1 files changed, 34 insertions, 0 deletions
diff --git a/lib/dtas/state_file.rb b/lib/dtas/state_file.rb
new file mode 100644
index 0000000..cfd83d5
--- /dev/null
+++ b/lib/dtas/state_file.rb
@@ -0,0 +1,34 @@
+# -*- encoding: binary -*-
+# :stopdoc:
+# Copyright (C) 2013, Eric Wong <normalperson@yhbt.net>
+# License: GPLv3 or later (https://www.gnu.org/licenses/gpl-3.0.txt)
+require 'yaml'
+require 'tempfile'
+class DTAS::StateFile
+  def initialize(path, do_fsync = false)
+    @path = path
+    @do_fsync = do_fsync
+  end
+
+  def tryload
+    YAML.load(IO.binread(@path)) if File.readable?(@path)
+  end
+
+  def dump(obj, force_fsync = false)
+    yaml = obj.to_hsh.to_yaml.b
+
+    # do not replace existing state file if there are no changes
+    # this will be racy if we ever do async dumps or shared state
+    # files, but we don't do that...
+    return if File.readable?(@path) && IO.binread(@path) == yaml
+
+    dir = File.dirname(@path)
+    Tempfile.open(%w(player.state .tmp), dir) do |tmp|
+      tmp.binmode
+      tmp.write(yaml)
+      tmp.flush
+      tmp.fsync if @do_fsync || force_fsync
+      File.rename(tmp.path, @path)
+    end
+  end
+end