Move base64 conversions off of the main thread

js/util_worker_tasks.js

@@ -0,0 +1,44 @@
+/* global dcodeIO */
+/* eslint-disable strict */
+
+'use strict';
+
+const functions = {
+  stringToArrayBufferBase64,
+  arrayBufferToStringBase64,
+};
+
+onmessage = async e => {
+  const [jobId, fnName, ...args] = e.data;
+
+  try {
+    const fn = functions[fnName];
+    if (!fn) {
+      throw new Error(`Worker: job ${jobId} did not find function ${fnName}`);
+    }
+    const result = await fn(...args);
+    postMessage([jobId, null, result]);
+  } catch (error) {
+    const errorForDisplay = prepareErrorForPostMessage(error);
+    postMessage([jobId, errorForDisplay]);
+  }
+};
+
+function prepareErrorForPostMessage(error) {
+  if (!error) {
+    return null;
+  }
+
+  if (error.stack) {
+    return error.stack;
+  }
+
+  return error.message;
+}
+
+function stringToArrayBufferBase64(string) {
+  return dcodeIO.ByteBuffer.wrap(string, 'base64').toArrayBuffer();
+}
+function arrayBufferToStringBase64(arrayBuffer) {
+  return dcodeIO.ByteBuffer.wrap(arrayBuffer).toString('base64');
+}