From c250f7cf2d8bb7a35772033db3d2aa07d6fd3c82 Mon Sep 17 00:00:00 2001
From: Carl Hetherington <cth@carlh.net>
Date: Mon, 26 Feb 2018 13:14:31 +0000
Subject: [PATCH 1/1] Make a backup of configuration when we load in a Version
 2 file, and bump our config file version to 3.

---
 src/lib/config.cc | 37 +++++++++++++++++++++++--------------
 src/lib/config.h  |  3 +++
 2 files changed, 26 insertions(+), 14 deletions(-)

diff --git a/src/lib/config.cc b/src/lib/config.cc
index 503ca9c5f..ec5b05afa 100644
--- a/src/lib/config.cc
+++ b/src/lib/config.cc
@@ -64,6 +64,7 @@ using boost::algorithm::trim;
 using dcp::raw_convert;
 
 Config* Config::_instance = 0;
+int const Config::_current_version = 3;
 boost::signals2::signal<void ()> Config::FailedToLoad;
 boost::signals2::signal<void (string)> Config::Warning;
 boost::optional<boost::filesystem::path> Config::test_path;
@@ -180,6 +181,21 @@ Config::create_certificate_chain ()
 		);
 }
 
+void
+Config::backup ()
+{
+	/* Make a copy of the configuration */
+	try {
+		int n = 1;
+		while (n < 100 && boost::filesystem::exists(path(String::compose("config.xml.%1", n)))) {
+			++n;
+		}
+
+		boost::filesystem::copy_file(path("config.xml", false), path(String::compose("config.xml.%1", n), false));
+		boost::filesystem::copy_file(path("cinemas.xml", false), path(String::compose("cinemas.xml.%1", n), false));
+	} catch (...) {}
+}
+
 void
 Config::read ()
 try
@@ -188,6 +204,10 @@ try
 	f.read_file (config_file ());
 
 	optional<int> version = f.optional_number_child<int> ("Version");
+	if (version && *version < _current_version) {
+		/* Back up the old config before we re-write it in a back-incompatible way */
+		backup ();
+	}
 
 	if (f.optional_number_child<int>("NumLocalEncodingThreads")) {
 		_master_encoding_threads = _server_encoding_threads = f.optional_number_child<int>("NumLocalEncodingThreads").get();
@@ -400,18 +420,7 @@ try
 }
 catch (...) {
 	if (have_existing ("config.xml")) {
-
-		/* Make a copy of the configuration */
-		try {
-			int n = 1;
-			while (n < 100 && boost::filesystem::exists(path(String::compose("config.xml.%1", n)))) {
-				++n;
-			}
-
-			boost::filesystem::copy_file(path("config.xml", false), path(String::compose("config.xml.%1", n), false));
-			boost::filesystem::copy_file(path("cinemas.xml", false), path(String::compose("cinemas.xml.%1", n), false));
-		} catch (...) {}
-
+		backup ();
 		/* We have a config file but it didn't load */
 		FailedToLoad ();
 	}
@@ -476,8 +485,8 @@ Config::write_config () const
 	xmlpp::Document doc;
 	xmlpp::Element* root = doc.create_root_node ("Config");
 
-	/* [XML] Version The version number of the configuration file format; currently 2. */
-	root->add_child("Version")->add_child_text ("2");
+	/* [XML] Version The version number of the configuration file format */
+	root->add_child("Version")->add_child_text (String::compose ("%1", _current_version));
 	/* [XML] MasterEncodingThreads Number of encoding threads to use when running as master. */
 	root->add_child("MasterEncodingThreads")->add_child_text (raw_convert<string> (_master_encoding_threads));
 	/* [XML] ServerEncodingThreads Number of encoding threads to use when running as server. */
diff --git a/src/lib/config.h b/src/lib/config.h
index d50e585e3..90ebb0b33 100644
--- a/src/lib/config.h
+++ b/src/lib/config.h
@@ -729,6 +729,7 @@ private:
 	boost::shared_ptr<dcp::CertificateChain> create_certificate_chain ();
 	boost::filesystem::path directory_or (boost::optional<boost::filesystem::path> dir, boost::filesystem::path a) const;
 	void add_to_history_internal (std::vector<boost::filesystem::path>& h, boost::filesystem::path p);
+	void backup ();
 
 	template <class T>
 	void maybe_set (T& member, T new_value, Property prop = OTHER) {
@@ -844,6 +845,8 @@ private:
 	int _frames_in_memory_multiplier;
 	boost::optional<int> _decode_reduction;
 
+	static int const _current_version;
+
 	/** Singleton instance, or 0 */
 	static Config* _instance;
 };
-- 
2.30.2