source: Dev/trunk/src/client/dojox/secure/fromJson.js

dojo.provide("dojox.secure.fromJson");

// Used with permission from Mike Samuel of Google (has CCLA), from the json-sans-eval project:
// http://code.google.com/p/json-sans-eval/
//      Mike Samuel <mikesamuel@gmail.com>



dojox.secure.fromJson = typeof JSON != "undefined" ? JSON.parse :
// summary:
//              Parses a string of well-formed JSON text.
// description:
//              Parses a string of well-formed JSON text. If the input is not well-formed,
//              then behavior is undefined, but it is
//              deterministic and is guaranteed not to modify any object other than its
//              return value.
//
//              This does not use `eval` so is less likely to have obscure security bugs than
//              json2.js.
//              It is optimized for speed, so is much faster than json_parse.js.
//
//              This library should be used whenever security is a concern (when JSON may
//              come from an untrusted source), speed is a concern, and erroring on malformed
//              JSON is *not* a concern.
//
//              json2.js is very fast, but potentially insecure since it calls `eval` to
//              parse JSON data, so an attacker might be able to supply strange JS that
//              looks like JSON, but that executes arbitrary javascript.
//
//              To configure dojox.secure.fromJson as the JSON parser for all Dojo
//              JSON parsing, simply do:
//              |       dojo.require("dojox.secure.fromJson");
//              |       dojo.fromJson = dojox.secure.fromJson;
//              or alternately you could configure dojox.secure.fromJson to only handle
//              XHR responses:
//              |       dojo._contentHandlers.json = function(xhr){
//              |               return dojox.secure.fromJson.fromJson(xhr.responseText);
//              |       };
// json: String
//              per RFC 4627
// optReviver: Function (this:Object, string, *)
//              optional function
//              that reworks JSON objects post-parse per Chapter 15.12 of EcmaScript3.1.
//              If supplied, the function is called with a string key, and a value.
//              The value is the property of 'this'.    The reviver should return
//              the value to use in its place.  So if dates were serialized as
//              `{ "type": "Date", "time": 1234 }`, then a reviver might look like
// |    function (key, value) {
// |            if (value && typeof value === 'object' && 'Date' === value.type) {
// |                    return new Date(value.time);
// |            } else {
// |                    return value;
// |            }
// |    }}.
//              If the reviver returns {@code undefined} then the property named by key
//              will be deleted from its container.
//              `this` is bound to the object containing the specified property.
// returns: Object|Array
(function () {
        var number
                        = '(?:-?\\b(?:0|[1-9][0-9]*)(?:\\.[0-9]+)?(?:[eE][+-]?[0-9]+)?\\b)';
        var oneChar = '(?:[^\\0-\\x08\\x0a-\\x1f\"\\\\]'
                        + '|\\\\(?:[\"/\\\\bfnrt]|u[0-9A-Fa-f]{4}))';
        var string = '(?:\"' + oneChar + '*\")';

        // Will match a value in a well-formed JSON file.
        // If the input is not well-formed, may match strangely, but not in an unsafe
        // way.
        // Since this only matches value tokens, it does not match whitespace, colons,
        // or commas.
        var jsonToken = new RegExp(
                        '(?:false|true|null|[\\{\\}\\[\\]]'
                        + '|' + number
                        + '|' + string
                        + ')', 'g');

        // Matches escape sequences in a string literal
        var escapeSequence = new RegExp('\\\\(?:([^u])|u(.{4}))', 'g');

        // Decodes escape sequences in object literals
        var escapes = {
                '"': '"',
                '/': '/',
                '\\': '\\',
                'b': '\b',
                'f': '\f',
                'n': '\n',
                'r': '\r',
                't': '\t'
        };
        function unescapeOne(_, ch, hex) {
                return ch ? escapes[ch] : String.fromCharCode(parseInt(hex, 16));
        }

        // A non-falsy value that coerces to the empty string when used as a key.
        var EMPTY_STRING = new String('');
        var SLASH = '\\';

        // Constructor to use based on an open token.
        var firstTokenCtors = { '{': Object, '[': Array };

        var hop = Object.hasOwnProperty;

        return function (json, opt_reviver) {
                // Split into tokens
                var toks = json.match(jsonToken);
                // Construct the object to return
                var result;
                var tok = toks[0];
                var topLevelPrimitive = false;
                if ('{' === tok) {
                        result = {};
                } else if ('[' === tok) {
                        result = [];
                } else {
                        // The RFC only allows arrays or objects at the top level, but the JSON.parse
                        // defined by the EcmaScript 5 draft does allow strings, booleans, numbers, and null
                        // at the top level.
                        result = [];
                        topLevelPrimitive = true;
                }

                // If undefined, the key in an object key/value record to use for the next
                // value parsed.
                var key;
                // Loop over remaining tokens maintaining a stack of uncompleted objects and
                // arrays.
                var stack = [result];
                for (var i = 1 - topLevelPrimitive, n = toks.length; i < n; ++i) {
                        tok = toks[i];

                        var cont;
                        switch (tok.charCodeAt(0)) {
                                default:        // sign or digit
                                        cont = stack[0];
                                        cont[key || cont.length] = +(tok);
                                        key = void 0;
                                        break;
                                case 0x22:      // '"'
                                        tok = tok.substring(1, tok.length - 1);
                                        if (tok.indexOf(SLASH) !== -1) {
                                                tok = tok.replace(escapeSequence, unescapeOne);
                                        }
                                        cont = stack[0];
                                        if (!key) {
                                                if (cont instanceof Array) {
                                                        key = cont.length;
                                                } else {
                                                        key = tok || EMPTY_STRING;      // Use as key for next value seen.
                                                        break;
                                                }
                                        }
                                        cont[key] = tok;
                                        key = void 0;
                                        break;
                                case 0x5b:      // '['
                                        cont = stack[0];
                                        stack.unshift(cont[key || cont.length] = []);
                                        key = void 0;
                                        break;
                                case 0x5d:      // ']'
                                        stack.shift();
                                        break;
                                case 0x66:      // 'f'
                                        cont = stack[0];
                                        cont[key || cont.length] = false;
                                        key = void 0;
                                        break;
                                case 0x6e:      // 'n'
                                        cont = stack[0];
                                        cont[key || cont.length] = null;
                                        key = void 0;
                                        break;
                                case 0x74:      // 't'
                                        cont = stack[0];
                                        cont[key || cont.length] = true;
                                        key = void 0;
                                        break;
                                case 0x7b:      // '{'
                                        cont = stack[0];
                                        stack.unshift(cont[key || cont.length] = {});
                                        key = void 0;
                                        break;
                                case 0x7d:      // '}'
                                        stack.shift();
                                        break;
                        }
                }
                // Fail if we've got an uncompleted object.
                if (topLevelPrimitive) {
                        if (stack.length !== 1) { throw new Error(); }
                        result = result[0];
                } else {
                        if (stack.length) { throw new Error(); }
                }

                if (opt_reviver) {
                        // Based on walk as implemented in http://www.json.org/json2.js
                        var walk = function (holder, key) {
                                var value = holder[key];
                                if (value && typeof value === 'object') {
                                        var toDelete = null;
                                        for (var k in value) {
                                                if (hop.call(value, k) && value !== holder) {
                                                        // Recurse to properties first. This has the effect of causing
                                                        // the reviver to be called on the object graph depth-first.

                                                        // Since 'this' is bound to the holder of the property, the
                                                        // reviver can access sibling properties of k including ones
                                                        // that have not yet been revived.

                                                        // The value returned by the reviver is used in place of the
                                                        // current value of property k.
                                                        // If it returns undefined then the property is deleted.
                                                        var v = walk(value, k);
                                                        if (v !== void 0) {
                                                                value[k] = v;
                                                        } else {
                                                                // Deleting properties inside the loop has vaguely defined
                                                                // semantics in ES3 and ES3.1.
                                                                if (!toDelete) { toDelete = []; }
                                                                toDelete.push(k);
                                                        }
                                                }
                                        }
                                        if (toDelete) {
                                                for (var i = toDelete.length; --i >= 0;) {
                                                        delete value[toDelete[i]];
                                                }
                                        }
                                }
                                return opt_reviver.call(holder, key, value);
                        };
                        result = walk({ '': result }, '');
                }

                return result;
        };
})();