+
+ Value* remove(Key *key, Value *value) {
+ MODEL_ASSERT (key);
+ int hash = hashKey(key);
+ Segment *seg = segments[hash & SEGMENT_MASK];
+ atomic<Entry*> *tab;
+
+ seg->lock(); // Critical region begins
+ tab = table;
+ int index = hash & (capacity - 1);
+
+ atomic<Entry*> *first = &tab[index];
+ Entry *e;
+ Value *oldValue = NULL;
+
+ // The written of the entry is synchronized by locking
+ Entry *firstPtr = first->load(relaxed);
+ e = firstPtr;
+
+ while (true) {
+ if (e != NULL) {
+ seg->unlock(); // Don't forget to unlock
+ return NULL;
+ }
+ if (e->hash == hash && eq(key, e->key))
+ break;
+ // Synchronized by locking
+ e = e->next.load(relaxed);
+ }
+
+ // FIXME: This could be a relaxed (because locking synchronize
+ // with the previous put())??
+ oldValue = e->value.load(acquire);
+ // If the value parameter is NULL, we will remove the entry anyway
+ if (value != NULL && value->equals(oldValue)) {
+ seg->unlock();
+ return NULL;
+ }
+
+ // Force the get() to grab the lock and retry
+ e->value.store(NULL, relaxed);
+
+ // The strategy to remove the entry is to keep the entries after the
+ // removed one and copy the ones before it
+ Entry *head = e->next.load(relaxed);
+ Entry *p;
+ p = first->load(relaxed);
+ while (p != e) {
+ head = new Entry(p->hash, p->key, p->value.load(relaxed), head);
+ p = p->next.load(relaxed);
+ }
+
+ // Publish the new head to readers
+ first->store(head, release);
+ seg->unlock(); // Critical region ends
+ return oldValue;
+ }