Keeper management modernisation and improvements

* use a std::variant to manage the distinction between one or more keeper states. Use std::unique_ptr<Keeper[]> to manage the multiple keeper case.
* setting "nb_keepers" renamed "nb_user_keepers", to indicate these are in addition to internal keeper #0 used for timers.
* stricter lanes.linda() argument checking. group is imposed if more than one keeper is used.
* more tests

1 files changed, 48 insertions, 5 deletions

diff --git a/src/keeper.h b/src/keeper.h
index a902caa..682c710 100644
--- a/src/keeper.h
+++ b/src/keeper.h
@@ -11,8 +11,10 @@ extern "C"
 
 #include "uniquekey.h"
 
-#include <optional>
+#include <atomic>
 #include <mutex>
+#include <optional>
+#include <variant>
 
 // forwards
 class Linda;
@@ -21,22 +23,63 @@ class Universe;
 
 using KeeperState = Unique<lua_State*>;
 
+// #################################################################################################
+
 struct Keeper
 {
     std::mutex mutex;
     KeeperState L{ nullptr };
-    // int count;
+
+    [[nodiscard]] static void* operator new[](size_t size_, Universe* U_) noexcept;
+    // can't actually delete the operator because the compiler generates stack unwinding code that could call it in case of exception
+    static void operator delete[](void* p_, Universe* U_);
+
+
+    ~Keeper() = default;
+    Keeper() = default;
+    // non-copyable, non-movable
+    Keeper(Keeper const&) = delete;
+    Keeper(Keeper const&&) = delete;
+    Keeper& operator=(Keeper const&) = delete;
+    Keeper& operator=(Keeper const&&) = delete;
 };
 
+// #################################################################################################
+
 struct Keepers
 {
+    private:
+    struct DeleteKV
+    {
+        Universe* U{};
+        int count{};
+        void operator()(Keeper* k_) const;
+    };
+    // can't use std::vector<Keeper> because Keeper contains a mutex, so we need a raw memory buffer
+    struct KV
+    {
+        std::unique_ptr<Keeper[], DeleteKV> keepers{};
+        size_t nbKeepers{};
+    };
+    std::variant<std::monostate, Keeper, KV> keeper_array;
+    std::atomic_flag isClosing;
+
+    public:
     int gc_threshold{ 0 };
-    int nb_keepers{ 0 };
-    Keeper keeper_array[1];
 
-    static void CreateFifosTable(lua_State* L_);
+    public:
+    // can only be instanced as a data member
+    static void* operator new(size_t size_) = delete;
+
+    Keepers() = default;
+    void close();
+    [[nodiscard]] Keeper* getKeeper(int idx_);
+    [[nodiscard]] int getNbKeepers() const;
+    void initialize(Universe& U_, lua_State* L_, int nbKeepers_, int gc_threshold_);
 };
 
+// #################################################################################################
+
 // xxh64 of string "kNilSentinel" generated at https://www.pelock.com/products/hash-calculator
 static constexpr UniqueKey kNilSentinel{ 0xC457D4EDDB05B5E4ull, "lanes.null" };