A Minecraft Java Edition server core written in Go

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Master290 65a7445a78 LRU chunk eviction (bounded cache, default 1024 chunks / ~200MB) The in-memory chunk+frame cache no longer grows unbounded as players explore. An LRU policy (doubly-linked list + index map, O(1) per op) evicts least-recently-used chunks when the cache exceeds MaxCachedChunks, dropping both the chunk and its cached frame. Dirty chunks are skipped until the autosave flushes them, so no edit is ever lost to eviction. - world/cache.go: maxChunks field + order/index LRU bookkeeping; touch (move-to-front) on every chunkAt/Frame/SetBlock hit; evictIfNeeded on miss; NewCacheWithLimit constructor (0 = unbounded, backward-compat). Dirty chunks are bumped to MRU and left in place rather than doing region I/O under the cache mutex. - server/server.go: Config.MaxCachedChunks (default 1024); New wires it into NewCacheWithLimit when a world dir is set. - cmd/regionio/main.go: -maxcache flag. - Tests: limit cap, LRU ordering (touched chunk survives), both-maps drop, dirty-keep, reload-on-access, and edits-survive-eviction+reload (end-to-end via the store).		2026-06-25 13:56:06 +03:00
cmd/regionio	LRU chunk eviction (bounded cache, default 1024 chunks / ~200MB)	2026-06-25 13:56:06 +03:00
internal	LRU chunk eviction (bounded cache, default 1024 chunks / ~200MB)	2026-06-25 13:56:06 +03:00
.gitignore	Initial commit: RegionIO Minecraft server core (26.1.2/protocol 775)	2026-06-24 00:32:51 +03:00
go.mod	Initial commit: RegionIO Minecraft server core (26.1.2/protocol 775)	2026-06-24 00:32:51 +03:00
README.md	Initial commit: RegionIO Minecraft server core (26.1.2/protocol 775)	2026-06-24 00:32:51 +03:00

README.md

RegionIO

A Minecraft Java Edition server core written in Go, targeting version 26.1.2 (protocol 775). RegionIO implements the connection lifecycle (status → login → configuration → play), chunk streaming, block editing, and a vanilla-faithful overworld generator built on the real noise_router final_density tree.

Status

Network: full handshake/status/login (offline mode)/configuration/play state machine with zlib compression, keep-alive, and chunk streaming.
Registries: 28 synchronized registries + tags, captured verbatim from the 26.1.2 vanilla server and sent during configuration.
World: in-memory chunk cache with memoized, compression-ready level_chunk_with_light frames; paletted block containers; heightmaps.
Generation: bit-faithful overworld terrain from the embedded datapack (ImprovedNoise/PerlinNoise/BlendedNoise/NormalNoise + the density function interpreter), plus multi-noise biomes (per-chunk, surface layer) via the vanilla Climate finder over the official biome parameter table.
Gameplay: creative block place/break, hotbar item→block mapping, chat, teleport ack, and a randomized bedrock floor / beach & gravel surface pass.

Build & run

go build ./...
go run ./cmd/regionio -seed 12345

The world seed defaults to 0; override it with the -seed flag or the REGIONIO_SEED environment variable. The server listens on 0.0.0.0:25565.

Testing

go test ./...

Parity tests (internal/world/vanilla_parity_test.go) compare generated surface heights against captures from the official server and skip when no capture is present.

Project layout

cmd/regionio/      entry point (config, listener, graceful shutdown)
internal/
  protocol/        wire primitives: VarInt, framing, compression, packet IDs
  nbt/             NBT encoder/decoder (with modified UTF-8)
  registry/        embedded synchronized registries + tags
  world/           chunk model, level_chunk encoder, cache, generators, biomes
  worldgen/        noise core + density-function interpreter + climate finder
  network/         per-connection state machine (handler/conn/play/login/...)
  server/          shared core: config, status response, profiles

Notes

The vanilla server.jar and its unpacked libraries//versions/ are not included (obtain them from Mojang). The embedded data under internal/ (registries, biome parameters, the overworld datapack) is derived from vanilla reports and is all that is required to build and run.