text: //
  // Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2021
  //
  // Distributed under the Boost Software License, Version 1.0. (See accompanying
  // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  //
  #pragma once
  
  #include "td/utils/common.h"
  #include "td/utils/Slice.h"
  #include "td/utils/StringBuilder.h"
  
  namespace td {
  
  class Bitmask {
   public:
    struct Decode {};
    struct Ones {};
    Bitmask() = default;
    Bitmask(Decode, Slice data);
    Bitmask(Ones, int64 count);
    std::string encode(int32 prefix_count = -1);
    int64 get_ready_prefix_size(int64 offset, int64 part_size, int64 file_size) const;
    int64 get_total_size(int64 part_size, int64 file_size) const;
    bool get(int64 offset_part) const;
  
    int64 get_ready_parts(int64 offset_part) const;
  
    std::vector<int32> as_vector() const;
    void set(int64 offset_part);
    int64 size() const;
  
    Bitmask compress(int k) const;
  
   private:
    std::string data_;
  };
  
  StringBuilder &operator<<(StringBuilder &sb, const Bitmask &mask);
  
  }  // namespace td
  