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WebDriverAgentLib/Utilities/LRUCache/LRUCache.m

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+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * See the NOTICE file distributed with this work for additional
+ * information regarding copyright ownership.
+ * 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.
+ */
+
+#import "LRUCache.h"
+#import "LRUCacheNode.h"
+
+@interface LRUCache ()
+@property (nonatomic) NSMutableDictionary *store;
+@property (nonatomic, nullable) LRUCacheNode *headNode;
+@property (nonatomic, nullable) LRUCacheNode *tailNode;
+@end
+
+@implementation LRUCache
+
+- (instancetype)initWithCapacity:(NSUInteger)capacity
+{
+  if ((self = [super init])) {
+    _store = [NSMutableDictionary dictionary];
+    _capacity = capacity;
+  }
+  return self;
+}
+
+- (void)setObject:(id)object forKey:(id<NSCopying>)key
+{
+  NSAssert(nil != object && nil != key, @"LRUCache cannot store nil objects");
+
+  LRUCacheNode *previousNode = self.store[key];
+  if (nil != previousNode) {
+    [self removeNode:previousNode];
+  }
+
+  LRUCacheNode *newNode = [LRUCacheNode nodeWithValue:object key:key];
+  self.store[key] = newNode;
+  [self addNodeToHead:newNode];
+  if (nil == previousNode) {
+    [self alignSize];
+  }
+}
+
+- (id)objectForKey:(id<NSCopying>)key
+{
+  LRUCacheNode *node = self.store[key];
+  return [self moveNodeToHead:node].value;
+}
+
+- (NSArray *)allObjects
+{
+  NSMutableArray *result = [[NSMutableArray alloc] initWithCapacity:self.store.count];
+  LRUCacheNode *node = self.headNode;
+  while (node != nil) {
+    [result addObject:node.value];
+    node = node.next;
+  }
+  return result.copy;
+}
+
+- (nullable LRUCacheNode *)moveNodeToHead:(nullable LRUCacheNode *)node
+{
+  if (nil == node || node == self.headNode) {
+    return node;
+  }
+
+  LRUCacheNode *previousNode = node.prev;
+  if (nil != previousNode) {
+    previousNode.next = node.next;
+  }
+  LRUCacheNode *nextNode = node.next;
+  if (nil != nextNode) {
+    nextNode.prev = node.prev;
+  }
+  if (node == self.tailNode) {
+    self.tailNode = previousNode;
+  }
+  return [self addNodeToHead:node];
+}
+
+- (void)removeNode:(nullable LRUCacheNode *)node
+{
+  if (nil == node) {
+    return;
+  }
+
+  if (nil != node.next) {
+    node.next.prev = node.prev;
+  }
+  if (node == self.headNode) {
+    self.headNode = node.next;
+  }
+  if (nil != node.prev) {
+    node.prev.next = node.next;
+  }
+  if (node == self.tailNode) {
+    self.tailNode = node.prev;
+  }
+  [self.store removeObjectForKey:(id)node.key];
+}
+
+- (nullable LRUCacheNode *)addNodeToHead:(nullable LRUCacheNode *)node
+{
+  if (nil == node || node == self.headNode) {
+    return node;
+  }
+
+  LRUCacheNode *previousHead = self.headNode;
+  if (nil != previousHead) {
+    previousHead.prev = node;
+  }
+  node.next = previousHead;
+  node.prev = nil;
+  self.headNode = node;
+  if (nil == self.tailNode) {
+    self.tailNode = previousHead ?: node;
+  }
+  return node;
+}
+
+- (void)alignSize
+{
+  if (self.store.count > self.capacity && nil != self.tailNode) {
+    [self removeNode:self.tailNode];
+  }
+}
+
+- (void)removeObjectForKey:(id<NSCopying>)key
+{
+  LRUCacheNode *node = self.store[key];
+  if (node != nil) {
+    [self removeNode:node];
+  }
+}
+
+@end