php 实现 Promise.all 和 Promise.race

• 测试

$promise1 = function () {
    msleep(500);
    return 'one';
};
$promise2 = function () {
    msleep(100);
    return 'two';
};
$promise3 = function () {
    msleep(50);
    throw new \Exception('Reject');
};
var_dump(promise_all([$promise1, $promise2]));
var_dump(promise_race([$promise1, $promise2]));
var_dump(promise_race([$promise1, $promise2, $promise3]));

• 结果

# php promise.php
array(2) {
  [1]=>
  string(3) "two"
  [0]=>
  string(3) "one"
}
string(3) "two"
object(Exception)#15 (7) {}

• 实现

<?php

declare(strict_types=1);

use Swow\Coroutine;
use Swow\Channel;
use Swow\Sync\WaitGroup;
use function Swow\defer;

/**
 * @param array $callbacks 
 * @param int $parallel 并发数量
 * @return array 
 */
function promise_all(array $callbacks, int $parallel = -1)
{
	$wg = new WaitGroup();
	$channel = new Channel($parallel);
	$results = [];
	foreach ($callbacks as $key => $callback) {
		$wg->add();
		$channel->push(true);
		Coroutine::run(static function () use ($wg, $channel, $callback, $key, &$results) {
			try {
				$results[$key] = $callback();
			} catch (\Throwable) {
			} finally {
				$channel->pop();
				$wg->done();
			}
		});
	}
	$wg->wait();
	return $results;
}

/**
 * @param array $callbacks
 * @param int $timeout 超时
 * @param bool $throw 是否抛出异常
 * @return mixed
 */
function promise_race(array $callbacks, int $timeout = -1, bool $throw = true): mixed
{
	$coroutines = [];
	defer(static function () use (&$coroutines) {
		foreach ($coroutines as $coroutine) {
			if ($coroutine->isExecuting()) {
				$coroutine->kill();
			}
		}
	});
	$channel = new Channel();
	foreach ($callbacks as $callback) {
		$coroutines[] = Coroutine::run(static function () use ($channel, $callback) {
			try {
				$channel->push($callback());
			} catch (\Throwable $e) {
				$channel->push($e);
			}
		});
	}
	try {
		return $channel->pop($timeout);
	} catch (\Throwable $e) {
		if ($throw) {
			throw $e;
		}
	}
	return false;
}