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|
-- atomic.lua
-- Utilities for transaction-like handling of serialized state files
-- Also for multiple files that must be synchronous, as advtrains currently requires.
-- Managing files and backups
-- ==========================
--[[
The plain scheme just overwrites the file in place. This however poses problems when we are interrupted right within
the write, so we have incomplete data. So, the following scheme is applied:
Unix:
1. writes to <filename>.new
2. moves <filename>.new to <filename>, clobbering previous file
Windows:
1. writes to <filename>.new
2. delete <filename>
3. moves <filename>.new to <filename>
We count a new version of the state as "committed" after stage 2.
During loading, we apply the following order of precedence:
1. <filename>
2. <filename>.new (windows only, in case we were interrupted just before 3. when saving)
All of these functions return either true on success or nil, error on error.
]]--
local ser = serialize_lib.serialize
local windows_mode = false
-- == local functions ==
local function save_atomic_move_file(filename)
--2. if windows mode, delete main file
if windows_mode then
local delsucc, err = os.remove(filename)
if not delsucc then
serialize_lib.log_error("Unable to delete old savefile '"..filename.."':")
serialize_lib.log_error(err)
return nil, err
end
end
--3. move file
local mvsucc, err = os.rename(filename..".new", filename)
if not mvsucc then
if minetest.settings:get_bool("serialize_lib_no_auto_windows_mode") or windows_mode then
serialize_lib.log_error("Unable to move '"..filename.."':")
serialize_lib.log_error(err)
return nil, err
else
-- enable windows mode and try again
serialize_lib.log_info("Enabling Windows mode for atomic saving...")
windows_mode = true
return save_atomic_move_file(filename)
end
end
return true
end
local function open_file_and_save_callback(callback, filename)
|
