simple_variable_len_msg_frame.hpp

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#ifndef SIMPLE_VARIABLE_LEN_MSG_FRAME_HPP_INCLUDED
#define SIMPLE_VARIABLE_LEN_MSG_FRAME_HPP_INCLUDED
 
#include "asio/buffer.hpp"
 
#include <cstddef> // std::size_t, std::byte
 
namespace chops {
namespace net {
 
using hdr_decoder_func = std::size_t (*)(const std::byte* ptr, std::size_t sz);
 
 
class simple_variable_len_msg_frame {
private:
  hdr_decoder_func m_hdr_decoder_func;
  bool             m_hdr_processed;
public:
  simple_variable_len_msg_frame(hdr_decoder_func func) noexcept : 
      m_hdr_decoder_func(func), m_hdr_processed(false) { }
 
  std::size_t operator() (asio::mutable_buffer buf) noexcept {
    if (!m_hdr_processed) {
      auto sz = m_hdr_decoder_func(static_cast<const std::byte*>(buf.data()), buf.size());
      m_hdr_processed = (sz != 0u);
      return sz;
    }
    m_hdr_processed = false;
    return 0u;
  }
};
 
} // end net namespace
} // end chops namespace
 
#endif