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

   1 #include "db.h"
   2 #include "io_uring_engine.h"
   3 #include "vp4.h"
   4
   5 #include <algorithm>
   6 #include <arpa/inet.h>
   7 #include <chrono>
   8 #include <endian.h>
   9 #include <fcntl.h>
  10 #include <functional>
  11 #include <getopt.h>
  12 #include <memory>
  13 #include <stdio.h>
  14 #include <string.h>
  15 #include <string>
  16 #include <unistd.h>
  17 #include <unordered_map>
  18 #include <vector>
  19 #include <zstd.h>
  20
  21 using namespace std;
  22 using namespace std::chrono;
  23
  24 #define dprintf(...)
  25 //#define dprintf(...) fprintf(stderr, __VA_ARGS__);
  26
  27 class Serializer {
  28 public:
  29         void do_or_wait(int seq, function<void()> cb);
  30
  31 private:
  32         int next_seq = 0;
  33         struct Element {
  34                 int seq;
  35                 function<void()> cb;
  36
  37                 bool operator<(const Element &other) const
  38                 {
  39                         return seq > other.seq;
  40                 }
  41         };
  42         priority_queue<Element> pending;
  43 };
  44
  45 void Serializer::do_or_wait(int seq, function<void()> cb)
  46 {
  47         if (seq != next_seq) {
  48                 pending.emplace(Element{ seq, move(cb) });
  49                 return;
  50         }
  51
  52         cb();
  53         ++next_seq;
  54
  55         while (!pending.empty() && pending.top().seq == next_seq) {
  56                 pending.top().cb();
  57                 pending.pop();
  58                 ++next_seq;
  59         }
  60 }
  61
  62 static inline uint32_t read_unigram(const string &s, size_t idx)
  63 {
  64         if (idx < s.size()) {
  65                 return (unsigned char)s[idx];
  66         } else {
  67                 return 0;
  68         }
  69 }
  70
  71 static inline uint32_t read_trigram(const string &s, size_t start)
  72 {
  73         return read_unigram(s, start) | (read_unigram(s, start + 1) << 8) |
  74                 (read_unigram(s, start + 2) << 16);
  75 }
  76
  77 bool has_access(const char *filename,
  78                 unordered_map<string, bool> *access_rx_cache)
  79 {
  80         const char *end = strchr(filename + 1, '/');
  81         while (end != nullptr) {
  82                 string parent_path(filename, end);
  83                 auto it = access_rx_cache->find(parent_path);
  84                 bool ok;
  85                 if (it == access_rx_cache->end()) {
  86                         ok = access(parent_path.c_str(), R_OK | X_OK) == 0;
  87                         access_rx_cache->emplace(move(parent_path), ok);
  88                 } else {
  89                         ok = it->second;
  90                 }
  91                 if (!ok) {
  92                         return false;
  93                 }
  94                 end = strchr(end + 1, '/');
  95         }
  96
  97         return true;
  98 }
  99
 100 class Corpus {
 101 public:
 102         Corpus(int fd, IOUringEngine *engine);
 103         ~Corpus();
 104         void find_trigram(uint32_t trgm, function<void(const Trigram *trgmptr, size_t len)> cb);
 105         void get_compressed_filename_block(uint32_t docid, function<void(string)> cb) const;
 106         size_t get_num_filename_blocks() const;
 107         off_t offset_for_block(uint32_t docid) const
 108         {
 109                 return hdr.filename_index_offset_bytes + docid * sizeof(uint64_t);
 110         }
 111
 112 public:
 113         const int fd;
 114         IOUringEngine *const engine;
 115
 116         Header hdr;
 117 };
 118
 119 Corpus::Corpus(int fd, IOUringEngine *engine)
 120         : fd(fd), engine(engine)
 121 {
 122         // Enable to test cold-cache behavior (except for access()).
 123         if (false) {
 124                 off_t len = lseek(fd, 0, SEEK_END);
 125                 if (len == -1) {
 126                         perror("lseek");
 127                         exit(1);
 128                 }
 129                 posix_fadvise(fd, 0, len, POSIX_FADV_DONTNEED);
 130         }
 131
 132         complete_pread(fd, &hdr, sizeof(hdr), /*offset=*/0);
 133         if (memcmp(hdr.magic, "\0plocate", 8) != 0) {
 134                 fprintf(stderr, "plocate.db is corrupt or an old version; please rebuild it.\n");
 135                 exit(1);
 136         }
 137         if (hdr.version != 0) {
 138                 fprintf(stderr, "plocate.db has version %u, expected 0; please rebuild it.\n", hdr.version);
 139                 exit(1);
 140         }
 141 }
 142
 143 Corpus::~Corpus()
 144 {
 145         close(fd);
 146 }
 147
 148 void Corpus::find_trigram(uint32_t trgm, function<void(const Trigram *trgmptr, size_t len)> cb)
 149 {
 150         uint32_t bucket = hash_trigram(trgm, hdr.hashtable_size);
 151         engine->submit_read(fd, sizeof(Trigram) * (hdr.extra_ht_slots + 2), hdr.hash_table_offset_bytes + sizeof(Trigram) * bucket, [this, trgm, bucket, cb{ move(cb) }](string s) {
 152                 const Trigram *trgmptr = reinterpret_cast<const Trigram *>(s.data());
 153                 for (unsigned i = 0; i < hdr.extra_ht_slots + 1; ++i) {
 154                         if (trgmptr[i].trgm == trgm) {
 155                                 cb(trgmptr + i, trgmptr[i + 1].offset - trgmptr[i].offset);
 156                                 return;
 157                         }
 158                 }
 159
 160                 // Not found.
 161                 cb(nullptr, 0);
 162         });
 163 }
 164
 165 void Corpus::get_compressed_filename_block(uint32_t docid, function<void(string)> cb) const
 166 {
 167         // Read the file offset from this docid and the next one.
 168         // This is always allowed, since we have a sentinel block at the end.
 169         engine->submit_read(fd, sizeof(uint64_t) * 2, offset_for_block(docid), [this, cb{ move(cb) }](string s) {
 170                 const uint64_t *ptr = reinterpret_cast<const uint64_t *>(s.data());
 171                 off_t offset = ptr[0];
 172                 size_t len = ptr[1] - ptr[0];
 173                 engine->submit_read(fd, len, offset, cb);
 174         });
 175 }
 176
 177 size_t Corpus::get_num_filename_blocks() const
 178 {
 179         // The beginning of the filename blocks is the end of the filename index blocks.
 180         uint64_t end;
 181         complete_pread(fd, &end, sizeof(end), hdr.filename_index_offset_bytes);
 182
 183         // Subtract the sentinel block.
 184         return (end - hdr.filename_index_offset_bytes) / sizeof(uint64_t) - 1;
 185 }
 186
 187 size_t scan_file_block(const vector<string> &needles, string_view compressed,
 188                        unordered_map<string, bool> *access_rx_cache)
 189 {
 190         size_t matched = 0;
 191
 192         unsigned long long uncompressed_len = ZSTD_getFrameContentSize(compressed.data(), compressed.size());
 193         if (uncompressed_len == ZSTD_CONTENTSIZE_UNKNOWN || uncompressed_len == ZSTD_CONTENTSIZE_ERROR) {
 194                 fprintf(stderr, "ZSTD_getFrameContentSize() failed\n");
 195                 exit(1);
 196         }
 197
 198         string block;
 199         block.resize(uncompressed_len + 1);
 200
 201         size_t err = ZSTD_decompress(&block[0], block.size(), compressed.data(),
 202                                      compressed.size());
 203         if (ZSTD_isError(err)) {
 204                 fprintf(stderr, "ZSTD_decompress(): %s\n", ZSTD_getErrorName(err));
 205                 exit(1);
 206         }
 207         block[block.size() - 1] = '\0';
 208
 209         for (const char *filename = block.data();
 210              filename != block.data() + block.size();
 211              filename += strlen(filename) + 1) {
 212                 bool found = true;
 213                 for (const string &needle : needles) {
 214                         if (strstr(filename, needle.c_str()) == nullptr) {
 215                                 found = false;
 216                                 break;
 217                         }
 218                 }
 219                 if (found && has_access(filename, access_rx_cache)) {
 220                         ++matched;
 221                         printf("%s\n", filename);
 222                 }
 223         }
 224         return matched;
 225 }
 226
 227 size_t scan_docids(const vector<string> &needles, const vector<uint32_t> &docids, const Corpus &corpus, IOUringEngine *engine)
 228 {
 229         Serializer docids_in_order;
 230         unordered_map<string, bool> access_rx_cache;
 231         size_t matched = 0;
 232         for (size_t i = 0; i < docids.size(); ++i) {
 233                 uint32_t docid = docids[i];
 234                 corpus.get_compressed_filename_block(docid, [i, &matched, &needles, &access_rx_cache, &docids_in_order](string compressed) {
 235                         docids_in_order.do_or_wait(i, [&matched, &needles, compressed{ move(compressed) }, &access_rx_cache] {
 236                                 matched += scan_file_block(needles, compressed, &access_rx_cache);
 237                         });
 238                 });
 239         }
 240         engine->finish();
 241         return matched;
 242 }
 243
 244 // We do this sequentially, as it's faster than scattering
 245 // a lot of I/O through io_uring and hoping the kernel will
 246 // coalesce it plus readahead for us.
 247 void scan_all_docids(const vector<string> &needles, int fd, const Corpus &corpus, IOUringEngine *engine)
 248 {
 249         unordered_map<string, bool> access_rx_cache;
 250         uint32_t num_blocks = corpus.get_num_filename_blocks();
 251         unique_ptr<uint64_t[]> offsets(new uint64_t[num_blocks + 1]);
 252         complete_pread(fd, offsets.get(), (num_blocks + 1) * sizeof(uint64_t), corpus.offset_for_block(0));
 253         string compressed;
 254         for (uint32_t io_docid = 0; io_docid < num_blocks; io_docid += 32) {
 255                 uint32_t last_docid = std::min(io_docid + 32, num_blocks);
 256                 size_t io_len = offsets[last_docid] - offsets[io_docid];
 257                 if (compressed.size() < io_len) {
 258                         compressed.resize(io_len);
 259                 }
 260                 complete_pread(fd, &compressed[0], io_len, offsets[io_docid]);
 261
 262                 for (uint32_t docid = io_docid; docid < last_docid; ++docid) {
 263                         size_t relative_offset = offsets[docid] - offsets[io_docid];
 264                         size_t len = offsets[docid + 1] - offsets[docid];
 265                         scan_file_block(needles, { &compressed[relative_offset], len }, &access_rx_cache);
 266                 }
 267         }
 268 }
 269
 270 void do_search_file(const vector<string> &needles, const char *filename)
 271 {
 272         int fd = open(filename, O_RDONLY);
 273         if (fd == -1) {
 274                 perror(filename);
 275                 exit(1);
 276         }
 277
 278         // Drop privileges.
 279         if (setgid(getgid()) != 0) {
 280                 perror("setgid");
 281                 exit(EXIT_FAILURE);
 282         }
 283
 284         steady_clock::time_point start __attribute__((unused)) = steady_clock::now();
 285         if (access("/", R_OK | X_OK)) {
 286                 // We can't find anything, no need to bother...
 287                 return;
 288         }
 289
 290         IOUringEngine engine;
 291         Corpus corpus(fd, &engine);
 292         dprintf("Corpus init done after %.1f ms.\n", 1e3 * duration<float>(steady_clock::now() - start).count());
 293
 294         vector<pair<Trigram, size_t>> trigrams;
 295         for (const string &needle : needles) {
 296                 if (needle.size() < 3) continue;
 297                 for (size_t i = 0; i < needle.size() - 2; ++i) {
 298                         uint32_t trgm = read_trigram(needle, i);
 299                         corpus.find_trigram(trgm, [trgm, &trigrams](const Trigram *trgmptr, size_t len) {
 300                                 if (trgmptr == nullptr) {
 301                                         dprintf("trigram %06x isn't found, we abort the search\n", trgm);
 302                                         return;
 303                                 }
 304                                 trigrams.emplace_back(*trgmptr, len);
 305                         });
 306                 }
 307         }
 308         engine.finish();
 309         dprintf("Hashtable lookups done after %.1f ms.\n", 1e3 * duration<float>(steady_clock::now() - start).count());
 310
 311         if (trigrams.empty()) {
 312                 // Too short for trigram matching. Apply brute force.
 313                 // (We could have searched through all trigrams that matched
 314                 // the pattern and done a union of them, but that's a lot of
 315                 // work for fairly unclear gain.)
 316                 scan_all_docids(needles, fd, corpus, &engine);
 317                 return;
 318         }
 319         sort(trigrams.begin(), trigrams.end());
 320         {
 321                 auto last = unique(trigrams.begin(), trigrams.end());
 322                 trigrams.erase(last, trigrams.end());
 323         }
 324         sort(trigrams.begin(), trigrams.end(),
 325              [&](const pair<Trigram, size_t> &a, const pair<Trigram, size_t> &b) {
 326                      return a.first.num_docids < b.first.num_docids;
 327              });
 328
 329         vector<uint32_t> in1, in2, out;
 330         bool done = false;
 331         for (auto [trgmptr, len] : trigrams) {
 332                 if (!in1.empty() && trgmptr.num_docids > in1.size() * 100) {
 333                         uint32_t trgm __attribute__((unused)) = trgmptr.trgm;
 334                         dprintf("trigram '%c%c%c' (%zu bytes) has %u entries, ignoring the rest (will "
 335                                 "weed out false positives later)\n",
 336                                 trgm & 0xff, (trgm >> 8) & 0xff, (trgm >> 16) & 0xff,
 337                                 len, trgmptr.num_docids);
 338                         break;
 339                 }
 340
 341                 // Only stay a certain amount ahead, so that we don't spend I/O
 342                 // on reading the latter, large posting lists. We are unlikely
 343                 // to need them anyway, even if they should come in first.
 344                 if (engine.get_waiting_reads() >= 5) {
 345                         engine.finish();
 346                         if (done)
 347                                 break;
 348                 }
 349                 engine.submit_read(fd, len, trgmptr.offset, [trgmptr, len, &done, &in1, &in2, &out](string s) {
 350                         if (done)
 351                                 return;
 352                         uint32_t trgm __attribute__((unused)) = trgmptr.trgm;
 353                         size_t num = trgmptr.num_docids;
 354                         unsigned char *pldata = reinterpret_cast<unsigned char *>(s.data());
 355                         if (in1.empty()) {
 356                                 in1.resize(num + 128);
 357                                 p4nd1dec128v32(pldata, num, &in1[0]);
 358                                 in1.resize(num);
 359                                 dprintf("trigram '%c%c%c' (%zu bytes) decoded to %zu entries\n", trgm & 0xff,
 360                                         (trgm >> 8) & 0xff, (trgm >> 16) & 0xff, len, num);
 361                         } else {
 362                                 if (in2.size() < num + 128) {
 363                                         in2.resize(num + 128);
 364                                 }
 365                                 p4nd1dec128v32(pldata, num, &in2[0]);
 366
 367                                 out.clear();
 368                                 set_intersection(in1.begin(), in1.end(), in2.begin(), in2.begin() + num,
 369                                                  back_inserter(out));
 370                                 swap(in1, out);
 371                                 dprintf("trigram '%c%c%c' (%zu bytes) decoded to %zu entries, %zu left\n",
 372                                         trgm & 0xff, (trgm >> 8) & 0xff, (trgm >> 16) & 0xff,
 373                                         len, num, in1.size());
 374                                 if (in1.empty()) {
 375                                         dprintf("no matches (intersection list is empty)\n");
 376                                         done = true;
 377                                 }
 378                         }
 379                 });
 380         }
 381         engine.finish();
 382         if (done) {
 383                 return;
 384         }
 385         dprintf("Intersection done after %.1f ms. Doing final verification and printing:\n",
 386                 1e3 * duration<float>(steady_clock::now() - start).count());
 387
 388         size_t matched __attribute__((unused)) = scan_docids(needles, in1, corpus, &engine);
 389         dprintf("Done in %.1f ms, found %zu matches.\n",
 390                 1e3 * duration<float>(steady_clock::now() - start).count(), matched);
 391 }
 392
 393 const char *dbpath = "/var/lib/mlocate/plocate.db";
 394
 395 void usage()
 396 {
 397         printf("Usage: slocate [OPTION]... PATTERN...\n");
 398         printf("  -d, --database DBPATH  use DBPATH instead of default database (which is\n");
 399         printf("                         %s)\n", dbpath);
 400         printf("  -h, --help             print this help\n");
 401 }
 402
 403 int main(int argc, char **argv)
 404 {
 405         static const struct option long_options[] = {
 406                 { "help", no_argument, 0, 'h' },
 407                 { "database", required_argument, 0, 'd' },
 408                 { 0, 0, 0, 0 }
 409         };
 410
 411         for (;;) {
 412                 int option_index = 0;
 413                 int c = getopt_long(argc, argv, "d:h:", long_options, &option_index);
 414                 if (c == -1) {
 415                         break;
 416                 }
 417                 switch (c) {
 418                 case 'd':
 419                         dbpath = strdup(optarg);
 420                         break;
 421                 case 'h':
 422                         usage();
 423                         exit(0);
 424                 }
 425         }
 426
 427         vector<string> needles;
 428         for (int i = optind; i < argc; ++i) {
 429                 needles.push_back(argv[i]);
 430         }
 431         if (needles.empty()) {
 432                 fprintf(stderr, "slocate: no pattern to search for specified\n");
 433                 exit(0);
 434         }
 435         do_search_file(needles, dbpath);
 436 }