sdk/lib/internal/symbol.dart

// Copyright (c) 2013, 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.

part of dart._internal;

/**
 * Implementation of [core.Symbol].  This class uses the same name as
 * a core class so a user can't tell the difference.
 *
 * The purpose of this class is to hide [_name] from user code, but
 * make it accessible to Dart platform code via the static method
 * [getName].
 */
class Symbol implements core.Symbol {
  final String _name;

  static final RegExp validationPattern =
      new RegExp(r'^(?:[a-zA-Z$][a-zA-Z$0-9_]*\.)*(?:[a-zA-Z$][a-zA-Z$0-9_]*=?|'
                 r'-|'
                 r'unary-|'
                 r'\[\]=|'
                 r'~|'
                 r'==|'
                 r'\[\]|'
                 r'\*|'
                 r'/|'
                 r'%|'
                 r'~/|'
                 r'\+|'
                 r'<<|'
                 r'>>|'
                 r'>=|'
                 r'>|'
                 r'<=|'
                 r'<|'
                 r'&|'
                 r'\^|'
                 r'\|'
                 r')$');

  external const Symbol(String name);

  /**
   * Platform-private method used by the mirror system to create
   * otherwise invalid names.
   */
  const Symbol.unvalidated(this._name);

  // This is called by dart2js.
  Symbol.validated(String name)
      : this._name = validate(name);

  bool operator ==(other) => other is Symbol && _name == other._name;

  int get hashCode {
    const arbitraryPrime = 664597;
    return 0x1fffffff & (arbitraryPrime * _name.hashCode);
  }

  toString() => 'Symbol("$_name")';

  /// Platform-private accessor which cannot be called from user libraries.
  static String getName(Symbol symbol) => symbol._name;

  static String validate(String name) {
    if (name.isEmpty) return name;
    if (name.startsWith('_')) {
      throw new ArgumentError('"$name" is a private identifier');
    }
    if (!validationPattern.hasMatch(name)) {
      throw new ArgumentError(
          '"$name" is not an identifier or an empty String');
    }
    return name;
  }
}