Function GetFileSize

src/leveldb/include/leveldb/env.h:354–356

    return target_->DeleteDir(d);
  }
  Status GetFileSize(const std::string& f, uint64_t* s) override {
    return target_->GetFileSize(f, s);
  }
  Status RenameFile(const std::string& s, const std::string& t) override {
    return target_->RenameFile(s, t);
  }