Refactor native extension shared library lookup.

runtime/bin/builtin.dart

Index: runtime/bin/builtin.dart
diff --git a/runtime/bin/builtin.dart b/runtime/bin/builtin.dart
index 2a9bd3014d886ff412086023c815603b12b94c01..6fefc4f621e77923bae7b0e23887218556ee07fe 100644
--- a/runtime/bin/builtin.dart
+++ b/runtime/bin/builtin.dart
@@ -262,3 +262,67 @@ String _filePathFromPackageUri(Uri uri) {
                     _packageRoot;
   return _filePathFromUri(packageRoot.resolve(uri.path).toString());
 }
+
+
+// Returns the directory part, the filename part, and the name

[Søren Gjesse, 2014/03/04 13:09:02]

How about calling "directory part" for location?

[Bill Hesse, 2014/03/04 14:36:31]

Done.

+// 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) {
+  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);
+  }
+  var uri = Uri.parse(path);
+  _logResolution('# Getting native extension path from: $uri');
+
+  switch (uri.scheme) {
+    case '':
+    case 'file':
+      path = uri.toFilePath();
+      break;
+    case 'package':
+      path = _filePathFromPackageUri(uri);
+      break;
+    case 'http':
+      path = uri.toString();
+    default:
+      // Only handling file, http, and package URIs
+      // in standalone binary.
+      _logResolution('# Unknown scheme (${uri.scheme}) in $uri.');
+      throw 'Not a known scheme: $uri';
+  }
+
+  if (Platform.isLinux) {
+    filename = 'lib$name.so';
+  } 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];
+}