stream: simpler and faster Readable async iterator

Reimplement as an async generator instead of a custom
iterator class.

PR-URL: https://github.com/nodejs/node/pull/34035
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 42 insertions, 0 deletions

diff --git a/benchmark/streams/readable-async-iterator.js b/benchmark/streams/readable-async-iterator.js
new file mode 100644
index 00000000000..0455f67195f
--- /dev/null
+++ b/benchmark/streams/readable-async-iterator.js
@@ -0,0 +1,42 @@
+'use strict';
+
+const common = require('../common');
+const Readable = require('stream').Readable;
+
+const bench = common.createBenchmark(main, {
+  n: [1e5],
+  sync: ['yes', 'no'],
+});
+
+async function main({ n, sync }) {
+  sync = sync === 'yes';
+
+  const s = new Readable({
+    objectMode: true,
+    read() {
+      if (sync) {
+        this.push(1);
+      } else {
+        process.nextTick(() => {
+          this.push(1);
+        });
+      }
+    }
+  });
+
+  bench.start();
+
+  let x = 0;
+  for await (const chunk of s) {
+    x += chunk;
+    if (x > n) {
+      break;
+    }
+  }
+
+  // Side effect to ensure V8 does not optimize away the
+  // loop as a noop.
+  console.log(x);
+
+  bench.end(n);
+}