Reduce the amount of lseek() syscalls; evidently, ftell() does not cache the position.

diff --git a/database-builder.cpp b/database-builder.cpp
index 75b05f6a2cf1a898c014fd1227b4c6471c4f0148..066b60eaeb56ecd6ccc556fb1a091d2faff40d8b 100644 (file)
--- a/database-builder.cpp
+++ b/database-builder.cpp
@@ -208,6 +208,7 @@ private:
 
        std::unique_ptr<PostingListBuilder *[]> invindex;
        FILE *outfp;
+       off_t outfp_pos;  // Cheaper than calling ftell(outfp) all the time.
        std::string current_block;
        std::string tempbuf;
        const size_t block_size;
@@ -221,7 +222,7 @@ private:
 
 
 EncodingCorpus::EncodingCorpus(FILE *outfp, size_t block_size, ZSTD_CDict *cdict, bool store_dir_times)
-       : invindex(new PostingListBuilder *[NUM_TRIGRAMS]), outfp(outfp), block_size(block_size), store_dir_times(store_dir_times), cdict(cdict)
+       : invindex(new PostingListBuilder *[NUM_TRIGRAMS]), outfp(outfp), outfp_pos(ftell(outfp)), block_size(block_size), store_dir_times(store_dir_times), cdict(cdict)
 {
        fill(invindex.get(), invindex.get() + NUM_TRIGRAMS, nullptr);
        if (store_dir_times) {
@@ -336,12 +337,13 @@ void EncodingCorpus::flush_block()
        }
 
        // Compress and add the filename block.
-       filename_blocks.push_back(ftell(outfp));
+       filename_blocks.push_back(outfp_pos);
        string compressed = zstd_compress(current_block, cdict, &tempbuf);
        if (fwrite(compressed.data(), compressed.size(), 1, outfp) != 1) {
                perror("fwrite()");
                exit(1);
        }
+       outfp_pos += compressed.size();
 
        current_block.clear();
        num_files_in_block = 0;