Organized modules, added indirection for FFI vs extension loading (#10)

* mv src -> ext, lib -> src to be more in line with PHP module expectations

* Fixed dependency for ffi test

* Fixed path in format-check to C source

* CRT will now try the extension first, then FFI

src/AWS/CRT/Internal/Extension.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace AWS\CRT\Internal;
+
+use \RuntimeException;
+
+/**
+ * @internal
+ * Forwards calls on to awscrt PHP extension functions
+ */
+final class Extension {
+    function __construct() {
+        if (!extension_loaded('awscrt')) {
+            throw new RuntimeException('awscrt extension is not loaded');
+        }
+    }
+
+    /**
+     * Forwards any call made on this object to the extension function of the
+     * same name with the supplied arguments. Argument type hinting and checking
+     * occurs at the CRT wrapper.
+     */
+    function __call(string $name, $args) {
+        return call_user_func_array($name, $args);
+    }
+}

src/AWS/CRT/Internal/FFI.php

@@ -0,0 +1,51 @@
+<?php
+
+namespace AWS\CRT\Internal;
+
+use \Exception;
+use \RuntimeException;
+
+/**
+ * @internal
+ * Forwards calls on to libaws-crt-ffi via FFI
+ */
+final class FFI {
+    private static $ffi = null;
+    private static $refcount = 0;
+
+    function __construct() {
+        if (is_null(self::$ffi)) {
+            try {
+                self::$ffi = \FFI::cdef(file_get_contents(__DIR__ . "/../../../api.h"), __DIR__ . "/../../../libaws-crt-ffi.so");
+                self::init();
+            } catch (Exception $e) {
+                throw new RuntimeException('Exception while initializing CRT via FFI', 0, $e);
+            }
+        }
+        ++self::$refcount;
+    }
+
+    function __destruct() {
+        if (--self::$refcount == 0) {
+            self::clean_up();
+            self::$ffi = null;
+        }
+    }
+
+    /**
+     * Forwards any call made on this object to the FFI function of the
+     * same name with the supplied arguments. Argument type hinting and checking
+     * occurs at the CRT wrapper.
+     */
+    function __call(string $name, $args) {
+        return call_user_func_array(array(self::$ffi, $name), $args);
+    }
+
+    private static function init() {
+        return self::$ffi->aws_crt_init();
+    }
+
+    private static function clean_up() {
+        return self::$ffi->aws_crt_clean_up();
+    }
+}