Boost Asio, chat example: How do I manually write in the body of the message? [chat_message.hpp]

Question

I am following the " chat example " from Boost Asio's tutorials. As I don't have much experience with Boost Asio, I am implementing my own client server application using the chat example and modifying it according to my needs.

Now I am defining a Protocol.hpp file, which contains keywords for the network protocol. For example:

Protocol.hpp

#ifndef PROTOCOL_HPP
#define PROTOCOL_HPP

#include <iostream>

extern const char ACK;

#endif

Protocol.cpp

#include "Protocol.hpp"

const char ACK = "1";

If you take a look at the "chat_message.hpp" class, you will find the following:

  const char* data() const
  {
    return data_;
  }

  char* data()
  {
    return data_;
  }

I have tried the following:

std::sprintf(write_msgs_.data(), ACK, 2);

As well as trying to assign directly the desired code like this —however I guess that I am obtaining the const function—:

write_msgs_.data() = ACK;

I have thought of using the string class and then somehow convert it to char , in order to copy it in the write_msgs_.data() , or even adding every character with a loop. I am relatively new to C++, and I don't seem to find a good solution for this. Is there any proper way of doing this?

Thank you very much in advance.

Answer 1

I found it. I should have checked how the example application does it, and it simply uses memcpy from the cstring library. Therefore, anyone having the same problem as me should use the following:

main of the chat_client.cpp file:

char line[chat_message::max_body_length + 1];
while (std::cin.getline(line, chat_message::max_body_length + 1))
{
  using namespace std; // For strlen and memcpy.
  chat_message msg;
  msg.body_length(strlen(line));
  memcpy(msg.body(), line, msg.body_length());
  msg.encode_header();
  c.write(msg);
}

As you can see there is a char line variable that will hold the written text. After this, memcpy is used to copy the line to the body of the message.