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 <assert.h>
   8 #include <chrono>
   9 #include <endian.h>
  10 #include <fcntl.h>
  11 #include <functional>
  12 #include <getopt.h>
  13 #include <memory>
  14 #include <stdio.h>
  15 #include <string.h>
  16 #include <string>
  17 #include <unistd.h>
  18 #include <unordered_map>
  19 #include <vector>
  20 #include <zstd.h>
  21
  22 using namespace std;
  23 using namespace std::chrono;
  24
  25 #define dprintf(...)
  26 //#define dprintf(...) fprintf(stderr, __VA_ARGS__);
  27
  28 const char *dbpath = "/var/lib/mlocate/plocate.db";
  29 bool print_nul = false;
  30
  31 class Serializer {
  32 public:
  33         bool ready_to_print(int seq) { return next_seq == seq; }
  34         void print_delayed(int seq, const vector<string> msg);
  35         void release_current();
  36
  37 private:
  38         int next_seq = 0;
  39         struct Element {
  40                 int seq;
  41                 vector<string> msg;
  42
  43                 bool operator<(const Element &other) const
  44                 {
  45                         return seq > other.seq;
  46                 }
  47         };
  48         priority_queue<Element> pending;
  49 };
  50
  51 void Serializer::print_delayed(int seq, const vector<string> msg)
  52 {
  53         pending.push(Element{ seq, move(msg) });
  54 }
  55
  56 void Serializer::release_current()
  57 {
  58         ++next_seq;
  59
  60         // See if any delayed prints can now be dealt with.
  61         while (!pending.empty() && pending.top().seq == next_seq) {
  62                 for (const string &msg : pending.top().msg) {
  63                         if (print_nul) {
  64                                 printf("%s%c", msg.c_str(), 0);
  65                         } else {
  66                                 printf("%s\n", msg.c_str());
  67                         }
  68                 }
  69                 pending.pop();
  70                 ++next_seq;
  71         }
  72 }
  73
  74 static inline uint32_t read_unigram(const string &s, size_t idx)
  75 {
  76         if (idx < s.size()) {
  77                 return (unsigned char)s[idx];
  78         } else {
  79                 return 0;
  80         }
  81 }
  82
  83 static inline uint32_t read_trigram(const string &s, size_t start)
  84 {
  85         return read_unigram(s, start) | (read_unigram(s, start + 1) << 8) |
  86                 (read_unigram(s, start + 2) << 16);
  87 }
  88
  89 bool has_access(const char *filename,
  90                 unordered_map<string, bool> *access_rx_cache)
  91 {
  92         const char *end = strchr(filename + 1, '/');
  93         while (end != nullptr) {
  94                 string parent_path(filename, end);
  95                 auto it = access_rx_cache->find(parent_path);
  96                 bool ok;
  97                 if (it == access_rx_cache->end()) {
  98                         ok = access(parent_path.c_str(), R_OK | X_OK) == 0;
  99                         access_rx_cache->emplace(move(parent_path), ok);
 100                 } else {
 101                         ok = it->second;
 102                 }
 103                 if (!ok) {
 104                         return false;
 105                 }
 106                 end = strchr(end + 1, '/');
 107         }
 108
 109         return true;
 110 }
 111
 112 class Corpus {
 113 public:
 114         Corpus(int fd, IOUringEngine *engine);
 115         ~Corpus();
 116         void find_trigram(uint32_t trgm, function<void(const Trigram *trgmptr, size_t len)> cb);
 117         void get_compressed_filename_block(uint32_t docid, function<void(string)> cb) const;
 118         size_t get_num_filename_blocks() const;
 119         off_t offset_for_block(uint32_t docid) const
 120         {
 121                 return hdr.filename_index_offset_bytes + docid * sizeof(uint64_t);
 122         }
 123
 124 public:
 125         const int fd;
 126         IOUringEngine *const engine;
 127
 128         Header hdr;
 129 };
 130
 131 Corpus::Corpus(int fd, IOUringEngine *engine)
 132         : fd(fd), engine(engine)
 133 {
 134         // Enable to test cold-cache behavior (except for access()).
 135         if (false) {
 136                 off_t len = lseek(fd, 0, SEEK_END);
 137                 if (len == -1) {
 138                         perror("lseek");
 139                         exit(1);
 140                 }
 141                 posix_fadvise(fd, 0, len, POSIX_FADV_DONTNEED);
 142         }
 143
 144         complete_pread(fd, &hdr, sizeof(hdr), /*offset=*/0);
 145         if (memcmp(hdr.magic, "\0plocate", 8) != 0) {
 146                 fprintf(stderr, "plocate.db is corrupt or an old version; please rebuild it.\n");
 147                 exit(1);
 148         }
 149         if (hdr.version != 0) {
 150                 fprintf(stderr, "plocate.db has version %u, expected 0; please rebuild it.\n", hdr.version);
 151                 exit(1);
 152         }
 153 }
 154
 155 Corpus::~Corpus()
 156 {
 157         close(fd);
 158 }
 159
 160 void Corpus::find_trigram(uint32_t trgm, function<void(const Trigram *trgmptr, size_t len)> cb)
 161 {
 162         uint32_t bucket = hash_trigram(trgm, hdr.hashtable_size);
 163         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) {
 164                 const Trigram *trgmptr = reinterpret_cast<const Trigram *>(s.data());
 165                 for (unsigned i = 0; i < hdr.extra_ht_slots + 1; ++i) {
 166                         if (trgmptr[i].trgm == trgm) {
 167                                 cb(trgmptr + i, trgmptr[i + 1].offset - trgmptr[i].offset);
 168                                 return;
 169                         }
 170                 }
 171
 172                 // Not found.
 173                 cb(nullptr, 0);
 174         });
 175 }
 176
 177 void Corpus::get_compressed_filename_block(uint32_t docid, function<void(string)> cb) const
 178 {
 179         // Read the file offset from this docid and the next one.
 180         // This is always allowed, since we have a sentinel block at the end.
 181         engine->submit_read(fd, sizeof(uint64_t) * 2, offset_for_block(docid), [this, cb{ move(cb) }](string s) {
 182                 const uint64_t *ptr = reinterpret_cast<const uint64_t *>(s.data());
 183                 off_t offset = ptr[0];
 184                 size_t len = ptr[1] - ptr[0];
 185                 engine->submit_read(fd, len, offset, cb);
 186         });
 187 }
 188
 189 size_t Corpus::get_num_filename_blocks() const
 190 {
 191         // The beginning of the filename blocks is the end of the filename index blocks.
 192         uint64_t end;
 193         complete_pread(fd, &end, sizeof(end), hdr.filename_index_offset_bytes);
 194
 195         // Subtract the sentinel block.
 196         return (end - hdr.filename_index_offset_bytes) / sizeof(uint64_t) - 1;
 197 }
 198
 199 size_t scan_file_block(const vector<string> &needles, string_view compressed,
 200                        unordered_map<string, bool> *access_rx_cache, int seq,
 201                        Serializer *serializer)
 202 {
 203         size_t matched = 0;
 204
 205         unsigned long long uncompressed_len = ZSTD_getFrameContentSize(compressed.data(), compressed.size());
 206         if (uncompressed_len == ZSTD_CONTENTSIZE_UNKNOWN || uncompressed_len == ZSTD_CONTENTSIZE_ERROR) {
 207                 fprintf(stderr, "ZSTD_getFrameContentSize() failed\n");
 208                 exit(1);
 209         }
 210
 211         string block;
 212         block.resize(uncompressed_len + 1);
 213
 214         size_t err = ZSTD_decompress(&block[0], block.size(), compressed.data(),
 215                                      compressed.size());
 216         if (ZSTD_isError(err)) {
 217                 fprintf(stderr, "ZSTD_decompress(): %s\n", ZSTD_getErrorName(err));
 218                 exit(1);
 219         }
 220         block[block.size() - 1] = '\0';
 221
 222         bool immediate_print = (serializer == nullptr || serializer->ready_to_print(seq));
 223         vector<string> delayed;
 224
 225         for (const char *filename = block.data();
 226              filename != block.data() + block.size();
 227              filename += strlen(filename) + 1) {
 228                 bool found = true;
 229                 for (const string &needle : needles) {
 230                         if (strstr(filename, needle.c_str()) == nullptr) {
 231                                 found = false;
 232                                 break;
 233                         }
 234                 }
 235                 if (found && has_access(filename, access_rx_cache)) {
 236                         ++matched;
 237                         if (immediate_print) {
 238                                 if (print_nul) {
 239                                         printf("%s%c", filename, 0);
 240                                 } else {
 241                                         printf("%s\n", filename);
 242                                 }
 243                         } else {
 244                                 delayed.push_back(filename);
 245                         }
 246                 }
 247         }
 248         if (serializer != nullptr) {
 249                 if (immediate_print) {
 250                         serializer->release_current();
 251                 } else {
 252                         serializer->print_delayed(seq, move(delayed));
 253                 }
 254         }
 255         return matched;
 256 }
 257
 258 size_t scan_docids(const vector<string> &needles, const vector<uint32_t> &docids, const Corpus &corpus, IOUringEngine *engine)
 259 {
 260         Serializer docids_in_order;
 261         unordered_map<string, bool> access_rx_cache;
 262         size_t matched = 0;
 263         for (size_t i = 0; i < docids.size(); ++i) {
 264                 uint32_t docid = docids[i];
 265                 corpus.get_compressed_filename_block(docid, [i, &matched, &needles, &access_rx_cache, &docids_in_order](string compressed) {
 266                         matched += scan_file_block(needles, compressed, &access_rx_cache, i, &docids_in_order);
 267                 });
 268         }
 269         engine->finish();
 270         return matched;
 271 }
 272
 273 // We do this sequentially, as it's faster than scattering
 274 // a lot of I/O through io_uring and hoping the kernel will
 275 // coalesce it plus readahead for us.
 276 void scan_all_docids(const vector<string> &needles, int fd, const Corpus &corpus, IOUringEngine *engine)
 277 {
 278         unordered_map<string, bool> access_rx_cache;
 279         uint32_t num_blocks = corpus.get_num_filename_blocks();
 280         unique_ptr<uint64_t[]> offsets(new uint64_t[num_blocks + 1]);
 281         complete_pread(fd, offsets.get(), (num_blocks + 1) * sizeof(uint64_t), corpus.offset_for_block(0));
 282         string compressed;
 283         for (uint32_t io_docid = 0; io_docid < num_blocks; io_docid += 32) {
 284                 uint32_t last_docid = std::min(io_docid + 32, num_blocks);
 285                 size_t io_len = offsets[last_docid] - offsets[io_docid];
 286                 if (compressed.size() < io_len) {
 287                         compressed.resize(io_len);
 288                 }
 289                 complete_pread(fd, &compressed[0], io_len, offsets[io_docid]);
 290
 291                 for (uint32_t docid = io_docid; docid < last_docid; ++docid) {
 292                         size_t relative_offset = offsets[docid] - offsets[io_docid];
 293                         size_t len = offsets[docid + 1] - offsets[docid];
 294                         scan_file_block(needles, { &compressed[relative_offset], len }, &access_rx_cache, 0, nullptr);
 295                 }
 296         }
 297 }
 298
 299 void do_search_file(const vector<string> &needles, const char *filename)
 300 {
 301         int fd = open(filename, O_RDONLY);
 302         if (fd == -1) {
 303                 perror(filename);
 304                 exit(1);
 305         }
 306
 307         // Drop privileges.
 308         if (setgid(getgid()) != 0) {
 309                 perror("setgid");
 310                 exit(EXIT_FAILURE);
 311         }
 312
 313         steady_clock::time_point start __attribute__((unused)) = steady_clock::now();
 314         if (access("/", R_OK | X_OK)) {
 315                 // We can't find anything, no need to bother...
 316                 return;
 317         }
 318
 319         IOUringEngine engine;
 320         Corpus corpus(fd, &engine);
 321         dprintf("Corpus init done after %.1f ms.\n", 1e3 * duration<float>(steady_clock::now() - start).count());
 322
 323         vector<pair<Trigram, size_t>> trigrams;
 324         for (const string &needle : needles) {
 325                 if (needle.size() < 3)
 326                         continue;
 327                 for (size_t i = 0; i < needle.size() - 2; ++i) {
 328                         uint32_t trgm = read_trigram(needle, i);
 329                         corpus.find_trigram(trgm, [trgm, &trigrams](const Trigram *trgmptr, size_t len) {
 330                                 if (trgmptr == nullptr) {
 331                                         dprintf("trigram %06x isn't found, we abort the search\n", trgm);
 332                                         exit(0);
 333                                 }
 334                                 trigrams.emplace_back(*trgmptr, len);
 335                         });
 336                 }
 337         }
 338         engine.finish();
 339         dprintf("Hashtable lookups done after %.1f ms.\n", 1e3 * duration<float>(steady_clock::now() - start).count());
 340
 341         if (trigrams.empty()) {
 342                 // Too short for trigram matching. Apply brute force.
 343                 // (We could have searched through all trigrams that matched
 344                 // the pattern and done a union of them, but that's a lot of
 345                 // work for fairly unclear gain.)
 346                 scan_all_docids(needles, fd, corpus, &engine);
 347                 return;
 348         }
 349         sort(trigrams.begin(), trigrams.end());
 350         {
 351                 auto last = unique(trigrams.begin(), trigrams.end());
 352                 trigrams.erase(last, trigrams.end());
 353         }
 354         sort(trigrams.begin(), trigrams.end(),
 355              [&](const pair<Trigram, size_t> &a, const pair<Trigram, size_t> &b) {
 356                      return a.first.num_docids < b.first.num_docids;
 357              });
 358
 359         vector<uint32_t> in1, in2, out;
 360         bool done = false;
 361         for (auto [trgmptr, len] : trigrams) {
 362                 if (!in1.empty() && trgmptr.num_docids > in1.size() * 100) {
 363                         uint32_t trgm __attribute__((unused)) = trgmptr.trgm;
 364                         dprintf("trigram '%c%c%c' (%zu bytes) has %u entries, ignoring the rest (will "
 365                                 "weed out false positives later)\n",
 366                                 trgm & 0xff, (trgm >> 8) & 0xff, (trgm >> 16) & 0xff,
 367                                 len, trgmptr.num_docids);
 368                         break;
 369                 }
 370
 371                 // Only stay a certain amount ahead, so that we don't spend I/O
 372                 // on reading the latter, large posting lists. We are unlikely
 373                 // to need them anyway, even if they should come in first.
 374                 if (engine.get_waiting_reads() >= 5) {
 375                         engine.finish();
 376                         if (done)
 377                                 break;
 378                 }
 379                 engine.submit_read(fd, len, trgmptr.offset, [trgmptr, len, &done, &in1, &in2, &out](string s) {
 380                         if (done)
 381                                 return;
 382                         uint32_t trgm __attribute__((unused)) = trgmptr.trgm;
 383                         size_t num = trgmptr.num_docids;
 384                         unsigned char *pldata = reinterpret_cast<unsigned char *>(s.data());
 385                         if (in1.empty()) {
 386                                 in1.resize(num + 128);
 387                                 p4nd1dec128v32(pldata, num, &in1[0]);
 388                                 in1.resize(num);
 389                                 dprintf("trigram '%c%c%c' (%zu bytes) decoded to %zu entries\n", trgm & 0xff,
 390                                         (trgm >> 8) & 0xff, (trgm >> 16) & 0xff, len, num);
 391                         } else {
 392                                 if (in2.size() < num + 128) {
 393                                         in2.resize(num + 128);
 394                                 }
 395                                 p4nd1dec128v32(pldata, num, &in2[0]);
 396
 397                                 out.clear();
 398                                 set_intersection(in1.begin(), in1.end(), in2.begin(), in2.begin() + num,
 399                                                  back_inserter(out));
 400                                 swap(in1, out);
 401                                 dprintf("trigram '%c%c%c' (%zu bytes) decoded to %zu entries, %zu left\n",
 402                                         trgm & 0xff, (trgm >> 8) & 0xff, (trgm >> 16) & 0xff,
 403                                         len, num, in1.size());
 404                                 if (in1.empty()) {
 405                                         dprintf("no matches (intersection list is empty)\n");
 406                                         done = true;
 407                                 }
 408                         }
 409                 });
 410         }
 411         engine.finish();
 412         if (done) {
 413                 return;
 414         }
 415         dprintf("Intersection done after %.1f ms. Doing final verification and printing:\n",
 416                 1e3 * duration<float>(steady_clock::now() - start).count());
 417
 418         size_t matched __attribute__((unused)) = scan_docids(needles, in1, corpus, &engine);
 419         dprintf("Done in %.1f ms, found %zu matches.\n",
 420                 1e3 * duration<float>(steady_clock::now() - start).count(), matched);
 421 }
 422
 423 void usage()
 424 {
 425         // The help text comes from mlocate.
 426         printf("Usage: plocate [OPTION]... PATTERN...\n");
 427         printf("  -d, --database DBPATH  use DBPATH instead of default database (which is\n");
 428         printf("                         %s)\n", dbpath);
 429         printf("  -h, --help             print this help\n");
 430         printf("  -0, --null             separate entries with NUL on output\n");
 431 }
 432
 433 int main(int argc, char **argv)
 434 {
 435         static const struct option long_options[] = {
 436                 { "help", no_argument, 0, 'h' },
 437                 { "database", required_argument, 0, 'd' },
 438                 { "null", no_argument, 0, '0' },
 439                 { 0, 0, 0, 0 }
 440         };
 441
 442         for (;;) {
 443                 int option_index = 0;
 444                 int c = getopt_long(argc, argv, "d:h0", long_options, &option_index);
 445                 if (c == -1) {
 446                         break;
 447                 }
 448                 switch (c) {
 449                 case 'd':
 450                         dbpath = strdup(optarg);
 451                         break;
 452                 case 'h':
 453                         usage();
 454                         exit(0);
 455                 case '0':
 456                         print_nul = true;
 457                         break;
 458                 default:
 459                         exit(1);
 460                 }
 461         }
 462
 463         vector<string> needles;
 464         for (int i = optind; i < argc; ++i) {
 465                 needles.push_back(argv[i]);
 466         }
 467         if (needles.empty()) {
 468                 fprintf(stderr, "plocate: no pattern to search for specified\n");
 469                 exit(0);
 470         }
 471         do_search_file(needles, dbpath);
 472 }