thread than the constructing destroys this. |
| void EnableDestructionByAnyThread() { |
| constructing_thread_id_ = kSbThreadInvalidId; |
| } |
| |
| // Thread Local Objects are destroyed after this call. |
| ~ThreadLocalObject() { |
| CheckCurrentThreadAllowedToDestruct(); |
| if (SB_DLOG_IS_ON(FATAL)) { |
| SB_DCHECK(entry_set_.size() < 2) |
| << "Logic error: Some threads may still be accessing the objects that " |
| << "are about to be destroyed. Only one object is expected and that " |
| << "should be for the main thread. The caller should ensure that " |
| << "other threads that access this object are externally " |
| << "synchronized."; |
| } |
| // No locking is done because the entries should not be accessed by |
| // different threads while this object is shutting down. If access is |
| // occuring then the caller has a race condition, external to this class. |
| typedef typename Set::iterator Iter; |
| for (Iter it = entry_set_.begin(); it != entry_set_.end(); ++it) { |
| Entry* entry = *it; |
| SB_DCHECK(entry->owner_ == this); |
| delete entry->ptr_; |
| delete entry; |
| } |
| |
| // Cleanup the thread local key. |
| SbThreadDestroyLocalKey(slot_); |
| } |
| |
| // Warns if there is a misuse of this object. |
| void CheckCurrentThreadAllowedToDestruct() const { |
| if (kSbThreadInvalidId == constructing_thread_id_) { |
| return; // EnableDestructionByAnyThread() called. |
| } |
| const SbThreadId curr_thread_id = SbThreadGetId(); |
| if (curr_thread_id == constructing_thread_id_) { |
| return; // Same thread that constructed this. |
| } |
| |
| if (SB_DLOG_IS_ON(FATAL)) { |
| SB_DCHECK(false) |
| << "ThreadLocalObject<T> was created in thread " |
| << constructing_thread_id_ << "\nbut was destroyed by " |
| << curr_thread_id << ". If this is intentional then call " |
| << "EnableDestructionByAnyThread() to silence this " |
| << "warning."; |
| } |
| } |
| |
| // Either returns the created pointer for the current thread, or otherwise |
| // constructs the object using the default constructor and returns it. |
| Type* GetOrCreate() { |
| Type* object = GetIfExists(); |
| if (!object) { // create object. |
| object = new Type(); |
| Entry* entry = new Entry(this, object); |
| // Insert into the set of tls entries. |
| // Performance: Its assumed that creation of objects is much less |
| // frequent than getting an object. |
| { |
| starboard::ScopedLock lock(entry_set_mutex_); |
| entry_set_.insert(entry); |
| } |
| SbThreadSetLocalValue(slot_, entry); |
| } |
| return object; |
| } |
| |
| // Returns the pointer if it exists in the current thread, otherwise NULL. |
| Type* GetIfExists() const { |
| Entry* entry = GetEntryIfExists(); |
| if (!entry) { return NULL; } |
| return entry->ptr_; |
| } |
| |
| // Releases ownership of the pointer FROM THE CURRENT THREAD. |
| // The caller has responsibility to make sure that the pointer is destroyed. |
| Type* Release() { |
| if (Entry* entry = GetEntryIfExists()) { |
| // The entry will no longer run it's destructor on thread join. |
| SbThreadSetLocalValue(slot_, NULL); // NULL out pointer for TLS. |
| Type* object = entry->ptr_; |
| RemoveEntry(entry); |
| return object; |
| } else { |
| return NULL; |
| } |
| } |
| |
| private: |
| struct Entry { |
| Entry(ThreadLocalObject* own, Type* ptr) : owner_(own), ptr_(ptr) { |
| } |
| ~Entry() { |
| ptr_ = NULL; |
| owner_ = NULL; |
| } |
| ThreadLocalObject* owner_; |
| Type* ptr_; |
| }; |
| |
| // Deletes the TLSEntry. |
| static void DeleteEntry(void* ptr) { |
| if (!ptr) { |
| SB_NOTREACHED(); |
| return; |
| } |
| Entry* entry = reinterpret_cast<Entry*>(ptr); |
| ThreadLocalObject* tls = entry->owner_; |
| Type* object = entry->ptr_; |
| tls->RemoveEntry(entry); |
| delete object; |
| } |
| |
| void RemoveEntry(Entry* entry) { |
| { |
| starboard::ScopedLock lock(entry_set_mutex_); |
| entry_set_.erase(entry); |
| } |
| delete entry; |
| } |
| |
| Entry* GetEntryIfExists() const { |
| void* ptr = SbThreadGetLocalValue(slot_); |
| Entry* entry = static_cast<Entry*>(ptr); |
| return entry; |
| } |
| |
| typedef std::set<Entry*> Set; |
| // Allows GetIfExists() to be const. |
| mutable SbThreadLocalKey slot_; |
| // entry_set_ contains all the outstanding entries for the thread local |
| // objects that have been created. |
| Set entry_set_; |
| mutable starboard::Mutex entry_set_mutex_; |
| // Used to warn when there is a mismatch between thread that constructed and |
| // thread that destroyed this object. |
| SbThreadId constructing_thread_id_; |
| |
| SB_DISALLOW_COPY_AND_ASSIGN(ThreadLocalObject<Type>); |
| }; |
| |
| } // namespace nb |
| |
| #endif // NB_THREAD_LOCAL_OBJECT_H_ |