al/eax/exception.cpp

   1 #include "config.h"
   2
   3 #include "exception.h"
   4
   5 #include <cassert>
   6 #include <string>
   7
   8
   9 EaxException::EaxException(
  10     const char* context,
  11     const char* message)
  12     :
  13     std::runtime_error{make_message(context, message)}
  14 {
  15 }
  16
  17 std::string EaxException::make_message(
  18     const char* context,
  19     const char* message)
  20 {
  21     const auto context_size = (context ? std::string::traits_type::length(context) : 0);
  22     const auto has_contex = (context_size > 0);
  23
  24     const auto message_size = (message ? std::string::traits_type::length(message) : 0);
  25     const auto has_message = (message_size > 0);
  26
  27     if (!has_contex && !has_message)
  28     {
  29         return std::string{};
  30     }
  31
  32     static constexpr char left_prefix[] = "[";
  33     const auto left_prefix_size = std::string::traits_type::length(left_prefix);
  34
  35     static constexpr char right_prefix[] = "] ";
  36     const auto right_prefix_size = std::string::traits_type::length(right_prefix);
  37
  38     const auto what_size =
  39         (
  40             has_contex ?
  41             left_prefix_size + context_size + right_prefix_size :
  42             0) +
  43         message_size +
  44         1;
  45
  46     auto what = std::string{};
  47     what.reserve(what_size);
  48
  49     if (has_contex)
  50     {
  51         what.append(left_prefix, left_prefix_size);
  52         what.append(context, context_size);
  53         what.append(right_prefix, right_prefix_size);
  54     }
  55
  56     if (has_message)
  57     {
  58         what.append(message, message_size);
  59     }
  60
  61     return what;
  62 }