Work around legacy HHVM which doesn't report pipe open mode

Author: clue

.github/workflows/ci.yml

@@ -46,6 +46,6 @@ jobs:
       - uses: azjezz/setup-hhvm@v1
         with:
           version: lts-3.30
-      - run: hhvm $(which composer) require phpunit/phpunit:^5 --dev # requires legacy phpunit
+      - run: hhvm $(which composer) install
       - run: hhvm vendor/bin/phpunit
       - run: hhvm examples/13-benchmark-throughput.php

src/Process.php

@@ -231,10 +231,13 @@ public function start(LoopInterface $loop, $interval = 0.1)
         }
 
         foreach ($pipes as $n => $fd) {
+            // use open mode from stream meta data or fall back to pipe open mode for legacy HHVM
             $meta = \stream_get_meta_data($fd);
-            if ($meta['mode'] === 'r+') {
+            $mode = $meta['mode'] === '' ? ($this->fds[$n][1] === 'r' ? 'w' : 'r') : $meta['mode'];
+
+            if ($mode === 'r+') {
                 $stream = new DuplexResourceStream($fd, $loop);
-            } elseif ($meta['mode'] === 'w') {
+            } elseif ($mode === 'w') {
                 $stream = new WritableResourceStream($fd, $loop);
             } else {
                 $stream = new ReadableResourceStream($fd, $loop);