1 /*
2  * Copyright (C) 2019 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef _UI_INPUT_INPUTDISPATCHER_QUEUE_H
18 #define _UI_INPUT_INPUTDISPATCHER_QUEUE_H
19 
20 namespace android::inputdispatcher {
21 
22 // Generic queue implementation.
23 template <typename T>
24 struct Queue {
25     T* head;
26     T* tail;
27     uint32_t entryCount;
28 
QueueQueue29     inline Queue() : head(nullptr), tail(nullptr), entryCount(0) {}
30 
isEmptyQueue31     inline bool isEmpty() const { return !head; }
32 
enqueueAtTailQueue33     inline void enqueueAtTail(T* entry) {
34         entryCount++;
35         entry->prev = tail;
36         if (tail) {
37             tail->next = entry;
38         } else {
39             head = entry;
40         }
41         entry->next = nullptr;
42         tail = entry;
43     }
44 
enqueueAtHeadQueue45     inline void enqueueAtHead(T* entry) {
46         entryCount++;
47         entry->next = head;
48         if (head) {
49             head->prev = entry;
50         } else {
51             tail = entry;
52         }
53         entry->prev = nullptr;
54         head = entry;
55     }
56 
dequeueQueue57     inline void dequeue(T* entry) {
58         entryCount--;
59         if (entry->prev) {
60             entry->prev->next = entry->next;
61         } else {
62             head = entry->next;
63         }
64         if (entry->next) {
65             entry->next->prev = entry->prev;
66         } else {
67             tail = entry->prev;
68         }
69     }
70 
dequeueAtHeadQueue71     inline T* dequeueAtHead() {
72         entryCount--;
73         T* entry = head;
74         head = entry->next;
75         if (head) {
76             head->prev = nullptr;
77         } else {
78             tail = nullptr;
79         }
80         return entry;
81     }
82 
countQueue83     uint32_t count() const { return entryCount; }
84 };
85 
86 } // namespace android::inputdispatcher
87 
88 #endif // _UI_INPUT_INPUTDISPATCHER_QUEUE_H
89