#include <stdio.h>
#include <string.h>
#include <string>
-#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
string zstd_compress(const string &src, string *tempbuf);
+constexpr unsigned num_overflow_slots = 16;
+
static inline uint32_t read_unigram(const string_view s, size_t idx)
{
if (idx < s.size()) {
class Corpus {
public:
- Corpus(size_t block_size)
- : block_size(block_size) {}
+ Corpus(FILE *outfp, size_t block_size)
+ : outfp(outfp), block_size(block_size) {}
void add_file(string filename);
void flush_block();
- vector<string> filename_blocks;
+ vector<uint64_t> filename_blocks;
unordered_map<uint32_t, PostingListBuilder> invindex;
size_t num_files = 0, num_files_in_block = 0, num_blocks = 0;
private:
+ FILE *outfp;
string current_block;
string tempbuf;
const size_t block_size;
}
// Compress and add the filename block.
- filename_blocks.push_back(zstd_compress(current_block, &tempbuf));
+ filename_blocks.push_back(ftell(outfp));
+ string compressed = zstd_compress(current_block, &tempbuf);
+ if (fwrite(compressed.data(), compressed.size(), 1, outfp) != 1) {
+ perror("fwrite()");
+ exit(1);
+ }
current_block.clear();
num_files_in_block = 0;
++num_blocks;
}
-const char *handle_directory(const char *ptr, Corpus *corpus)
+string read_cstr(FILE *fp)
+{
+ string ret;
+ for ( ;; ) {
+ int ch = getc(fp);
+ if (ch == -1) {
+ perror("getc");
+ exit(1);
+ }
+ if (ch == 0) {
+ return ret;
+ }
+ ret.push_back(ch);
+ }
+}
+
+void handle_directory(FILE *fp, Corpus *corpus)
{
- ptr += sizeof(db_directory);
+ db_directory dummy;
+ if (fread(&dummy, sizeof(dummy), 1, fp) != 1) {
+ if (feof(fp)) {
+ return;
+ } else {
+ perror("fread");
+ }
+ }
- string dir_path = ptr;
- ptr += dir_path.size() + 1;
+ string dir_path = read_cstr(fp);
if (dir_path == "/") {
dir_path = "";
}
for (;;) {
- uint8_t type = *ptr++;
+ int type = getc(fp);
if (type == DBE_NORMAL) {
- string filename = ptr;
+ string filename = read_cstr(fp);
corpus->add_file(dir_path + "/" + filename);
- ptr += filename.size() + 1;
} else if (type == DBE_DIRECTORY) {
- string dirname = ptr;
+ string dirname = read_cstr(fp);
corpus->add_file(dir_path + "/" + dirname);
- ptr += dirname.size() + 1;
} else {
- return ptr;
+ return; // Probably end.
}
}
}
void read_mlocate(const char *filename, Corpus *corpus)
{
- int fd = open(filename, O_RDONLY);
- if (fd == -1) {
+ FILE *fp = fopen(filename, "rb");
+ if (fp == nullptr) {
perror(filename);
exit(1);
}
- off_t len = lseek(fd, 0, SEEK_END);
- if (len == -1) {
- perror("lseek");
- exit(1);
- }
- const char *data = (char *)mmap(nullptr, len, PROT_READ, MAP_SHARED, fd, /*offset=*/0);
- if (data == MAP_FAILED) {
- perror("mmap");
+
+ db_header hdr;
+ if (fread(&hdr, sizeof(hdr), 1, fp) != 1) {
+ perror("short read");
exit(1);
}
- const db_header *hdr = (const db_header *)data;
-
// TODO: Care about the base path.
- string path = data + sizeof(db_header);
- uint64_t offset = sizeof(db_header) + path.size() + 1 + ntohl(hdr->conf_size);
-
- const char *ptr = data + offset;
- while (ptr < data + len) {
- ptr = handle_directory(ptr, corpus);
+ string path = read_cstr(fp);
+ while (!feof(fp)) {
+ handle_directory(fp, corpus);
}
-
- munmap((void *)data, len);
- close(fd);
+ fclose(fp);
}
string zstd_compress(const string &src, string *tempbuf)
{
steady_clock::time_point start __attribute__((unused)) = steady_clock::now();
- Corpus corpus(block_size);
+ umask(0027);
+ FILE *outfp = fopen(outfile, "wb");
+
+ // Write the header.
+ Header hdr;
+ memcpy(hdr.magic, "\0plocate", 8);
+ hdr.version = -1; // Mark as broken.
+ hdr.hashtable_size = 0; // Not known yet.
+ hdr.extra_ht_slots = num_overflow_slots;
+ hdr.hash_table_offset_bytes = -1; // We don't know these offsets yet.
+ hdr.filename_index_offset_bytes = -1;
+ fwrite(&hdr, sizeof(hdr), 1, outfp);
+
+ Corpus corpus(outfp, block_size);
read_mlocate(infile, &corpus);
if (false) { // To read a plain text file.
corpus.flush_block();
dprintf("Read %zu files from %s\n", corpus.num_files, infile);
+ // Stick an empty block at the end as sentinel.
+ corpus.filename_blocks.push_back(ftell(outfp));
+ const size_t bytes_for_filenames = corpus.filename_blocks.back() - corpus.filename_blocks.front();
+
+ // Write the offsets to the filenames.
+ hdr.filename_index_offset_bytes = ftell(outfp);
+ const size_t bytes_for_filename_index = corpus.filename_blocks.size() * sizeof(uint64_t);
+ fwrite(corpus.filename_blocks.data(), corpus.filename_blocks.size(), sizeof(uint64_t), outfp);
+ corpus.filename_blocks.clear();
+ corpus.filename_blocks.shrink_to_fit();
+
+ // Finish up encoding the posting lists.
size_t trigrams = 0, longest_posting_list = 0;
- size_t bytes_used = 0;
+ size_t bytes_for_posting_lists = 0;
for (auto &[trigram, pl_builder] : corpus.invindex) {
pl_builder.finish();
longest_posting_list = max(longest_posting_list, pl_builder.num_docids);
trigrams += pl_builder.num_docids;
- bytes_used += pl_builder.encoded.size();
+ bytes_for_posting_lists += pl_builder.encoded.size();
}
dprintf("%zu files, %zu different trigrams, %zu entries, avg len %.2f, longest %zu\n",
corpus.num_files, corpus.invindex.size(), trigrams, double(trigrams) / corpus.invindex.size(), longest_posting_list);
- dprintf("%zu bytes used for posting lists (%.2f bits/entry)\n", bytes_used, 8 * bytes_used / double(trigrams));
+ dprintf("%zu bytes used for posting lists (%.2f bits/entry)\n", bytes_for_posting_lists, 8 * bytes_for_posting_lists / double(trigrams));
dprintf("Building posting lists took %.1f ms.\n\n", 1e3 * duration<float>(steady_clock::now() - start).count());
}
sort(all_trigrams.begin(), all_trigrams.end());
+ // Create the hash table.
unique_ptr<Trigram[]> hashtable;
uint32_t ht_size = next_prime(all_trigrams.size());
- constexpr unsigned num_overflow_slots = 16;
for (;;) {
hashtable = create_hashtable(corpus, all_trigrams, ht_size, num_overflow_slots);
if (hashtable == nullptr) {
}
}
- umask(0027);
- FILE *outfp = fopen(outfile, "wb");
-
// Find the offsets for each posting list.
size_t bytes_for_hashtable = (ht_size + num_overflow_slots + 1) * sizeof(Trigram);
- uint64_t offset = sizeof(Header) + bytes_for_hashtable;
+ uint64_t offset = ftell(outfp) + bytes_for_hashtable;
for (unsigned i = 0; i < ht_size + num_overflow_slots + 1; ++i) {
hashtable[i].offset = offset; // Needs to be there even for empty slots.
if (hashtable[i].num_docids == 0) {
continue;
}
- const PostingListBuilder &pl_builder = corpus.invindex[hashtable[i].trgm];
- offset += pl_builder.encoded.size();
+ const string &encoded = corpus.invindex[hashtable[i].trgm].encoded;
+ offset += encoded.size();
}
- // Write the header.
- Header hdr;
- memcpy(hdr.magic, "\0plocate", 8);
- hdr.version = 0;
- hdr.hashtable_size = ht_size;
- hdr.extra_ht_slots = num_overflow_slots;
- hdr.hash_table_offset_bytes = sizeof(hdr); // This member is just there for flexibility.
- hdr.filename_index_offset_bytes = offset;
- fwrite(&hdr, sizeof(hdr), 1, outfp);
-
// Write the hash table.
+ hdr.hash_table_offset_bytes = ftell(outfp);
+ hdr.hashtable_size = ht_size;
fwrite(hashtable.get(), ht_size + num_overflow_slots + 1, sizeof(Trigram), outfp);
// Write the actual posting lists.
- size_t bytes_for_posting_lists = 0;
for (unsigned i = 0; i < ht_size + num_overflow_slots + 1; ++i) {
if (hashtable[i].num_docids == 0) {
continue;
}
const string &encoded = corpus.invindex[hashtable[i].trgm].encoded;
fwrite(encoded.data(), encoded.size(), 1, outfp);
- bytes_for_posting_lists += encoded.size();
- }
-
- // Stick an empty block at the end as sentinel.
- corpus.filename_blocks.push_back("");
-
- // Write the offsets to the filenames.
- size_t bytes_for_filename_index = 0, bytes_for_filenames = 0;
- offset = hdr.filename_index_offset_bytes + corpus.filename_blocks.size() * sizeof(offset);
- for (const string &filename : corpus.filename_blocks) {
- fwrite(&offset, sizeof(offset), 1, outfp);
- offset += filename.size();
- bytes_for_filename_index += sizeof(offset);
- bytes_for_filenames += filename.size();
- }
-
- // Write the actual filenames.
- for (const string &filename : corpus.filename_blocks) {
- fwrite(filename.data(), filename.size(), 1, outfp);
}
+ // Rewind, and write the updated header.
+ hdr.version = 0;
+ fseek(outfp, 0, SEEK_SET);
+ fwrite(&hdr, sizeof(hdr), 1, outfp);
fclose(outfp);
size_t total_bytes __attribute__((unused)) = (bytes_for_hashtable + bytes_for_posting_lists + bytes_for_filename_index + bytes_for_filenames);
projects / plocate / blobdiff