Do not switch to a range request for small PDFs

src/core/pdf_manager.js

@@ -19,6 +19,9 @@
 
 'use strict';
 
+// The maximum number of bytes fetched per range request
+var RANGE_CHUNK_SIZE = 65536;
+
 // TODO(mack): Make use of PDFJS.Util.inherit() when it becomes available
 var BasePdfManager = (function BasePdfManagerClosure() {
   function BasePdfManager() {
@@ -132,9 +135,6 @@ var LocalPdfManager = (function LocalPdfManagerClosure() {
 })();
 
 var NetworkPdfManager = (function NetworkPdfManagerClosure() {
-
-  var CHUNK_SIZE = 65536;
-
   function NetworkPdfManager(args, msgHandler) {
 
     this.msgHandler = msgHandler;
@@ -147,7 +147,7 @@ var NetworkPdfManager = (function NetworkPdfManagerClosure() {
       disableAutoFetch: args.disableAutoFetch,
       initialData: args.initialData
     };
-    this.streamManager = new ChunkedStreamManager(args.length, CHUNK_SIZE,
+    this.streamManager = new ChunkedStreamManager(args.length, RANGE_CHUNK_SIZE,
                                                   args.url, params);
 
     this.pdfModel = new PDFDocument(this, this.streamManager.getStream(),

src/core/worker.js

@@ -18,7 +18,7 @@
            MissingPDFException, PasswordException, PDFJS, Promise,
            UnknownErrorException, NetworkManager, LocalPdfManager,
            NetworkPdfManager, XRefParseException, LegacyPromise,
-           isInt, PasswordResponses, MessageHandler, Ref */
+           isInt, PasswordResponses, MessageHandler, Ref, RANGE_CHUNK_SIZE */
 
 'use strict';
 
@@ -119,6 +119,13 @@ var WorkerMessageHandler = PDFJS.WorkerMessageHandler = {
           if (!isInt(length)) {
             return;
           }
+          source.length = length;
+          if (length <= 2 * RANGE_CHUNK_SIZE) {
+            // The file size is smaller than the size of two chunks, so it does
+            // not make any sense to abort the request and retry with a range
+            // request.
+            return;
+          }
 
           // NOTE: by cancelling the full request, and then issuing range
           // requests, there will be an issue for sites where you can only
@@ -126,7 +133,6 @@ var WorkerMessageHandler = PDFJS.WorkerMessageHandler = {
           // server should not be returning that it can support range requests.
           networkManager.abortRequest(fullRequestXhrId);
 
-          source.length = length;
           try {
             pdfManager = new NetworkPdfManager(source, handler);
             pdfManagerPromise.resolve(pdfManager);