From 33e3c76f21ca5ea6b2bbb91519824ae56d6184c3 Mon Sep 17 00:00:00 2001
From: Andrea Marchesini <amarchesini@mozilla.com>
Date: Fri, 5 May 2017 14:45:14 +0200
Subject: [PATCH] Bug 1360807 - FileReaderSync must work with sync inputStream
 - part 4 - Base64EncodeInputStream needs a sync inputStream, r=smaug

---
 dom/file/FileReader.cpp        |  6 ++---
 dom/workers/FileReaderSync.cpp | 41 +++++++++++++++++++++++++---------
 2 files changed, 34 insertions(+), 13 deletions(-)

diff --git a/dom/file/FileReader.cpp b/dom/file/FileReader.cpp
index e8e3fa4f66e4..27fd9b91e88e 100644
--- a/dom/file/FileReader.cpp
+++ b/dom/file/FileReader.cpp
@@ -645,10 +645,10 @@ FileReader::OnInputStreamReady(nsIAsyncInputStream* aStream)
 
   if (NS_SUCCEEDED(rv) && count) {
     rv = DoReadData(count);
-  }
 
-  if (NS_SUCCEEDED(rv)) {
-    rv = DoAsyncWait();
+    if (NS_SUCCEEDED(rv)) {
+      rv = DoAsyncWait();
+    }
   }
 
   if (NS_FAILED(rv) || !count) {
diff --git a/dom/workers/FileReaderSync.cpp b/dom/workers/FileReaderSync.cpp
index 9f9a008666d0..a8da4abd3ea9 100644
--- a/dom/workers/FileReaderSync.cpp
+++ b/dom/workers/FileReaderSync.cpp
@@ -21,6 +21,7 @@
 #include "nsIConverterInputStream.h"
 #include "nsIInputStream.h"
 #include "nsIMultiplexInputStream.h"
+#include "nsStreamUtils.h"
 #include "nsStringStream.h"
 #include "nsISupportsImpl.h"
 #include "nsNetUtil.h"
@@ -82,7 +83,12 @@ FileReaderSync::ReadAsArrayBuffer(JSContext* aCx,
   if (NS_WARN_IF(aRv.Failed())) {
     return;
   }
-  NS_ASSERTION(numRead == blobSize, "failed to read data");
+
+  // The file is changed in the meantime?
+  if (numRead != blobSize) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return;
+  }
 
   JSObject* arrayBuffer = JS_NewArrayBufferWithContents(aCx, blobSize, bufferData.get());
   if (!arrayBuffer) {
@@ -150,6 +156,12 @@ FileReaderSync::ReadAsText(Blob& aBlob,
     return;
   }
 
+  // No data, we don't need to continue.
+  if (numRead == 0) {
+    aResult.Truncate();
+    return;
+  }
+
   // The BOM sniffing is baked into the "decode" part of the Encoding
   // Standard, which the File API references.
   if (!nsContentUtils::CheckForBOM((const unsigned char*)sniffBuf.BeginReading(),
@@ -244,19 +256,30 @@ FileReaderSync::ReadAsDataURL(Blob& aBlob, nsAString& aResult,
     return;
   }
 
-  uint64_t size = aBlob.GetSize(aRv);
+  nsCOMPtr<nsIInputStream> syncStream;
+  aRv = ConvertAsyncToSyncStream(stream, getter_AddRefs(syncStream));
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  uint64_t size;
+  aRv = syncStream->Available(&size);
+  if (NS_WARN_IF(aRv.Failed())) {
+    return;
+  }
+
+  uint64_t blobSize = aBlob.GetSize(aRv);
   if (NS_WARN_IF(aRv.Failed())){
     return;
   }
 
-  nsCOMPtr<nsIInputStream> bufferedStream;
-  aRv = NS_NewBufferedInputStream(getter_AddRefs(bufferedStream), stream, size);
-  if (NS_WARN_IF(aRv.Failed())){
+  // The file is changed in the meantime?
+  if (blobSize != size) {
     return;
   }
 
   nsAutoString encodedData;
-  aRv = Base64EncodeInputStream(bufferedStream, encodedData, size);
+  aRv = Base64EncodeInputStream(syncStream, encodedData, size);
   if (NS_WARN_IF(aRv.Failed())){
     return;
   }
@@ -445,12 +468,10 @@ nsresult
 FileReaderSync::ConvertAsyncToSyncStream(nsIInputStream* aAsyncStream,
                                          nsIInputStream** aSyncStream)
 {
-  // If the stream is not async, we have nothing to do here.
+  // If the stream is not async, we just need it to be bufferable.
   nsCOMPtr<nsIAsyncInputStream> asyncStream = do_QueryInterface(aAsyncStream);
   if (!asyncStream) {
-    nsCOMPtr<nsIInputStream> stream = aAsyncStream;
-    stream.forget(aSyncStream);
-    return NS_OK;
+    return NS_NewBufferedInputStream(aSyncStream, aAsyncStream, 4096);
   }
 
   uint64_t length;