src/chunk.cpp

   1 #include "chunk.hpp"
   2
   3 #include "generator.hpp"
   4
   5 #include <limits>
   6 #include <queue>
   7 #include <glm/gtx/transform.hpp>
   8
   9
  10 namespace blank {
  11
  12 Chunk::Chunk(const BlockTypeRegistry &types)
  13 : types(&types)
  14 , neighbor{ 0, 0, 0, 0, 0, 0 }
  15 , blocks()
  16 , light()
  17 , model()
  18 , position(0, 0, 0)
  19 , dirty(false) {
  20
  21 }
  22
  23 Chunk::Chunk(Chunk &&other)
  24 : types(other.types)
  25 , blocks(std::move(other.blocks))
  26 , light(std::move(other.light))
  27 , model(std::move(other.model))
  28 , position(other.position)
  29 , dirty(other.dirty) {
  30         for (size_t i = 0; i < Block::FACE_COUNT; ++i) {
  31                 neighbor[i] = other.neighbor[i];
  32         }
  33 }
  34
  35 Chunk &Chunk::operator =(Chunk &&other) {
  36         types = other.types;
  37         for (size_t i = 0; i < Block::FACE_COUNT; ++i) {
  38                 neighbor[i] = other.neighbor[i];
  39         }
  40         blocks = std::move(other.blocks);
  41         light = std::move(other.light);
  42         model = std::move(other.model);
  43         position = other.position;
  44         dirty = other.dirty;
  45         return *this;
  46 }
  47
  48
  49 void Chunk::SetNeighbor(Chunk &other) {
  50         if (other.position == position + Pos(-1, 0, 0)) {
  51                 neighbor[Block::FACE_LEFT] = &other;
  52                 other.neighbor[Block::FACE_RIGHT] = this;
  53         } else if (other.position == position + Pos(1, 0, 0)) {
  54                 neighbor[Block::FACE_RIGHT] = &other;
  55                 other.neighbor[Block::FACE_LEFT] = this;
  56         } else if (other.position == position + Pos(0, -1, 0)) {
  57                 neighbor[Block::FACE_DOWN] = &other;
  58                 other.neighbor[Block::FACE_UP] = this;
  59         } else if (other.position == position + Pos(0, 1, 0)) {
  60                 neighbor[Block::FACE_UP] = &other;
  61                 other.neighbor[Block::FACE_DOWN] = this;
  62         } else if (other.position == position + Pos(0, 0, -1)) {
  63                 neighbor[Block::FACE_BACK] = &other;
  64                 other.neighbor[Block::FACE_FRONT] = this;
  65         } else if (other.position == position + Pos(0, 0, 1)) {
  66                 neighbor[Block::FACE_FRONT] = &other;
  67                 other.neighbor[Block::FACE_BACK] = this;
  68         }
  69 }
  70
  71 void Chunk::ClearNeighbors() {
  72         for (int i = 0; i < Block::FACE_COUNT; ++i) {
  73                 neighbor[i] = nullptr;
  74         }
  75 }
  76
  77 void Chunk::Unlink() {
  78         if (neighbor[Block::FACE_UP]) {
  79                 neighbor[Block::FACE_UP]->neighbor[Block::FACE_DOWN] = nullptr;
  80         }
  81         if (neighbor[Block::FACE_DOWN]) {
  82                 neighbor[Block::FACE_DOWN]->neighbor[Block::FACE_UP] = nullptr;
  83         }
  84         if (neighbor[Block::FACE_LEFT]) {
  85                 neighbor[Block::FACE_LEFT]->neighbor[Block::FACE_RIGHT] = nullptr;
  86         }
  87         if (neighbor[Block::FACE_RIGHT]) {
  88                 neighbor[Block::FACE_RIGHT]->neighbor[Block::FACE_LEFT] = nullptr;
  89         }
  90         if (neighbor[Block::FACE_FRONT]) {
  91                 neighbor[Block::FACE_FRONT]->neighbor[Block::FACE_BACK] = nullptr;
  92         }
  93         if (neighbor[Block::FACE_BACK]) {
  94                 neighbor[Block::FACE_BACK]->neighbor[Block::FACE_FRONT] = nullptr;
  95         }
  96 }
  97
  98 void Chunk::Relink() {
  99         if (neighbor[Block::FACE_UP]) {
 100                 neighbor[Block::FACE_UP]->neighbor[Block::FACE_DOWN] = this;
 101         }
 102         if (neighbor[Block::FACE_DOWN]) {
 103                 neighbor[Block::FACE_DOWN]->neighbor[Block::FACE_UP] = this;
 104         }
 105         if (neighbor[Block::FACE_LEFT]) {
 106                 neighbor[Block::FACE_LEFT]->neighbor[Block::FACE_RIGHT] = this;
 107         }
 108         if (neighbor[Block::FACE_RIGHT]) {
 109                 neighbor[Block::FACE_RIGHT]->neighbor[Block::FACE_LEFT] = this;
 110         }
 111         if (neighbor[Block::FACE_FRONT]) {
 112                 neighbor[Block::FACE_FRONT]->neighbor[Block::FACE_BACK] = this;
 113         }
 114         if (neighbor[Block::FACE_BACK]) {
 115                 neighbor[Block::FACE_BACK]->neighbor[Block::FACE_FRONT] = this;
 116         }
 117 }
 118
 119
 120 namespace {
 121
 122 struct SetNode {
 123
 124         Chunk *chunk;
 125         Chunk::Pos pos;
 126
 127         SetNode(Chunk *chunk, Chunk::Pos pos)
 128         : chunk(chunk), pos(pos) { }
 129
 130         int Get() const { return chunk->GetLight(pos); }
 131         void Set(int level) { chunk->SetLight(pos, level); }
 132
 133         bool HasNext(Block::Face face) {
 134                 const Block *next = chunk->FindNext(pos, face);
 135                 return next && !chunk->Type(*next).block_light;
 136         }
 137         SetNode GetNext(Block::Face face) {
 138                 Chunk::Pos next_pos(pos + Block::FaceNormal(face));
 139                 if (Chunk::InBounds(next_pos)) {
 140                         return SetNode(chunk, next_pos);
 141                 } else {
 142                         return SetNode(&chunk->GetNeighbor(face), next_pos - (Block::FaceNormal(face) * Chunk::Extent()));
 143                 }
 144         }
 145
 146 };
 147
 148 struct UnsetNode
 149 : public SetNode {
 150
 151         int level;
 152
 153         UnsetNode(Chunk *chunk, Chunk::Pos pos)
 154         : SetNode(chunk, pos), level(Get()) { }
 155
 156         UnsetNode(const SetNode &set)
 157         : SetNode(set), level(Get()) { }
 158
 159         UnsetNode GetNext(Block::Face face) { return UnsetNode(SetNode::GetNext(face)); }
 160
 161 };
 162
 163 std::queue<SetNode> light_queue;
 164 std::queue<UnsetNode> dark_queue;
 165
 166 void work_light() {
 167         while (!light_queue.empty()) {
 168                 SetNode node = light_queue.front();
 169                 light_queue.pop();
 170
 171                 int level = node.Get() - 1;
 172                 for (int face = 0; face < Block::FACE_COUNT; ++face) {
 173                         if (node.HasNext(Block::Face(face))) {
 174                                 SetNode other = node.GetNext(Block::Face(face));
 175                                 if (other.Get() < level) {
 176                                         other.Set(level);
 177                                         light_queue.emplace(other);
 178                                 }
 179                         }
 180                 }
 181         }
 182 }
 183
 184 void work_dark() {
 185         while (!dark_queue.empty()) {
 186                 UnsetNode node = dark_queue.front();
 187                 dark_queue.pop();
 188
 189                 for (int face = 0; face < Block::FACE_COUNT; ++face) {
 190                         if (node.HasNext(Block::Face(face))) {
 191                                 UnsetNode other = node.GetNext(Block::Face(face));
 192                                 // TODO: if there a light source here with the same level this will err
 193                                 if (other.Get() != 0 && other.Get() < node.level) {
 194                                         other.Set(0);
 195                                         dark_queue.emplace(other);
 196                                 } else {
 197                                         light_queue.emplace(other);
 198                                 }
 199                         }
 200                 }
 201         }
 202 }
 203
 204 }
 205
 206 void Chunk::SetBlock(int index, const Block &block) {
 207         const BlockType &old_type = Type(blocks[index]);
 208         const BlockType &new_type = Type(block);
 209
 210         blocks[index] = block;
 211
 212         if (&old_type == &new_type) return;
 213
 214         if (new_type.luminosity > old_type.luminosity) {
 215                 // light added
 216                 SetLight(index, new_type.luminosity);
 217                 light_queue.emplace(this, ToPos(index));
 218                 work_light();
 219         } else if (new_type.luminosity < old_type.luminosity) {
 220                 // light removed
 221                 dark_queue.emplace(this, ToPos(index));
 222                 SetLight(index, 0);
 223                 work_dark();
 224                 SetLight(index, new_type.luminosity);
 225                 light_queue.emplace(this, ToPos(index));
 226                 work_light();
 227         } else if (new_type.block_light && !old_type.block_light) {
 228                 // obstacle added
 229                 dark_queue.emplace(this, ToPos(index));
 230                 SetLight(index, 0);
 231                 work_dark();
 232                 work_light();
 233         } else if (!new_type.block_light && old_type.block_light) {
 234                 // obstacle removed
 235                 int level = 0;
 236                 for (int face = 0; face < Block::FACE_COUNT; ++face) {
 237                         Pos next_pos(ToPos(index) + Block::FaceNormal(Block::Face(face)));
 238                         int next_level = 0;
 239                         if (InBounds(next_pos)) {
 240                                 next_level = GetLight(next_pos);
 241                         } else {
 242                                 if (HasNeighbor(Block::Face(face))) {
 243                                         next_pos -= (Block::FaceNormal(Block::Face(face)) * Chunk::Extent());
 244                                         next_level = GetNeighbor(Block::Face(face)).GetLight(next_pos);
 245                                 }
 246                         }
 247                         if (level < next_level) {
 248                                 level = next_level;
 249                         }
 250                 }
 251                 if (level > 1) {
 252                         SetLight(index, level - 1);
 253                         light_queue.emplace(this, ToPos(index));
 254                         work_light();
 255                 }
 256         }
 257 }
 258
 259 const Block *Chunk::FindNext(const Pos &pos, Block::Face face) const {
 260         Pos next_pos(pos + Block::FaceNormal(face));
 261         if (InBounds(next_pos)) {
 262                 return &BlockAt(pos + Block::FaceNormal(face));
 263         } else if (HasNeighbor(face)) {
 264                 return &GetNeighbor(face).BlockAt(next_pos - (Block::FaceNormal(face) * Extent()));
 265         } else {
 266                 return nullptr;
 267         }
 268 }
 269
 270
 271 void Chunk::SetLight(int index, int level) {
 272         light[index] = level;
 273 }
 274
 275 int Chunk::GetLight(int index) const {
 276         return light[index];
 277 }
 278
 279
 280 bool Chunk::IsSurface(const Pos &pos) const {
 281         const Block &block = BlockAt(pos);
 282         if (!Type(block).visible) {
 283                 return false;
 284         }
 285         for (int face = 0; face < Block::FACE_COUNT; ++face) {
 286                 const Block *next = FindNext(pos, Block::Face(face));
 287                 if (!next || !Type(*next).visible) {
 288                         return true;
 289                 }
 290         }
 291         return false;
 292 }
 293
 294
 295 void Chunk::Allocate() {
 296         blocks.resize(Size(), Block(0));
 297         light.resize(Size(), 0);
 298 }
 299
 300
 301 void Chunk::Draw() {
 302         if (dirty) {
 303                 Update();
 304         }
 305         model.Draw();
 306 }
 307
 308
 309 bool Chunk::Intersection(
 310         const Ray &ray,
 311         const glm::mat4 &M,
 312         int &blkid,
 313         float &dist,
 314         glm::vec3 &normal
 315 ) const {
 316         // TODO: should be possible to heavily optimize this
 317         int id = 0;
 318         blkid = -1;
 319         dist = std::numeric_limits<float>::infinity();
 320         for (int z = 0; z < Depth(); ++z) {
 321                 for (int y = 0; y < Height(); ++y) {
 322                         for (int x = 0; x < Width(); ++x, ++id) {
 323                                 if (!Type(blocks[id]).visible) {
 324                                         continue;
 325                                 }
 326                                 float cur_dist;
 327                                 glm::vec3 cur_norm;
 328                                 if (Type(blocks[id]).shape->Intersects(ray, M * ToTransform(id), cur_dist, cur_norm)) {
 329                                         if (cur_dist < dist) {
 330                                                 blkid = id;
 331                                                 dist = cur_dist;
 332                                                 normal = cur_norm;
 333                                         }
 334                                 }
 335                         }
 336                 }
 337         }
 338
 339         if (blkid < 0) {
 340                 return false;
 341         } else {
 342                 normal = glm::vec3(BlockAt(blkid).Transform() * glm::vec4(normal, 0.0f));
 343                 return true;
 344         }
 345 }
 346
 347 void Chunk::Position(const Pos &pos) {
 348         position = pos;
 349 }
 350
 351 glm::mat4 Chunk::Transform(const Pos &offset) const {
 352         return glm::translate((position - offset) * Extent());
 353 }
 354
 355
 356 namespace {
 357
 358 Model::Buffer buf;
 359
 360 }
 361
 362 void Chunk::CheckUpdate() {
 363         if (dirty) {
 364                 Update();
 365         }
 366 }
 367
 368 void Chunk::Update() {
 369         int vtx_count = 0, idx_count = 0;
 370         for (const auto &block : blocks) {
 371                 const Shape *shape = Type(block).shape;
 372                 vtx_count += shape->VertexCount();
 373                 idx_count += shape->VertexIndexCount();
 374         }
 375         buf.Clear();
 376         buf.Reserve(vtx_count, idx_count);
 377
 378         Model::Index vtx_counter = 0;
 379         for (size_t i = 0; i < Size(); ++i) {
 380                 const BlockType &type = Type(blocks[i]);
 381
 382                 if (!type.visible || Obstructed(i)) continue;
 383
 384                 type.FillModel(buf, ToTransform(i), vtx_counter);
 385                 vtx_counter += type.shape->VertexCount();
 386         }
 387
 388         model.Update(buf);
 389         dirty = false;
 390 }
 391
 392 bool Chunk::Obstructed(int idx) const {
 393         Chunk::Pos pos(ToPos(idx));
 394
 395         Chunk::Pos left_pos(pos + Chunk::Pos(-1, 0, 0));
 396         const Block *left_block = nullptr;
 397         if (InBounds(left_pos)) {
 398                 left_block = &BlockAt(left_pos);
 399         } else if (HasNeighbor(Block::FACE_LEFT)) {
 400                 left_pos += Chunk::Pos(Width(), 0, 0);
 401                 left_block = &GetNeighbor(Block::FACE_LEFT).BlockAt(left_pos);
 402         } else {
 403                 return false;
 404         }
 405         if (!Type(*left_block).FaceFilled(*left_block, Block::FACE_RIGHT)) {
 406                 return false;
 407         }
 408
 409         Chunk::Pos right_pos(pos + Chunk::Pos(1, 0, 0));
 410         const Block *right_block = nullptr;
 411         if (InBounds(right_pos)) {
 412                 right_block = &BlockAt(right_pos);
 413         } else if (HasNeighbor(Block::FACE_RIGHT)) {
 414                 right_pos += Chunk::Pos(-Width(), 0, 0);
 415                 right_block = &GetNeighbor(Block::FACE_RIGHT).BlockAt(right_pos);
 416         } else {
 417                 return false;
 418         }
 419         if (!Type(*right_block).FaceFilled(*right_block, Block::FACE_LEFT)) {
 420                 return false;
 421         }
 422
 423         Chunk::Pos down_pos(pos + Chunk::Pos(0, -1, 0));
 424         const Block *down_block = nullptr;
 425         if (InBounds(down_pos)) {
 426                 down_block = &BlockAt(down_pos);
 427         } else if (HasNeighbor(Block::FACE_DOWN)) {
 428                 down_pos += Chunk::Pos(0, Height(), 0);
 429                 down_block = &GetNeighbor(Block::FACE_DOWN).BlockAt(down_pos);
 430         } else {
 431                 return false;
 432         }
 433         if (!Type(*down_block).FaceFilled(*down_block, Block::FACE_UP)) {
 434                 return false;
 435         }
 436
 437         Chunk::Pos up_pos(pos + Chunk::Pos(0, 1, 0));
 438         const Block *up_block = nullptr;
 439         if (InBounds(up_pos)) {
 440                 up_block = &BlockAt(up_pos);
 441         } else if (HasNeighbor(Block::FACE_UP)) {
 442                 up_pos += Chunk::Pos(0, -Height(), 0);
 443                 up_block = &GetNeighbor(Block::FACE_UP).BlockAt(up_pos);
 444         } else {
 445                 return false;
 446         }
 447         if (!Type(*up_block).FaceFilled(*up_block, Block::FACE_DOWN)) {
 448                 return false;
 449         }
 450
 451         Chunk::Pos back_pos(pos + Chunk::Pos(0, 0, -1));
 452         const Block *back_block = nullptr;
 453         if (InBounds(back_pos)) {
 454                 back_block = &BlockAt(back_pos);
 455         } else if (HasNeighbor(Block::FACE_BACK)) {
 456                 back_pos += Chunk::Pos(0, 0, Depth());
 457                 back_block = &GetNeighbor(Block::FACE_BACK).BlockAt(back_pos);
 458         } else {
 459                 return false;
 460         }
 461         if (!Type(*back_block).FaceFilled(*back_block, Block::FACE_FRONT)) {
 462                 return false;
 463         }
 464
 465         Chunk::Pos front_pos(pos + Chunk::Pos(0, 0, 1));
 466         const Block *front_block = nullptr;
 467         if (InBounds(front_pos)) {
 468                 front_block = &BlockAt(front_pos);
 469         } else if (HasNeighbor(Block::FACE_FRONT)) {
 470                 front_pos += Chunk::Pos(0, 0, -Depth());
 471                 front_block = &GetNeighbor(Block::FACE_FRONT).BlockAt(front_pos);
 472         } else {
 473                 return false;
 474         }
 475         if (!Type(*front_block).FaceFilled(*front_block, Block::FACE_BACK)) {
 476                 return false;
 477         }
 478
 479         return true;
 480 }
 481
 482 glm::mat4 Chunk::ToTransform(int idx) const {
 483         return glm::translate(glm::mat4(1.0f), ToCoords(idx)) * blocks[idx].Transform();
 484 }
 485
 486
 487 ChunkLoader::ChunkLoader(const Config &config, const BlockTypeRegistry &reg, const Generator &gen)
 488 : base(0, 0, 0)
 489 , reg(reg)
 490 , gen(gen)
 491 , loaded()
 492 , to_generate()
 493 , to_free()
 494 , load_dist(config.load_dist)
 495 , unload_dist(config.unload_dist) {
 496
 497 }
 498
 499 namespace {
 500
 501 struct ChunkLess {
 502
 503         explicit ChunkLess(const Chunk::Pos &base)
 504         : base(base) { }
 505
 506         bool operator ()(const Chunk::Pos &a, const Chunk::Pos &b) const {
 507                 Chunk::Pos da(base - a);
 508                 Chunk::Pos db(base - b);
 509                 return
 510                         da.x * da.x + da.y * da.y + da.z * da.z <
 511                         db.x * db.x + db.y * db.y + db.z * db.z;
 512         }
 513
 514         Chunk::Pos base;
 515
 516 };
 517
 518 }
 519
 520 void ChunkLoader::Generate(const Chunk::Pos &from, const Chunk::Pos &to) {
 521         for (int z = from.z; z < to.z; ++z) {
 522                 for (int y = from.y; y < to.y; ++y) {
 523                         for (int x = from.x; x < to.x; ++x) {
 524                                 Chunk::Pos pos(x, y, z);
 525                                 if (Known(pos)) {
 526                                         continue;
 527                                 } else if (pos == base) {
 528                                         Generate(pos);
 529
 530                                 //      orientation testing
 531                                 //      for (int i = 0; i < Block::FACE_COUNT; ++i) {
 532                                 //              for (int j = 0; j < Block::TURN_COUNT; ++j) {
 533                                 //                      loaded.back().BlockAt(512 * j + 2 * i) = Block(3 * (j + 1), Block::Face(i), Block::Turn(j));
 534                                 //              }
 535                                 //      }
 536                                 //      loaded.back().Invalidate();
 537                                 //      loaded.back().CheckUpdate();
 538                                 } else {
 539                                         to_generate.emplace_back(pos);
 540                                 }
 541                         }
 542                 }
 543         }
 544         to_generate.sort(ChunkLess(base));
 545 }
 546
 547 Chunk &ChunkLoader::Generate(const Chunk::Pos &pos) {
 548         loaded.emplace_back(reg);
 549         Chunk &chunk = loaded.back();
 550         chunk.Position(pos);
 551         Insert(chunk);
 552         gen(chunk);
 553         return chunk;
 554 }
 555
 556 void ChunkLoader::Insert(Chunk &chunk) {
 557         for (Chunk &other : loaded) {
 558                 chunk.SetNeighbor(other);
 559         }
 560 }
 561
 562 void ChunkLoader::Remove(Chunk &chunk) {
 563         chunk.Unlink();
 564 }
 565
 566 Chunk *ChunkLoader::Loaded(const Chunk::Pos &pos) {
 567         for (Chunk &chunk : loaded) {
 568                 if (chunk.Position() == pos) {
 569                         return &chunk;
 570                 }
 571         }
 572         return nullptr;
 573 }
 574
 575 bool ChunkLoader::Queued(const Chunk::Pos &pos) {
 576         for (const Chunk::Pos &chunk : to_generate) {
 577                 if (chunk == pos) {
 578                         return true;
 579                 }
 580         }
 581         return nullptr;
 582 }
 583
 584 bool ChunkLoader::Known(const Chunk::Pos &pos) {
 585         if (Loaded(pos)) return true;
 586         return Queued(pos);
 587 }
 588
 589 Chunk &ChunkLoader::ForceLoad(const Chunk::Pos &pos) {
 590         Chunk *chunk = Loaded(pos);
 591         if (chunk) {
 592                 return *chunk;
 593         }
 594
 595         for (auto iter(to_generate.begin()), end(to_generate.end()); iter != end; ++iter) {
 596                 if (*iter == pos) {
 597                         to_generate.erase(iter);
 598                         break;
 599                 }
 600         }
 601
 602         return Generate(pos);
 603 }
 604
 605 void ChunkLoader::Rebase(const Chunk::Pos &new_base) {
 606         if (new_base == base) {
 607                 return;
 608         }
 609         base = new_base;
 610
 611         // unload far away chunks
 612         for (auto iter(loaded.begin()), end(loaded.end()); iter != end;) {
 613                 if (std::abs(base.x - iter->Position().x) > unload_dist
 614                                 || std::abs(base.y - iter->Position().y) > unload_dist
 615                                 || std::abs(base.z - iter->Position().z) > unload_dist) {
 616                         auto saved = iter;
 617                         Remove(*saved);
 618                         ++iter;
 619                         to_free.splice(to_free.end(), loaded, saved);
 620                 } else {
 621                         ++iter;
 622                 }
 623         }
 624         // abort far away queued chunks
 625         for (auto iter(to_generate.begin()), end(to_generate.end()); iter != end;) {
 626                 if (std::abs(base.x - iter->x) > unload_dist
 627                                 || std::abs(base.y - iter->y) > unload_dist
 628                                 || std::abs(base.z - iter->z) > unload_dist) {
 629                         iter = to_generate.erase(iter);
 630                 } else {
 631                         ++iter;
 632                 }
 633         }
 634         // add missing new chunks
 635         GenerateSurrounding(base);
 636 }
 637
 638 void ChunkLoader::GenerateSurrounding(const Chunk::Pos &pos) {
 639         const Chunk::Pos offset(load_dist, load_dist, load_dist);
 640         Generate(pos - offset, pos + offset);
 641 }
 642
 643 void ChunkLoader::Update() {
 644         bool reused = false;
 645         if (!to_generate.empty()) {
 646                 Chunk::Pos pos(to_generate.front());
 647
 648                 for (auto iter(to_free.begin()), end(to_free.end()); iter != end; ++iter) {
 649                         if (iter->Position() == pos) {
 650                                 iter->Relink();
 651                                 loaded.splice(loaded.end(), to_free, iter);
 652                                 reused = true;
 653                                 break;
 654                         }
 655                 }
 656
 657                 if (!reused) {
 658                         if (to_free.empty()) {
 659                                 loaded.emplace_back(reg);
 660                         } else {
 661                                 to_free.front().ClearNeighbors();
 662                                 loaded.splice(loaded.end(), to_free, to_free.begin());
 663                                 reused = true;
 664                         }
 665                         Chunk &chunk = loaded.back();
 666                         chunk.Position(pos);
 667                         Insert(chunk);
 668                         gen(chunk);
 669                 }
 670                 to_generate.pop_front();
 671         }
 672
 673         if (!reused && !to_free.empty()) {
 674                 to_free.pop_front();
 675         }
 676 }
 677
 678 }