docs: Web Streams Example (#360)

Co-authored-by: James M Snell <jasnell@gmail.com>
Co-authored-by: Rafael Gonzaga <rafael.nunu@hotmail.com>

examples/webstreams-transform/index.mjs

@@ -0,0 +1,38 @@
+import Piscina from 'piscina';
+import {
+  ReadableStream,
+  TransformStream,
+  WritableStream
+} from 'node:stream/web';
+
+const pool = new Piscina({
+  filename: new URL('./worker.mjs', import.meta.url).href
+});
+
+const readable = new ReadableStream({
+  start () {
+    this.chunks = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0];
+  },
+
+  pull (controller) {
+    const chunk = this.chunks.shift();
+    controller.enqueue(chunk);
+    if (this.chunks.length === 0) {
+      controller.close();
+    }
+  }
+});
+
+const writable = new WritableStream({
+  write (chunk) {
+    console.log(chunk);
+  }
+});
+
+const transform = new TransformStream({
+  async transform (chunk, controller) {
+    controller.enqueue(await pool.run(chunk));
+  }
+});
+
+readable.pipeThrough(transform).pipeTo(writable);

examples/webstreams-transform/worker.mjs

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+export default async function (num) {
+  return 'ABC'.repeat(num * num);
+}

examples/webstreams/index.mjs

@@ -0,0 +1,31 @@
+import Piscina from 'piscina';
+import {
+  ReadableStream,
+  WritableStream
+} from 'node:stream/web';
+
+const pool = new Piscina({
+  filename: new URL('./worker.mjs', import.meta.url).href
+});
+
+const readable = new ReadableStream({
+  start () {
+    this.chunks = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0];
+  },
+
+  pull (controller) {
+    const chunk = this.chunks.shift();
+    controller.enqueue(chunk);
+    if (this.chunks.length === 0) {
+      controller.close();
+    }
+  }
+});
+
+const writable = new WritableStream({
+  write (chunk) {
+    console.log(chunk);
+  }
+});
+
+await pool.run({ readable, writable }, { transferList: [readable, writable] });

examples/webstreams/worker.mjs

@@ -0,0 +1,7 @@
+export default async function ({ readable, writable }) {
+  const writer = writable.getWriter();
+  for await (const chunk of readable) {
+    await writer.write(chunk);
+  }
+  writer.close();
+}