feat(std/encoding): add base64 (#5811)

std/encoding/base64.ts

@@ -0,0 +1,41 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+/**
+ * Converts given data with base64 encoding
+ * @param data input to encode
+ */
+export function encode(data: string | ArrayBuffer): string {
+  if (typeof data === "string") {
+    return window.btoa(data);
+  } else {
+    const d = new Uint8Array(data);
+    let dataString = "";
+    for (let i = 0; i < d.length; ++i) {
+      dataString += String.fromCharCode(d[i]);
+    }
+
+    return window.btoa(dataString);
+  }
+}
+
+/**
+ * Converts given base64 encoded data back to original
+ * @param data input to decode
+ */
+export function decode(data: string): ArrayBuffer {
+  const binaryString = decodeString(data);
+  const binary = new Uint8Array(binaryString.length);
+  for (let i = 0; i < binary.length; ++i) {
+    binary[i] = binaryString.charCodeAt(i);
+  }
+
+  return binary.buffer;
+}
+
+/**
+ * Decodes data assuming the output is in string type
+ * @param data input to decode
+ */
+export function decodeString(data: string): string {
+  return window.atob(data);
+}

std/encoding/base64_test.ts

@@ -0,0 +1,47 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+const { test } = Deno;
+import { assertEquals } from "../testing/asserts.ts";
+import { encode, decode, decodeString } from "./base64.ts";
+
+const testsetString = [
+  ["", ""],
+  ["f", "Zg=="],
+  ["fo", "Zm8="],
+  ["foo", "Zm9v"],
+  ["foob", "Zm9vYg=="],
+  ["fooba", "Zm9vYmE="],
+  ["foobar", "Zm9vYmFy"],
+];
+
+const testsetBinary = [
+  [new TextEncoder().encode("\x00"), "AA=="],
+  [new TextEncoder().encode("\x00\x00"), "AAA="],
+  [new TextEncoder().encode("\x00\x00\x00"), "AAAA"],
+  [new TextEncoder().encode("\x00\x00\x00\x00"), "AAAAAA=="],
+];
+
+test("[encoding/base64] testBase64EncodeString", () => {
+  for (const [input, output] of testsetString) {
+    assertEquals(encode(input), output);
+  }
+});
+
+test("[encoding/base64] testBase64DecodeString", () => {
+  for (const [input, output] of testsetString) {
+    assertEquals(decodeString(output), input);
+  }
+});
+
+test("[encoding/base64] testBase64EncodeBinary", () => {
+  for (const [input, output] of testsetBinary) {
+    assertEquals(encode(input), output);
+  }
+});
+
+test("[encoding/base64] testBase64DecodeBinary", () => {
+  for (const [input, output] of testsetBinary) {
+    const outputBinary = new Uint8Array(decode(output as string));
+    assertEquals(outputBinary, input as Uint8Array);
+  }
+});