fix memory arena alloc

src/game/Global.cpp

@@ -37,21 +37,20 @@ namespace Game
         GameInst = &instance;
     }
 
-    uint8_t* AllocateScratch(size_t byteCount, size_t align)
+    uint8_t* AllocateScratch(uint64_t byteCount, uint32_t align)
     {
-        size_t offset = GetInstance().UsedScratchAmount;
-        uint8_t* base = GetShared().Game.TransientArena.Ptr;
-        uint8_t* current = base + offset;
-        size_t offsetAligned = ((offset + align - 1) / align) * align;
-        uint8_t* ptrAligned = base + offsetAligned;
-        size_t newOffset = offsetAligned + byteCount;
-        if (newOffset > GetShared().Game.TransientArena.Size) return nullptr;
-        GetInstance().UsedScratchAmount = newOffset;
-        GetShared().Game.TransientArena.LastAllocSize = byteCount;
+        assert(align <= 64); // The alignment of the arena limits the alignment that can be specified here!
+        auto& arena = GetShared().Game.TransientArena;
+        uint64_t offsetAligned = ((arena.Used + align - 1) / align) * align;
+        uint8_t* ptrAligned = arena.Base + offsetAligned;
+        uint64_t newOffset = offsetAligned + byteCount;
+        if (newOffset > arena.MaxSize) return nullptr;
+        arena.Used = newOffset;
+        arena.LastAllocSize = byteCount;
         return ptrAligned;
     }
 
-    bool ResizeLastScratchAlloc(size_t newByteCount)
+    bool ResizeLastScratchAlloc(uint64_t newByteCount)
     {
         auto& arena = GetShared().Game.TransientArena;
         if (newByteCount > arena.LastAllocSize)
@@ -59,8 +58,17 @@ namespace Game
             LOG_ERROR("Can't resize to more than previous size!");
             return false;
         }
-        arena.Ptr -= arena.LastAllocSize;
-        arena.Ptr += newByteCount;
+        LOG("Resizing last allocation from %llu to %llu", arena.LastAllocSize, newByteCount);
+        arena.Used -= arena.LastAllocSize;
+        arena.Used += newByteCount;
+        LOG("New total: %llu", arena.Used);
         return true;
     }
+
+    void ResetScratch()
+    {
+        auto& arena = GetShared().Game.TransientArena;
+        arena.Used = 0;
+        arena.LastAllocSize = 0;
+    }
 } // namespace Game