Chore: async write stream & mkdirp

Build/lib/async-write-to-stream.ts

@@ -0,0 +1,9 @@
+import type { Writable } from 'node:stream';
+import { once } from 'node:events';
+
+export const asyncWriteToStream = <T>(stream: Writable, chunk: T) => {
+  const res = stream.write(chunk);
+  if (!res) {
+    return once(stream, 'drain'); // returns a promise only if needed
+  }
+};

Build/lib/convert-clash-meta-mrs.ts

@@ -7,6 +7,7 @@ import zlib from 'node:zlib';
 import process from 'node:process';
 
 import { async as ezspawn } from '@jsdevtools/ez-spawn';
+import { mkdirp } from './misc';
 
 const mihomoBinaryDir = path.join(__dirname, '../../node_modules/.cache/mihomo');
 const mihomoBinaryPath = path.join(mihomoBinaryDir, 'mihomo');
@@ -22,7 +23,7 @@ const mihomoBinaryUrl: Partial<Record<NodeJS.Platform, Partial<Record<NodeJS.Arc
 };
 
 const ensureMihomoBinary = async () => {
-  await fsp.mkdir(mihomoBinaryDir, { recursive: true });
+  await mkdirp(mihomoBinaryDir);
   if (!fs.existsSync(mihomoBinaryPath)) {
     const writeStream = fs.createWriteStream(mihomoBinaryPath);
 

Build/lib/create-file.ts

@@ -10,6 +10,7 @@ import stringify from 'json-stringify-pretty-compact';
 import { ipCidrListToSingbox, surgeDomainsetToSingbox, surgeRulesetToSingbox } from './singbox';
 import { createTrie } from './trie';
 import { pack, unpackFirst, unpackSecond } from './bitwise';
+import { asyncWriteToStream } from './async-write-to-stream';
 
 export async function compareAndWriteFile(span: Span, linesA: string[], filePath: string) {
   let isEqual = true;
@@ -67,17 +68,24 @@ export async function compareAndWriteFile(span: Span, linesA: string[], filePath
   }
 
   await span.traceChildAsync(`writing ${filePath}`, async () => {
-    // if (linesALen < 10000) {
-    return writeFile(filePath, fastStringArrayJoin(linesA, '\n') + '\n');
-    // }
-    // const writer = file.writer();
+    // The default highwater mark is normally 16384,
+    // So we make sure direct write to file if the content is
+    // most likely less than 500 lines
+    if (linesALen < 500) {
+      return writeFile(filePath, fastStringArrayJoin(linesA, '\n') + '\n');
+    }
 
-    // for (let i = 0; i < linesALen; i++) {
-    //   writer.write(linesA[i]);
-    //   writer.write('\n');
-    // }
-
-    // return writer.end();
+    const writeStream = fs.createWriteStream(filePath);
+    for (let i = 0; i < linesALen; i++) {
+      let p = asyncWriteToStream(writeStream, linesA[i]);
+      // eslint-disable-next-line no-await-in-loop -- stream high water mark
+      if (p) await p;
+      p = asyncWriteToStream(writeStream, '\n');
+      // eslint-disable-next-line no-await-in-loop -- stream high water mark
+      if (p) await p;
+    }
+    await asyncWriteToStream(writeStream, '\n');
+    writeStream.end();
   });
 }
 

Build/lib/misc.ts

@@ -23,9 +23,17 @@ interface Write {
   ): Promise<unknown>
 }
 
+export const mkdirp = (dir: string) => {
+  if (fs.existsSync(dir)) {
+    return;
+  }
+  return fsp.mkdir(dir, { recursive: true });
+};
+
 export const writeFile: Write = async (destination: string, input, dir = dirname(destination)) => {
-  if (!fs.existsSync(dir)) {
-    await fsp.mkdir(dir, { recursive: true });
+  const p = mkdirp(dir);
+  if (p) {
+    await p;
   }
   return fsp.writeFile(destination, input, { encoding: 'utf-8' });
 };