Refactor native extension shared library lookup.

runtime/bin/builtin.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library builtin;
 import 'dart:io';
 import 'dart:async';
 // import 'root_library'; happens here from C Code
 
 // The root library (aka the script) is imported into this library. The
@@ skipping 203 matching lines @@
     var uri = userString.substring(_DART_EXT.length);
     return '$_DART_EXT${baseUri.resolve(uri)}';
   } else {
     return '${baseUri.resolve(userString)}';
   }
 }
 
 
 // Returns either a file path or a URI starting with http:, as a String.
 String _filePathFromUri(String userUri) {
-  if (userUri.startsWith(_DART_EXT)) {
-    userUri = userUri.substring(_DART_EXT.length);
-  }
   var uri = Uri.parse(userUri);
   _logResolution('# Getting file path from: $uri');
 
   var path;
   switch (uri.scheme) {
     case '':
     case 'file':
       return uri.toFilePath();
       break;
     case 'package':
@@ skipping 18 matching lines @@
 
     throw "URIs using the 'package:' scheme should look like "
           "'$right', not '$wrong'.";
   }
 
   var packageRoot = _packageRoot == null ?
                     _entryPointScript.resolve('packages/') :
                     _packageRoot;
   return _filePathFromUri(packageRoot.resolve(uri.path).toString());
 }
+
+
+// Returns the directory part, the filename part, and the name
+// of a native extension URL as a list [directory, filename, name].
+// The directory part is either a file system path or an HTTP(S) URL.
+// The filename part is the extension name, with the platform-dependent
+// prefixes and extensions added.
+String _extensionPathFromUri(String userUri) {

[Ivan Posva, 2014/03/04 20:03:56]

Please remove the types in this file. They will only serve the purpose of
causing checked mode failures as can be seen here where we are returning a List
but the function is typed to return a String.

+  if (!userUri.startsWith(_DART_EXT)) {
+    throw 'Unexpected internal error: Extension URI $userUri missing dart-ext:';
+  }
+  userUri = userUri.substring(_DART_EXT.length);
+
+  if (userUri.contains('\\')) {
+    throw 'Unexpected internal error: Extension URI $userUri contains \\';
+  }
+
+  String filename;
+  String name;
+  String path;  // Will end in '/'.
+  int index = userUri.lastIndexOf('/');
+  if (index == -1) {
+    name = userUri;
+    path = './';
+  } else if (index == userUri.length - 1) {
+    throw 'Extension name missing in $extensionUri';
+  } else {
+    name = userUri.substring(index + 1);
+    path = userUri.substring(0, index + 1);
+  }
+
+  path = _filePathFromUri(path);
+
+  if (Platform.isLinux || Platform.isAndroid) {
+    filename = 'lib$name.so';

[Ivan Posva, 2014/03/04 20:03:56]

We will also have to have a plan to deal with different OS and architecture
combinations being served from the same location.

This didn't use to be as much of an issue as the extensions were only available
locally.

+  } else if (Platform.isMacOS) {
+    filename = 'lib$name.dylib';
+  } else if (Platform.isWindows) {
+    filename = '$name.dll';
+  } else {
+    _logResolution(
+        'Native extensions not supported on ${Platform.operatingSystem}');
+    throw 'Native extensions not supported on ${Platform.operatingSystem}';
+  }
+
+  return [path, filename, name];
+}