perf(ext/node): improve Buffer.from(buffer) (#24352)

Benchmark code from #24341. ```shellsession $ deno run --allow-hrtime bench.mjs 6479.111583 $ target/release/deno run --allow-hrtime bench.mjs 962.753875 $ node bench.mjs 855.174875 ```
denoland · Jun 26, 2024 · 86e0292 · 86e0292
1 parent 77ba001
commit 86e0292
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Showing 2 changed files with 11 additions and 10 deletions.
diff --git a/ext/node/polyfills/internal/buffer.mjs b/ext/node/polyfills/internal/buffer.mjs
@@ -220,12 220,9 @@ function fromString(string, encoding) {
  return buf;
 }
 
-function fromArrayLike(array) {
- const length = array.length < 0 ? 0 : checked(array.length) | 0;
- const buf = createBuffer(length);
- for (let i = 0; i < length; i  = 1) {
- buf[i] = array[i] & 255;
- }
 function fromArrayLike(obj) {
  const buf = new Uint8Array(obj);
  Object.setPrototypeOf(buf, Buffer.prototype);
  return buf;
 }
 
@@ -234,6 231,7 @@ function fromObject(obj) {
  if (typeof obj.length !== "number") {
  return createBuffer(0);
  }
 
  return fromArrayLike(obj);
  }
 

diff --git a/tests/unit_node/buffer_test.ts b/tests/unit_node/buffer_test.ts
@@ -534,15 534,18 @@ Deno.test({
 });
 
 Deno.test({
- name: "[node/buffer] Buffer from another buffer creates a Buffer",
  name: "[node/buffer] Buffer from another buffer creates a copy",
  fn() {
- const buffer: Buffer = Buffer.from(Buffer.from("test"));
- assertEquals(buffer.length, 4, "Buffer length should be 4");
  const buffer1: Buffer = Buffer.from("test");
  const buffer2: Buffer = Buffer.from(buffer1);
  assertEquals(buffer2.length, 4, "Buffer length should be 4");
  assertEquals(
- buffer.toString(),
  buffer2.toString(),
  "test",
  "Buffer to string should recover the string",
  );
  buffer1[0] = 114;
  assertEquals(buffer2.toString(), "test", "Buffer should be a copy");
  },
 });