decalog / includes / libraries / lock / util / Loop.php

Loop.php in DecaLog 4.4.0, at includes/libraries/lock/util/Loop.php

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1	<?php
2
3	declare(strict_types=1);
4
5	namespace malkusch\lock\util;
6
7	use LengthException;
8	use malkusch\lock\exception\TimeoutException;
9
10	/**
11	* Repeats executing a code until it was successful.
12	*
13	* @author Markus Malkusch <markus@malkusch.de>
14	* @link bitcoin:1P5FAZ4QhXCuwYPnLZdk3PJsqePbu1UDDA Donations
15	* @license WTFPL
16	* @internal
17	*/
18	class Loop
19	{
20	/**
21	* Minimum time that we want to wait, between lock checks. In micro seconds.
22	*
23	* @var double
24	*/
25	private const MINIMUM_WAIT_US = 1e4; // 0.01 seconds
26
27	/**
28	* Maximum time that we want to wait, between lock checks. In micro seconds.
29	*
30	* @var double
31	*/
32	private const MAXIMUM_WAIT_US = 5e5; // 0.50 seconds
33
34	/**
35	* @var int The timeout in seconds.
36	*/
37	private $timeout;
38
39	/**
40	* @var bool True while code execution is repeating.
41	*/
42	private $looping;
43
44	/**
45	* Sets the timeout. The default is 3 seconds.
46	*
47	* @param int $timeout The timeout in seconds. The default is 3 seconds.
48	* @throws \LengthException The timeout must be greater than 0.
49	*/
50	public function __construct(int $timeout = 3)
51	{
52	if ($timeout <= 0) {
53	throw new LengthException(\sprintf(
54	'The timeout must be greater than 0. %d was given.',
55	$timeout
56	));
57	}
58
59	$this->timeout = $timeout;
60	$this->looping = false;
61	}
62
63	/**
64	* Notifies that this was the last iteration.
65	*
66	* @return void
67	*/
68	public function end(): void
69	{
70	$this->looping = false;
71	}
72
73	/**
74	* Repeats executing a code until it was successful.
75	*
76	* The code has to be designed in a way that it can be repeated without any
77	* side effects. When execution was successful it should notify that event
78	* by calling {@link \malkusch\lock\util\Loop::end()}. I.e. the only side
79	* effects of the code may happen after a successful execution.
80	*
81	* If the code throws an exception it will stop repeating the execution.
82	*
83	* @param callable $code The to be executed code callback.
84	* @throws \Exception The execution callback threw an exception.
85	* @throws \malkusch\lock\exception\TimeoutException The timeout has been
86	* reached.
87	* @return mixed The return value of the executed code callback.
88	*
89	*/
90	public function execute(callable $code)
91	{
92	$this->looping = true;
93
94	// At this time, the lock will time out.
95	$deadline = microtime(true) + $this->timeout;
96
97	$result = null;
98	for ($i = 0; $this->looping && microtime(true) < $deadline; ++$i) {
99	$result = $code();
100	if (!$this->looping) { // @phpstan-ignore-line
101	break;
102	}
103
104	// Calculate max time remaining, don't sleep any longer than that.
105	$usecRemaining = intval(($deadline - microtime(true)) * 1e6);
106
107	// We've ran out of time.
108	if ($usecRemaining <= 0) {
109	throw TimeoutException::create($this->timeout);
110	}
111
112	$min = min(
113	(int) self::MINIMUM_WAIT_US * 1.25 ** $i,
114	self::MAXIMUM_WAIT_US
115	);
116	$max = min($min * 2, self::MAXIMUM_WAIT_US);
117
118	$usecToSleep = min($usecRemaining, random_int((int)$min, (int)$max));
119
120	usleep($usecToSleep);
121	}
122
123	if (microtime(true) >= $deadline) {
124	throw TimeoutException::create($this->timeout);
125	}
126
127	return $result;
128	}
129	}
130