source/game/accessguard.h

   1 #ifndef MSP_GAME_ACCESSGUARD_H_
   2 #define MSP_GAME_ACCESSGUARD_H_
   3
   4 #include <cstdint>
   5 #include <stdexcept>
   6 #include <string>
   7 #include <vector>
   8 #include <msp/core/noncopyable.h>
   9
  10 namespace Msp::Game {
  11
  12 class invalid_access: public std::logic_error
  13 {
  14 public:
  15         invalid_access(const std::string &w): logic_error(w) { }
  16 };
  17
  18
  19 class AccessGuard
  20 {
  21 public:
  22         struct Create { static std::string describe() { return "create"; } };
  23         struct Destroy { static std::string describe() { return "destroy"; } };
  24
  25         template<typename T = void>
  26         struct BlockForScope: NonCopyable
  27         {
  28                 BlockForScope() { get_instance().block<T>(); }
  29                 ~BlockForScope() { get_instance().unblock<T>(); }
  30         };
  31
  32 private:
  33         const uint8_t UNBLOCKED = 0;
  34         const uint8_t BLOCKED = 1;
  35
  36         std::uint8_t default_flag = UNBLOCKED;
  37         std::vector<std::uint8_t> flags;
  38
  39         static thread_local AccessGuard *instance;
  40
  41 public:
  42         AccessGuard();
  43         AccessGuard(AccessGuard &&);
  44         AccessGuard &operator=(AccessGuard &&);
  45         ~AccessGuard();
  46
  47         static AccessGuard &get_instance();
  48
  49         void block_all();
  50         void unblock_all();
  51
  52 private:
  53         static unsigned get_next_index();
  54
  55         template<typename T>
  56         static unsigned get_index();
  57
  58         template<typename T>
  59         std::uint8_t &get();
  60
  61 public:
  62         template<typename T>
  63         void block() { get<T>() = BLOCKED; }
  64
  65         template<typename T>
  66         void unblock() { get<T>() = UNBLOCKED; }
  67
  68         template<typename T>
  69         void check() { if(get<T>()!=UNBLOCKED) throw invalid_access(T::describe()); }
  70 };
  71
  72
  73 template<typename T>
  74 inline unsigned AccessGuard::get_index()
  75 {
  76         static unsigned index = get_next_index();
  77         return index;
  78 }
  79
  80 template<typename T>
  81 inline std::uint8_t &AccessGuard::get()
  82 {
  83         unsigned index = get_index<T>();
  84         if(flags.size()<=index)
  85                 flags.resize(index+1, default_flag);
  86         return flags[index];
  87 }
  88
  89 template<>
  90 inline void AccessGuard::block<void>()
  91 { block_all(); }
  92
  93 template<>
  94 inline void AccessGuard::unblock<void>()
  95 { unblock_all(); }
  96
  97 } // namespace Msp::Game
  98
  99 #endif