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