bencoder
Version:
bencode encoder/decoder written in TypeScript
196 lines (195 loc) • 5.76 kB
JavaScript
;
var buffer_1 = require('buffer');
/*
Encoding
*/
function encodeString(s) {
var bytes = buffer_1.Buffer.from(s);
return buffer_1.Buffer.concat([
buffer_1.Buffer.from(bytes.length.toString()),
buffer_1.Buffer.from(':'),
bytes]);
}
function encodeInteger(i) {
return buffer_1.Buffer.from("i" + i + "e");
}
function encodeArray(l) {
var result = [buffer_1.Buffer.from('l')];
l.forEach(function (element) {
result.push(_encode(element));
});
result.push(buffer_1.Buffer.from('e'));
return buffer_1.Buffer.concat(result);
}
function encodeDict(d) {
var result = [buffer_1.Buffer.from('d')];
var keys = Object.keys(d).sort();
keys.forEach(function (k) {
result.push(encodeString(k));
result.push(encode(d[k]));
});
result.push(buffer_1.Buffer.from('e'));
return buffer_1.Buffer.concat(result);
}
function _encode(data) {
switch (typeof data) {
case 'string':
return encodeString(data);
case 'number':
return encodeInteger(data);
case 'object':
if (Array.isArray(data)) {
return encodeArray(data);
}
else {
return encodeDict(data);
}
}
}
/**
* Encodes data in bencode.
*
* @param {Array|String|Object|Number} data
* @return {Buffer}
*/
function encode(data) {
return new buffer_1.Buffer(_encode(data));
}
exports.encode = encode;
/*
Decoding
*/
var Delimeters;
(function (Delimeters) {
Delimeters[Delimeters["i"] = 105] = "i";
Delimeters[Delimeters["e"] = 101] = "e";
Delimeters[Delimeters["l"] = 108] = "l";
Delimeters[Delimeters["d"] = 100] = "d";
Delimeters[Delimeters["colon"] = 58] = "colon";
})(Delimeters || (Delimeters = {}));
function decodeString(data, encoding) {
var firstColonIndex = null;
for (var i = 0; i < data.length; i++) {
if (data[i] === Delimeters.colon) {
firstColonIndex = i;
break;
}
}
if (!firstColonIndex) {
throw new Error("Error while decoding " + data.toString(encoding) + ". Missing colon.");
}
var expectedLength = parseInt(data.slice(0, firstColonIndex).toString());
var value = data.slice(firstColonIndex + 1, firstColonIndex + 1 + expectedLength);
return { value: value.toString(encoding), rest: data.slice(firstColonIndex + 1 + expectedLength) };
}
function decodeInteger(data) {
var endIndex = null; // The first 'e' symbol index
for (var i = 1; i < data.length; i++) {
if (data[i] === Delimeters.e) {
endIndex = i;
break;
}
}
if (!endIndex) {
throw new Error("Invalid data. 'e' symbol expected");
}
return {
value: parseInt(data.slice(1, endIndex).toString()),
rest: data.slice(endIndex + 1)
};
}
function decodeList(data, encoding) {
// TODO: Check for 'e' symbol in the end.
var result = [];
var rest = data.slice(1); // l...
var value = null;
while (true) {
var firstByte = rest[0];
if (firstByte === Delimeters.i) {
(_a = decodeInteger(rest), value = _a.value, rest = _a.rest, _a);
result.push(value);
continue;
}
if (encodesDigit(firstByte)) {
(_b = decodeString(rest, encoding), value = _b.value, rest = _b.rest, _b);
result.push(value);
continue;
}
if (firstByte === Delimeters.l) {
(_c = decodeList(rest, encoding), value = _c.value, rest = _c.rest, _c);
result.push(value);
continue;
}
if (firstByte === Delimeters.d) {
(_d = decodeDict(rest, encoding), value = _d.value, rest = _d.rest, _d);
result.push(value);
continue;
}
if (firstByte === Delimeters.e) {
rest = rest.slice(1);
break;
}
throw new Error("Expected d, i, l or digit, got " + rest.toString(encoding));
}
return { value: result, rest: rest };
var _a, _b, _c, _d;
}
function decodeDict(data, encoding) {
var result = {};
var rest = data.slice(1); // d...
var value = null;
var key;
while (rest.length !== 0) {
var firstByte = rest[0];
if (firstByte === Delimeters.e) {
rest = rest.slice(1);
break;
}
(_a = decodeString(rest, encoding), key = _a.value, rest = _a.rest, _a);
(_b = _decode(rest, encoding), value = _b.value, rest = _b.rest, _b);
result[key] = value;
}
return { value: result, rest: rest };
var _a, _b;
}
function encodesDigit(x) {
return (x >= 0x30) && (x <= 0x39);
}
function _decode(data, encoding) {
var value = null;
var rest = null;
var firstByte = data[0];
if (firstByte === Delimeters.i) {
return decodeInteger(data);
}
else if (encodesDigit(firstByte)) {
return decodeString(data, encoding);
}
else if (firstByte === Delimeters.l) {
return decodeList(data, encoding);
}
else if (firstByte === Delimeters.d) {
return decodeDict(data, encoding);
}
else {
throw new Error("Expected d, i, l or digit, got \"" + data.toString() + "\"");
}
}
/**
* Decodes bencoded data.
*
* @param {Buffer} data
* @param {String} encoding (optional)
* @return {Object|Array|String|Number}
*/
function decode(data, encoding) {
var value;
var rest;
(_a = _decode(data, encoding), value = _a.value, rest = _a.rest, _a);
if (rest.length) {
throw new Error("Unexpected continuation: \"" + rest.toString() + "\"");
}
return value;
var _a;
}
exports.decode = decode;