compressed_file_reader.h

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#ifndef META_COMPRESSED_FILE_READER_H_
#define META_COMPRESSED_FILE_READER_H_

#include <functional>
#include <memory>
#include <stdexcept>
#include <string>

namespace meta
{
namespace io
{

class mmap_file;

enum ReaderStatus
{
    notDone,
    readerDone,
    userDone
};

class compressed_file_reader
{
  public:
    compressed_file_reader(const mmap_file& file,
                           std::function<uint64_t(uint64_t)> mapping);

    compressed_file_reader(const std::string& filename,
                           std::function<uint64_t(uint64_t)> mapping);

    ~compressed_file_reader();

    void reset();

    void close();

    void seek(uint64_t bit_offset);

    bool has_next() const;

    uint64_t next();

    std::string next_string();

    uint64_t bit_location() const;

    operator bool() const
    {
        return status_ != userDone;
    }

  private:
    void get_next();

    bool read_bit();

    std::unique_ptr<mmap_file> file_;

    char* start_;

    uint64_t size_;

    int status_;

    uint64_t current_value_;

    uint64_t current_char_;

    uint8_t current_bit_;

    std::function<uint64_t(uint64_t)> mapping_;

  public:
    class compressed_file_reader_exception : public std::runtime_error
    {
      public:
        using std::runtime_error::runtime_error;
    };
};

uint64_t default_compression_reader_func(uint64_t value);
}
}

#endif