feat: Deno.core.{encode,decode}; standalone UTF-8 encoding/decoding (#4349)

This commits add two new methods to "Deno.core" namespace: "encode" and "decode".

Those methods are bound in Rust to provide a) fast b) generally available of encoding and decoding UTF-8 strings. 

Both methods are now used in "cli/js/dispatch_json.ts".

1 files changed, 40 insertions, 0 deletions

diff --git a/core/encode_decode_test.js b/core/encode_decode_test.js
new file mode 100644
index 000000000..8a366dd66
--- /dev/null
+++ b/core/encode_decode_test.js
@@ -0,0 +1,40 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+function assertArrayEquals(a1, a2) {
+  if (a1.length !== a2.length) throw Error("assert");
+
+  for (const index in a1) {
+    if (a1[index] !== a2[index]) {
+      throw Error("assert");
+    }
+  }
+}
+
+function main() {
+  // prettier-ignore
+  const fixture1 = [
+    0xf0, 0x9d, 0x93, 0xbd,
+    0xf0, 0x9d, 0x93, 0xae,
+    0xf0, 0x9d, 0x94, 0x81,
+    0xf0, 0x9d, 0x93, 0xbd
+  ];
+  // prettier-ignore
+  const fixture2 = [ 
+    72, 101, 108, 108, 
+    111, 32, 239, 191, 
+    189, 239, 191, 189, 
+    32, 87, 111, 114, 
+    108, 100 
+  ];
+
+  assertArrayEquals(Array.from(Deno.core.encode("𝓽𝓮𝔁𝓽")), fixture1);
+  assertArrayEquals(
+    Array.from(Deno.core.encode("Hello \udc12\ud834 World")),
+    fixture2
+  );
+
+  assert(Deno.core.decode(new Uint8Array(fixture1)) === "𝓽𝓮𝔁𝓽");
+  assert(Deno.core.decode(new Uint8Array(fixture2)) === "Hello �� World");
+}
+
+main();