perf: Optimize TextEncoder and TextDecoder (#4430)

* add tests for "Deno.core.encode" and "Deno.core.decode" for empty inputs
* use "Deno.core.encode" in "TextEncoder"
* use "Deno.core.decode" in "TextDecoder"
* remove "core_decode" and "core_encode" benchmarks

2 files changed, 20 insertions, 1 deletions

diff --git a/core/bindings.rs b/core/bindings.rs
index 3745abf69..88bdf7f30 100644
--- a/core/bindings.rs
+++ b/core/bindings.rs
@@ -632,7 +632,20 @@ fn encode(
   };
   let text_str = text.to_rust_string_lossy(scope);
   let text_bytes = text_str.as_bytes().to_vec().into_boxed_slice();
-  let buf = boxed_slice_to_uint8array(scope, text_bytes);
+
+  let buf = if text_bytes.is_empty() {
+    let ab = v8::ArrayBuffer::new(scope, 0);
+    v8::Uint8Array::new(ab, 0, 0).expect("Failed to create UintArray8")
+  } else {
+    let buf_len = text_bytes.len();
+    let backing_store =
+      v8::ArrayBuffer::new_backing_store_from_boxed_slice(text_bytes);
+    let mut backing_store_shared = backing_store.make_shared();
+    let ab =
+      v8::ArrayBuffer::with_backing_store(scope, &mut backing_store_shared);
+    v8::Uint8Array::new(ab, 0, buf_len).expect("Failed to create UintArray8")
+  };
+
   rv.set(buf.into())
 }
 
diff --git a/core/encode_decode_test.js b/core/encode_decode_test.js
index 8a366dd66..294144593 100644
--- a/core/encode_decode_test.js
+++ b/core/encode_decode_test.js
@@ -27,12 +27,18 @@ function main() {
     108, 100 
   ];
 
+  const empty = Deno.core.encode("");
+  if (empty.length !== 0) throw new Error("assert");
+
   assertArrayEquals(Array.from(Deno.core.encode("𝓽𝓮𝔁𝓽")), fixture1);
   assertArrayEquals(
     Array.from(Deno.core.encode("Hello \udc12\ud834 World")),
     fixture2
   );
 
+  const emptyBuf = Deno.core.decode(new Uint8Array(0));
+  if (emptyBuf !== "") throw new Error("assert");
+
   assert(Deno.core.decode(new Uint8Array(fixture1)) === "𝓽𝓮𝔁𝓽");
   assert(Deno.core.decode(new Uint8Array(fixture2)) === "Hello �� World");
 }