From 5a84c8336ea97d9c77472d12e3d22080acfc88eb Mon Sep 17 00:00:00 2001
From: Niklas Keller <me@kelunik.com>
Date: Fri, 13 May 2016 23:41:54 +0200
Subject: [PATCH] Add Loop::supports to check for optional features

---
 src/Loop.php                        | 12 ++++++++++++
 src/LoopDriver.php                  | 16 ++++++++++++++++
 src/UnsupportedFeatureException.php |  9 +++++++++
 3 files changed, 37 insertions(+)
 create mode 100644 src/UnsupportedFeatureException.php

diff --git a/src/Loop.php b/src/Loop.php
index 059f2b9..ac8ae49 100644
--- a/src/Loop.php
+++ b/src/Loop.php
@@ -210,6 +210,18 @@ final class Loop
         self::get()->unreference($eventIdentifier);
     }
 
+    /**
+     * Check whether an optional feature is supported by the current event loop
+     * driver.
+     *
+     * @param int $feature Loop::FEATURE_* constant
+     *
+     * @return bool
+     */
+    public static function supports($feature) {
+        return self::get()->supports($feature);
+    }
+
     /**
      * Disable construction as this is a static class.
      */
diff --git a/src/LoopDriver.php b/src/LoopDriver.php
index 1d800d8..0ab913a 100644
--- a/src/LoopDriver.php
+++ b/src/LoopDriver.php
@@ -4,6 +4,8 @@ namespace Interop\Async\EventLoop;
 
 interface LoopDriver
 {
+    const FEATURE_SIGNAL_HANDLING = 0b001;
+
     /**
      * Start the event loop.
      *
@@ -135,4 +137,18 @@ interface LoopDriver
      * @return void
      */
     public function unreference($eventIdentifier);
+
+    /**
+     * Check whether an optional features is supported by this implementation
+     * and system.
+     *
+     * Example: If the implementation can handle signals using PCNTL, but the
+     * PCNTL extension is not available, the feature MUST NOT be marked as
+     * supported.
+     *
+     * @param int $feature FEATURE constant
+     *
+     * @return bool
+     */
+    public function supports($feature);
 }
diff --git a/src/UnsupportedFeatureException.php b/src/UnsupportedFeatureException.php
new file mode 100644
index 0000000..c4ee1b8
--- /dev/null
+++ b/src/UnsupportedFeatureException.php
@@ -0,0 +1,9 @@
+<?php
+
+use Interop\Async\EventLoop;
+
+/**
+ * Must be thrown if an optional feature is not supported by the current driver
+ * or system.
+ */
+class UnsupportedFeatureException extends \RuntimeException { }