SafeSaves - Hytale early plugin

SafeSaves provides safe, atomic save-file writes for Hytale servers by replacing or augmenting the default BSON save path. It prevents corruption by using a write-to-temporary-file → backup → atomic-move pattern.

What it does

• Ensures safe, atomic writes of save files to avoid data loss or corruption if the process is interrupted.
• Two implementation approaches included:
  • SafeSaveTransformer — an ASM-based, inline class transformer that replaces BsonUtil.writeDocument(Path, BsonDocument, boolean) to perform atomic writes (write .new, optionally move original to .bak, then move .new → final file). No helper classes are required at runtime for this approach.
  • SafeSaveHelper — a helper that performs safe writes using reflection to call BsonUtil.toJson(...) and a temporary file approach (creates <file>.new, optionally renames existing file to <file>.bak, then atomically moves the temp file into place). This is loaded by the early plugin classloader.

Internals & Notes

• The transformer is implemented with ASM (ASM9) and generates bytecode inline — it finds the target method and replaces it with a safe-write implementation at classload time.
• A few stub classes exist only for compile-time convenience (their real implementations are supplied by Hytale at runtime):
  • com.hypixel.hytale.server.core.util.BsonUtil (stub)
  • com.hypixel.hytale.server.core.util.PathUtil (stub)
  • com.hypixel.hytale.sneakythrow.SneakyThrow (stub)
  • com.hypixel.hytale.plugin.early.ClassTransformer (stub interface)
• The project places an entry under src/main/resources/META-INF/services/com.hypixel.hytale.plugin.early.ClassTransformer so the runtime can discover the transformer via service loading.

⚠️ This code runs at plugin/class-transform time and modifies bytecode. Test thoroughly on staging environments before using in production.

Building

Requirements:

• JDK (25)

Usage

• Package the plugin JAR and place it in the server’s early plugin directory (default: /Hytale/UserData/earlyplugins) or follow your server/plugin loader guidelines.
• The transformer will automatically attempt to replace BsonUtil.writeDocument(...) at load time; if not present the helper can be used directly by other code that wants to perform safe writes.