using namespace std;
using namespace std::chrono;
+
+string zstd_compress(const string &src, string *tempbuf);
-static inline uint32_t read_unigram(const string &s, size_t idx)
+static inline uint32_t read_unigram(const string_view s, size_t idx)
{
if (idx < s.size()) {
return (unsigned char)s[idx];
}
}
-static inline uint32_t read_trigram(const string &s, size_t start)
+static inline uint32_t read_trigram(const string_view s, size_t start)
{
return read_unigram(s, start) |
(read_unigram(s, start + 1) << 8) |
uint8_t pad[4];
};
-const char *handle_directory(const char *ptr, vector<string> *files)
+class Corpus {
+public:
+ Corpus(size_t block_size) : block_size(block_size) {}
+ void add_file(string filename);
+ void flush_block();
+
+ vector<string> filename_blocks;
+ unordered_map<uint32_t, vector<uint32_t>> invindex;
+ size_t num_files = 0, num_files_in_block = 0, num_blocks = 0;
+
+private:
+ string current_block;
+ string tempbuf;
+ const size_t block_size;
+};
+
+void Corpus::add_file(string filename)
+{
+ ++num_files;
+ if (!current_block.empty()) {
+ current_block.push_back('\0');
+ }
+ current_block += filename;
+ if (++num_files_in_block == block_size) {
+ flush_block();
+ }
+}
+
+void Corpus::flush_block()
+{
+ if (current_block.empty()) {
+ return;
+ }
+
+ uint32_t docid = num_blocks;
+
+ // Create trigrams.
+ const char *ptr = current_block.c_str();
+ while (ptr < current_block.c_str() + current_block.size()) {
+ string_view s(ptr);
+ if (s.size() >= 3) {
+ for (size_t j = 0; j < s.size() - 2; ++j) {
+ uint32_t trgm = read_trigram(s, j);
+ vector<uint32_t> &docids = invindex[trgm];
+ if (docids.empty() || docids.back() != docid) {
+ docids.push_back(docid);
+ }
+ }
+ }
+ ptr += s.size() + 1;
+ }
+
+ // Compress and add the filename block.
+ filename_blocks.push_back(zstd_compress(current_block, &tempbuf));
+
+ current_block.clear();
+ num_files_in_block = 0;
+ ++num_blocks;
+}
+
+const char *handle_directory(const char *ptr, Corpus *corpus)
{
ptr += sizeof(db_directory);
uint8_t type = *ptr++;
if (type == DBE_NORMAL) {
string filename = ptr;
- files->push_back(dir_path + "/" + filename);
+ corpus->add_file(dir_path + "/" + filename);
ptr += filename.size() + 1;
} else if (type == DBE_DIRECTORY) {
string dirname = ptr;
- files->push_back(dir_path + "/" + dirname);
+ corpus->add_file(dir_path + "/" + dirname);
ptr += dirname.size() + 1;
} else {
return ptr;
}
}
-void read_mlocate(const char *filename, vector<string> *files)
+void read_mlocate(const char *filename, Corpus *corpus)
{
int fd = open(filename, O_RDONLY);
if (fd == -1) {
const char *ptr = data + offset;
while (ptr < data + len) {
- ptr = handle_directory(ptr, files);
+ ptr = handle_directory(ptr, corpus);
}
munmap((void *)data, len);
{
//steady_clock::time_point start = steady_clock::now();
- vector<string> files;
- read_mlocate(infile, &files);
+ Corpus corpus(block_size);
+
+ read_mlocate(infile, &corpus);
if (false) { // To read a plain text file.
FILE *fp = fopen(infile, "r");
while (!feof(fp)) {
}
string s(buf);
if (s.back() == '\n') s.pop_back();
- files.push_back(move(s));
+ corpus.add_file(move(s));
}
fclose(fp);
}
- dprintf("Read %zu files from %s\n", files.size(), infile);
-
- unordered_map<uint32_t, string> pl;
- size_t trigrams = 0, longest_posting_list = 0;
- unordered_map<uint32_t, vector<uint32_t>> invindex;
- for (size_t i = 0; i < files.size(); ++i) {
- uint32_t docid = i / block_size;
- const string &s = files[i];
- if (s.size() >= 3) {
- for (size_t j = 0; j < s.size() - 2; ++j) {
- uint32_t trgm = read_trigram(s, j);
- vector<uint32_t> &docids = invindex[trgm];
- if (docids.empty() || docids.back() != docid) {
- docids.push_back(docid);
- }
- }
- }
- }
+ corpus.flush_block();
+ dprintf("Read %zu files from %s\n", corpus.num_files, infile);
+
+ // Compress posting lists.
string buf;
+ size_t trigrams = 0, longest_posting_list = 0;
size_t bytes_used = 0;
- for (auto &[trigram, docids] : invindex) {
+ unordered_map<uint32_t, string> pl;
+ for (auto &[trigram, docids] : corpus.invindex) {
longest_posting_list = max(longest_posting_list, docids.size());
trigrams += docids.size();
bytes_used += bytes;
}
dprintf("%zu files, %zu different trigrams, %zu entries, avg len %.2f, longest %zu\n",
- files.size(), invindex.size(), trigrams, double(trigrams) / invindex.size(), longest_posting_list);
+ 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));
//steady_clock::time_point end = steady_clock::now();
dprintf("Building posting lists took %.1f ms.\n\n", 1e3 * duration<float>(end - start).count());
vector<uint32_t> all_trigrams;
- for (auto &[trigram, docids] : invindex) {
+ for (auto &[trigram, docids] : corpus.invindex) {
all_trigrams.push_back(trigram);
}
sort(all_trigrams.begin(), all_trigrams.end());
FILE *outfp = fopen(outfile, "wb");
// Write the header.
- uint64_t num_trigrams = invindex.size(); // 64 to get alignment.
+ uint64_t num_trigrams = corpus.invindex.size(); // 64 to get alignment.
fwrite(&num_trigrams, sizeof(num_trigrams), 1, outfp);
// Find out where the posting lists will end.
for (uint32_t trgm : all_trigrams) {
// 16 bytes: trgm (4), number of docids (4), byte offset (8)
fwrite(&trgm, sizeof(trgm), 1, outfp); // One byte wasted, but OK.
- uint32_t num_docids = invindex[trgm].size();
+ uint32_t num_docids = corpus.invindex[trgm].size();
fwrite(&num_docids, sizeof(num_docids), 1, outfp);
fwrite(&offset, sizeof(offset), 1, outfp);
offset += pl[trgm].size();
bytes_for_posting_lists += pl[trgm].size();
}
- // Compress the filenames into blocks.
- vector<string> filename_blocks;
- string uncompressed_filenames;
- int num_files_this_block = 0;
-
- string dst, tempbuf;
- for (string &filename : files) {
- uncompressed_filenames += filename;
- filename.clear();
- if (++num_files_this_block == block_size) {
- filename_blocks.push_back(zstd_compress(uncompressed_filenames, &tempbuf));
- uncompressed_filenames.clear();
- num_files_this_block = 0;
- } else {
- uncompressed_filenames.push_back('\0');
- }
- }
- if (num_files_this_block > 0) {
- filename_blocks.push_back(zstd_compress(uncompressed_filenames, &tempbuf));
- }
- files.clear();
-
// Stick an empty block at the end as sentinel.
- filename_blocks.push_back("");
+ corpus.filename_blocks.push_back("");
// Write the offsets to the filenames.
- offset = filename_index_offset + filename_blocks.size() * sizeof(offset);
- for (const string &filename : filename_blocks) {
+ offset = filename_index_offset + 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);
}
// Write the actual filenames.
- for (const string &filename : filename_blocks) {
+ for (const string &filename : corpus.filename_blocks) {
fwrite(filename.data(), filename.size(), 1, outfp);
}
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