Add observatory_pub_packages snapshot to third_party

observatory_pub_packages/analyzer/source/package_map_resolver.dart

+// Copyright (c) 2014, 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 source.package_map_resolver;
+
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer/src/generated/source.dart';
+
+
+/**
+ * A [UriResolver] implementation for the `package:` scheme that uses a map of
+ * package names to their directories.
+ */
+class PackageMapUriResolver extends UriResolver {
+  /**
+   * The name of the `package` scheme.
+   */
+  static const String PACKAGE_SCHEME = "package";
+
+  /**
+   * A table mapping package names to the path of the directories containing
+   * the package.
+   */
+  final Map<String, List<Folder>> packageMap;
+
+  /**
+   * The [ResourceProvider] for this resolver.
+   */
+  final ResourceProvider resourceProvider;
+
+  /**
+   * Create a new [PackageMapUriResolver].
+   *
+   * [packageMap] is a table mapping package names to the paths of the
+   * directories containing the package
+   */
+  PackageMapUriResolver(this.resourceProvider, this.packageMap);
+
+  @override
+  Source resolveAbsolute(Uri uri) {
+    if (!isPackageUri(uri)) {
+      return null;
+    }
+    // Prepare path.
+    String path = uri.path;
+    // Prepare path components.
+    String pkgName;
+    String relPath;
+    int index = path.indexOf('/');
+    if (index == -1 || index == 0) {
+      return null;
+    } else {
+      // <pkgName>/<relPath>
+      pkgName = path.substring(0, index);
+      relPath = path.substring(index + 1);
+    }
+    // Try to find an existing file.
+    List<Folder> packageDirs = packageMap[pkgName];
+    if (packageDirs != null) {
+      for (Folder packageDir in packageDirs) {
+        if (packageDir.exists) {
+          Resource result = packageDir.getChild(relPath);
+          if (result is File && result.exists) {
+            return result.createSource(uri);
+          }
+        }
+      }
+    }
+    // Return a NonExistingSource instance.
+    // This helps provide more meaningful error messages to users
+    // (a missing file error, as opposed to an invalid URI error).
+    return new NonExistingSource(uri.toString(), UriKind.PACKAGE_URI);
+  }
+
+  @override
+  Uri restoreAbsolute(Source source) {
+    String sourcePath = source.fullName;
+    for (String pkgName in packageMap.keys) {
+      List<Folder> pkgFolders = packageMap[pkgName];
+      for (Folder pkgFolder in pkgFolders) {
+        String pkgFolderPath = pkgFolder.path;
+        if (sourcePath.startsWith(pkgFolderPath)) {
+          String relPath = sourcePath.substring(pkgFolderPath.length);
+          return new Uri(path: '${PACKAGE_SCHEME}:$pkgName$relPath');
+        }
+      }
+    }
+    return null;
+  }
+
+  /**
+   * Returns `true` if [uri] is a `package` URI.
+   */
+  static bool isPackageUri(Uri uri) {
+    return uri.scheme == PACKAGE_SCHEME;
+  }
+}