pkg/compiler/lib/src/js_emitter/native_generator.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;

import 'package:js_runtime/synced/embedded_names.dart' as embedded_names;

import '../js/js.dart' as js_ast;
import '../js/js.dart' show js;
import '../js_backend/backend_usage.dart' show BackendUsage;

class NativeGenerator {
  static bool needsIsolateAffinityTagInitialization(BackendUsage backendUsage) {
    return backendUsage.needToInitializeIsolateAffinityTag;
  }

  /// Generates the code for isolate affinity tags.
  ///
  /// Independently Dart programs on the same page must not interfere and
  /// this code sets up the variables needed to guarantee that behavior.
  static js_ast.Statement generateIsolateAffinityTagInitialization(
    BackendUsage backendUsage,
    js_ast.Expression Function(String global) generateEmbeddedGlobalAccess,
    js_ast.Expression internStringFunction,
  ) {
    assert(backendUsage.needToInitializeIsolateAffinityTag);

    js_ast.Expression getIsolateTagAccess = generateEmbeddedGlobalAccess(
      embedded_names.GET_ISOLATE_TAG,
    );
    js_ast.Expression isolateTagAccess = generateEmbeddedGlobalAccess(
      embedded_names.ISOLATE_TAG,
    );
    js_ast.Expression dispatchPropertyNameAccess = generateEmbeddedGlobalAccess(
      embedded_names.DISPATCH_PROPERTY_NAME,
    );

    return js.statement(
      '''
      !function() {
        var intern = #internStringFunction;

        #getIsolateTag = function(name) {
          return intern("___dart_" + name + #isolateTag);
        };

        // To ensure that different programs loaded into the same context (page)
        // use distinct dispatch properties, we place an object on `Object` to
        // contain the names already in use.
        var tableProperty = "___dart_isolate_tags_";
        var usedProperties = Object[tableProperty] ||
            (Object[tableProperty] = Object.create(null));

        var rootProperty = "_${generateIsolateTagRoot()}";
        for (var i = 0; ; i++) {
          var property = intern(rootProperty + "_" + i + "_");
          if (!(property in usedProperties)) {
            usedProperties[property] = 1;
            #isolateTag = property;
            break;
          }
        }
        if (#initializeDispatchProperty) {
          #dispatchPropertyName = #getIsolateTag("dispatch_record");
        }
      }();
    ''',
      {
        'initializeDispatchProperty':
            backendUsage.needToInitializeDispatchProperty,
        'internStringFunction': internStringFunction,
        'getIsolateTag': getIsolateTagAccess,
        'isolateTag': isolateTagAccess,
        'dispatchPropertyName': dispatchPropertyNameAccess,
      },
    );
  }

  static String generateIsolateTagRoot() {
    // TODO(sra): MD5 of contributing source code or URIs?
    return 'ZxYxX';
  }
}