Question

I have

       std::ostringstream out;
       out << name << len << data;
       std::string const value = out.str();

I want to copy this const value to a char*

        char* buff; 
        size_t length = strlen(value); 
        buff = new char[(strlen(value))+ 1]; 
        memcpy(nm, value , length + 1); 

but it is still giving me error? Can you please tell me what I am doing wrong? Thank you.

Answer 1

Use value.size() instead of strlen(value).

 char* buff; 
 size_t length = value.size();
 buff = new char[length+1]; 
 memcpy(buff, value.c_str() , length + 1); 
       //^^^^  ^^^^^^^^^^^ also note this

Or you can copy in this as well:

 std::string copy = value;
 const char * buff = copy.c_str();

But note that buff will exist as long as the variable copy exists. In other words, the lifetime of buff is tied with the lifetime of the variable copy, and you don’t need to write delete buff in this case.