Rework decompression implementations to not be Workers, but instead communicate to the host via a MessagePort. This doesn't address issue #44 directly yet (still need a way to swap out port connection with a non-Web Worker).

archive/untar.js

@@ -10,9 +10,6 @@
  * TAR format: http://www.gnu.org/software/automake/manual/tar/Standard.html
  */
 
-// This file expects to be invoked as a Worker (see onmessage below).
-// TODO: Make this a plain ES Module and then write a thin wrapper around it for Worker-ization.
-//     This will allow us to write proper unit tests for it.
 import { ByteStream } from '../io/bytestream.js';
 
 const UnarchiveState = {
@@ -22,6 +19,9 @@ const UnarchiveState = {
   FINISHED: 3,
 };
 
+/** @type {MessagePort} */
+let hostPort;
+
 // State - consider putting these into a class.
 let unarchiveState = UnarchiveState.NOT_STARTED;
 let bytestream = null;
@@ -38,13 +38,13 @@ let totalFilesInArchive = 0;
 
 // Helper functions.
 const info = function (str) {
-  postMessage({ type: 'info', msg: str });
+  hostPort.postMessage({ type: 'info', msg: str });
 };
 const err = function (str) {
-  postMessage({ type: 'error', msg: str });
+  hostPort.postMessage({ type: 'error', msg: str });
 };
 const postProgress = function () {
-  postMessage({
+  hostPort.postMessage({
     type: 'progress',
     currentFilename,
     currentFileNumber,
@@ -156,7 +156,7 @@ const untar = function () {
       currentFileNumber = totalFilesInArchive++;
       currentBytesUnarchivedInFile = oneLocalFile.size;
       currentBytesUnarchived += oneLocalFile.size;
-      postMessage({ type: 'extract', unarchivedFile: oneLocalFile }, [oneLocalFile.fileData.buffer]);
+      hostPort.postMessage({ type: 'extract', unarchivedFile: oneLocalFile }, [oneLocalFile.fileData.buffer]);
       postProgress();
     }
   }
@@ -169,7 +169,7 @@ const untar = function () {
 
 // event.data.file has the first ArrayBuffer.
 // event.data.bytes has all subsequent ArrayBuffers.
-onmessage = function (event) {
+const onmessage = function (event) {
   const bytes = event.data.file || event.data.bytes;
   logToConsole = !!event.data.logToConsole;
 
@@ -189,7 +189,7 @@ onmessage = function (event) {
     totalFilesInArchive = 0;
     allLocalFiles = [];
 
-    postMessage({ type: 'start' });
+    hostPort.postMessage({ type: 'start' });
 
     unarchiveState = UnarchiveState.UNARCHIVING;
 
@@ -201,7 +201,7 @@ onmessage = function (event) {
     try {
       untar();
       unarchiveState = UnarchiveState.FINISHED;
-      postMessage({ type: 'finish', metadata: {} });
+      hostPort.postMessage({ type: 'finish', metadata: {} });
     } catch (e) {
       if (typeof e === 'string' && e.startsWith('Error!  Overflowed')) {
         // Overrun the buffer.
@@ -214,3 +214,15 @@ onmessage = function (event) {
     }
   }
 };
+
+/**
+ * Connect the host to the untar implementation with the given MessagePort.
+ * @param {MessagePort} port
+ */
+export function connect(port) {
+  if (hostPort) {
+    throw `hostPort already connected`;
+  }
+  hostPort = port;
+  port.onmessage = onmessage;
+}