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channel.ts
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channel.ts
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import { ByteBuffer } from '@xmcl/bytebuffer'
import { EventEmitter } from 'events'
import { NetConnectOpts, Socket } from 'net'
import { Transform, TransformCallback, Writable } from 'stream'
import { unzip } from 'zlib'
import { Coder } from './coders'
import { PacketRegistryEntry, Side, PacketMetadata } from './packet'
export type State = keyof States
interface States {
handshake: PacketCoders
login: PacketCoders
status: PacketCoders
play: PacketCoders
}
/**
* The channel for send and listen the Minecraft packet.
*/
export class Channel extends EventEmitter {
state: State = 'handshake'
private readonly states = {
client: {
handshake: new PacketCoders(),
login: new PacketCoders(),
status: new PacketCoders(),
play: new PacketCoders(),
},
server: {
handshake: new PacketCoders(),
login: new PacketCoders(),
status: new PacketCoders(),
play: new PacketCoders(),
},
}
private connection: Socket = new Socket({ allowHalfOpen: false })
private outbound: Writable
private inbound: Writable
private listened = false
private enableCompression = false
private compressionThreshold = -1
constructor() {
super()
this.outbound = new MinecraftPacketEncoder(this)
this.outbound.pipe(new MinecraftPacketOutbound()).pipe(this.connection)
this.inbound = new MinecraftPacketInBound()
this.inbound
.pipe(new PacketDecompress({
get enableCompression() {
return false
},
get compressionThreshold() {
return -1
},
}))
.pipe(new MinecraftPacketDecoder(this))
.pipe(new PacketEmitter(this))
this.connection.pipe(this.inbound)
}
/**
* Is the connection ready to read and write
*/
get ready() {
return this.connection.readable && this.connection.writable && this.listened
}
findCoderById(packetId: number, side: Side): Coder<any> {
const all = this.states[side][this.state]
return all.packetIdCoders[packetId]
}
getPacketId(packetInst: any, side: Side): number {
const packetName = Object.getPrototypeOf(packetInst).constructor.name
const all = this.states[side][this.state]
return all.packetNameToId[packetName]
}
registerPacketType(clazz: new (...args: any) => any) {
const entry: PacketRegistryEntry = clazz.prototype[PacketMetadata]
const { state, side, id, name, coder } = entry
const coders = this.states[side][state]
coders.packetIdCoders[id] = coder
coders.packetNameToId[name] = id
}
registerPacket(entry: PacketRegistryEntry) {
const { state, side, id, name, coder } = entry
const coders = this.states[side][state]
coders.packetIdCoders[id] = coder
coders.packetNameToId[name] = id
}
/**
* Open the connection and start to listen the port.
*/
async listen(option: NetConnectOpts & { keepalive?: boolean | number }) {
await new Promise<void>((resolve, reject) => {
this.connection.connect(option, () => {
resolve()
})
if (option.timeout) {
this.connection.setTimeout(option.timeout)
}
if (option.keepalive) {
this.connection.setKeepAlive(true, typeof option.keepalive === 'boolean' ? 3500 : option.keepalive)
}
this.connection.once('error', (e) => { reject(e) })
this.connection.once('timeout', () => { reject(new Error('Connection timeout.')) })
})
this.connection.on('error', (e) => { this.emit('error', e) })
this.emit('listen')
this.listened = true
}
disconnect() {
if (!this.listened || !this.ready) {
return Promise.resolve()
}
this.listened = false
return new Promise<void>((resolve, reject) => {
this.connection.once('close', (err) => {
if (err) {
reject(err)
} else {
resolve()
}
})
this.connection.end()
})
}
/**
* Sent a packet to server.
*/
send<T>(message: T, skeleton?: Partial<T>) {
if (!this.connection.writable) { throw new Error("Cannot write if the connection isn't writable!") }
if (skeleton) { Object.assign((message as any), skeleton) }
return new Promise<void>((resolve, reject) => {
this.outbound.write(message, (err) => {
if (err) {
reject(err)
} else {
this.emit('send', message)
resolve()
}
})
})
}
/**
* Listen for sepcific packet by its class name.
*/
onPacket<T>(packet: new (...args: any[]) => T, listener: (event: T) => void): this {
return this.on(`packet:${packet.name}`, listener)
}
oncePacket<T>(packet: new (...args: any[]) => T, listener: (event: T) => void): this {
return this.once(`packet:${packet.name}`, listener)
}
}
export interface Channel extends EventEmitter {
on<T>(channel: string, listener: (event: T) => void): this
once<T>(channel: string, listener: (event: T) => void): this
}
export abstract class PacketInBound extends Transform {
private buffer: ByteBuffer = ByteBuffer.allocate(1024)
protected abstract readPacketLength(bb: ByteBuffer): number
_transform(chunk: Buffer, encoding: string, callback: TransformCallback) {
this.buffer.ensureCapacity(chunk.length + this.buffer.offset)
this.buffer.append(chunk)
this.buffer.flip()
let unresolvedBytes
do {
const packetLength = this.readPacketLength(this.buffer)
unresolvedBytes = this.buffer.remaining()
if (packetLength <= unresolvedBytes) {
const result = Buffer.alloc(packetLength)
// TODO: check if this src refactor is correct
const src = Buffer.from(this.buffer.buffer)
src.copy(result, 0, this.buffer.offset, this.buffer.offset + packetLength)
this.push(result)
src.copyWithin(0, packetLength) // clear emitted bytes
this.buffer.offset = 0 // reset read offset to the front
this.buffer.limit -= packetLength // reduce the limit by emitted bytes
unresolvedBytes -= packetLength
} else {
this.buffer.offset = this.buffer.limit
this.buffer.limit = this.buffer.capacity()
break
}
} while (unresolvedBytes > 0)
callback()
}
}
class MinecraftPacketInBound extends PacketInBound {
protected readPacketLength(bb: ByteBuffer): number {
return bb.readVarint32()
}
}
class PacketDecompress extends Transform {
constructor(private option: { readonly enableCompression: boolean; readonly compressionThreshold: number }) {
super()
}
_transform(chunk: Buffer, encoding: string, callback: TransformCallback) {
if (!this.option.enableCompression) {
this.push(chunk)
callback()
return
}
const message = ByteBuffer.wrap(chunk)
const dataLength = message.readVarint32()
if (dataLength === 0 || dataLength < this.option.compressionThreshold) {
this.push(message.buffer.slice(message.offset))
callback()
} else {
const compressedContent = message.buffer.slice(message.offset)
unzip(compressedContent, (err, result) => {
if (err) {
callback(err)
} else {
this.push(result)
callback()
}
})
}
}
}
export interface PacketRegistry {
findCoderById(packetId: number, side: 'client' | 'server'): Coder<any>
getPacketId(message: any, side: 'client' | 'server'): number
}
export abstract class PacketDecoder extends Transform {
constructor(private client: PacketRegistry) {
super({ writableObjectMode: true, readableObjectMode: true })
}
abstract readPacketId(message: ByteBuffer): number
_transform(chunk: Buffer, encoding: string, callback: TransformCallback) {
const message = ByteBuffer.wrap(chunk)
const packetId = this.readPacketId(message)
const packetContent = message.slice()
const coder = this.client.findCoderById(packetId, 'server')
if (coder) {
this.push(coder.decode(packetContent))
} else {
console.error(`Unknown packet ${packetId} : ${packetContent.buffer}.`)
}
callback()
}
}
class MinecraftPacketDecoder extends PacketDecoder {
readPacketId(message: ByteBuffer): number {
return message.readVarint32()
}
}
export class PacketEmitter extends Writable {
constructor(private eventBus: EventEmitter) {
super({ objectMode: true })
}
_write(inst: any, encoding: string, callback: (error?: Error | null) => void): void {
this.eventBus.emit(`packet:${Object.getPrototypeOf(inst).constructor.name}`, inst)
callback()
}
}
export abstract class PacketEncoder extends Transform {
constructor(private client: PacketRegistry) {
super({ writableObjectMode: true, readableObjectMode: true })
}
protected abstract writePacketId(bb: ByteBuffer, id: number): void
_transform(message: any, encoding: string, callback: TransformCallback) {
const id = this.client.getPacketId(message, 'client')
const coder = this.client.findCoderById(id, 'client')
if (coder && coder.encode) {
const buf = new ByteBuffer()
this.writePacketId(buf, id)
coder.encode(buf, message, this.client)
buf.flip()
const arr = buf.buffer.slice(0, buf.limit)
this.push(Buffer.from(arr))
callback()
} else {
callback(new Error(`Cannot find coder for message. ${JSON.stringify(message)}`))
}
}
}
class MinecraftPacketEncoder extends PacketEncoder {
protected writePacketId(bb: ByteBuffer, id: number): void {
bb.writeByte(id)
}
}
export abstract class PacketOutbound extends Transform {
protected abstract writePacketLength(bb: ByteBuffer, len: number): void
_transform(packet: Buffer, encoding: string, callback: TransformCallback) {
const buffer = new ByteBuffer()
this.writePacketLength(buffer, packet.length)
buffer.append(packet)
buffer.flip()
this.push(Buffer.from(buffer.buffer.slice(0, buffer.limit)))
callback()
}
}
class MinecraftPacketOutbound extends PacketOutbound {
protected writePacketLength(bb: ByteBuffer, len: number): void {
bb.writeVarint32(len)
}
}
class PacketCoders {
packetIdCoders: { [packetId: number]: Coder<any> } = {}
packetNameToId: { [name: string]: number } = {}
}