bencode.js

var bencode = exports;


function decode_int(x, f) {
	f++;
	var newf = x.indexOf('e', f);
	var n = parseInt(x.substring(f,newf));
	if (x.charAt(f) == '-' && x.charAt(f+1) == '0') {
		throw("ValueError");
	} else if (x.charAt(f) == '0' && newf != f+1) {
		throw("ValueError");
	}
	return [n, newf+1];
}

function decode_string(x, f) {
	var colon = x.indexOf(':', f);
	var n = parseInt(x.substring(f,colon));
	if (x.charAt(f) == '0' && colon != f+1) {
		throw("ValueError");
	}
	colon++;
	return [x.substring(colon,colon+n), colon+n];
}

function decode_list(x, f) {
	var r = []; f++;
	while (x.charAt(f) != 'e') {
		var a = decode_func[x.charAt(f)](x, f);
		var v = a[0]; f = a[1];
		r.push(v);
	}
	return [r, f + 1];
}

function decode_dict(x, f) {
	var r = {}; f++;
	while (x.charAt(f) != 'e') {
		var a = decode_string(x, f);
		var k = a[0]; f = a[1];
		a = decode_func[x.charAt(f)](x, f);
		r[k] = a[0]; f = a[1];
	}
	return [r, f + 1];
}

decode_func = {};
decode_func['l'] = decode_list;
decode_func['d'] = decode_dict;
decode_func['i'] = decode_int;
decode_func['0'] = decode_string;
decode_func['1'] = decode_string;
decode_func['2'] = decode_string;
decode_func['3'] = decode_string;
decode_func['4'] = decode_string;
decode_func['5'] = decode_string;
decode_func['6'] = decode_string;
decode_func['7'] = decode_string;
decode_func['8'] = decode_string;
decode_func['9'] = decode_string;

function bdecode(x) {
	try {
		var a = decode_func[x.charAt(0)](x, 0);
		var r = a[0]; var l = a[1];
	} catch(e) {
		throw("not a valid bencoded string");
	}
	if (l != x.length) {
		throw("invalid bencoded value (data after valid prefix)");
	}
	return r;
}

function encode_int(x,r) {
	r.push('i'); r.push(x+''); r.push('e');
}

function encode_string(x,r) {
	r.push(x.length+''); r.push(':'); r.push(x);
}

function encode_list(x,r) {
	r.push('l');
	for (var i in x){
		var type = typeof(x[i]);
		type = (type == 'object') ? ((x[i] instanceof Array) ? 'list' : 'dict') : type;
		encode_func[type](x[i], r);
	}
	r.push('e');
}

function encode_dict(x,r) {
	r.push('d');
	var keys = [], ilist = {};
	for (var i in x) {
		keys.push(i);
	}
	keys.sort();
	for (var j in keys) {
		ilist[keys[j]] = x[keys[j]];
	}
	for (var k in ilist) {
		r.push(k.length+''); r.push(':'); r.push(k);
		var v = ilist[k];
		var type = typeof(v);
		type = (type == 'object') ? ((v instanceof Array) ? 'list' : 'dict') : type;
		encode_func[type](v, r);
	}
	r.push('e');
}

function encode_dict_1st(x,r) {
	r.push('d');
	var keys = [], ilist = {};
	for (var i in x) {
		keys.push(i);
	}
	keys.sort();
	for (var j in keys) {
		ilist[keys[j]] = x[keys[j]];
	}
	for (var k in ilist) {
		r.push(k.length+''); r.push(':'); r.push(k);
		var v = ilist[k];
		var type = typeof(v);
		type = (type == 'object') ? ((v instanceof Array) ? 'list' : 'dict') : type;
		encode_func[type](v, r);
	}
	r.push('e');
}

encode_func = {};
encode_func['number']  = encode_int;
encode_func['string']  = encode_string;
encode_func['list']	= encode_list;
encode_func['dict']	= encode_dict;

bencode.bencode = function bencode(x) {
	var r = [];
	var type = typeof(x);
	type = (type == 'object') ? ((x instanceof Array) ? 'list' : 'dict') : type;/*
	if(type == 'dict')
		encode_dict_1st(x, r);
	else
		encode_func[type](x, r);*/
	encode_func[type](x, r);
	return r.join('');
};