torrent-read/index.js

The simplest torrent file parser.

var crypto = require('crypto');
module.exports = function(data) {
    var i = 0,
        e = ('e').charCodeAt(0),
        root = [],
        info_from,
        info_to;

    function parse(char, parent) {
        var rtn;
        switch (char) {
            case 105: //'i':
                var val = '';
                while (i < data.length) {
                    if (data[i] >= 48 && data[i] <= 57) {
                        val += String.fromCharCode(data[i]);
                    } else if (data[i] == e) {
                        break;
                    }
                    i++;
                }
                rtn = val;
                break;
            case 100: //'d':
                var dict = {},
                    key,
                    temp;
                while ((data[++i] != e) && (temp = parse(data[i], dict))) {
                    if (key) {
                        if (key === 'info') {
                            info_to = i;
                            dict.info_hash = crypto.createHash('sha1').update(data.slice(info_from + 1, info_to + 1), 'binary').digest('hex').toUpperCase();
                        }
                        if (key !== 'pieces') {
                            dict[key] = temp;
                            key = null;
                        }
                    } else {
                        key = temp;
                        if (key === 'info') {
                            info_from = i;
                        }
                    }
                }
                rtn = dict;
                parent === root && parent.push(dict);
                break;
            case 108: //'l':
                var list = [],
                    temp;
                while ((data[++i] != e) && (temp = parse(data[i], list))) {
                    list.push(temp);
                }
                rtn = list;
                break;
            default:
                var len = String.fromCharCode(char);
                while (++i < data.length) {
                    if (data[i] < 48 || data[i] > 57) {
                        break;
                    }
                    len += String.fromCharCode(data[i]);
                }
                len <<= 0;
                rtn = data.slice(i + 1, i + 1 + len).toString();
                i += len;
                break;
        }
        return rtn;
    }
    parse(data[i], root);
    return root[0] || {};
};