diff -r 000000000000 -r 6474c204b198 modules/libjar/zipwriter/src/StreamFunctions.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/modules/libjar/zipwriter/src/StreamFunctions.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,48 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include "nscore.h"
+#include "nsIInputStream.h"
+#include "nsIOutputStream.h"
+
+/*
+ * Fully reads the required amount of data. Keeps reading until all the
+ * data is retrieved or an error is hit.
+ */
+NS_HIDDEN_(nsresult) ZW_ReadData(nsIInputStream *aStream, char *aBuffer, uint32_t aCount)
+{
+    while (aCount > 0) {
+        uint32_t read;
+        nsresult rv = aStream->Read(aBuffer, aCount, &read);
+        NS_ENSURE_SUCCESS(rv, rv);
+        aCount -= read;
+        aBuffer += read;
+        // If we hit EOF before reading the data we need then throw.
+        if (read == 0 && aCount > 0)
+            return NS_ERROR_FAILURE;
+    }
+
+    return NS_OK;
+}
+
+/*
+ * Fully writes the required amount of data. Keeps writing until all the
+ * data is written or an error is hit.
+ */
+NS_HIDDEN_(nsresult) ZW_WriteData(nsIOutputStream *aStream, const char *aBuffer,
+                                  uint32_t aCount)
+{
+    while (aCount > 0) {
+        uint32_t written;
+        nsresult rv = aStream->Write(aBuffer, aCount, &written);
+        NS_ENSURE_SUCCESS(rv, rv);
+        if (written <= 0)
+            return NS_ERROR_FAILURE;
+        aCount -= written;
+        aBuffer += written;
+    }
+
+    return NS_OK;
+}