refactor: Improve Chunk and SCTPTimerManager classes with enhanced error handling and parsing methods; add DTO conversion methods

Author: shinyoshiaki

packages/sctp/src/chunk.ts

@@ -46,7 +46,9 @@ export class Chunk {
   }
 
   get bytes() {
-    if (!this.body) throw new Error();
+    if (!this.body) {
+      throw new Error("Chunk body is undefined");
+    }
 
     const header = Buffer.alloc(4);
     header.writeUInt8(this.type, 0);
@@ -60,6 +62,17 @@ export class Chunk {
     ]);
     return data;
   }
+
+  static parse(data: Buffer) {
+    if (data.length < 4) {
+      throw new Error("Chunk header length is less than 4 bytes");
+    }
+    const type = data.readUInt8(0);
+    const flags = data.readUInt8(1);
+    const length = data.readUInt16BE(2);
+    const body = data.subarray(4, length);
+    return { type, flags, length, body };
+  }
 }
 
 export class BaseInitChunk extends Chunk {
@@ -484,7 +497,7 @@ function padL(l: number) {
 function encodeParams(params: [number, Buffer][]) {
   let body = Buffer.from("");
   let padding = Buffer.from("");
-  params.forEach(([type, value]) => {
+  for (const [type, value] of params) {
     const length = value.length + 4;
     const paramHeader = Buffer.alloc(4);
     paramHeader.writeUInt16BE(type, 0);
@@ -493,7 +506,7 @@ function encodeParams(params: [number, Buffer][]) {
     padding = Buffer.concat(
       [...Array(padL(length))].map(() => Buffer.from("\x00")),
     );
-  });
+  }
   return body;
 }
 
@@ -509,6 +522,20 @@ export function decodeParams(body: Buffer): [number, Buffer][] {
   return params;
 }
 
+export const parseChunk = (data: Buffer) => {
+  const { type, flags, length, body } = Chunk.parse(data);
+
+  const ChunkClass = CHUNK_BY_TYPE[type.toString()];
+  if (!ChunkClass) {
+    throw new Error("unknown");
+  }
+
+  return {
+    chunk: new ChunkClass(flags, body),
+    length,
+  };
+};
+
 export function parsePacket(data: Buffer): [number, number, number, Chunk[]] {
   if (data.length < 12)
     throw new Error("SCTP packet length is less than 12 bytes");
@@ -532,17 +559,9 @@ export function parsePacket(data: Buffer): [number, number, number, Chunk[]] {
   const chunks: Chunk[] = [];
   let pos = 12;
   while (pos + 4 <= data.length) {
-    const chunkType = data.readUInt8(pos);
-    const chunkFlags = data.readUInt8(pos + 1);
-    const chunkLength = data.readUInt16BE(pos + 2);
-    const chunkBody = data.slice(pos + 4, pos + chunkLength);
-    const ChunkClass = CHUNK_BY_TYPE[chunkType.toString()];
-    if (ChunkClass) {
-      chunks.push(new ChunkClass(chunkFlags, chunkBody));
-    } else {
-      throw new Error("unknown");
-    }
-    pos += chunkLength + padL(chunkLength);
+    const { length, chunk } = parseChunk(data.subarray(pos));
+    chunks.push(chunk);
+    pos += length + padL(length);
   }
   return [sourcePort, destinationPort, verificationTag, chunks];
 }

packages/sctp/src/timer.ts

@@ -1,4 +1,4 @@
-import type { Chunk } from "./chunk";
+import { type Chunk, parseChunk } from "./chunk";
 import {
   SCTP_MAX_ASSOCIATION_RETRANS,
   SCTP_MAX_INIT_RETRANS,
@@ -19,16 +19,14 @@ export enum SCTPTimerType {
   RECONFIG = "reconfig", // re-configuration
 }
 
+interface Deps {
+  sendChunk: (chunk: Chunk) => Promise<void>;
+}
+
 /**
  * SCTP タイマーの管理を行うクラス
  */
 export class SCTPTimerManager {
-  // タイマーハンドラ
-  private t1Handle?: NodeJS.Timeout;
-  private t2Handle?: NodeJS.Timeout;
-  private t3Handle?: NodeJS.Timeout;
-  private reconfigHandle?: NodeJS.Timeout;
-
   // タイマー関連の状態管理
   private t1Chunk?: Chunk;
   private t1Failures = 0;
@@ -38,17 +36,20 @@ export class SCTPTimerManager {
   rto: number = SCTP_RTO_INITIAL;
   private srtt?: number;
   private rttvar?: number;
-  onT1Expired = new Event<[number]>();
-  onT2Expired = new Event<[number]>();
-  onT3Expired = new Event<[]>();
-  onReconfigExpired = new Event<[number]>();
-  private sendChunk: (chunk: Chunk) => Promise<void>;
-
-  constructor({
-    sendChunk,
-  }: {
-    sendChunk: (chunk: Chunk) => Promise<void>;
-  }) {
+
+  // タイマーハンドラ
+  private t1Handle?: NodeJS.Timeout;
+  private t2Handle?: NodeJS.Timeout;
+  private t3Handle?: NodeJS.Timeout;
+  private reconfigHandle?: NodeJS.Timeout;
+
+  readonly onT1Expired = new Event<[number]>();
+  readonly onT2Expired = new Event<[number]>();
+  readonly onT3Expired = new Event<[]>();
+  readonly onReconfigExpired = new Event<[number]>();
+  private readonly sendChunk: (chunk: Chunk) => Promise<void>;
+
+  constructor({ sendChunk }: Deps) {
     this.sendChunk = sendChunk;
   }
 
@@ -303,4 +304,42 @@ export class SCTPTimerManager {
       Math.min(this.srtt + 4 * this.rttvar, SCTP_RTO_MAX),
     );
   }
+
+  toDto(): SCTPTimerDto {
+    return {
+      t1Chunk: this.t1Chunk?.bytes,
+      t1Failures: this.t1Failures,
+      t2Chunk: this.t2Chunk?.bytes,
+      t2Failures: this.t2Failures,
+      reconfigFailures: this.reconfigFailures,
+      rto: this.rto,
+      srtt: this.srtt,
+      rttvar: this.rttvar,
+    };
+  }
+
+  static fromDto(dto: SCTPTimerDto, deps: Deps): SCTPTimerManager {
+    const timerManager = new SCTPTimerManager(deps);
+    timerManager.t1Chunk = dto.t1Chunk && parseChunk(dto.t1Chunk).chunk;
+    timerManager.t1Failures = dto.t1Failures;
+    timerManager.t2Chunk = dto.t2Chunk && parseChunk(dto.t2Chunk).chunk;
+    timerManager.t2Failures = dto.t2Failures;
+    timerManager.reconfigFailures = dto.reconfigFailures;
+    timerManager.rto = dto.rto;
+    timerManager.srtt = dto.srtt;
+    timerManager.rttvar = dto.rttvar;
+
+    return timerManager;
+  }
+}
+
+interface SCTPTimerDto {
+  t1Chunk: Buffer | undefined;
+  t1Failures: number;
+  t2Chunk: Buffer | undefined;
+  t2Failures: number;
+  reconfigFailures: number;
+  rto: number;
+  srtt: number | undefined;
+  rttvar: number | undefined;
 }