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