Add README

README.md

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+# AutoSave
+
+Server module for Blockland v21. While you host, it saves every brick on the server to `saves/autosave/` on a timer. A save is written a few milliseconds at a time, so the server keeps ticking during a large save.
+
+The files use the stock `.bls` format and can be loaded from the normal load screen.
+
+## Install
+
+Place `AutoSave.dll` in the game's `modules` folder, then quit and start Blockland from Steam. A DLL that is already loaded stays mapped until that restart.
+
+It only saves while this game is the server: a local single-player or multiplayer host, or a dedicated server.
+
+## Files
+
+Each save is named for the local time it started, for example `saves/autosave/2026-10-26 00-29-28.bls`. Windows does not allow colons in file names, so the time uses hyphens; the description line inside the file uses colons. If a file with that name already exists, ` (2)`, ` (3)` and so on is added.
+
+The save is written to `saves/autosave/writing.bls.tmp` and renamed when it is complete, so a crash or cancel never leaves a half-written `.bls`. Old autosaves are not deleted.
+
+`$pref::SaveOwnership` and `$pref::SaveExtendedBrickInfo` are followed the same way the stock save follows them. No screenshot is taken.
+
+## When it saves
+
+The first save after starting always runs. After that, a save is skipped if nothing changed. Planting, loading, removing or killing a brick counts as a change. So does adding or clearing events, renaming a brick, and changing its color, paint effect, shape effect, print, collision, raycasting, rendering, light, emitter, item, music, sound or vehicle.
+
+A save is also skipped while bricks are loading, while bricks are being cleared, and while the mission is being cleaned up. If a load or a clear starts in the middle of a save, the save stops, its temp file is removed, and the next interval tries again.
+
+## Large builds
+
+Each slice handles up to the chunk size and stops after 8 ms, then waits at least 12 ms before the next slice. Progress is written to the console every 2 seconds.
+
+Up to 75000 bricks, bricks are sorted by height like the stock save. Over 75000, the sort and the wrench-extras pass are skipped and the file is written in one pass. The brick count in the header is filled in when the write finishes.
+
+## Chat commands
+
+Anyone can use:
+
+- `/autosaver help`
+- `/autosaver status`
+
+Admins can use:
+
+- `/autosaver on` and `/autosaver off`
+- `/autosaver save` (or `now`): save right away
+- `/autosaver load` (or `reload`): clear all bricks, then load the newest file in `saves/autosave/`
+- `/autosaver interval <seconds>`: 30 to 86400, default 300
+- `/autosaver chunk <bricks>`: bricks per slice, 1 to 20000, default 4000
+- `/autosaver tick <milliseconds>`: pause between slices, 1 to 1000, default 1 (never less than 12 ms in practice)
+
+Out-of-range values are clamped. Changes are announced to everyone. They are not stored, so the defaults return when the game restarts.
+
+`load` uses the file with the newest modified time on disk, including saves made since the game started. It loads with saved ownership and exact colors. The command is case-insensitive.
+
+## Console
+
+- `autoSave()` starts a save now
+- `autoSaveNewest()` returns the newest autosave path
+- `autoSaveApply()` clamps the settings and restarts the timer
+- `$AutoSave::Enabled`, `$AutoSave::Interval`, `$AutoSave::Chunk`, `$AutoSave::Tick`
+
+## Build
+
+Blockland is a 32-bit program, so the DLL has to be built with a 32-bit MinGW toolchain (`i686-w64-mingw32`). Put that toolchain's `bin` directory first on `PATH` so CMake finds that `gcc` and `mingw32-make`.
+
+`find_package(TSFUNCS)` needs a tsfuncs 1.0.1 package: `tsfuncs-config.cmake` next to `include/` and `lib/`. MinHook's cmake package lives under that package's `lib/minhook`. Pass the package directory as `CMAKE_PREFIX_PATH`.
+
+From this repo:
+
+```
+cmake -G "MinGW Makefiles" -DCMAKE_BUILD_TYPE=Release -DCMAKE_POLICY_VERSION_MINIMUM=3.5 -DCMAKE_PREFIX_PATH=C:/path/to/tsfuncs -S . -B build
+cmake --build build
+```
+
+The result is `build/AutoSave.dll`. CMake is set so the filename has no `lib` prefix. The link line is tsfuncs, MinHook and `psapi`, with static libgcc and libstdc++.
+
+Source is `src/main.cpp` and `CMakeLists.txt`. The current DLL is attached to the v1.0.0 release.