laurent@371: json_parse = (function () {
laurent@371:
laurent@371: // This is a function that can parse a JSON text, producing a JavaScript
laurent@371: // data structure. It is a simple, recursive descent parser. It does not use
laurent@371: // eval or regular expressions, so it can be used as a model for implementing
laurent@371: // a JSON parser in other languages.
laurent@371:
laurent@371: // We are defining the function inside of another function to avoid creating
laurent@371: // global variables.
laurent@371:
laurent@371: var at, // The index of the current character
laurent@371: ch, // The current character
laurent@371: escapee = {
laurent@371: '"': '"',
laurent@371: '\\': '\\',
laurent@371: '/': '/',
laurent@371: b: '\b',
laurent@371: f: '\f',
laurent@371: n: '\n',
laurent@371: r: '\r',
laurent@371: t: '\t'
laurent@371: },
laurent@371: text,
laurent@371:
laurent@371: error = function (m) {
laurent@371:
laurent@371: // Call error when something is wrong.
laurent@371:
laurent@371: throw {
laurent@371: name: 'SyntaxError',
laurent@371: message: m,
laurent@371: at: at,
laurent@371: text: text
laurent@371: };
laurent@371: },
laurent@371:
laurent@371: next = function (c) {
laurent@371:
laurent@371: // If a c parameter is provided, verify that it matches the current character.
laurent@371:
laurent@371: if (c && c !== ch) {
laurent@371: error("Expected '" + c + "' instead of '" + ch + "'");
laurent@371: }
laurent@371:
laurent@371: // Get the next character. When there are no more characters,
laurent@371: // return the empty string.
laurent@371:
laurent@371: ch = text.charAt(at);
laurent@371: at += 1;
laurent@371: return ch;
laurent@371: },
laurent@371:
laurent@371: number = function () {
laurent@371:
laurent@371: // Parse a number value.
laurent@371:
laurent@371: var number,
laurent@371: string = '';
laurent@371:
laurent@371: if (ch === '-') {
laurent@371: string = '-';
laurent@371: next('-');
laurent@371: }
laurent@371: while (ch >= '0' && ch <= '9') {
laurent@371: string += ch;
laurent@371: next();
laurent@371: }
laurent@371: if (ch === '.') {
laurent@371: string += '.';
laurent@371: while (next() && ch >= '0' && ch <= '9') {
laurent@371: string += ch;
laurent@371: }
laurent@371: }
laurent@371: if (ch === 'e' || ch === 'E') {
laurent@371: string += ch;
laurent@371: next();
laurent@371: if (ch === '-' || ch === '+') {
laurent@371: string += ch;
laurent@371: next();
laurent@371: }
laurent@371: while (ch >= '0' && ch <= '9') {
laurent@371: string += ch;
laurent@371: next();
laurent@371: }
laurent@371: }
laurent@371: number = +string;
laurent@371: if (isNaN(number)) {
laurent@371: error("Bad number");
laurent@371: } else {
laurent@371: return number;
laurent@371: }
laurent@371: },
laurent@371:
laurent@371: string = function () {
laurent@371:
laurent@371: // Parse a string value.
laurent@371:
laurent@371: var hex,
laurent@371: i,
laurent@371: string = '',
laurent@371: uffff;
laurent@371:
laurent@371: // When parsing for string values, we must look for " and \ characters.
laurent@371:
laurent@371: if (ch === '"') {
laurent@371: while (next()) {
laurent@371: if (ch === '"') {
laurent@371: next();
laurent@371: return string;
laurent@371: } else if (ch === '\\') {
laurent@371: next();
laurent@371: if (ch === 'u') {
laurent@371: uffff = 0;
laurent@371: for (i = 0; i < 4; i += 1) {
laurent@371: hex = parseInt(next(), 16);
laurent@371: if (!isFinite(hex)) {
laurent@371: break;
laurent@371: }
laurent@371: uffff = uffff * 16 + hex;
laurent@371: }
laurent@371: string += String.fromCharCode(uffff);
laurent@371: } else if (typeof escapee[ch] === 'string') {
laurent@371: string += escapee[ch];
laurent@371: } else {
laurent@371: break;
laurent@371: }
laurent@371: } else {
laurent@371: string += ch;
laurent@371: }
laurent@371: }
laurent@371: }
laurent@371: error("Bad string");
laurent@371: },
laurent@371:
laurent@371: white = function () {
laurent@371:
laurent@371: // Skip whitespace.
laurent@371:
laurent@371: while (ch && ch <= ' ') {
laurent@371: next();
laurent@371: }
laurent@371: },
laurent@371:
laurent@371: word = function () {
laurent@371:
laurent@371: // true, false, or null.
laurent@371:
laurent@371: switch (ch) {
laurent@371: case 't':
laurent@371: next('t');
laurent@371: next('r');
laurent@371: next('u');
laurent@371: next('e');
laurent@371: return true;
laurent@371: case 'f':
laurent@371: next('f');
laurent@371: next('a');
laurent@371: next('l');
laurent@371: next('s');
laurent@371: next('e');
laurent@371: return false;
laurent@371: case 'n':
laurent@371: next('n');
laurent@371: next('u');
laurent@371: next('l');
laurent@371: next('l');
laurent@371: return null;
laurent@371: }
laurent@371: error("Unexpected '" + ch + "'");
laurent@371: },
laurent@371:
laurent@371: value, // Place holder for the value function.
laurent@371:
laurent@371: array = function () {
laurent@371:
laurent@371: // Parse an array value.
laurent@371:
laurent@371: var array = [];
laurent@371:
laurent@371: if (ch === '[') {
laurent@371: next('[');
laurent@371: white();
laurent@371: if (ch === ']') {
laurent@371: next(']');
laurent@371: return array; // empty array
laurent@371: }
laurent@371: while (ch) {
laurent@371: array.push(value());
laurent@371: white();
laurent@371: if (ch === ']') {
laurent@371: next(']');
laurent@371: return array;
laurent@371: }
laurent@371: next(',');
laurent@371: white();
laurent@371: }
laurent@371: }
laurent@371: error("Bad array");
laurent@371: },
laurent@371:
laurent@371: object = function () {
laurent@371:
laurent@371: // Parse an object value.
laurent@371:
laurent@371: var key,
laurent@371: object = {};
laurent@371:
laurent@371: if (ch === '{') {
laurent@371: next('{');
laurent@371: white();
laurent@371: if (ch === '}') {
laurent@371: next('}');
laurent@371: return object; // empty object
laurent@371: }
laurent@371: while (ch) {
laurent@371: key = string();
laurent@371: white();
laurent@371: next(':');
laurent@371: if (Object.hasOwnProperty.call(object, key)) {
laurent@371: error('Duplicate key "' + key + '"');
laurent@371: }
laurent@371: object[key] = value();
laurent@371: white();
laurent@371: if (ch === '}') {
laurent@371: next('}');
laurent@371: return object;
laurent@371: }
laurent@371: next(',');
laurent@371: white();
laurent@371: }
laurent@371: }
laurent@371: error("Bad object");
laurent@371: };
laurent@371:
laurent@371: value = function () {
laurent@371:
laurent@371: // Parse a JSON value. It could be an object, an array, a string, a number,
laurent@371: // or a word.
laurent@371:
laurent@371: white();
laurent@371: switch (ch) {
laurent@371: case '{':
laurent@371: return object();
laurent@371: case '[':
laurent@371: return array();
laurent@371: case '"':
laurent@371: return string();
laurent@371: case '-':
laurent@371: return number();
laurent@371: default:
laurent@371: return ch >= '0' && ch <= '9' ? number() : word();
laurent@371: }
laurent@371: };
laurent@371:
laurent@371: // Return the json_parse function. It will have access to all of the above
laurent@371: // functions and variables.
laurent@371:
laurent@371: return function (source, reviver) {
laurent@371: var result;
laurent@371:
laurent@371: text = source;
laurent@371: at = 0;
laurent@371: ch = ' ';
laurent@371: result = value();
laurent@371: white();
laurent@371: if (ch) {
laurent@371: error("Syntax error");
laurent@371: }
laurent@371:
laurent@371: // If there is a reviver function, we recursively walk the new structure,
laurent@371: // passing each name/value pair to the reviver function for possible
laurent@371: // transformation, starting with a temporary root object that holds the result
laurent@371: // in an empty key. If there is not a reviver function, we simply return the
laurent@371: // result.
laurent@371:
laurent@371: return typeof reviver === 'function' ? (function walk(holder, key) {
laurent@371: var k, v, value = holder[key];
laurent@371: if (value && typeof value === 'object') {
laurent@371: for (k in value) {
laurent@371: if (Object.hasOwnProperty.call(value, k)) {
laurent@371: v = walk(value, k);
laurent@371: if (v !== undefined) {
laurent@371: value[k] = v;
laurent@371: } else {
laurent@371: delete value[k];
laurent@371: }
laurent@371: }
laurent@371: }
laurent@371: }
laurent@371: return reviver.call(holder, key, value);
laurent@371: }({'': result}, '')) : result;
laurent@371: };
laurent@371: }());