Close file descriptors of created files

[bgs99]

• Add native_handle_type to temporary files
• Add file::native_handle method
• Save the native handle
• Close the file on destruction, releasing or moving

[bugdea1er]

Actually it would be better to store the descriptor for the created file and close it explicitly when deleting it

create_file should return a pair of native handle and created path:

std::pair<fs::path, file::native_handle_type> create_file(std::string_view prefix, std::string_view suffix)

file should get a new private constructor to initialize both fields:

file::file(std::pair<fs::path, file::native_handle_type> handle, bool binary)
    : tmp::path(std::move(handle.first)),
      binary(binary),
      handle(handle.second) {}

file::file(std::string_view prefix, std::string_view suffix, bool binary)
    : file(create_file(prefix, suffix), binary) {}

And remove function should explicitly close the file before deleting, something like this:

#ifdef WIN32
            CloseHandle(handle);
#else
            close(handle);
#endif

[bugdea1er]

And since file will store a handle, it would be a good idea to add a public getter method for it:

/// Returns the underlying implementation-defined handle
[[nodiscard]] native_handle_type file::native_handle() const noexcept;

[bgs99]

Added native handle management

[bgs99]

Suggested change

	/// @param file The file to close
	/// @param file The file to close