benchmark: fix text-decoder benchmark

PR-URL: #45363
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>

benchmark/util/text-decoder.js

@@ -0,0 +1,21 @@
+'use strict';
+
+const common = require('../common.js');
+
+const bench = common.createBenchmark(main, {
+  encoding: ['utf-8', 'latin1', 'iso-8859-3'],
+  ignoreBOM: [0, 1],
+  len: [256, 1024 * 16, 1024 * 512],
+  n: [1e6]
+});
+
+function main({ encoding, len, n, ignoreBOM }) {
+  const buf = Buffer.allocUnsafe(len);
+  const decoder = new TextDecoder(encoding, { ignoreBOM });
+
+  bench.start();
+  for (let i = 0; i < n; i++) {
+    decoder.decode(buf);
+  }
+  bench.end(n);
+}