awful.util: add table.keys

Signed-off-by: Gregor Best <farhaven@googlemail.com>
Signed-off-by: Julien Danjou <julien@danjou.info>

lib/awful/util.lua.in

@@ -12,6 +12,8 @@ local loadstring = loadstring
 local loadfile = loadfile
 local debug = debug
 local print = print
+local pairs = pairs
+local ipairs = ipairs
 local type = type
 local rtable = table
 local pairs = pairs
@@ -282,4 +284,18 @@ function linewrap(text, width, indent)
         end)
 end
 
+--- Get a sorted table with all integer keys from a table
+-- @param t the table for which the keys to get
+-- @return A table with keys
+function table.keys(t)
+    local keys = { }
+    for k, _ in pairs(t) do
+        rtable.insert(keys, k)
+    end
+    rtable.sort(keys, function (a, b)
+        return type(a) == type(b) and a < b or false
+    end)
+    return keys
+end
+
 -- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=80