file_reader.hpp

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#ifndef PLSSVM_DETAIL_IO_FILE_READER_HPP_
#define PLSSVM_DETAIL_IO_FILE_READER_HPP_
#pragma once
 
// check if memory mapping can be supported
#if __has_include(<fcntl.h>) && __has_include(<sys/mman.h>) && __has_include(<sys/stat.h>) && __has_include(<unistd.h>)
    // supported (UNIX system)
    #define PLSSVM_HAS_MEMORY_MAPPING
    #define PLSSVM_HAS_MEMORY_MAPPING_UNIX
#elif __has_include(<windows.h>)
    // supported (Windows system)
    #define PLSSVM_HAS_MEMORY_MAPPING
    #define PLSSVM_HAS_MEMORY_MAPPING_WINDOWS
 
    #include <windows.h>  // HANDLE
#endif
 
#include <filesystem>   // std::filesystem::path
#include <ios>          // std::streamsize
#include <string>       // std::string
#include <string_view>  // std::string_view
#include <vector>       // std::vector
 
namespace plssvm::detail::io {
 
class file_reader {
  public:
    file_reader() = default;
    explicit file_reader(const char *filename);
    explicit file_reader(const std::string &filename);
    explicit file_reader(const std::filesystem::path &filename);
    ~file_reader();
 
    file_reader(const file_reader &) = delete;
    file_reader(file_reader &&other) noexcept;
    file_reader &operator=(const file_reader &) = delete;
    file_reader &operator=(file_reader &&other) noexcept;
 
    void open(const char *filename);
    void open(const std::string &filename);
    void open(const std::filesystem::path &filename);
    [[nodiscard]] bool is_open() const noexcept;
    void close();
 
    void swap(file_reader &other);
 
    const std::vector<std::string_view> &read_lines(std::string_view comment = { "\n" });
    const std::vector<std::string_view> &read_lines(char comment);
 
    [[nodiscard]] typename std::vector<std::string_view>::size_type num_lines() const noexcept;
    [[nodiscard]] std::string_view line(typename std::vector<std::string_view>::size_type pos) const;
    [[nodiscard]] const std::vector<std::string_view> &lines() const noexcept;
    [[nodiscard]] const char *buffer() const noexcept;
 
  private:
    void open_memory_mapped_file_unix(const char *filename);
 
    void open_memory_mapped_file_windows(const char *filename);
 
    void open_file(const char *filename);
 
#if defined(PLSSVM_HAS_MEMORY_MAPPING)
    #if defined(PLSSVM_HAS_MEMORY_MAPPING_UNIX)
    int file_descriptor_{ 0 };
    #elif defined(PLSSVM_HAS_MEMORY_MAPPING_WINDOWS)
    HANDLE file_{};
    HANDLE mapped_file_{};
    #endif
    bool must_unmap_file_{ false };
#endif
    char *file_content_{ nullptr };
    std::streamsize num_bytes_{ 0 };
    std::vector<std::string_view> lines_{};
    bool is_open_{ false };
};
 
void swap(file_reader &lhs, file_reader &rhs);
 
}  // namespace plssvm::detail::io
 
#endif  // PLSSVM_DETAIL_IO_FILE_READER_HPP_