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

   1 #include <stdio.h>
   2 #include <string.h>
   3 #include <algorithm>
   4 #include <unordered_map>
   5 #include <string>
   6 #include <vector>
   7 #include <chrono>
   8 #include <unistd.h>
   9 #include <fcntl.h>
  10 #include <sys/mman.h>
  11 #include <arpa/inet.h>
  12 #include <endian.h>
  13 #include <sys/types.h>
  14 #include <sys/stat.h>
  15 #include <zstd.h>
  16
  17 #include "vp4.h"
  18
  19 #define P4NENC_BOUND(n) ((n+127)/128+(n+32)*sizeof(uint32_t))
  20 #define dprintf(...)
  21 //#define dprintf(...) fprintf(stderr, __VA_ARGS__);
  22
  23 using namespace std;
  24 using namespace std::chrono;
  25
  26 static inline uint32_t read_unigram(const string &s, size_t idx)
  27 {
  28         if (idx < s.size()) {
  29                 return (unsigned char)s[idx];
  30         } else {
  31                 return 0;
  32         }
  33 }
  34
  35 static inline uint32_t read_trigram(const string &s, size_t start)
  36 {
  37         return read_unigram(s, start) |
  38                 (read_unigram(s, start + 1) << 8) |
  39                 (read_unigram(s, start + 2) << 16);
  40 }
  41
  42 enum
  43 {
  44         DBE_NORMAL          = 0,    /* A non-directory file */
  45         DBE_DIRECTORY       = 1,    /* A directory */
  46         DBE_END             = 2   /* End of directory contents; contains no name */
  47 };
  48
  49 // From mlocate.
  50 struct db_header
  51 {
  52         uint8_t magic[8];
  53         uint32_t conf_size;
  54         uint8_t version;
  55         uint8_t check_visibility;
  56         uint8_t pad[2];
  57 };
  58
  59 // From mlocate.
  60 struct db_directory
  61 {
  62         uint64_t time_sec;
  63         uint32_t time_nsec;
  64         uint8_t pad[4];
  65 };
  66
  67 const char *handle_directory(const char *ptr, vector<string> *files)
  68 {
  69         ptr += sizeof(db_directory);
  70
  71         string dir_path = ptr;
  72         ptr += dir_path.size() + 1;
  73         if (dir_path == "/") {
  74                 dir_path = "";
  75         }
  76
  77         for ( ;; ) {
  78                 uint8_t type = *ptr++;
  79                 if (type == DBE_NORMAL) {
  80                         string filename = ptr;
  81                         files->push_back(dir_path + "/" + filename);
  82                         ptr += filename.size() + 1;
  83                 } else if (type == DBE_DIRECTORY) {
  84                         string dirname = ptr;
  85                         files->push_back(dir_path + "/" + dirname);
  86                         ptr += dirname.size() + 1;
  87                 } else {
  88                         return ptr;
  89                 }
  90         }
  91 }
  92
  93 void read_mlocate(const char *filename, vector<string> *files)
  94 {
  95         int fd = open(filename, O_RDONLY);
  96         if (fd == -1) {
  97                 perror(filename);
  98                 exit(1);
  99         }
 100         off_t len = lseek(fd, 0, SEEK_END);
 101         if (len == -1) {
 102                 perror("lseek");
 103                 exit(1);
 104         }
 105         const char *data = (char *)mmap(nullptr, len, PROT_READ, MAP_SHARED, fd, /*offset=*/0);
 106         if (data == MAP_FAILED) {
 107                 perror("mmap");
 108                 exit(1);
 109         }
 110
 111         const db_header *hdr = (const db_header *)data;
 112
 113         // TODO: Care about the base path.
 114         string path = data + sizeof(db_header);
 115         uint64_t offset = sizeof(db_header) + path.size() + 1 + ntohl(hdr->conf_size);
 116
 117         const char *ptr = data + offset;
 118         while (ptr < data + len) {
 119                 ptr = handle_directory(ptr, files);
 120         }
 121
 122         munmap((void *)data, len);
 123         close(fd);
 124 }
 125
 126 string zstd_compress(const string &src)
 127 {
 128         size_t max_size = ZSTD_compressBound(src.size());
 129         string dst;
 130         dst.resize(max_size);
 131         size_t size = ZSTD_compress(&dst[0], max_size, src.data(), src.size(), /*level=*/6);
 132         dst.resize(size);
 133         return dst;
 134 }
 135
 136 void do_build(const char *infile, const char *outfile, int block_size)
 137 {
 138         //steady_clock::time_point start = steady_clock::now();
 139
 140         vector<string> files;
 141         read_mlocate(infile, &files);
 142         if (false) {  // To read a plain text file.
 143                 FILE *fp = fopen(infile, "r");
 144                 while (!feof(fp)) {
 145                         char buf[1024];
 146                         if (fgets(buf, 1024, fp) == nullptr || feof(fp)) {
 147                                 break;
 148                         }
 149                         string s(buf);
 150                         if (s.back() == '\n') s.pop_back();
 151                         files.push_back(move(s));
 152                 }
 153                 fclose(fp);
 154         }
 155         dprintf("Read %zu files from %s\n", files.size(), infile);
 156
 157         unordered_map<uint32_t, string> pl;
 158         size_t trigrams = 0, longest_posting_list = 0;
 159         unordered_map<uint32_t, vector<uint32_t>> invindex;
 160         for (size_t i = 0; i < files.size(); ++i) {
 161                 const string &s = files[i];
 162                 if (s.size() >= 3) {
 163                         for (size_t j = 0; j < s.size() - 2; ++j) {
 164                                 uint32_t trgm = read_trigram(s, j);
 165                                 invindex[trgm].push_back(i / block_size);
 166                         }
 167                 }
 168         }
 169         string buf;
 170         size_t bytes_used = 0;
 171         for (auto &[trigram, docids] : invindex) {
 172                 auto last = unique(docids.begin(), docids.end());
 173                 docids.erase(last, docids.end());
 174                 longest_posting_list = max(longest_posting_list, docids.size());
 175                 trigrams += docids.size();
 176
 177                 size_t bytes_needed = P4NENC_BOUND(docids.size());
 178                 if (buf.size() < bytes_needed) buf.resize(bytes_needed);
 179                 size_t bytes = p4nd1enc128v32(&docids[0], docids.size(), reinterpret_cast<unsigned char *>(&buf[0]));
 180                 pl[trigram] = string(buf.data(), bytes);
 181                 bytes_used += bytes;
 182         }
 183         dprintf("%zu files, %zu different trigrams, %zu entries, avg len %.2f, longest %zu\n",
 184                 files.size(), invindex.size(), trigrams, double(trigrams) / invindex.size(), longest_posting_list);
 185
 186         dprintf("%zu bytes used for posting lists (%.2f bits/entry)\n", bytes_used, 8 * bytes_used / double(trigrams));
 187         //steady_clock::time_point end = steady_clock::now();
 188         dprintf("Building posting lists took %.1f ms.\n\n", 1e3 * duration<float>(end - start).count());
 189
 190         vector<uint32_t> all_trigrams;
 191         for (auto &[trigram, docids] : invindex) {
 192                 all_trigrams.push_back(trigram);
 193         }
 194         sort(all_trigrams.begin(), all_trigrams.end());
 195
 196         umask(0027);
 197         FILE *outfp = fopen(outfile, "wb");
 198
 199         // Write the header.
 200         uint64_t num_trigrams = invindex.size();  // 64 to get alignment.
 201         fwrite(&num_trigrams, sizeof(num_trigrams), 1, outfp);
 202
 203         // Find out where the posting lists will end.
 204         uint64_t offset = sizeof(uint64_t) * 2 + 16 * all_trigrams.size();
 205         uint64_t filename_index_offset = offset;
 206         for (uint32_t trgm : all_trigrams) {
 207                 filename_index_offset += pl[trgm].size();
 208         }
 209         fwrite(&filename_index_offset, sizeof(filename_index_offset), 1, outfp);
 210
 211         size_t bytes_for_trigrams = 0, bytes_for_posting_lists = 0, bytes_for_filename_index = 0, bytes_for_filenames = 0;
 212
 213         for (uint32_t trgm : all_trigrams) {
 214                 // 16 bytes: trgm (4), number of docids (4), byte offset (8)
 215                 fwrite(&trgm, sizeof(trgm), 1, outfp);  // One byte wasted, but OK.
 216                 uint32_t num_docids = invindex[trgm].size();
 217                 fwrite(&num_docids, sizeof(num_docids), 1, outfp);
 218                 fwrite(&offset, sizeof(offset), 1, outfp);
 219                 offset += pl[trgm].size();
 220                 bytes_for_trigrams += 16;
 221         }
 222
 223         // Write the actual posting lists.
 224         for (uint32_t trgm : all_trigrams) {
 225                 fwrite(pl[trgm].data(), pl[trgm].size(), 1, outfp);
 226                 bytes_for_posting_lists += pl[trgm].size();
 227         }
 228
 229         // Compress the filenames into blocks.
 230         vector<string> filename_blocks;
 231         string uncompressed_filenames;
 232         int num_files_this_block = 0;
 233
 234         string dst;
 235
 236         for (string &filename : files) {
 237                 uncompressed_filenames += filename;
 238                 filename.clear();
 239                 if (++num_files_this_block == block_size) {
 240                         filename_blocks.push_back(zstd_compress(uncompressed_filenames));
 241                         uncompressed_filenames.clear();
 242                         num_files_this_block = 0;
 243                 } else {
 244                         uncompressed_filenames.push_back('\0');
 245                 }
 246         }
 247         if (num_files_this_block > 0) {
 248                 filename_blocks.push_back(zstd_compress(uncompressed_filenames));
 249         }
 250         files.clear();
 251
 252         // Stick an empty block at the end as sentinel.
 253         filename_blocks.push_back("");
 254
 255         // Write the offsets to the filenames.
 256         offset = filename_index_offset + filename_blocks.size() * sizeof(offset);
 257         for (const string &filename : filename_blocks) {
 258                 fwrite(&offset, sizeof(offset), 1, outfp);
 259                 offset += filename.size();
 260                 bytes_for_filename_index += sizeof(offset);
 261                 bytes_for_filenames += filename.size();
 262         }
 263
 264         // Write the actual filenames.
 265         for (const string &filename : filename_blocks) {
 266                 fwrite(filename.data(), filename.size(), 1, outfp);
 267         }
 268
 269         fclose(outfp);
 270
 271         //size_t total_bytes = (bytes_for_trigrams + bytes_for_posting_lists + bytes_for_filename_index + bytes_for_filenames);
 272
 273         dprintf("Block size:     %7d files\n", block_size);
 274         dprintf("Trigrams:       %'7.1f MB\n", bytes_for_trigrams / 1048576.0);
 275         dprintf("Posting lists:  %'7.1f MB\n", bytes_for_posting_lists / 1048576.0);
 276         dprintf("Filename index: %'7.1f MB\n", bytes_for_filename_index / 1048576.0);
 277         dprintf("Filenames:      %'7.1f MB\n", bytes_for_filenames / 1048576.0);
 278         dprintf("Total:          %'7.1f MB\n", total_bytes / 1048576.0);
 279         dprintf("\n");
 280 }
 281
 282 int main(int argc, char **argv)
 283 {
 284         do_build(argv[1], argv[2], 32);
 285         exit(EXIT_SUCCESS);
 286 }