git.sesse.net Git - plocate/blob - database-builder.cpp

   1 #include "database-builder.h"
   2
   3 #include "dprintf.h"
   4 #include "turbopfor-encode.h"
   5
   6 #include <algorithm>
   7 #include <assert.h>
   8 #ifdef HAS_ENDIAN_H
   9 #include <endian.h>
  10 #endif
  11 #include <fcntl.h>
  12 #include <string.h>
  13 #include <string_view>
  14 #include <sys/stat.h>
  15 #include <sys/time.h>
  16 #include <sys/types.h>
  17 #include <unistd.h>
  18 #include <zdict.h>
  19 #include <zstd.h>
  20
  21 #define P4NENC_BOUND(n) ((n + 127) / 128 + (n + 32) * sizeof(uint32_t))
  22
  23 #define NUM_TRIGRAMS 16777216
  24
  25 using namespace std;
  26 using namespace std::chrono;
  27
  28 constexpr unsigned num_overflow_slots = 16;
  29
  30 string zstd_compress(const string &src, ZSTD_CDict *cdict, string *tempbuf);
  31
  32 // NOTE: Will read one byte past the end of the trigram, but it's OK,
  33 // since we always call it from contexts where there's a terminating zero byte.
  34 static inline uint32_t read_trigram(const string_view s, size_t start)
  35 {
  36         uint32_t trgm;
  37         memcpy(&trgm, s.data() + start, sizeof(trgm));
  38         trgm = le32toh(trgm);
  39         return trgm & 0xffffff;
  40 }
  41
  42 class PostingListBuilder {
  43 public:
  44         inline void add_docid(uint32_t docid);
  45         inline void add_first_docid(uint32_t docid);
  46         void finish();
  47
  48         vector<unsigned char> encoded;
  49         size_t get_num_docids() const {
  50                 // Updated only when we flush, so check that we're finished.
  51                 assert(pending_deltas.empty());
  52                 return num_docids;
  53         }
  54
  55 private:
  56         void write_header(uint32_t docid);
  57         void append_block();
  58
  59         vector<uint32_t> pending_deltas;
  60
  61         uint32_t num_docids = 0;  // Should be size_t, except the format only supports 2^32 docids per posting list anyway.
  62         uint32_t last_docid = -1;
  63 };
  64
  65 void PostingListBuilder::add_docid(uint32_t docid)
  66 {
  67         // Deduplicate against the last inserted value, if any.
  68         if (docid == last_docid) {
  69                 return;
  70         }
  71
  72         pending_deltas.push_back(docid - last_docid - 1);
  73         last_docid = docid;
  74         if (pending_deltas.size() == 128) {
  75                 append_block();
  76                 pending_deltas.clear();
  77                 num_docids += 128;
  78         }
  79 }
  80
  81 void PostingListBuilder::add_first_docid(uint32_t docid)
  82 {
  83         write_header(docid);
  84         ++num_docids;
  85         last_docid = docid;
  86 }
  87
  88 void PostingListBuilder::finish()
  89 {
  90         if (pending_deltas.empty()) {
  91                 return;
  92         }
  93
  94         assert(!encoded.empty());  // write_header() should already have run.
  95
  96         // No interleaving for partial blocks.
  97         unsigned char buf[P4NENC_BOUND(128)];
  98         unsigned char *end = encode_pfor_single_block<128>(pending_deltas.data(), pending_deltas.size(), /*interleaved=*/false, buf);
  99         encoded.insert(encoded.end(), buf, end);
 100
 101         num_docids += pending_deltas.size();
 102         pending_deltas.clear();
 103 }
 104
 105 void PostingListBuilder::append_block()
 106 {
 107         unsigned char buf[P4NENC_BOUND(128)];
 108         assert(pending_deltas.size() == 128);
 109         unsigned char *end = encode_pfor_single_block<128>(pending_deltas.data(), 128, /*interleaved=*/true, buf);
 110         encoded.insert(encoded.end(), buf, end);
 111 }
 112
 113 void PostingListBuilder::write_header(uint32_t docid)
 114 {
 115         unsigned char buf[P4NENC_BOUND(1)];
 116         unsigned char *end = write_baseval(docid, buf);
 117         encoded.insert(encoded.end(), buf, end);
 118 }
 119
 120 void DictionaryBuilder::add_file(string filename, dir_time)
 121 {
 122         if (keep_current_block) {  // Only bother saving the filenames if we're actually keeping the block.
 123                 if (!current_block.empty()) {
 124                         current_block.push_back('\0');
 125                 }
 126                 current_block += filename;
 127         }
 128         if (++num_files_in_block == block_size) {
 129                 flush_block();
 130         }
 131 }
 132
 133 void DictionaryBuilder::flush_block()
 134 {
 135         if (keep_current_block) {
 136                 if (slot_for_current_block == -1) {
 137                         lengths.push_back(current_block.size());
 138                         sampled_blocks.push_back(move(current_block));
 139                 } else {
 140                         lengths[slot_for_current_block] = current_block.size();
 141                         sampled_blocks[slot_for_current_block] = move(current_block);
 142                 }
 143         }
 144         current_block.clear();
 145         num_files_in_block = 0;
 146         ++block_num;
 147
 148         if (block_num < blocks_to_keep) {
 149                 keep_current_block = true;
 150                 slot_for_current_block = -1;
 151         } else {
 152                 // Keep every block with equal probability (reservoir sampling).
 153                 uint64_t idx = uniform_int_distribution<uint64_t>(0, block_num)(reservoir_rand);
 154                 keep_current_block = (idx < blocks_to_keep);
 155                 slot_for_current_block = idx;
 156         }
 157 }
 158
 159 string DictionaryBuilder::train(size_t buf_size)
 160 {
 161         string dictionary_buf;
 162         sort(sampled_blocks.begin(), sampled_blocks.end());  // Seemingly important for decompression speed.
 163         for (const string &block : sampled_blocks) {
 164                 dictionary_buf += block;
 165         }
 166
 167         string buf;
 168         buf.resize(buf_size);
 169         size_t ret = ZDICT_trainFromBuffer(&buf[0], buf_size, dictionary_buf.data(), lengths.data(), lengths.size());
 170         if (ZDICT_isError(ret)) {
 171                 return "";
 172         }
 173         dprintf("Sampled %zu bytes in %zu blocks, built a dictionary of size %zu\n", dictionary_buf.size(), lengths.size(), ret);
 174         buf.resize(ret);
 175
 176         sampled_blocks.clear();
 177         lengths.clear();
 178
 179         return buf;
 180 }
 181
 182 class EncodingCorpus : public DatabaseReceiver {
 183 public:
 184         EncodingCorpus(FILE *outfp, size_t block_size, ZSTD_CDict *cdict, bool store_dir_times);
 185         ~EncodingCorpus();
 186
 187         void add_file(std::string filename, dir_time dt) override;
 188         void flush_block() override;
 189         void finish() override;
 190
 191         std::vector<uint64_t> filename_blocks;
 192         size_t num_files = 0, num_files_in_block = 0, num_blocks = 0;
 193         bool seen_trigram(uint32_t trgm)
 194         {
 195                 return invindex[trgm] != nullptr;
 196         }
 197         size_t num_files_seen() const override { return num_files; }
 198         PostingListBuilder &get_pl_builder(uint32_t trgm)
 199         {
 200                 return *invindex[trgm];
 201         }
 202
 203         void add_docid(uint32_t trgm, uint32_t docid)
 204         {
 205                 if (invindex[trgm] == nullptr) {
 206                         invindex[trgm] = new PostingListBuilder;
 207                         invindex[trgm]->add_first_docid(docid);
 208                 } else {
 209                         invindex[trgm]->add_docid(docid);
 210                 }
 211         }
 212
 213         size_t num_trigrams() const;
 214         std::string get_compressed_dir_times();
 215
 216 private:
 217         void compress_dir_times(size_t allowed_slop);
 218
 219         std::unique_ptr<PostingListBuilder *[]> invindex;
 220         FILE *outfp;
 221         std::string current_block;
 222         std::string tempbuf;
 223         const size_t block_size;
 224         const bool store_dir_times;
 225         ZSTD_CDict *cdict;
 226
 227         ZSTD_CStream *dir_time_ctx = nullptr;
 228         std::string dir_times;  // Buffer of still-uncompressed data.
 229         std::string dir_times_compressed;
 230 };
 231
 232
 233 EncodingCorpus::EncodingCorpus(FILE *outfp, size_t block_size, ZSTD_CDict *cdict, bool store_dir_times)
 234         : invindex(new PostingListBuilder *[NUM_TRIGRAMS]), outfp(outfp), block_size(block_size), store_dir_times(store_dir_times), cdict(cdict)
 235 {
 236         fill(invindex.get(), invindex.get() + NUM_TRIGRAMS, nullptr);
 237         if (store_dir_times) {
 238                 dir_time_ctx = ZSTD_createCStream();
 239                 ZSTD_initCStream(dir_time_ctx, /*level=*/6);
 240         }
 241 }
 242
 243 EncodingCorpus::~EncodingCorpus()
 244 {
 245         for (unsigned i = 0; i < NUM_TRIGRAMS; ++i) {
 246                 delete invindex[i];
 247         }
 248 }
 249
 250 void EncodingCorpus::add_file(string filename, dir_time dt)
 251 {
 252         ++num_files;
 253         if (!current_block.empty()) {
 254                 current_block.push_back('\0');
 255         }
 256         current_block += filename;
 257         if (++num_files_in_block == block_size) {
 258                 flush_block();
 259         }
 260
 261         if (store_dir_times) {
 262                 if (dt.sec == -1) {
 263                         // Not a directory.
 264                         dir_times.push_back('\0');
 265                 } else {
 266                         dir_times.push_back('\1');
 267                         dir_times.append(reinterpret_cast<char *>(&dt.sec), sizeof(dt.sec));
 268                         dir_times.append(reinterpret_cast<char *>(&dt.nsec), sizeof(dt.nsec));
 269                 }
 270                 compress_dir_times(/*allowed_slop=*/4096);
 271         }
 272 }
 273
 274 void EncodingCorpus::compress_dir_times(size_t allowed_slop)
 275 {
 276         while (dir_times.size() >= allowed_slop) {
 277                 size_t old_size = dir_times_compressed.size();
 278                 dir_times_compressed.resize(old_size + 4096);
 279
 280                 ZSTD_outBuffer outbuf;
 281                 outbuf.dst = dir_times_compressed.data() + old_size;
 282                 outbuf.size = 4096;
 283                 outbuf.pos = 0;
 284
 285                 ZSTD_inBuffer inbuf;
 286                 inbuf.src = dir_times.data();
 287                 inbuf.size = dir_times.size();
 288                 inbuf.pos = 0;
 289
 290                 int ret = ZSTD_compressStream(dir_time_ctx, &outbuf, &inbuf);
 291                 if (ret < 0) {
 292                         fprintf(stderr, "ZSTD_compressStream() failed\n");
 293                         exit(1);
 294                 }
 295
 296                 dir_times_compressed.resize(old_size + outbuf.pos);
 297                 dir_times.erase(dir_times.begin(), dir_times.begin() + inbuf.pos);
 298
 299                 if (outbuf.pos == 0 && inbuf.pos == 0) {
 300                         // Nothing happened (not enough data?), try again later.
 301                         return;
 302                 }
 303         }
 304 }
 305
 306 void EncodingCorpus::flush_block()
 307 {
 308         if (current_block.empty()) {
 309                 return;
 310         }
 311
 312         uint32_t docid = num_blocks;
 313
 314         // Create trigrams.
 315         const char *ptr = current_block.c_str();
 316         while (ptr < current_block.c_str() + current_block.size()) {
 317                 string_view s(ptr);
 318                 if (s.size() >= 3) {
 319                         for (size_t j = 0; j < s.size() - 2; ++j) {
 320                                 uint32_t trgm = read_trigram(s, j);
 321                                 add_docid(trgm, docid);
 322                         }
 323                 }
 324                 ptr += s.size() + 1;
 325         }
 326
 327         // Compress and add the filename block.
 328         filename_blocks.push_back(ftell(outfp));
 329         string compressed = zstd_compress(current_block, cdict, &tempbuf);
 330         if (fwrite(compressed.data(), compressed.size(), 1, outfp) != 1) {
 331                 perror("fwrite()");
 332                 exit(1);
 333         }
 334
 335         current_block.clear();
 336         num_files_in_block = 0;
 337         ++num_blocks;
 338 }
 339
 340 void EncodingCorpus::finish()
 341 {
 342         flush_block();
 343 }
 344
 345 size_t EncodingCorpus::num_trigrams() const
 346 {
 347         size_t num = 0;
 348         for (unsigned trgm = 0; trgm < NUM_TRIGRAMS; ++trgm) {
 349                 if (invindex[trgm] != nullptr) {
 350                         ++num;
 351                 }
 352         }
 353         return num;
 354 }
 355
 356 string EncodingCorpus::get_compressed_dir_times()
 357 {
 358         if (!store_dir_times) {
 359                 return "";
 360         }
 361         compress_dir_times(/*allowed_slop=*/0);
 362         assert(dir_times.empty());
 363
 364         for (;;) {
 365                 size_t old_size = dir_times_compressed.size();
 366                 dir_times_compressed.resize(old_size + 4096);
 367
 368                 ZSTD_outBuffer outbuf;
 369                 outbuf.dst = dir_times_compressed.data() + old_size;
 370                 outbuf.size = 4096;
 371                 outbuf.pos = 0;
 372
 373                 int ret = ZSTD_endStream(dir_time_ctx, &outbuf);
 374                 if (ret < 0) {
 375                         fprintf(stderr, "ZSTD_compressStream() failed\n");
 376                         exit(1);
 377                 }
 378
 379                 dir_times_compressed.resize(old_size + outbuf.pos);
 380
 381                 if (ret == 0) {
 382                         // All done.
 383                         break;
 384                 }
 385         }
 386
 387         return dir_times_compressed;
 388 }
 389
 390 string zstd_compress(const string &src, ZSTD_CDict *cdict, string *tempbuf)
 391 {
 392         static ZSTD_CCtx *ctx = nullptr;
 393         if (ctx == nullptr) {
 394                 ctx = ZSTD_createCCtx();
 395         }
 396
 397         size_t max_size = ZSTD_compressBound(src.size());
 398         if (tempbuf->size() < max_size) {
 399                 tempbuf->resize(max_size);
 400         }
 401         size_t size;
 402         if (cdict == nullptr) {
 403                 size = ZSTD_compressCCtx(ctx, &(*tempbuf)[0], max_size, src.data(), src.size(), /*level=*/6);
 404         } else {
 405                 size = ZSTD_compress_usingCDict(ctx, &(*tempbuf)[0], max_size, src.data(), src.size(), cdict);
 406         }
 407         return string(tempbuf->data(), size);
 408 }
 409
 410 bool is_prime(uint32_t x)
 411 {
 412         if ((x % 2) == 0 || (x % 3) == 0) {
 413                 return false;
 414         }
 415         uint32_t limit = ceil(sqrt(x));
 416         for (uint32_t factor = 5; factor <= limit; ++factor) {
 417                 if ((x % factor) == 0) {
 418                         return false;
 419                 }
 420         }
 421         return true;
 422 }
 423
 424 uint32_t next_prime(uint32_t x)
 425 {
 426         if ((x % 2) == 0) {
 427                 ++x;
 428         }
 429         while (!is_prime(x)) {
 430                 x += 2;
 431         }
 432         return x;
 433 }
 434
 435 unique_ptr<Trigram[]> create_hashtable(EncodingCorpus &corpus, const vector<uint32_t> &all_trigrams, uint32_t ht_size, uint32_t num_overflow_slots)
 436 {
 437         unique_ptr<Trigram[]> ht(new Trigram[ht_size + num_overflow_slots + 1]);  // 1 for the sentinel element at the end.
 438         for (unsigned i = 0; i < ht_size + num_overflow_slots + 1; ++i) {
 439                 ht[i].trgm = uint32_t(-1);
 440                 ht[i].num_docids = 0;
 441                 ht[i].offset = 0;
 442         }
 443         for (uint32_t trgm : all_trigrams) {
 444                 // We don't know offset yet, so set it to zero.
 445                 Trigram to_insert{ trgm, uint32_t(corpus.get_pl_builder(trgm).get_num_docids()), 0 };
 446
 447                 uint32_t bucket = hash_trigram(trgm, ht_size);
 448                 unsigned distance = 0;
 449                 while (ht[bucket].num_docids != 0) {
 450                         // Robin Hood hashing; reduces the longest distance by a lot.
 451                         unsigned other_distance = bucket - hash_trigram(ht[bucket].trgm, ht_size);
 452                         if (distance > other_distance) {
 453                                 swap(to_insert, ht[bucket]);
 454                                 distance = other_distance;
 455                         }
 456
 457                         ++bucket, ++distance;
 458                         if (distance > num_overflow_slots) {
 459                                 return nullptr;
 460                         }
 461                 }
 462                 ht[bucket] = to_insert;
 463         }
 464         return ht;
 465 }
 466
 467 DatabaseBuilder::DatabaseBuilder(const char *outfile, gid_t owner, int block_size, string dictionary, bool check_visibility)
 468         : outfile(outfile), block_size(block_size)
 469 {
 470         umask(0027);
 471
 472         string path = outfile;
 473         path.resize(path.find_last_of('/') + 1);
 474         if (path.empty()) {
 475                 path = ".";
 476         }
 477 #ifdef O_TMPFILE
 478         int fd = open(path.c_str(), O_WRONLY | O_TMPFILE, 0640);
 479         if (fd == -1) {
 480                 perror(path.c_str());
 481                 exit(1);
 482         }
 483 #else
 484         temp_filename = string(outfile) + ".XXXXXX";
 485         int fd = mkstemp(&temp_filename[0]);
 486         if (fd == -1) {
 487                 perror(temp_filename.c_str());
 488                 exit(1);
 489         }
 490         if (fchmod(fd, 0640) == -1) {
 491                 perror("fchmod");
 492                 exit(1);
 493         }
 494 #endif
 495
 496         if (owner != (gid_t)-1) {
 497                 if (fchown(fd, (uid_t)-1, owner) == -1) {
 498                         perror("fchown");
 499                         exit(1);
 500                 }
 501         }
 502
 503         outfp = fdopen(fd, "wb");
 504         if (outfp == nullptr) {
 505                 perror(outfile);
 506                 exit(1);
 507         }
 508
 509         // Write the header.
 510         memcpy(hdr.magic, "\0plocate", 8);
 511         hdr.version = -1;  // Mark as broken.
 512         hdr.hashtable_size = 0;  // Not known yet.
 513         hdr.extra_ht_slots = num_overflow_slots;
 514         hdr.num_docids = 0;
 515         hdr.hash_table_offset_bytes = -1;  // We don't know these offsets yet.
 516         hdr.max_version = 2;
 517         hdr.filename_index_offset_bytes = -1;
 518         hdr.zstd_dictionary_length_bytes = -1;
 519         hdr.check_visibility = check_visibility;
 520         fwrite(&hdr, sizeof(hdr), 1, outfp);
 521
 522         if (dictionary.empty()) {
 523                 hdr.zstd_dictionary_offset_bytes = 0;
 524                 hdr.zstd_dictionary_length_bytes = 0;
 525         } else {
 526                 hdr.zstd_dictionary_offset_bytes = ftell(outfp);
 527                 fwrite(dictionary.data(), dictionary.size(), 1, outfp);
 528                 hdr.zstd_dictionary_length_bytes = dictionary.size();
 529                 cdict = ZSTD_createCDict(dictionary.data(), dictionary.size(), /*level=*/6);
 530         }
 531
 532         hdr.directory_data_length_bytes = 0;
 533         hdr.directory_data_offset_bytes = 0;
 534         hdr.next_zstd_dictionary_length_bytes = 0;
 535         hdr.next_zstd_dictionary_offset_bytes = 0;
 536         hdr.conf_block_length_bytes = 0;
 537         hdr.conf_block_offset_bytes = 0;
 538 }
 539
 540 DatabaseReceiver *DatabaseBuilder::start_corpus(bool store_dir_times)
 541 {
 542         corpus_start = steady_clock::now();
 543         corpus = new EncodingCorpus(outfp, block_size, cdict, store_dir_times);
 544         return corpus;
 545 }
 546
 547 void DatabaseBuilder::set_next_dictionary(std::string next_dictionary)
 548 {
 549         this->next_dictionary = move(next_dictionary);
 550 }
 551
 552 void DatabaseBuilder::set_conf_block(std::string conf_block)
 553 {
 554         this->conf_block = move(conf_block);
 555 }
 556
 557 void DatabaseBuilder::finish_corpus()
 558 {
 559         corpus->finish();
 560         hdr.num_docids = corpus->filename_blocks.size();
 561
 562         // Stick an empty block at the end as sentinel.
 563         corpus->filename_blocks.push_back(ftell(outfp));
 564         const size_t bytes_for_filenames = corpus->filename_blocks.back() - corpus->filename_blocks.front();
 565
 566         // Write the offsets to the filenames.
 567         hdr.filename_index_offset_bytes = ftell(outfp);
 568         const size_t bytes_for_filename_index = corpus->filename_blocks.size() * sizeof(uint64_t);
 569         fwrite(corpus->filename_blocks.data(), corpus->filename_blocks.size(), sizeof(uint64_t), outfp);
 570         corpus->filename_blocks.clear();
 571         corpus->filename_blocks.shrink_to_fit();
 572
 573         // Finish up encoding the posting lists.
 574         size_t trigrams = 0, longest_posting_list = 0;
 575         size_t bytes_for_posting_lists = 0;
 576         for (unsigned trgm = 0; trgm < NUM_TRIGRAMS; ++trgm) {
 577                 if (!corpus->seen_trigram(trgm))
 578                         continue;
 579                 PostingListBuilder &pl_builder = corpus->get_pl_builder(trgm);
 580                 pl_builder.finish();
 581                 longest_posting_list = max(longest_posting_list, pl_builder.get_num_docids());
 582                 trigrams += pl_builder.get_num_docids();
 583                 bytes_for_posting_lists += pl_builder.encoded.size();
 584         }
 585         size_t num_trigrams = corpus->num_trigrams();
 586         dprintf("%zu files, %zu different trigrams, %zu entries, avg len %.2f, longest %zu\n",
 587                 corpus->num_files, num_trigrams, trigrams, double(trigrams) / num_trigrams, longest_posting_list);
 588         dprintf("%zu bytes used for posting lists (%.2f bits/entry)\n", bytes_for_posting_lists, 8 * bytes_for_posting_lists / double(trigrams));
 589
 590         dprintf("Building posting lists took %.1f ms.\n\n", 1e3 * duration<float>(steady_clock::now() - corpus_start).count());
 591
 592         // Find the used trigrams.
 593         vector<uint32_t> all_trigrams;
 594         for (unsigned trgm = 0; trgm < NUM_TRIGRAMS; ++trgm) {
 595                 if (corpus->seen_trigram(trgm)) {
 596                         all_trigrams.push_back(trgm);
 597                 }
 598         }
 599
 600         // Create the hash table.
 601         unique_ptr<Trigram[]> hashtable;
 602         uint32_t ht_size = next_prime(all_trigrams.size());
 603         for (;;) {
 604                 hashtable = create_hashtable(*corpus, all_trigrams, ht_size, num_overflow_slots);
 605                 if (hashtable == nullptr) {
 606                         dprintf("Failed creating hash table of size %u, increasing by 5%% and trying again.\n", ht_size);
 607                         ht_size = next_prime(ht_size * 1.05);
 608                 } else {
 609                         dprintf("Created hash table of size %u.\n\n", ht_size);
 610                         break;
 611                 }
 612         }
 613
 614         // Find the offsets for each posting list.
 615         size_t bytes_for_hashtable = (ht_size + num_overflow_slots + 1) * sizeof(Trigram);
 616         uint64_t offset = ftell(outfp) + bytes_for_hashtable;
 617         for (unsigned i = 0; i < ht_size + num_overflow_slots + 1; ++i) {
 618                 hashtable[i].offset = offset;  // Needs to be there even for empty slots.
 619                 if (hashtable[i].num_docids == 0) {
 620                         continue;
 621                 }
 622
 623                 const vector<unsigned char> &encoded = corpus->get_pl_builder(hashtable[i].trgm).encoded;
 624                 offset += encoded.size();
 625         }
 626
 627         // Write the hash table.
 628         hdr.hash_table_offset_bytes = ftell(outfp);
 629         hdr.hashtable_size = ht_size;
 630         fwrite(hashtable.get(), ht_size + num_overflow_slots + 1, sizeof(Trigram), outfp);
 631
 632         // Write the actual posting lists.
 633         for (unsigned i = 0; i < ht_size + num_overflow_slots + 1; ++i) {
 634                 if (hashtable[i].num_docids == 0) {
 635                         continue;
 636                 }
 637                 const vector<unsigned char> &encoded = corpus->get_pl_builder(hashtable[i].trgm).encoded;
 638                 fwrite(encoded.data(), encoded.size(), 1, outfp);
 639         }
 640
 641         // Finally, write the directory times (for updatedb).
 642         string compressed_dir_times = corpus->get_compressed_dir_times();
 643         size_t bytes_for_compressed_dir_times = 0;
 644         if (!compressed_dir_times.empty()) {
 645                 hdr.directory_data_offset_bytes = ftell(outfp);
 646                 hdr.directory_data_length_bytes = compressed_dir_times.size();
 647                 fwrite(compressed_dir_times.data(), compressed_dir_times.size(), 1, outfp);
 648                 bytes_for_compressed_dir_times = compressed_dir_times.size();
 649                 compressed_dir_times.clear();
 650         }
 651
 652         // Write the recommended dictionary for next update.
 653         if (!next_dictionary.empty()) {
 654                 hdr.next_zstd_dictionary_offset_bytes = ftell(outfp);
 655                 hdr.next_zstd_dictionary_length_bytes = next_dictionary.size();
 656                 fwrite(next_dictionary.data(), next_dictionary.size(), 1, outfp);
 657         }
 658
 659         // And the configuration block.
 660         if (!conf_block.empty()) {
 661                 hdr.conf_block_offset_bytes = ftell(outfp);
 662                 hdr.conf_block_length_bytes = conf_block.size();
 663                 fwrite(conf_block.data(), conf_block.size(), 1, outfp);
 664         }
 665
 666         // Rewind, and write the updated header.
 667         hdr.version = 1;
 668         fseek(outfp, 0, SEEK_SET);
 669         fwrite(&hdr, sizeof(hdr), 1, outfp);
 670
 671 #ifdef O_TMPFILE
 672         // Give the file a proper name, making it visible in the file system.
 673         // TODO: It would be nice to be able to do this atomically, like with rename.
 674         unlink(outfile.c_str());
 675         char procpath[256];
 676         snprintf(procpath, sizeof(procpath), "/proc/self/fd/%d", fileno(outfp));
 677         if (linkat(AT_FDCWD, procpath, AT_FDCWD, outfile.c_str(), AT_SYMLINK_FOLLOW) == -1) {
 678                 perror("linkat");
 679                 exit(1);
 680         }
 681 #else
 682         if (rename(temp_filename.c_str(), outfile.c_str()) == -1) {
 683                 perror("rename");
 684                 exit(1);
 685         }
 686 #endif
 687
 688         fclose(outfp);
 689
 690         size_t total_bytes = (bytes_for_hashtable + bytes_for_posting_lists + bytes_for_filename_index + bytes_for_filenames + bytes_for_compressed_dir_times);
 691
 692         dprintf("Block size:     %7d files\n", block_size);
 693         dprintf("Dictionary:     %'7.1f MB\n", hdr.zstd_dictionary_length_bytes / 1048576.0);
 694         dprintf("Hash table:     %'7.1f MB\n", bytes_for_hashtable / 1048576.0);
 695         dprintf("Posting lists:  %'7.1f MB\n", bytes_for_posting_lists / 1048576.0);
 696         dprintf("Filename index: %'7.1f MB\n", bytes_for_filename_index / 1048576.0);
 697         dprintf("Filenames:      %'7.1f MB\n", bytes_for_filenames / 1048576.0);
 698         if (bytes_for_compressed_dir_times != 0) {
 699                 dprintf("Modify times:   %'7.1f MB\n", bytes_for_compressed_dir_times / 1048576.0);
 700         }
 701         dprintf("Total:          %'7.1f MB\n", total_bytes / 1048576.0);
 702         dprintf("\n");
 703 }