+ChunkLoader::ChunkLoader(const BlockTypeRegistry ®, const Generator &gen)
+: base(0, 0, 0)
+, reg(reg)
+, gen(gen)
+, loaded()
+, to_generate()
+, to_free()
+, load_dist(4)
+, unload_dist(5) {
+
+}
+
+namespace {
+
+struct ChunkLess {
+
+ explicit ChunkLess(const Chunk::Pos &base)
+ : base(base) { }
+
+ bool operator ()(const Chunk &a, const Chunk &b) const {
+ Chunk::Pos da(base - a.Position());
+ Chunk::Pos db(base - b.Position());
+ return
+ da.x * da.x + da.y * da.y + da.z * da.z <
+ db.x * db.x + db.y * db.y + db.z * db.z;
+ }
+
+ Chunk::Pos base;
+
+};
+
+}
+
+void ChunkLoader::Generate(const Chunk::Pos &from, const Chunk::Pos &to) {
+ for (int z = from.z; z < to.z; ++z) {
+ for (int y = from.y; y < to.y; ++y) {
+ for (int x = from.x; x < to.x; ++x) {
+ Chunk::Pos pos(x, y, z);
+ if (Known(pos)) {
+ continue;
+ } else if (x == 0 && y == 0 && z == 0) {
+ loaded.emplace_back(reg);
+ loaded.back().Position(pos);
+ gen(loaded.back());
+ } else {
+ to_generate.emplace_back(reg);
+ to_generate.back().Position(pos);
+ }
+ }
+ }
+ }
+ to_generate.sort(ChunkLess(base));
+}
+
+Chunk *ChunkLoader::Loaded(const Chunk::Pos &pos) {
+ for (Chunk &chunk : loaded) {
+ if (chunk.Position() == pos) {
+ return &chunk;
+ }
+ }
+ return nullptr;
+}
+
+Chunk *ChunkLoader::Queued(const Chunk::Pos &pos) {
+ for (Chunk &chunk : to_generate) {
+ if (chunk.Position() == pos) {
+ return &chunk;
+ }
+ }
+ return nullptr;
+}
+
+Chunk *ChunkLoader::Known(const Chunk::Pos &pos) {
+ Chunk *chunk = Loaded(pos);
+ if (chunk) return chunk;
+
+ return Queued(pos);
+}
+
+Chunk &ChunkLoader::ForceLoad(const Chunk::Pos &pos) {
+ Chunk *chunk = Loaded(pos);
+ if (chunk) {
+ return *chunk;
+ }
+
+ chunk = Queued(pos);
+ if (chunk) {
+ gen(*chunk);
+ return *chunk;
+ }
+
+ loaded.emplace_back(reg);
+ loaded.back().Position(pos);
+ gen(loaded.back());
+ return loaded.back();
+}
+
+void ChunkLoader::Rebase(const Chunk::Pos &new_base) {
+ if (new_base == base) {
+ return;
+ }
+ base = new_base;
+
+ // unload far away chunks
+ for (auto iter(loaded.begin()), end(loaded.end()); iter != end;) {
+ if (std::abs(base.x - iter->Position().x) > unload_dist
+ || std::abs(base.y - iter->Position().y) > unload_dist
+ || std::abs(base.z - iter->Position().z) > unload_dist) {
+ auto saved = iter;
+ ++iter;
+ to_free.splice(to_free.end(), loaded, saved);
+ } else {
+ ++iter;
+ }
+ }
+ // abort far away queued chunks
+ for (auto iter(to_generate.begin()), end(to_generate.end()); iter != end;) {
+ if (std::abs(base.x - iter->Position().x) > unload_dist
+ || std::abs(base.y - iter->Position().y) > unload_dist
+ || std::abs(base.z - iter->Position().z) > unload_dist) {
+ iter = to_generate.erase(iter);
+ } else {
+ ++iter;
+ }
+ }
+ // add missing new chunks
+ const Chunk::Pos offset(load_dist, load_dist, load_dist);
+ Generate(base - offset, base + offset);
+}
+
+void ChunkLoader::Update() {
+ if (!to_generate.empty()) {
+ gen(to_generate.front());
+ loaded.splice(loaded.end(), to_generate, to_generate.begin());
+ }
+
+ if (!to_free.empty()) {
+ to_free.pop_front();
+ }
+}
+