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Diffstat (limited to 'serialize_lib/atomic.lua')
| -rw-r--r-- | serialize_lib/atomic.lua | 217 |
1 files changed, 0 insertions, 217 deletions
diff --git a/serialize_lib/atomic.lua b/serialize_lib/atomic.lua deleted file mode 100644 index 182cf42..0000000 --- a/serialize_lib/atomic.lua +++ /dev/null @@ -1,217 +0,0 @@ --- 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_warn("Unable to delete old savefile '"..filename.."':") - serialize_lib.log_warn(err) - serialize_lib.log_info("Trying to replace the save file anyway now...") - 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 replace save file '"..filename.."':") - serialize_lib.log_error(err) - return nil, err - else - -- enable windows mode and try again - serialize_lib.log_info("Unable to replace save file '"..filename.."' by direct renaming:") - serialize_lib.log_info(err) - 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) - local file, err = io.open(filename, "w") - if not file then - error("Failed opening file '"..filename.."' for write:\n"..err) - end - - callback(file) - return true -end - -local function open_file_and_load_callback(filename, callback) - local file, err = io.open(filename, "r") - if not file then - error("Failed opening file '"..filename.."' for read:\n"..err) - end - - return callback(file) -end - --- == public functions == - --- Load a saved state (according to comment above) --- if 'callback' is nil: reads serialized table. --- returns the read table, or nil,err on error --- if 'callback' is a function (signature func(file_handle) ): --- Counterpart to save_atomic with function argument. Opens the file and calls callback on it. --- If the callback function throws an error, and strict loading is enabled, that error is propagated. --- The callback's first return value is returned by load_atomic -function serialize_lib.load_atomic(filename, callback) - - local cbfunc = callback or ser.read_from_fd - - -- try <filename> - local file, ret = io.open(filename, "r") - if file then - -- read the file using the callback - local success - success, ret = pcall(cbfunc, file) - if success then - return ret - end - end - - if minetest.settings:get_bool("serialize_lib_strict_loading") then - serialize_lib.save_lock = true - error("Loading data from file '"..filename.."' failed:\n" - ..ret.."\nDisable Strict Loading to ignore.") - end - - serialize_lib.log_warn("Loading data from file '"..filename.."' failed, trying .new fallback:") - serialize_lib.log_warn(ret) - - -- try <filename>.new - file, ret = io.open(filename..".new", "r") - if file then - -- read the file using the callback - local success - success, ret = pcall(cbfunc, file) - if success then - return ret - end - end - - serialize_lib.log_error("Unable to load data from '"..filename..".new':") - serialize_lib.log_error(ret) - serialize_lib.log_error("Note: This message is normal when the mod is loaded the first time on this world.") - - return nil, ret -end - --- Save a file atomically (as described above) --- 'data' is the data to be saved (when a callback is used, this can be nil) --- if 'callback' is nil: --- data must be a table, and is serialized into the file --- if 'callback' is a function (signature func(data, file_handle) ): --- Opens the file and calls callback on it. The 'data' argument is the data passed to save_atomic(). --- If the callback function throws an error, and strict loading is enabled, that error is propagated. --- The callback's first return value is returned by load_atomic --- Important: the callback must close the file in all cases! -function serialize_lib.save_atomic(data, filename, callback, config) - if serialize_lib.save_lock then - serialize_lib.log_warn("Instructed to save '"..filename.."', but save lock is active!") - return nil - end - - local cbfunc = callback or ser.write_to_fd - - local file, ret = io.open(filename..".new", "w") - if file then - -- save the file using the callback - local success - success, ret = pcall(cbfunc, data, file) - if success then - return save_atomic_move_file(filename) - end - end - serialize_lib.log_error("Unable to save data to '"..filename..".new':") - serialize_lib.log_error(ret) - return nil, ret -end - - --- Saves multiple files synchronously. First writes all data to all <filename>.new files, --- then moves all files in quick succession to avoid inconsistent backups. --- parts_table is a table where the keys are used as part of the filename and the values --- are the respective data written to it. --- e.g. if parts_table={foo={...}, bar={...}}, then <filename_prefix>foo and <filename_prefix>bar are written out. --- if 'callbacks_table' is defined, it is consulted for callbacks the same way save_atomic does. --- example: if callbacks_table = {foo = func()...}, then the callback is used during writing of file 'foo' (but not for 'bar') --- Note however that you must at least insert a "true" in the parts_table if you don't use the data argument. --- Important: the callback must close the file in all cases! -function serialize_lib.save_atomic_multiple(parts_table, filename_prefix, callbacks_table, config) - if serialize_lib.save_lock then - serialize_lib.log_warn("Instructed to save '"..filename_prefix.."' (multiple), but save lock is active!") - return nil - end - - for subfile, data in pairs(parts_table) do - local filename = filename_prefix..subfile - local cbfunc = ser.write_to_fd - if callbacks_table and callbacks_table[subfile] then - cbfunc = callbacks_table[subfile] - end - - local success = false - local file, ret = io.open(filename..".new", "w") - if file then - -- save the file using the callback - success, ret = pcall(cbfunc, data, file, config) - end - - if not success then - serialize_lib.log_error("Unable to save data to '"..filename..".new':") - serialize_lib.log_error(ret) - return nil, ret - end - end - - local first_error - for file, _ in pairs(parts_table) do - local filename = filename_prefix..file - local succ, err = save_atomic_move_file(filename) - if not succ and not first_error then - first_error = err - end - end - - return not first_error, first_error -- either true,nil or nil,error -end - - |