perf(ext/fetch): consume body using ops (#16038)

This commit adds a fast path to `Request` and `Response` that
make consuming request bodies much faster when using `Body#text`,
`Body#arrayBuffer`, and `Body#blob`, if the body is a FastStream.
Because the response bodies for `fetch` are FastStream, this speeds up
consuming `fetch` response bodies significantly.

1 files changed, 16 insertions, 0 deletions

diff --git a/cli/tests/unit/fetch_test.ts b/cli/tests/unit/fetch_test.ts
index 36c1926f2..e2ff0d5e0 100644
--- a/cli/tests/unit/fetch_test.ts
+++ b/cli/tests/unit/fetch_test.ts
@@ -1789,3 +1789,19 @@ Deno.test(
     assertEquals(await res.text(), "ok");
   },
 );
+
+Deno.test(
+  { permissions: { net: true } },
+  async function fetchResponseStreamIsLockedWhileReading() {
+    const response = await fetch("http://localhost:4545/echo_server", {
+      body: new Uint8Array(5000),
+      method: "POST",
+    });
+
+    assertEquals(response.body!.locked, false);
+    const promise = response.arrayBuffer();
+    assertEquals(response.body!.locked, true);
+
+    await promise;
+  },
+);