text: // Copyright 2006 The Closure Library Authors. All Rights Reserved.
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //      http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS-IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  
  /**
   * @fileoverview JSON utility functions.
   * @author arv@google.com (Erik Arvidsson)
   */
  
  
  goog.provide('goog.json');
  goog.provide('goog.json.Serializer');
  
  
  /**
   * Tests if a string is an invalid JSON string. This only ensures that we are
   * not using any invalid characters
   * @param {string} s The string to test.
   * @return {boolean} True if the input is a valid JSON string.
   * @private
   */
  goog.json.isValid_ = function(s) {
    // All empty whitespace is not valid.
    if (/^\s*$/.test(s)) {
      return false;
    }
  
    // This is taken from http://www.json.org/json2.js which is released to the
    // public domain.
    // Changes: We dissallow \u2028 Line separator and \u2029 Paragraph separator
    // inside strings.  We also treat \u2028 and \u2029 as whitespace which they
    // are in the RFC but IE and Safari does not match \s to these so we need to
    // include them in the reg exps in all places where whitespace is allowed.
    // We allowed \x7f inside strings because some tools don't escape it,
    // e.g. http://www.json.org/java/org/json/JSONObject.java
  
    // Parsing happens in three stages. In the first stage, we run the text
    // against regular expressions that look for non-JSON patterns. We are
    // especially concerned with '()' and 'new' because they can cause invocation,
    // and '=' because it can cause mutation. But just to be safe, we want to
    // reject all unexpected forms.
  
    // We split the first stage into 4 regexp operations in order to work around
    // crippling inefficiencies in IE's and Safari's regexp engines. First we
    // replace all backslash pairs with '@' (a non-JSON character). Second, we
    // replace all simple value tokens with ']' characters. Third, we delete all
    // open brackets that follow a colon or comma or that begin the text. Finally,
    // we look to see that the remaining characters are only whitespace or ']' or
    // ',' or ':' or '{' or '}'. If that is so, then the text is safe for eval.
  
    // Don't make these static since they have the global flag.
    var backslashesRe = /\\["\\\/bfnrtu]/g;
    var simpleValuesRe =
        /"[^"\\\n\r\u2028\u2029\x00-\x08\x0a-\x1f]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g;
    var openBracketsRe = /(?:^|:|,)(?:[\s\u2028\u2029]*\[)+/g;
    var remainderRe = /^[\],:{}\s\u2028\u2029]*$/;
  
    return remainderRe.test(s.replace(backslashesRe, '@').
        replace(simpleValuesRe, ']').
        replace(openBracketsRe, ''));
  };
  
  
  /**
   * Parses a JSON string and returns the result. This throws an exception if
   * the string is an invalid JSON string.
   *
   * Note that this is very slow on large strings. If you trust the source of
   * the string then you should use unsafeParse instead.
   *
   * @param {*} s The JSON string to parse.
   * @return {Object} The object generated from the JSON string.
   */
  goog.json.parse = function(s) {
    var o = String(s);
    if (goog.json.isValid_(o)) {
      /** @preserveTry */
      try {
        return /** @type {Object} */ (eval('(' + o + ')'));
      } catch (ex) {
      }
    }
    throw Error('Invalid JSON string: ' + o);
  };
  
  
  /**
   * Parses a JSON string and returns the result. This uses eval so it is open
   * to security issues and it should only be used if you trust the source.
   *
   * @param {string} s The JSON string to parse.
   * @return {Object} The object generated from the JSON string.
   */
  goog.json.unsafeParse = function(s) {
    return /** @type {Object} */ (eval('(' + s + ')'));
  };
  
  
  /**
   * JSON replacer, as defined in Section 15.12.3 of the ES5 spec.
   *
   * TODO(nicksantos): Array should also be a valid replacer.
   *
   * @typedef {function(this:Object, string, *): *}
   */
  goog.json.Replacer;
  
  
  /**
   * JSON reviver, as defined in Section 15.12.2 of the ES5 spec.
   *
   * @typedef {function(this:Object, string, *): *}
   */
  goog.json.Reviver;
  
  
  /**
   * Serializes an object or a value to a JSON string.
   *
   * @param {*} object The object to serialize.
   * @param {?goog.json.Replacer=} opt_replacer A replacer function
   *     called for each (key, value) pair that determines how the value
   *     should be serialized. By defult, this just returns the value
   *     and allows default serialization to kick in.
   * @throws Error if there are loops in the object graph.
   * @return {string} A JSON string representation of the input.
   */
  goog.json.serialize = function(object, opt_replacer) {
    // NOTE(nicksantos): Currently, we never use JSON.stringify.
    //
    // The last time I evaluated this, JSON.stringify had subtle bugs and behavior
    // differences on all browsers, and the performance win was not large enough
    // to justify all the issues. This may change in the future as browser
    // implementations get better.
    //
    // assertSerialize in json_test contains if branches for the cases
    // that fail.
    return new goog.json.Serializer(opt_replacer).serialize(object);
  };
  
  
  
  /**
   * Class that is used to serialize JSON objects to a string.
   * @param {?goog.json.Replacer=} opt_replacer Replacer.
   * @constructor
   */
  goog.json.Serializer = function(opt_replacer) {
    /**
     * @type {goog.json.Replacer|null|undefined}
     * @private
     */
    this.replacer_ = opt_replacer;
  };
  
  
  /**
   * Serializes an object or a value to a JSON string.
   *
   * @param {*} object The object to serialize.
   * @throws Error if there are loops in the object graph.
   * @return {string} A JSON string representation of the input.
   */
  goog.json.Serializer.prototype.serialize = function(object) {
    var sb = [];
    this.serialize_(object, sb);
    return sb.join('');
  };
  
  
  /**
   * Serializes a generic value to a JSON string
   * @private
   * @param {*} object The object to serialize.
   * @param {Array} sb Array used as a string builder.
   * @throws Error if there are loops in the object graph.
   */
  goog.json.Serializer.prototype.serialize_ = function(object, sb) {
    switch (typeof object) {
      case 'string':
        this.serializeString_((/** @type {string} */ object), sb);
        break;
      case 'number':
        this.serializeNumber_((/** @type {number} */ object), sb);
        break;
      case 'boolean':
        sb.push(object);
        break;
      case 'undefined':
        sb.push('null');
        break;
      case 'object':
        if (object == null) {
          sb.push('null');
          break;
        }
        if (goog.isArray(object)) {
          this.serializeArray((/** @type {!Array} */ object), sb);
          break;
        }
        // should we allow new String, new Number and new Boolean to be treated
        // as string, number and boolean? Most implementations do not and the
        // need is not very big
        this.serializeObject_((/** @type {Object} */ object), sb);
        break;
      case 'function':
        // Skip functions.
        // TODO(user) Should we return something here?
        break;
      default:
        throw Error('Unknown type: ' + typeof object);
    }
  };
  
  
  /**
   * Character mappings used internally for goog.string.quote
   * @private
   * @type {Object}
   */
  goog.json.Serializer.charToJsonCharCache_ = {
    '\"': '\\"',
    '\\': '\\\\',
    '/': '\\/',
    '\b': '\\b',
    '\f': '\\f',
    '\n': '\\n',
    '\r': '\\r',
    '\t': '\\t',
  
    '\x0B': '\\u000b' // '\v' is not supported in JScript
  };
  
  
  /**
   * Regular expression used to match characters that need to be replaced.
   * The S60 browser has a bug where unicode characters are not matched by
   * regular expressions. The condition below detects such behaviour and
   * adjusts the regular expression accordingly.
   * @private
   * @type {RegExp}
   */
  goog.json.Serializer.charsToReplace_ = /\uffff/.test('\uffff') ?
      /[\\\"\x00-\x1f\x7f-\uffff]/g : /[\\\"\x00-\x1f\x7f-\xff]/g;
  
  
  /**
   * Serializes a string to a JSON string
   * @private
   * @param {string} s The string to serialize.
   * @param {Array} sb Array used as a string builder.
   */
  goog.json.Serializer.prototype.serializeString_ = function(s, sb) {
    // The official JSON implementation does not work with international
    // characters.
    sb.push('"', s.replace(goog.json.Serializer.charsToReplace_, function(c) {
      // caching the result improves performance by a factor 2-3
      if (c in goog.json.Serializer.charToJsonCharCache_) {
        return goog.json.Serializer.charToJsonCharCache_[c];
      }
  
      var cc = c.charCodeAt(0);
      var rv = '\\u';
      if (cc < 16) {
        rv += '000';
      } else if (cc < 256) {
        rv += '00';
      } else if (cc < 4096) { // \u1000
        rv += '0';
      }
      return goog.json.Serializer.charToJsonCharCache_[c] = rv + cc.toString(16);
    }), '"');
  };
  
  
  /**
   * Serializes a number to a JSON string
   * @private
   * @param {number} n The number to serialize.
   * @param {Array} sb Array used as a string builder.
   */
  goog.json.Serializer.prototype.serializeNumber_ = function(n, sb) {
    sb.push(isFinite(n) && !isNaN(n) ? n : 'null');
  };
  
  
  /**
   * Serializes an array to a JSON string
   * @param {Array} arr The array to serialize.
   * @param {Array} sb Array used as a string builder.
   * @protected
   */
  goog.json.Serializer.prototype.serializeArray = function(arr, sb) {
    var l = arr.length;
    sb.push('[');
    var sep = '';
    for (var i = 0; i < l; i++) {
      sb.push(sep);
  
      var value = arr[i];
      this.serialize_(
          this.replacer_ ? this.replacer_.call(arr, String(i), value) : value,
          sb);
  
      sep = ',';
    }
    sb.push(']');
  };
  
  
  /**
   * Serializes an object to a JSON string
   * @private
   * @param {Object} obj The object to serialize.
   * @param {Array} sb Array used as a string builder.
   */
  goog.json.Serializer.prototype.serializeObject_ = function(obj, sb) {
    sb.push('{');
    var sep = '';
    for (var key in obj) {
      if (Object.prototype.hasOwnProperty.call(obj, key)) {
        var value = obj[key];
        // Skip functions.
        // TODO(ptucker) Should we return something for function properties?
        if (typeof value != 'function') {
          sb.push(sep);
          this.serializeString_(key, sb);
          sb.push(':');
  
          this.serialize_(
              this.replacer_ ? this.replacer_.call(obj, key, value) : value,
              sb);
  
          sep = ',';
        }
      }
    }
    sb.push('}');
  };
  