diff -r 000000000000 -r 6474c204b198 xpcom/base/nsIGZFileWriter.idl
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/base/nsIGZFileWriter.idl	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,74 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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 "nsISupports.idl"
+
+%{C++
+#include "nsDependentString.h"
+%}
+
+interface nsIFile;
+
+/**
+ * A simple interface for writing to a .gz file.
+ *
+ * Note that the file that this interface produces has a different format than
+ * what you'd get if you compressed your data as a gzip stream and dumped the
+ * result to a file.
+ *
+ * The standard gunzip tool cannot decompress a raw gzip stream, but can handle
+ * the files produced by this interface.
+ */
+[scriptable, uuid(a256f26a-c603-459e-b5a4-53b4877f2cd8)]
+interface nsIGZFileWriter : nsISupports
+{
+  /**
+   * Initialize this object.  We'll write our gzip'ed data to the given file,
+   * overwriting its contents if the file exists.
+   *
+   * init() will return an error if called twice.  It's an error to call any
+   * other method on this interface without first calling init().
+   */
+  void init(in nsIFile file);
+
+  /**
+   * Write the given string to the file.
+   */
+  void write(in AUTF8String str);
+
+  /*
+   * The following two overloads of Write() are C++ because we can't overload
+   * methods in XPIDL.  Anyway, they don't add much functionality for JS
+   * callers.
+   */
+  %{C++
+  /**
+   * Write the given char* to the file (not including the null-terminator).
+   */
+  nsresult Write(const char* str)
+  {
+    return Write(str, strlen(str));
+  }
+
+  /**
+   * Write |length| bytes of |str| to the file.
+   */
+  nsresult Write(const char* str, uint32_t len)
+  {
+    return Write(nsDependentCString(str, len));
+  }
+  %}
+
+  /**
+   * Close this nsIGZFileWriter.  Classes implementing nsIGZFileWriter will run
+   * this method when the underlying object is destroyed, so it's not strictly
+   * necessary to explicitly call it from your code.
+   *
+   * It's an error to call this method twice, and it's an error to call write()
+   * after finish() has been called.
+   */
+  void finish();
+};