factored out settings into own class

also started using OO paradigm

settings.lua

@@ -0,0 +1,38 @@
+DocSettings = {}
+DocSettings_mt = { __index = DocSettings }
+
+function DocSettings:open(docfile)
+	local new = {}
+	new.docdb, errno, errstr = sqlite3.open(docfile..".kpdfview")
+	if new.docdb ~= nil then
+		new.docdb:exec("CREATE TABLE IF NOT EXISTS settings (key TEXT PRIMARY KEY, value TEXT);")
+		new.stmt_readsetting = new.docdb:prepare("SELECT value FROM settings WHERE key = ?;")
+		new.stmt_savesetting = new.docdb:prepare("INSERT OR REPLACE INTO settings (key, value) VALUES (?, ?);")
+	end
+	return setmetatable(new, DocSettings_mt)
+end
+
+function DocSettings:readsetting(key)
+	if self.docdb ~= nil then
+		self.stmt_readsetting:reset()
+		self.stmt_readsetting:bind_values(key)
+		local result = self.stmt_readsetting:step()
+		if result == sqlite3.ROW then
+			return self.stmt_readsetting:get_value(0)
+		end
+	end
+end
+
+function DocSettings:savesetting(key, value)
+	if self.docdb ~= nil then
+		self.stmt_savesetting:reset()
+		self.stmt_savesetting:bind_values(key, value)
+		self.stmt_savesetting:step()
+	end
+end
+
+function DocSettings:close()
+	if self.docdb ~= nil then
+		self.docdb:close()
+	end
+end