yadro-task/include/tapelib/tape_util.h

#ifndef TAPE_UTIL_H
#define TAPE_UTIL_H

#include "filetape.h"
#include "tape.h"
#include <cstddef>
#include <cstdint>
#include <functional>
#include <memory>

using std::unique_ptr;

namespace tape {

/**
 * Lambda, which takes the amount of cells a tape should have and returns
 * a unique pointer to a temporary Tape with the specified amount of cells
 */
using TempTapeFactory = std::function<unique_ptr<Tape>(size_t)>;

/**
 * TempTapeFactory that creates a new temporary FileTape
 */
const static inline TempTapeFactory FILETAPE_FACTORY =
    [](size_t cells) -> unique_ptr<Tape> {
    return std::make_unique<FileTape>(FileTape(cells));
};

/**
 * External sort for Tape. Reads *ram_limit* cells into memory, sorts them,
 * writes them to a temporary Tape, does this until all data from input Tape is
 * sorted and put into temporary Tapes, then merges temporary Tapes sorted data
 * into output Tape. Heap sort is preffered due to reduction in seek operations.
 *
 * @param input Tape, data of which should be sorted
 * @param output Tape, where the sorted data is going to be written
 * @param tmp_tape_factory Lambda expression that defines how new temporary
 * Tapes are created
 * @param sort_limit Max amount of cells that can be loaded into memory to use
 * while sorting. Set to SIZE_MAX by default
 */
void external_sort(Tape &input, Tape &output, TempTapeFactory tmp_tape_factory,
                   size_t sort_limit = SIZE_MAX);

} // namespace tape

#endif // !TAPE_UTIL_H