geario.util.Lifecycle source code

1 /*
2  * Geario - A cross-platform abstraction library with asynchronous I/O.
3  *
4  * Copyright (C) 2021-2022 Kerisy.com
5  *
6  * Website: https://www.kerisy.com
7  *
8  * Licensed under the Apache-2.0 License.
9  *
10  */
11 
12 module geario.util.Lifecycle;
13 
14 import core.atomic;
15 
16 
17 import geario.logging;
18 
19 /**
20  * A common interface defining methods for start/stop lifecycle control.
21  * The typical use case for this is to control asynchronous processing.
22  */
23 interface Lifecycle {
24     /**
25      * Start this component.
26      * <p>Should not throw an exception if the component is already running.
27      * <p>In the case of a container, this will propagate the start signal to all
28      * components that apply.
29      */    
30     void Start();
31 
32     /**
33      * Stop this component, typically in a synchronous fashion, such that the component is
34      * fully stopped upon return of this method. 
35      */
36     void Stop();
37 
38 
39     /**
40      * Check whether this component is currently running.
41      * @return whether the component is currently running
42      */
43     bool IsRunning();
44 }
45 
46 
47 abstract class AbstractLifecycle : Lifecycle {
48 
49     protected shared bool _isRunning;
50 
51     this() {
52        
53     }
54 
55     bool IsRunning() {
56         return _isRunning;
57     }
58 
59     bool IsStopped() {
60         return !_isRunning;
61     }
62 
63     void Start() {
64         if (cas(&_isRunning, false, true)) {
65             Initialize();
66         } else {
67             version(GEAR_DEBUG) log.warn("Starting repeatedly!");
68         }
69     }
70 
71     void Stop() {
72         if (cas(&_isRunning, true, false)) {
73             Destroy();
74         } else {
75             version(GEAR_DEBUG) log.warn("Stopping repeatedly!");
76         }
77     }
78 
79     abstract protected void Initialize();
80 
81     abstract protected void Destroy();
82 }