util: make mime parsing faster

Signed-off-by: James M Snell <jasnell@gmail.com>
Assisted-by: Opencode

Author: jasnell

benchmark/mime/mimetype-parse.js

@@ -0,0 +1,53 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const { MIMEType } = require('util');
+
+const bench = common.createBenchmark(main, {
+  n: [1e5],
+  value: [
+    'application/json',
+    'text/html; charset=utf-8',
+    'multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW',
+    'text/plain; charset="utf-8"; foo="b\\"ar"; x=y',
+    'not a mime type',
+  ],
+  operation: ['parse', 'essence', 'params.get'],
+});
+
+function main({ n, value, operation }) {
+  const length = 1024;
+  const array = [];
+  let fn;
+  switch (operation) {
+    case 'parse':
+      fn = () => MIMEType.parse(value);
+      break;
+    case 'essence':
+      fn = () => MIMEType.parse(value)?.essence ?? null;
+      break;
+    case 'params.get':
+      fn = () => MIMEType.parse(value)?.params.get('charset') ?? null;
+      break;
+    default:
+      throw new Error(`Unsupported operation ${operation}`);
+  }
+
+  // Warm up.
+  for (let i = 0; i < length; ++i) {
+    array.push(fn());
+  }
+
+  bench.start();
+  for (let i = 0; i < n; ++i) {
+    array[i % length] = fn();
+  }
+  bench.end(n);
+
+  // Verify the entries to prevent dead code elimination from making
+  // the benchmark invalid.
+  for (let i = 0; i < length; ++i) {
+    assert.notStrictEqual(array[i], undefined);
+  }
+}