== cobalt/io/stream_file.hpp

The `stream_file` provides stream access to file.
If Asio does not support asynchronous file IO, Cobalt will fall back on synchronous operations.

[source,cpp]
----
struct stream_file : file, stream
{
  stream_file(const executor & executor = this_thread::get_executor());
  stream_file(const char * path, file::flags open_flags,
              const executor & executor = this_thread::get_executor());
  stream_file(const std::string & path, file::flags open_flags,
              const executor & executor = this_thread::get_executor());
  stream_file(const native_handle_type & native_file,
              const executor & executor = this_thread::get_executor());
  stream_file(stream_file && sf) noexcept;

  write_op write_some(const_buffer_sequence buffer);
  read_op read_some(mutable_buffer_sequence buffer);

  // advance the position in the file
  system::result<std::uint64_t> seek(
      std::int64_t offset,
      seek_basis whence);

};
----