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

   1 #include "access_rx_cache.h"
   2 #include "complete_pread.h"
   3 #include "db.h"
   4 #include "dprintf.h"
   5 #include "io_uring_engine.h"
   6 #include "needle.h"
   7 #include "parse_trigrams.h"
   8 #include "serializer.h"
   9 #include "turbopfor.h"
  10 #include "unique_sort.h"
  11
  12 #include <algorithm>
  13 #include <assert.h>
  14 #include <atomic>
  15 #include <chrono>
  16 #include <condition_variable>
  17 #include <deque>
  18 #include <fcntl.h>
  19 #include <functional>
  20 #include <getopt.h>
  21 #include <inttypes.h>
  22 #include <iterator>
  23 #include <limits>
  24 #include <locale.h>
  25 #include <memory>
  26 #include <mutex>
  27 #include <regex.h>
  28 #include <stdint.h>
  29 #include <stdio.h>
  30 #include <stdlib.h>
  31 #include <string.h>
  32 #include <string>
  33 #include <string_view>
  34 #include <sys/types.h>
  35 #include <sys/wait.h>
  36 #include <thread>
  37 #include <tuple>
  38 #include <unistd.h>
  39 #include <unordered_map>
  40 #include <unordered_set>
  41 #include <utility>
  42 #include <vector>
  43 #include <zstd.h>
  44
  45 using namespace std;
  46 using namespace std::chrono;
  47
  48 bool ignore_case = false;
  49 bool only_count = false;
  50 bool print_nul = false;
  51 bool use_debug = false;
  52 bool flush_cache = false;
  53 bool patterns_are_regex = false;
  54 bool use_extended_regex = false;
  55 bool match_basename = false;
  56 int64_t limit_matches = numeric_limits<int64_t>::max();
  57 int64_t limit_left = numeric_limits<int64_t>::max();
  58 bool stdout_is_tty = false;
  59 static bool in_forked_child = false;
  60
  61 steady_clock::time_point start;
  62 ZSTD_DDict *ddict = nullptr;
  63
  64 class Corpus {
  65 public:
  66         Corpus(int fd, IOUringEngine *engine);
  67         ~Corpus();
  68         void find_trigram(uint32_t trgm, function<void(const Trigram *trgmptr, size_t len)> cb);
  69         void get_compressed_filename_block(uint32_t docid, function<void(string_view)> cb) const;
  70         size_t get_num_filename_blocks() const;
  71         off_t offset_for_block(uint32_t docid) const
  72         {
  73                 return hdr.filename_index_offset_bytes + docid * sizeof(uint64_t);
  74         }
  75         const Header &get_hdr() const { return hdr; }
  76
  77 public:
  78         const int fd;
  79         IOUringEngine *const engine;
  80
  81         Header hdr;
  82 };
  83
  84 Corpus::Corpus(int fd, IOUringEngine *engine)
  85         : fd(fd), engine(engine)
  86 {
  87         if (flush_cache) {
  88                 off_t len = lseek(fd, 0, SEEK_END);
  89                 if (len == -1) {
  90                         perror("lseek");
  91                         exit(1);
  92                 }
  93                 posix_fadvise(fd, 0, len, POSIX_FADV_DONTNEED);
  94         }
  95
  96         complete_pread(fd, &hdr, sizeof(hdr), /*offset=*/0);
  97         if (memcmp(hdr.magic, "\0plocate", 8) != 0) {
  98                 fprintf(stderr, "plocate.db is corrupt or an old version; please rebuild it.\n");
  99                 exit(1);
 100         }
 101         if (hdr.version != 0 && hdr.version != 1) {
 102                 fprintf(stderr, "plocate.db has version %u, expected 0 or 1; please rebuild it.\n", hdr.version);
 103                 exit(1);
 104         }
 105         if (hdr.version == 0) {
 106                 // These will be junk data.
 107                 hdr.zstd_dictionary_offset_bytes = 0;
 108                 hdr.zstd_dictionary_length_bytes = 0;
 109         }
 110         if (hdr.max_version < 2) {
 111                 // This too. (We ignore the other max_version 2 fields.)
 112                 hdr.check_visibility = true;
 113         }
 114 }
 115
 116 Corpus::~Corpus()
 117 {
 118         close(fd);
 119 }
 120
 121 void Corpus::find_trigram(uint32_t trgm, function<void(const Trigram *trgmptr, size_t len)> cb)
 122 {
 123         uint32_t bucket = hash_trigram(trgm, hdr.hashtable_size);
 124         engine->submit_read(fd, sizeof(Trigram) * (hdr.extra_ht_slots + 2), hdr.hash_table_offset_bytes + sizeof(Trigram) * bucket, [this, trgm, cb{ move(cb) }](string_view s) {
 125                 const Trigram *trgmptr = reinterpret_cast<const Trigram *>(s.data());
 126                 for (unsigned i = 0; i < hdr.extra_ht_slots + 1; ++i) {
 127                         if (trgmptr[i].trgm == trgm) {
 128                                 cb(trgmptr + i, trgmptr[i + 1].offset - trgmptr[i].offset);
 129                                 return;
 130                         }
 131                 }
 132
 133                 // Not found.
 134                 cb(nullptr, 0);
 135         });
 136 }
 137
 138 void Corpus::get_compressed_filename_block(uint32_t docid, function<void(string_view)> cb) const
 139 {
 140         // Read the file offset from this docid and the next one.
 141         // This is always allowed, since we have a sentinel block at the end.
 142         engine->submit_read(fd, sizeof(uint64_t) * 2, offset_for_block(docid), [this, cb{ move(cb) }](string_view s) {
 143                 const uint64_t *ptr = reinterpret_cast<const uint64_t *>(s.data());
 144                 off_t offset = ptr[0];
 145                 size_t len = ptr[1] - ptr[0];
 146                 engine->submit_read(fd, len, offset, cb);
 147         });
 148 }
 149
 150 size_t Corpus::get_num_filename_blocks() const
 151 {
 152         return hdr.num_docids;
 153 }
 154
 155 void scan_file_block(const vector<Needle> &needles, string_view compressed,
 156                      AccessRXCache *access_rx_cache, uint64_t seq, ResultReceiver *serializer,
 157                      atomic<uint64_t> *matched)
 158 {
 159         unsigned long long uncompressed_len = ZSTD_getFrameContentSize(compressed.data(), compressed.size());
 160         if (uncompressed_len == ZSTD_CONTENTSIZE_UNKNOWN || uncompressed_len == ZSTD_CONTENTSIZE_ERROR) {
 161                 fprintf(stderr, "ZSTD_getFrameContentSize() failed\n");
 162                 exit(1);
 163         }
 164
 165         string block;
 166         block.resize(uncompressed_len + 1);
 167
 168         static thread_local ZSTD_DCtx *ctx = ZSTD_createDCtx();  // Reused across calls.
 169         size_t err;
 170
 171         if (ddict != nullptr) {
 172                 err = ZSTD_decompress_usingDDict(ctx, &block[0], block.size(), compressed.data(),
 173                                                  compressed.size(), ddict);
 174         } else {
 175                 err = ZSTD_decompressDCtx(ctx, &block[0], block.size(), compressed.data(),
 176                                           compressed.size());
 177         }
 178         if (ZSTD_isError(err)) {
 179                 fprintf(stderr, "ZSTD_decompress(): %s\n", ZSTD_getErrorName(err));
 180                 exit(1);
 181         }
 182         block[block.size() - 1] = '\0';
 183
 184         auto test_candidate = [&](const char *filename, uint64_t local_seq, uint64_t next_seq) {
 185                 access_rx_cache->check_access(filename, /*allow_async=*/true, [matched, serializer, local_seq, next_seq, filename{ strdup(filename) }](bool ok) {
 186                         if (ok) {
 187                                 ++*matched;
 188                                 serializer->print(local_seq, next_seq - local_seq, filename);
 189                         } else {
 190                                 serializer->print(local_seq, next_seq - local_seq, "");
 191                         }
 192                         free(filename);
 193                 });
 194         };
 195
 196         // We need to know the next sequence number before inserting into Serializer,
 197         // so always buffer one candidate.
 198         const char *pending_candidate = nullptr;
 199
 200         uint64_t local_seq = seq << 32;
 201         for (const char *filename = block.data();
 202              filename != block.data() + block.size();
 203              filename += strlen(filename) + 1) {
 204                 const char *haystack = filename;
 205                 if (match_basename) {
 206                         haystack = strrchr(filename, '/');
 207                         if (haystack == nullptr) {
 208                                 haystack = filename;
 209                         } else {
 210                                 ++haystack;
 211                         }
 212                 }
 213
 214                 bool found = true;
 215                 for (const Needle &needle : needles) {
 216                         if (!matches(needle, haystack)) {
 217                                 found = false;
 218                                 break;
 219                         }
 220                 }
 221                 if (found) {
 222                         if (pending_candidate != nullptr) {
 223                                 test_candidate(pending_candidate, local_seq, local_seq + 1);
 224                                 ++local_seq;
 225                         }
 226                         pending_candidate = filename;
 227                 }
 228         }
 229         if (pending_candidate == nullptr) {
 230                 serializer->print(seq << 32, 1ULL << 32, "");
 231         } else {
 232                 test_candidate(pending_candidate, local_seq, (seq + 1) << 32);
 233         }
 234 }
 235
 236 size_t scan_docids(const vector<Needle> &needles, const vector<uint32_t> &docids, const Corpus &corpus, IOUringEngine *engine)
 237 {
 238         Serializer docids_in_order;
 239         AccessRXCache access_rx_cache(engine, corpus.get_hdr().check_visibility);
 240         atomic<uint64_t> matched{ 0 };
 241         for (size_t i = 0; i < docids.size(); ++i) {
 242                 uint32_t docid = docids[i];
 243                 corpus.get_compressed_filename_block(docid, [i, &matched, &needles, &access_rx_cache, &docids_in_order](string_view compressed) {
 244                         scan_file_block(needles, compressed, &access_rx_cache, i, &docids_in_order, &matched);
 245                 });
 246         }
 247         engine->finish();
 248         return matched;
 249 }
 250
 251 struct WorkerThread {
 252         thread t;
 253
 254         // We use a result queue instead of synchronizing Serializer,
 255         // since a lock on it becomes a huge choke point if there are
 256         // lots of threads.
 257         mutex result_mu;
 258         struct Result {
 259                 uint64_t seq;
 260                 uint64_t skip;
 261                 string msg;
 262         };
 263         vector<Result> results;
 264 };
 265
 266 class WorkerThreadReceiver : public ResultReceiver {
 267 public:
 268         WorkerThreadReceiver(WorkerThread *wt)
 269                 : wt(wt) {}
 270
 271         void print(uint64_t seq, uint64_t skip, const string msg) override
 272         {
 273                 lock_guard<mutex> lock(wt->result_mu);
 274                 if (msg.empty() && !wt->results.empty() && wt->results.back().seq + wt->results.back().skip == seq) {
 275                         wt->results.back().skip += skip;
 276                 } else {
 277                         wt->results.emplace_back(WorkerThread::Result{ seq, skip, move(msg) });
 278                 }
 279         }
 280
 281 private:
 282         WorkerThread *wt;
 283 };
 284
 285 void deliver_results(WorkerThread *wt, Serializer *serializer)
 286 {
 287         vector<WorkerThread::Result> results;
 288         {
 289                 lock_guard<mutex> lock(wt->result_mu);
 290                 results = move(wt->results);
 291         }
 292         for (const WorkerThread::Result &result : results) {
 293                 serializer->print(result.seq, result.skip, move(result.msg));
 294         }
 295 }
 296
 297 // We do this sequentially, as it's faster than scattering
 298 // a lot of I/O through io_uring and hoping the kernel will
 299 // coalesce it plus readahead for us. Since we assume that
 300 // we will primarily be CPU-bound, we'll be firing up one
 301 // worker thread for each spare core (the last one will
 302 // only be doing I/O). access() is still synchronous.
 303 uint64_t scan_all_docids(const vector<Needle> &needles, int fd, const Corpus &corpus)
 304 {
 305         {
 306                 const Header &hdr = corpus.get_hdr();
 307                 if (hdr.zstd_dictionary_length_bytes > 0) {
 308                         string dictionary;
 309                         dictionary.resize(hdr.zstd_dictionary_length_bytes);
 310                         complete_pread(fd, &dictionary[0], hdr.zstd_dictionary_length_bytes, hdr.zstd_dictionary_offset_bytes);
 311                         ddict = ZSTD_createDDict(dictionary.data(), dictionary.size());
 312                 }
 313         }
 314
 315         AccessRXCache access_rx_cache(nullptr, corpus.get_hdr().check_visibility);
 316         Serializer serializer;
 317         uint32_t num_blocks = corpus.get_num_filename_blocks();
 318         unique_ptr<uint64_t[]> offsets(new uint64_t[num_blocks + 1]);
 319         complete_pread(fd, offsets.get(), (num_blocks + 1) * sizeof(uint64_t), corpus.offset_for_block(0));
 320         atomic<uint64_t> matched{ 0 };
 321
 322         mutex mu;
 323         condition_variable queue_added, queue_removed;
 324         deque<tuple<int, int, string>> work_queue;  // Under mu.
 325         bool done = false;  // Under mu.
 326
 327         unsigned num_threads = max<int>(sysconf(_SC_NPROCESSORS_ONLN) - 1, 1);
 328         dprintf("Using %u worker threads for linear scan.\n", num_threads);
 329         unique_ptr<WorkerThread[]> threads(new WorkerThread[num_threads]);
 330         for (unsigned i = 0; i < num_threads; ++i) {
 331                 threads[i].t = thread([&threads, &mu, &queue_added, &queue_removed, &work_queue, &done, &offsets, &needles, &access_rx_cache, &matched, i] {
 332                         // regcomp() takes a lock on the regex, so each thread will need its own.
 333                         const vector<Needle> *use_needles = &needles;
 334                         vector<Needle> recompiled_needles;
 335                         if (i != 0 && patterns_are_regex) {
 336                                 recompiled_needles = needles;
 337                                 for (Needle &needle : recompiled_needles) {
 338                                         needle.re = compile_regex(needle.str);
 339                                 }
 340                                 use_needles = &recompiled_needles;
 341                         }
 342
 343                         WorkerThreadReceiver receiver(&threads[i]);
 344                         for (;;) {
 345                                 uint32_t io_docid, last_docid;
 346                                 string compressed;
 347
 348                                 {
 349                                         unique_lock<mutex> lock(mu);
 350                                         queue_added.wait(lock, [&work_queue, &done] { return !work_queue.empty() || done; });
 351                                         if (done && work_queue.empty()) {
 352                                                 return;
 353                                         }
 354                                         tie(io_docid, last_docid, compressed) = move(work_queue.front());
 355                                         work_queue.pop_front();
 356                                         queue_removed.notify_all();
 357                                 }
 358
 359                                 for (uint32_t docid = io_docid; docid < last_docid; ++docid) {
 360                                         size_t relative_offset = offsets[docid] - offsets[io_docid];
 361                                         size_t len = offsets[docid + 1] - offsets[docid];
 362                                         scan_file_block(*use_needles, { &compressed[relative_offset], len }, &access_rx_cache, docid, &receiver, &matched);
 363                                 }
 364                         }
 365                 });
 366         }
 367
 368         string compressed;
 369         for (uint32_t io_docid = 0; io_docid < num_blocks; io_docid += 32) {
 370                 uint32_t last_docid = std::min(io_docid + 32, num_blocks);
 371                 size_t io_len = offsets[last_docid] - offsets[io_docid];
 372                 if (compressed.size() < io_len) {
 373                         compressed.resize(io_len);
 374                 }
 375                 complete_pread(fd, &compressed[0], io_len, offsets[io_docid]);
 376
 377                 {
 378                         unique_lock<mutex> lock(mu);
 379                         queue_removed.wait(lock, [&work_queue] { return work_queue.size() < 256; });  // Allow ~2MB of data queued up.
 380                         work_queue.emplace_back(io_docid, last_docid, move(compressed));
 381                         queue_added.notify_one();  // Avoid the thundering herd.
 382                 }
 383
 384                 // Pick up some results, so that we are sure that we won't just overload.
 385                 // (Seemingly, going through all of these causes slowness with many threads,
 386                 // but taking only one is OK.)
 387                 unsigned i = io_docid / 32;
 388                 deliver_results(&threads[i % num_threads], &serializer);
 389         }
 390         {
 391                 lock_guard<mutex> lock(mu);
 392                 done = true;
 393                 queue_added.notify_all();
 394         }
 395         for (unsigned i = 0; i < num_threads; ++i) {
 396                 threads[i].t.join();
 397                 deliver_results(&threads[i], &serializer);
 398         }
 399         return matched;
 400 }
 401
 402 // Takes the given posting list, unions it into the parts of the trigram disjunction
 403 // already read; if the list is complete, intersects with “cur_candidates”.
 404 //
 405 // Returns true if the search should be aborted (we are done).
 406 bool new_posting_list_read(TrigramDisjunction *td, vector<uint32_t> decoded, vector<uint32_t> *cur_candidates, vector<uint32_t> *tmp)
 407 {
 408         if (td->docids.empty()) {
 409                 td->docids = move(decoded);
 410         } else {
 411                 tmp->clear();
 412                 set_union(decoded.begin(), decoded.end(), td->docids.begin(), td->docids.end(), back_inserter(*tmp));
 413                 swap(*tmp, td->docids);
 414         }
 415         if (--td->remaining_trigrams_to_read > 0) {
 416                 // Need to wait for more.
 417                 if (ignore_case) {
 418                         dprintf("  ... %u reads left in OR group %u (%zu docids in list)\n",
 419                                 td->remaining_trigrams_to_read, td->index, td->docids.size());
 420                 }
 421                 return false;
 422         }
 423         if (cur_candidates->empty()) {
 424                 if (ignore_case) {
 425                         dprintf("  ... all reads done for OR group %u (%zu docids)\n",
 426                                 td->index, td->docids.size());
 427                 }
 428                 *cur_candidates = move(td->docids);
 429         } else {
 430                 tmp->clear();
 431                 set_intersection(cur_candidates->begin(), cur_candidates->end(),
 432                                  td->docids.begin(), td->docids.end(),
 433                                  back_inserter(*tmp));
 434                 swap(*cur_candidates, *tmp);
 435                 if (ignore_case) {
 436                         if (cur_candidates->empty()) {
 437                                 dprintf("  ... all reads done for OR group %u (%zu docids), intersected (none left, search is done)\n",
 438                                         td->index, td->docids.size());
 439                                 return true;
 440                         } else {
 441                                 dprintf("  ... all reads done for OR group %u (%zu docids), intersected (%zu left)\n",
 442                                         td->index, td->docids.size(), cur_candidates->size());
 443                         }
 444                 }
 445         }
 446         return false;
 447 }
 448
 449 uint64_t do_search_file(const vector<Needle> &needles, const std::string &filename)
 450 {
 451         int fd = open(filename.c_str(), O_RDONLY);
 452         if (fd == -1) {
 453                 perror(filename.c_str());
 454                 exit(1);
 455         }
 456
 457         // Drop privileges.
 458         if (setgid(getgid()) != 0) {
 459                 perror("setgid");
 460                 exit(EXIT_FAILURE);
 461         }
 462
 463         start = steady_clock::now();
 464         if (access("/", R_OK | X_OK)) {
 465                 // We can't find anything, no need to bother...
 466                 return 0;
 467         }
 468
 469         IOUringEngine engine(/*slop_bytes=*/16);  // 16 slop bytes as described in turbopfor.h.
 470         Corpus corpus(fd, &engine);
 471         dprintf("Corpus init done after %.1f ms.\n", 1e3 * duration<float>(steady_clock::now() - start).count());
 472
 473         vector<TrigramDisjunction> trigram_groups;
 474         if (patterns_are_regex) {
 475                 // We could parse the regex to find trigrams that have to be there
 476                 // (there are actually known algorithms to deal with disjunctions
 477                 // and such, too), but for now, we just go brute force.
 478                 // Using locate with regexes is pretty niche.
 479         } else {
 480                 for (const Needle &needle : needles) {
 481                         parse_trigrams(needle.str, ignore_case, &trigram_groups);
 482                 }
 483         }
 484
 485         unique_sort(
 486                 &trigram_groups,
 487                 [](const TrigramDisjunction &a, const TrigramDisjunction &b) { return a.trigram_alternatives < b.trigram_alternatives; },
 488                 [](const TrigramDisjunction &a, const TrigramDisjunction &b) { return a.trigram_alternatives == b.trigram_alternatives; });
 489
 490         // Give them names for debugging.
 491         unsigned td_index = 0;
 492         for (TrigramDisjunction &td : trigram_groups) {
 493                 td.index = td_index++;
 494         }
 495
 496         // Collect which trigrams we need to look up in the hash table.
 497         unordered_map<uint32_t, vector<TrigramDisjunction *>> trigrams_to_lookup;
 498         for (TrigramDisjunction &td : trigram_groups) {
 499                 for (uint32_t trgm : td.trigram_alternatives) {
 500                         trigrams_to_lookup[trgm].push_back(&td);
 501                 }
 502         }
 503         if (trigrams_to_lookup.empty()) {
 504                 // Too short for trigram matching. Apply brute force.
 505                 // (We could have searched through all trigrams that matched
 506                 // the pattern and done a union of them, but that's a lot of
 507                 // work for fairly unclear gain.)
 508                 uint64_t matched = scan_all_docids(needles, fd, corpus);
 509                 dprintf("Done in %.1f ms, found %" PRId64 " matches.\n",
 510                         1e3 * duration<float>(steady_clock::now() - start).count(), matched);
 511                 return matched;
 512         }
 513
 514         // Sneak in fetching the dictionary, if present. It's not necessarily clear
 515         // exactly where it would be cheapest to get it, but it needs to be present
 516         // before we can decode any of the posting lists. Most likely, it's
 517         // in the same filesystem block as the header anyway, so it should be
 518         // present in the cache.
 519         {
 520                 const Header &hdr = corpus.get_hdr();
 521                 if (hdr.zstd_dictionary_length_bytes > 0) {
 522                         engine.submit_read(fd, hdr.zstd_dictionary_length_bytes, hdr.zstd_dictionary_offset_bytes, [](string_view s) {
 523                                 ddict = ZSTD_createDDict(s.data(), s.size());
 524                                 dprintf("Dictionary initialized after %.1f ms.\n", 1e3 * duration<float>(steady_clock::now() - start).count());
 525                         });
 526                 }
 527         }
 528
 529         // Look them all up on disk.
 530         bool should_early_exit = false;
 531         for (auto &[trgm, trigram_groups] : trigrams_to_lookup) {
 532                 corpus.find_trigram(trgm, [trgm{ trgm }, trigram_groups{ &trigram_groups }, &should_early_exit](const Trigram *trgmptr, size_t len) {
 533                         if (trgmptr == nullptr) {
 534                                 dprintf("trigram %s isn't found\n", print_trigram(trgm).c_str());
 535                                 for (TrigramDisjunction *td : *trigram_groups) {
 536                                         --td->remaining_trigrams_to_read;
 537
 538                                         // If we now know this trigram group doesn't match anything at all,
 539                                         // we can do early exit; however, if we're in a forked child,
 540                                         // that would confuse the parent process (since we don't write
 541                                         // our count to the pipe), so we wait until we're back in to the
 542                                         // regular (non-async) context. This is a fairly rare case anyway,
 543                                         // and the gains from dropping the remaining trigram reads are limited.
 544                                         if (td->remaining_trigrams_to_read == 0 && td->read_trigrams.empty()) {
 545                                                 if (in_forked_child) {
 546                                                         should_early_exit = true;
 547                                                 } else {
 548                                                         dprintf("zero matches in %s, so we are done\n", print_td(*td).c_str());
 549                                                         if (only_count) {
 550                                                                 printf("0\n");
 551                                                         }
 552                                                         exit(0);
 553                                                 }
 554                                         }
 555                                 }
 556                                 return;
 557                         }
 558                         for (TrigramDisjunction *td : *trigram_groups) {
 559                                 --td->remaining_trigrams_to_read;
 560                                 td->max_num_docids += trgmptr->num_docids;
 561                                 td->read_trigrams.emplace_back(*trgmptr, len);
 562                         }
 563                 });
 564         }
 565         engine.finish();
 566         dprintf("Hashtable lookups done after %.1f ms.\n", 1e3 * duration<float>(steady_clock::now() - start).count());
 567
 568         if (should_early_exit) {
 569                 return 0;
 570         }
 571
 572         for (TrigramDisjunction &td : trigram_groups) {
 573                 // Reset for reads.
 574                 td.remaining_trigrams_to_read = td.read_trigrams.size();
 575
 576                 if (ignore_case) {  // If case-sensitive, they'll all be pretty obvious single-entry groups.
 577                         dprintf("OR group %u (max_num_docids=%u): %s\n", td.index, td.max_num_docids, print_td(td).c_str());
 578                 }
 579         }
 580
 581         // TODO: For case-insensitive (ie. more than one alternative in each),
 582         // prioritize the ones with fewer seeks?
 583         sort(trigram_groups.begin(), trigram_groups.end(),
 584              [&](const TrigramDisjunction &a, const TrigramDisjunction &b) {
 585                      return a.max_num_docids < b.max_num_docids;
 586              });
 587
 588         unordered_map<uint32_t, vector<TrigramDisjunction *>> uses_trigram;
 589         for (TrigramDisjunction &td : trigram_groups) {
 590                 for (uint32_t trgm : td.trigram_alternatives) {
 591                         uses_trigram[trgm].push_back(&td);
 592                 }
 593         }
 594
 595         unordered_set<uint32_t> trigrams_submitted_read;
 596         vector<uint32_t> cur_candidates, tmp, decoded;
 597         bool done = false;
 598         for (TrigramDisjunction &td : trigram_groups) {
 599                 if (!cur_candidates.empty() && td.max_num_docids > cur_candidates.size() * 100) {
 600                         dprintf("%s has up to %u entries, ignoring the rest (will "
 601                                 "weed out false positives later)\n",
 602                                 print_td(td).c_str(), td.max_num_docids);
 603                         break;
 604                 }
 605
 606                 for (auto &[trgmptr, len] : td.read_trigrams) {
 607                         if (trigrams_submitted_read.count(trgmptr.trgm) != 0) {
 608                                 continue;
 609                         }
 610                         trigrams_submitted_read.insert(trgmptr.trgm);
 611                         // Only stay a certain amount ahead, so that we don't spend I/O
 612                         // on reading the latter, large posting lists. We are unlikely
 613                         // to need them anyway, even if they should come in first.
 614                         if (engine.get_waiting_reads() >= 5) {
 615                                 engine.finish();
 616                                 if (done)
 617                                         break;
 618                         }
 619                         engine.submit_read(fd, len, trgmptr.offset, [trgmptr{ trgmptr }, len{ len }, &done, &cur_candidates, &tmp, &decoded, &uses_trigram](string_view s) {
 620                                 if (done)
 621                                         return;
 622
 623                                 uint32_t trgm = trgmptr.trgm;
 624                                 const unsigned char *pldata = reinterpret_cast<const unsigned char *>(s.data());
 625                                 size_t num = trgmptr.num_docids;
 626                                 decoded.resize(num);
 627                                 decode_pfor_delta1_128(pldata, num, /*interleaved=*/true, &decoded[0]);
 628
 629                                 assert(uses_trigram.count(trgm) != 0);
 630                                 bool was_empty = cur_candidates.empty();
 631                                 if (ignore_case) {
 632                                         dprintf("trigram %s (%zu bytes) decoded to %zu entries\n", print_trigram(trgm).c_str(), len, num);
 633                                 }
 634
 635                                 for (TrigramDisjunction *td : uses_trigram[trgm]) {
 636                                         done |= new_posting_list_read(td, decoded, &cur_candidates, &tmp);
 637                                         if (done)
 638                                                 break;
 639                                 }
 640                                 if (!ignore_case) {
 641                                         if (was_empty) {
 642                                                 dprintf("trigram %s (%zu bytes) decoded to %zu entries\n", print_trigram(trgm).c_str(), len, num);
 643                                         } else if (cur_candidates.empty()) {
 644                                                 dprintf("trigram %s (%zu bytes) decoded to %zu entries (none left, search is done)\n", print_trigram(trgm).c_str(), len, num);
 645                                         } else {
 646                                                 dprintf("trigram %s (%zu bytes) decoded to %zu entries (%zu left)\n", print_trigram(trgm).c_str(), len, num, cur_candidates.size());
 647                                         }
 648                                 }
 649                         });
 650                 }
 651         }
 652         engine.finish();
 653         if (done) {
 654                 return 0;
 655         }
 656         dprintf("Intersection done after %.1f ms. Doing final verification and printing:\n",
 657                 1e3 * duration<float>(steady_clock::now() - start).count());
 658
 659         uint64_t matched = scan_docids(needles, cur_candidates, corpus, &engine);
 660         dprintf("Done in %.1f ms, found %" PRId64 " matches.\n",
 661                 1e3 * duration<float>(steady_clock::now() - start).count(), matched);
 662         return matched;
 663 }
 664
 665 // Run do_search_file() in a child process.
 666 //
 667 // The reason for this is that we're not robust against malicious input, so we need
 668 // to drop privileges after opening the file. (Otherwise, we could fall prey to an attack
 669 // where a user does locate -d badfile.db:/var/lib/plocate/plocate.db, badfile.db contains
 670 // a buffer overflow that takes over the process, and then uses the elevated privileges
 671 // to print out otherwise inaccessible paths.) We solve this by forking and treating the
 672 // child process as untrusted after it has dropped its privileges (which it does before
 673 // reading any data from the file); it returns a single 64-bit number over a pipe,
 674 // and that's it. The parent keeps its privileges, and can then fork out new children
 675 // without fear of being taken over. (The child keeps stdout for outputting results.)
 676 //
 677 // The count is returned over the pipe, because it's needed both for --limit and --count.
 678 uint64_t do_search_file_in_child(const vector<Needle> &needles, const std::string &filename)
 679 {
 680         int pipefd[2];
 681         if (pipe(pipefd) == -1) {
 682                 perror("pipe");
 683                 exit(EXIT_FAILURE);
 684         }
 685
 686         pid_t child_pid = fork();
 687         switch (child_pid) {
 688         case 0: {
 689                 // Child.
 690                 close(pipefd[0]);
 691                 in_forked_child = true;
 692                 uint64_t matched = do_search_file(needles, filename);
 693                 int ret;
 694                 do {
 695                         ret = write(pipefd[1], &matched, sizeof(matched));
 696                 } while (ret == -1 && errno == EINTR);
 697                 if (ret != sizeof(matched)) {
 698                         perror("write");
 699                         _exit(EXIT_FAILURE);
 700                 }
 701                 fflush(stdout);
 702                 _exit(EXIT_SUCCESS);
 703         }
 704         case -1:
 705                 // Error.
 706                 perror("fork");
 707                 exit(EXIT_FAILURE);
 708         default:
 709                 // Parent.
 710                 close(pipefd[1]);
 711                 break;
 712         }
 713
 714         // Wait for the child to finish.
 715         int wstatus;
 716         pid_t err;
 717         do {
 718                 err = waitpid(child_pid, &wstatus, 0);
 719         } while (err == -1 && errno == EINTR);
 720         if (err == -1) {
 721                 perror("waitpid");
 722                 exit(EXIT_FAILURE);
 723         }
 724         if (WIFEXITED(wstatus)) {
 725                 if (WEXITSTATUS(wstatus) != 0) {
 726                         // The child has probably already printed out its error, so just propagate the exit status.
 727                         exit(WEXITSTATUS(wstatus));
 728                 }
 729                 // Success!
 730         } else if (!WIFEXITED(wstatus)) {
 731                 fprintf(stderr, "FATAL: Child died unexpectedly while processing %s\n", filename.c_str());
 732                 exit(1);
 733         }
 734
 735         // Now get the number of matches from the child.
 736         uint64_t matched;
 737         int ret;
 738         do {
 739                 ret = read(pipefd[0], &matched, sizeof(matched));
 740         } while (ret == -1 && errno == EINTR);
 741         if (ret == -1) {
 742                 perror("read");
 743                 exit(EXIT_FAILURE);
 744         } else if (ret != sizeof(matched)) {
 745                 fprintf(stderr, "FATAL: Short read through pipe (got %d bytes)\n", ret);
 746                 exit(EXIT_FAILURE);
 747         }
 748         close(pipefd[0]);
 749         return matched;
 750 }
 751
 752 // Parses a colon-separated list of strings and appends them onto the given vector.
 753 // Backslash escapes whatever comes after it.
 754 void parse_dbpaths(const char *ptr, vector<string> *output)
 755 {
 756         string str;
 757         while (*ptr != '\0') {
 758                 if (*ptr == '\\') {
 759                         if (ptr[1] == '\0') {
 760                                 fprintf(stderr, "ERROR: Escape character at the end of string\n");
 761                                 exit(EXIT_FAILURE);
 762                         }
 763                         // Escape.
 764                         str.push_back(ptr[1]);
 765                         ptr += 2;
 766                         continue;
 767                 }
 768                 if (*ptr == ':') {
 769                         // Separator.
 770                         output->push_back(move(str));
 771                         ++ptr;
 772                         continue;
 773                 }
 774                 str.push_back(*ptr++);
 775         }
 776         output->push_back(move(str));
 777 }
 778
 779 void usage()
 780 {
 781         printf(
 782                 "Usage: plocate [OPTION]... PATTERN...\n"
 783                 "\n"
 784                 "  -b, --basename         search only the file name portion of path names\n"
 785                 "  -c, --count            print number of matches instead of the matches\n"
 786                 "  -d, --database DBPATH  search for files in DBPATH\n"
 787                 "                         (default is " DBFILE ")\n"
 788                 "  -i, --ignore-case      search case-insensitively\n"
 789                 "  -l, --limit LIMIT      stop after LIMIT matches\n"
 790                 "  -0, --null             delimit matches by NUL instead of newline\n"
 791                 "  -r, --regexp           interpret patterns as basic regexps (slow)\n"
 792                 "      --regex            interpret patterns as extended regexps (slow)\n"
 793                 "  -w, --wholename        search the entire path name (default; see -b)\n"
 794                 "      --help             print this help\n"
 795                 "      --version          print version information\n");
 796 }
 797
 798 void version()
 799 {
 800         printf("%s %s\n", PACKAGE_NAME, PACKAGE_VERSION);
 801         printf("Copyright 2020 Steinar H. Gunderson\n");
 802         printf("License GPLv2+: GNU GPL version 2 or later <https://gnu.org/licenses/gpl.html>.\n");
 803         printf("This is free software: you are free to change and redistribute it.\n");
 804         printf("There is NO WARRANTY, to the extent permitted by law.\n");
 805         exit(0);
 806 }
 807
 808 int main(int argc, char **argv)
 809 {
 810         vector<string> dbpaths;
 811
 812         constexpr int EXTENDED_REGEX = 1000;
 813         constexpr int FLUSH_CACHE = 1001;
 814         static const struct option long_options[] = {
 815                 { "help", no_argument, 0, 'h' },
 816                 { "count", no_argument, 0, 'c' },
 817                 { "basename", no_argument, 0, 'b' },
 818                 { "database", required_argument, 0, 'd' },
 819                 { "ignore-case", no_argument, 0, 'i' },
 820                 { "limit", required_argument, 0, 'l' },
 821                 { "null", no_argument, 0, '0' },
 822                 { "version", no_argument, 0, 'V' },
 823                 { "regexp", no_argument, 0, 'r' },
 824                 { "regex", no_argument, 0, EXTENDED_REGEX },
 825                 { "wholename", no_argument, 0, 'w' },
 826                 { "debug", no_argument, 0, 'D' },  // Not documented.
 827                 // Enable to test cold-cache behavior (except for access()). Not documented.
 828                 { "flush-cache", no_argument, 0, FLUSH_CACHE },
 829                 { 0, 0, 0, 0 }
 830         };
 831
 832         setlocale(LC_ALL, "");
 833         for (;;) {
 834                 int option_index = 0;
 835                 int c = getopt_long(argc, argv, "bcd:hil:n:0rwVD", long_options, &option_index);
 836                 if (c == -1) {
 837                         break;
 838                 }
 839                 switch (c) {
 840                 case 'b':
 841                         match_basename = true;
 842                         break;
 843                 case 'c':
 844                         only_count = true;
 845                         break;
 846                 case 'd':
 847                         parse_dbpaths(optarg, &dbpaths);
 848                         break;
 849                 case 'h':
 850                         usage();
 851                         exit(0);
 852                 case 'i':
 853                         ignore_case = true;
 854                         break;
 855                 case 'l':
 856                 case 'n':
 857                         limit_matches = limit_left = atoll(optarg);
 858                         if (limit_matches <= 0) {
 859                                 fprintf(stderr, "Error: limit must be a strictly positive number.\n");
 860                                 exit(1);
 861                         }
 862                         break;
 863                 case '0':
 864                         print_nul = true;
 865                         break;
 866                 case 'r':
 867                         patterns_are_regex = true;
 868                         break;
 869                 case EXTENDED_REGEX:
 870                         patterns_are_regex = true;
 871                         use_extended_regex = true;
 872                         break;
 873                 case 'w':
 874                         match_basename = false;  // No-op unless -b is given first.
 875                         break;
 876                 case 'D':
 877                         use_debug = true;
 878                         break;
 879                 case FLUSH_CACHE:
 880                         flush_cache = true;
 881                         break;
 882                 case 'V':
 883                         version();
 884                         break;
 885                 default:
 886                         exit(1);
 887                 }
 888         }
 889
 890         if (use_debug || flush_cache) {
 891                 // Debug information would leak information about which files exist,
 892                 // so drop setgid before we open the file; one would either need to run
 893                 // as root, or use a locally-built file. Doing the same thing for
 894                 // flush_cache is mostly paranoia, in an attempt to prevent random users
 895                 // from making plocate slow for everyone else.
 896                 if (setgid(getgid()) != 0) {
 897                         perror("setgid");
 898                         exit(EXIT_FAILURE);
 899                 }
 900         }
 901
 902         if (!print_nul) {
 903                 stdout_is_tty = isatty(1);
 904         }
 905
 906         vector<Needle> needles;
 907         for (int i = optind; i < argc; ++i) {
 908                 Needle needle;
 909                 needle.str = argv[i];
 910
 911                 // See if there are any wildcard characters, which indicates we should treat it
 912                 // as an (anchored) glob.
 913                 bool any_wildcard = false;
 914                 for (size_t i = 0; i < needle.str.size(); i += read_unigram(needle.str, i).second) {
 915                         if (read_unigram(needle.str, i).first == WILDCARD_UNIGRAM) {
 916                                 any_wildcard = true;
 917                                 break;
 918                         }
 919                 }
 920
 921                 if (patterns_are_regex) {
 922                         needle.type = Needle::REGEX;
 923                         needle.re = compile_regex(needle.str);
 924                 } else if (any_wildcard) {
 925                         needle.type = Needle::GLOB;
 926                 } else if (ignore_case) {
 927                         // strcasestr() doesn't handle locales correctly (even though LSB
 928                         // claims it should), but somehow, fnmatch() does, and it's about
 929                         // the same speed as using a regex.
 930                         needle.type = Needle::GLOB;
 931                         needle.str = "*" + needle.str + "*";
 932                 } else {
 933                         needle.type = Needle::STRSTR;
 934                         needle.str = unescape_glob_to_plain_string(needle.str);
 935                 }
 936                 needles.push_back(move(needle));
 937         }
 938         if (needles.empty()) {
 939                 fprintf(stderr, "plocate: no pattern to search for specified\n");
 940                 exit(0);
 941         }
 942
 943         if (dbpaths.empty()) {
 944                 // No -d given, so use our default. Note that this happens
 945                 // even if LOCATE_PATH exists, to match mlocate behavior.
 946                 dbpaths.push_back(DBFILE);
 947         }
 948
 949         const char *locate_path = getenv("LOCATE_PATH");
 950         if (locate_path != nullptr) {
 951                 parse_dbpaths(locate_path, &dbpaths);
 952         }
 953
 954         uint64_t matched = 0;
 955         for (size_t i = 0; i < dbpaths.size(); ++i) {
 956                 uint64_t this_matched;
 957                 if (i != dbpaths.size() - 1) {
 958                         this_matched = do_search_file_in_child(needles, dbpaths[i]);
 959                 } else {
 960                         this_matched = do_search_file(needles, dbpaths[i]);
 961                 }
 962                 matched += this_matched;
 963                 limit_left -= this_matched;
 964         }
 965         if (only_count) {
 966                 printf("%" PRId64 "\n", matched);
 967         }
 968 }