Configuring love.filesystem backup restoration without atomic write guarantees

Reliable Restoration Strategy

To ensure a restored file exactly matches the original backup despite the lack of atomic write guarantees, you must implement a write-then-rename pattern. Since love.filesystem.write can leave a file in a partially written state if the application crashes or the OS fails, you should never write directly to the active backup or target file.

Implementation Steps

1. Write to Temporary File: Write the backup data to a temporary file (e.g., backup_temp.dat) using love.filesystem.write.
2. Verify Temporary File: Before replacing the target, read the temporary file and calculate its hash (e.g., SHA-256) or compare its size using love.filesystem.getSize() against the known backup metadata.
3. Atomic Swap: Use love.filesystem.rename to move the verified temporary file to the final destination. On most operating systems, the rename operation is significantly more reliable than a raw write, effectively acting as an atomic swap.
4. Post-Restoration Check: Perform a final read of the destination file to confirm the content matches the expected hash before flagging the restoration as successful.

Handling Simultaneous Read/Write

To avoid corruption by simultaneous access within a frame, implement a sequential state machine. Avoid calling write() and read() on the same file path within the same love.update() or love.draw() cycle. Instead, queue the operation:

• State 1: Write data to temp.
• State 2: Verify integrity.
• State 3: Rename temp to target.
• State 4: Confirm availability for reading.

Verification and Hashing

External hashing is not just recommended; it is necessary for absolute verification. This should occur at two points:

• Pre-Rename: To ensure the temporary file was written correctly to disk.
• Post-Restore: To ensure the rename operation completed and the file is readable.

Verification Commands (Conceptual)

While LÖVE does not provide a native hash() function, you can verify the basic file size as a first-pass check:

local expectedSize = 1024 -- bytes from metadata
local actualSize = love.filesystem.getSize("restored_file.dat")
if actualSize ~= expectedSize then
    -- Handle corruption
end

Diagnostic Detail Required: Are you targeting a specific operating system (e.g., Android vs. Windows)? love.filesystem.rename behavior regarding existing file overwrites can vary, which may require an explicit love.filesystem.remove() call before renaming.