1 files changed, 39 insertions, 0 deletions
diff --git a/xpcom/io/nsISafeOutputStream.idl b/xpcom/io/nsISafeOutputStream.idl
new file mode 100644
index 000000000..c62d85f07
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+++ b/xpcom/io/nsISafeOutputStream.idl
@@ -0,0 +1,39 @@
+/* -*- Mode: C++; tab-width: 2; 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/. */
+
+#include "nsISupports.idl"
+
+/**
+ * This interface provides a mechanism to control an output stream
+ * that takes care not to overwrite an existing target until it is known
+ * that all writes to the destination succeeded.
+ * 
+ * An object that supports this interface is intended to also support
+ * nsIOutputStream.
+ *
+ * For example, a file output stream that supports this interface writes to
+ * a temporary file, and moves it over the original file when |finish| is
+ * called only if the stream can be successfully closed and all writes
+ * succeeded.  If |finish| is called but something went wrong during
+ * writing, it will delete the temporary file and not touch the original.
+ * If the stream is closed by calling |close| directly, or the stream
+ * goes away, the original file will not be overwritten, and the temporary
+ * file will be deleted.
+ *
+ * Currently, this interface is implemented only for file output streams.
+ */
+[scriptable, uuid(5f914307-5c34-4e1f-8e32-ec749d25b27a)]
+interface nsISafeOutputStream : nsISupports
+{
+    /**
+     * Call this method to close the stream and cause the original target
+     * to be overwritten. Note: if any call to |write| failed to write out
+     * all of the data given to it, then calling this method will |close| the
+     * stream and return failure. Further, if closing the stream fails, this
+     * method will return failure. The original target will be overwritten only
+     * if all calls to |write| succeeded and the stream was successfully closed.
+     */
+    void finish();
+};