diffusion/src/node_modules/schema/xmljson.js

Diffusion JavaScript client

/*
 * A module for converting between JSON and XML representations for
 * the primary purpose of topic metadata.
 */
var ATTR = require('../schema/consts').ATTR;

// Parse a string of key/value pairs and produce a js object.
// NB: Does not handle embedded = or "
function attrs_str2js(str) {
    var js = {};
    
    var pairs = str.split(' ');
    for (var i = 0; i < pairs.length; i++) {
        var pair = pairs[i].split('=');
        js[pair[0]] = pair[1].match(/"(.*)"/)[1];
    }

    return js;
}

function escapeEntities(str) {
    return String(str).replace(/&/g, '&amp;')
        .replace(/</g, '&lt;')
        .replace(/>/g, '&gt;')
        .replace(/"/g, '&quot;')
        .replace(/'/g, '&#x27;');
}
    
function attrs_obj2arr(obj) {
    var attrs = [];
    if (typeof obj === 'object') {
        for (var key in obj) {
            attrs.push('' + key + '="' + escapeEntities(obj[key]) + '"');
        }
    }
    return attrs;
}

// This is a simple XML parser that can handle topic metadata received
// from Diffusion. It's not a fully-fledged XML parser, but it's a lot
// more lightweight.
function xml2json(xml, pos) {
    var js = {};

    if (pos === undefined) {
        // First call of this function.
        pos = {
            idx : 0,
            isRoot : true
        };

        // Strip off preamble. Because it's the first thing to be
        // found in the XML, we can limit searching for it to the
        // initial call to this function.
        var preamble = xml.match(/<\?.*?\?>/);
        if (preamble) {
            xml = xml.substr(preamble[0].length);
        }
    }
    
    var elem_match = null;

    for (;;) {
        elem_match = xml.substr(pos.idx).match(/<.*?>/);
        if (!elem_match) {
            break;
        }

        pos.idx += elem_match[0].length;
        
        var elem = elem_match[0].trim();

        if (elem.substr(0,2) === '</') {
            // Closing element, back to parent.
            return js;
        }

        var name = elem.match(/\b(.+?)\b/)[0];
        var attrs_match = elem.match(/<.+?\b(.*)\/?>/);
        var attrs_str = '';
        
        if (attrs_match) {
            attrs_str = attrs_match[1].trim();
        }
        
        var attrs = attrs_str2js(attrs_str);
        var child_count;
        if (elem.substr(-2) === '/>') {
            // Self-closing element, no children.

            // Root element, never repeated.
            if (pos.isRoot) {
                pos.isRoot = false;
                js[name] = xml2json(xml, pos);
                js[name][ATTR] = attrs;
            } else {
                if (!js[name]) {
                    js[name] = [];
                }

                child_count = js[name].push({});
                js[name][child_count - 1][ATTR] = attrs;
            }
        } else {
            // Opening a new element, which may have children.

            // Root element is never repeated.
            if (pos.isRoot) {
                pos.isRoot = false;
                js[name] = xml2json(xml, pos);
                js[name][ATTR] = attrs;
            } else {
                if (!js[name]) {
                    js[name] = [];
                }

                child_count = js[name].push(xml2json(xml, pos));
                js[name][child_count - 1][ATTR] = attrs;
            } 
        }
    }

    return js;
}

// Convert a JSON object (primarily, topic metadata) to a stringified
// XML representation. It is not intended to be a complete JSON->XML
// converter, but it is small, light, and does enough for our needs.
function json2xml(obj, recur) {
    var str = '';

    if (!recur) {
        str = '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>';
    }
    
    for (var key in obj) {
        if (key === ATTR) {
            continue;
        }
                          
        var val = obj[key];

        if (!(val instanceof Array)) {
            val = Array(val);
        }

        for (var i = 0; i < val.length; i++) {
            var attrs = attrs_obj2arr(val[i][ATTR]);

            str += '<' + key;
            if (attrs && attrs.length > 0) {
                str += ' ';
                str += attrs.join(' ');
            }

            // Check for non-attribute children of this element
            var child_str = json2xml(val[i], true);
            if (child_str && child_str.length > 0) {
                str += '>';
                str += child_str;
                str += '</' + key + '>';
            } else {
                // No children, close tag here.
                str += '/>';
            }
        }
    }
    
    return str;
}

module.exports = {
    xml2json : xml2json,
    json2xml : json2xml
};