diff -r 000000000000 -r 6474c204b198 xpcom/build/Omnijar.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/build/Omnijar.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,131 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * 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/. */
+
+#ifndef mozilla_Omnijar_h
+#define mozilla_Omnijar_h
+
+#include "nscore.h"
+#include "nsCOMPtr.h"
+#include "nsString.h"
+#include "nsIFile.h"
+#include "nsZipArchive.h"
+
+class nsIURI;
+
+namespace mozilla {
+
+class Omnijar {
+private:
+/**
+ * Store an nsIFile for an omni.jar. We can store two paths here, one
+ * for GRE (corresponding to resource://gre/) and one for APP
+ * (corresponding to resource:/// and resource://app/), but only
+ * store one when both point to the same location (unified).
+ */
+static nsIFile *sPath[2];
+
+/**
+ * Cached nsZipArchives for the corresponding sPath
+ */
+static nsZipArchive *sReader[2];
+
+/**
+ * Has Omnijar::Init() been called?
+ */
+static bool sInitialized;
+
+public:
+enum Type {
+    GRE = 0,
+    APP = 1
+};
+
+/**
+ * Returns whether SetBase has been called at least once with
+ * a valid nsIFile
+ */
+static inline bool
+IsInitialized()
+{
+    return sInitialized;
+}
+
+/**
+ * Initializes the Omnijar API with the given directory or file for GRE and
+ * APP. Each of the paths given can be:
+ * - a file path, pointing to the omnijar file,
+ * - a directory path, pointing to a directory containing an "omni.jar" file,
+ * - nullptr for autodetection of an "omni.jar" file.
+ */
+static void Init(nsIFile *aGrePath = nullptr, nsIFile *aAppPath = nullptr);
+
+/**
+ * Cleans up the Omnijar API
+ */
+static void CleanUp();
+
+/**
+ * Returns an nsIFile pointing to the omni.jar file for GRE or APP.
+ * Returns nullptr when there is no corresponding omni.jar.
+ * Also returns nullptr for APP in the unified case.
+ */
+static inline already_AddRefed<nsIFile>
+GetPath(Type aType)
+{
+    NS_ABORT_IF_FALSE(IsInitialized(), "Omnijar not initialized");
+    nsCOMPtr<nsIFile> path = sPath[aType];
+    return path.forget();
+}
+
+/**
+ * Returns whether GRE or APP use an omni.jar. Returns PR_False for
+ * APP when using an omni.jar in the unified case.
+ */
+static inline bool
+HasOmnijar(Type aType)
+{
+    NS_ABORT_IF_FALSE(IsInitialized(), "Omnijar not initialized");
+    return !!sPath[aType];
+}
+
+/**
+ * Returns a nsZipArchive pointer for the omni.jar file for GRE or
+ * APP. Returns nullptr in the same cases GetPath() would.
+ */
+static inline already_AddRefed<nsZipArchive>
+GetReader(Type aType)
+{
+    NS_ABORT_IF_FALSE(IsInitialized(), "Omnijar not initialized");
+    nsRefPtr<nsZipArchive> reader = sReader[aType];
+    return reader.forget();
+}
+
+/**
+ * Returns a nsZipArchive pointer for the given path IAOI the given
+ * path is the omni.jar for either GRE or APP.
+ */
+static already_AddRefed<nsZipArchive> GetReader(nsIFile *aPath);
+
+/**
+ * Returns the URI string corresponding to the omni.jar or directory
+ * for GRE or APP. i.e. jar:/path/to/omni.jar!/ for omni.jar and
+ * /path/to/base/dir/ otherwise. Returns an empty string for APP in
+ * the unified case.
+ * The returned URI is guaranteed to end with a slash.
+ */
+static nsresult GetURIString(Type aType, nsACString &result);
+
+private:
+/**
+ * Used internally, respectively by Init() and CleanUp()
+ */
+static void InitOne(nsIFile *aPath, Type aType);
+static void CleanUpOne(Type aType);
+
+}; /* class Omnijar */
+
+} /* namespace mozilla */
+
+#endif /* mozilla_Omnijar_h */