node-hca/lib/Messaging/message.js

Node.js client for HCA

'use strict';

var HcaResponse = require('./HcaResponse');

(function() {

    var parse = function(data) {
        var params = this.decode(data);
        var response = new HcaResponse();

        response.code = parseInt(params[0]);
        response.group = params[1];
        response.command = params[2];
        response.data = params.slice(3);

        return response;
    };

    var encode = function(parameters) {
        var separator = '    '; // 4 spaces.
        var paramCount = parameters.length;
        var preamble = '';
        var preambleLength = paramCount * 4;
        var data = '';

        for (var i = 0; i < paramCount; i++) {

            var param = parameters[i].toString();
            var curLength = preambleLength + separator.length + data.length;

            data += param;
            preamble += (curLength + param.length).pad(4);

        }

        return preamble + separator + data;
    };

    var decode = function(data) {
        // This method is a port from C to Javascript. Original HCA sample can be found at:
        // http://www.hcatech.com/download/V12/Doc/TechNote_ServerProtocol.pdf

        var iSep = data.indexOf('    '); // 4 spaces;

        if (iSep == -1)
            return (null);

        // Extract the part before the 4 blanks
        var pspec = data.substr(0, iSep);
        var sEnd;
        var text;

        // Make sure it contains a multiple of 4 characters
        if ((pspec.length % 4) != 0)
            return (null);

        // Determine count of parameters. Each one is defined by 4 characters
        var ctParams = pspec.length / 4;

        // Start of the parameter. Moved along as each is extracted
        var iStart = iSep + 4;
        var iEnd;

        var params = [];
        var paramCount = params;

        for (var i = 0; i < ctParams; i++) {
            sEnd = pspec.substr(i * 4, 4); // Extract out the spec for this parameter
            iEnd = parseInt(sEnd);

            if (isNaN(iEnd)) // Make into number form. Must convert ok
            {
                //delete params;
                params.length = 0;
                return (null);
            }

            if (iEnd > data.length) // This number tell us the end character. So
            // make sure we have sufficient in the string
            {
                //delete params;
                params.length = 0;
                return (null);
            }

            // Extract the text for this parameter. Could be a null string
            if ((iEnd - iStart) == 0)
                text = "";
            else
                text = data.substr(iStart, iEnd - iStart);

            params.push(text);
            paramCount++;
            iStart = iEnd;
        }

        return params;
    };

    Number.prototype.pad = function(size) {
        var s = String(this);

        while (s.length < (size || 2)) {
            s = "0" + s;
        }

        return s;
    };

    module.exports = {
        parse: parse,
        encode: encode,
        decode: decode
    };

})();