perf: add performance test for TextEncoder.encodeInto

cli/bench/main.rs

@@ -89,6 +89,11 @@ const EXEC_TIME_BENCHMARKS: &[(&str, &[&str], Option<i32>)] = &[
     &["run", "cli/tests/text_encoder_perf.js"],
     None,
   ),
+  (
+    "text_encoder_into",
+    &["run", "cli/tests/text_encoder_into_perf.js"],
+    None,
+  ),
   (
     "check",
     &[

cli/tests/text_encoder_into_perf.js

@@ -0,0 +1,34 @@
+const mixed = "@Ā๐😀";
+
+function generateRandom(bytes) {
+  let result = "";
+  let i = 0;
+  while (i < bytes) {
+    const toAdd = Math.floor(Math.random() * Math.min(4, bytes - i));
+    switch (toAdd) {
+      case 0:
+        result += mixed[0];
+        i++;
+        break;
+      case 1:
+        result += mixed[1];
+        i++;
+        break;
+      case 2:
+        result += mixed[2];
+        i++;
+        break;
+      case 3:
+        result += mixed[3];
+        result += mixed[4];
+        i += 2;
+        break;
+    }
+  }
+  return result;
+}
+
+const randomData = generateRandom(1024);
+const encoder = new TextEncoder();
+const targetBuffer = new Uint8Array(randomData.length * 4);
+for (let i = 0; i < 10_000; i++) encoder.encodeInto(randomData, targetBuffer);