do ert in lua

scripts/ert.lua

@@ -0,0 +1,66 @@
+_Ert_state = 0
+_Ert_oda_id = nil
+
+local function init_ert()
+    if _Ert_oda_id == nil then
+        _Ert_oda_id = register_oda(12, false, 0x6552, 1)
+        set_oda_handler(_Ert_oda_id, function ()
+            if string.byte(get_userdata_offset(257, 1)) == 1 then
+                local new_data = get_userdata_offset(0, 128)
+                local new_segments = string.byte(get_userdata_offset(128, 1))
+                set_userdata_offset(129, 128, new_data)
+                set_userdata_offset(257, 1, string.char(new_segments))
+                set_userdata_offset(258, 1, string.char(0))
+                _Ert_state = 0
+            end
+
+            local segments = string.byte(get_userdata_offset(257, 1))
+            if segments == 0 then segments = 1 end
+
+            local b = _Ert_state & 31
+            local chunk = get_userdata_offset(129 + _Ert_state * 4, 4)
+            local c = (string.byte(chunk, 1) << 8) | string.byte(chunk, 2)
+            local d = (string.byte(chunk, 3) << 8) | string.byte(chunk, 4)
+
+            _Ert_state = (_Ert_state + 1) % segments
+            return b, c, d
+        end)
+    end
+end
+
+function set_rds_ert(ert)
+    if #ert == 0 then
+        set_userdata_offset(128, 1, string.char(0))
+        set_userdata_offset(258, 1, string.char(1))
+        return
+    end
+
+    local data = ert .. "\r"
+    data = string.sub(data, 1, 128)
+
+    local padding = (4 - (#data % 4)) % 4
+    data = data .. string.rep("\0", padding)
+
+    set_userdata_offset(0, 128, data)
+
+    local segments = #data // 4
+    if segments > 32 then segments = 32 end
+
+    if string.byte(get_userdata_offset(257, 1)) == 0 then
+        init_ert()
+        set_userdata_offset(129, 128, data)
+        set_userdata_offset(257, 1, string.char(segments))
+    else set_userdata_offset(258, 1, string.char(1)) end
+
+    set_userdata_offset(128, 1, string.char(segments))
+end
+
+function get_rds_ert()
+    local data = get_userdata_offset(0, 128)
+    if string.byte(get_userdata_offset(128, 1)) == 0 then return "" end
+    return data:match("^(.-)[\r%z]*") or ""
+end
+
+function on_state()
+    if string.byte(get_userdata_offset(257, 1)) ~= 0 then init_ert() end
+end