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;
  }