#include #include #include #define KB(x) ((size_t) (x) << 10 ) #define MB(x) ((size_t) (x) << 20 ) #define ONE_MEGABYTE MB(1) struct MemoryAllocationHeader { void* pStart{ nullptr }; // pointer to the memory of user void* pNextFree{ nullptr }; // next free block of memory size_t size{ 0 }; // users allocated size in memory }; namespace { char pMemoryHeap[ONE_MEGABYTE]; //static array of one-megabye 1024 * 1024 const size_t SIZE_OF_MEMORY_HEADER = sizeof(MemoryAllocationHeader); } //overload new void* operator new(size_t size) { //Load the current header MemoryAllocationHeader* pHeader{ reinterpret_cast(pMemoryHeap) }; //Find a block with with a nullptr in the nextfree variable while (pHeader != nullptr && pHeader->pNextFree != nullptr) { pHeader = reinterpret_cast(pHeader->pNextFree); } pHeader->pStart = reinterpret_cast(pHeader) + SIZE_OF_MEMORY_HEADER; pHeader->pNextFree = reinterpret_cast(pHeader->pStart) + size; pHeader->size = size; return pHeader->pStart; } // overload delete void operator delete(void* pMemory) { MemoryAllocationHeader* pLast{ nullptr }; MemoryAllocationHeader* pCurrent{ reinterpret_cast(pMemoryHeap) }; while (pCurrent != nullptr && pCurrent->pStart != pMemory) { pLast = pCurrent; pCurrent = reinterpret_cast(pCurrent->pNextFree); } if (pLast != nullptr) { pLast->pNextFree = reinterpret_cast(pCurrent->pNextFree); } pCurrent->pStart = nullptr; pCurrent->pNextFree = nullptr; pCurrent->size = 0; } void PrintAllocations() { std::cout << "Memory Allocations"<< std::endl; MemoryAllocationHeader* pHeader = reinterpret_cast(pMemoryHeap); while (pHeader != nullptr) { std::cout << pHeader << std::endl; std::cout << pHeader->pStart << std::endl; std::cout << pHeader->pNextFree << std::endl; std::cout << pHeader->size << std::endl; pHeader = reinterpret_cast(pHeader->pNextFree); std::cout << std::endl << std::endl; } } class MyClass { private: int aValue {5}; public: MyClass () {} }; class AnotherClass { private: int aValue {18}; char aSymbol {'b'}; public: AnotherClass() {} }; int main() { memset(pMemoryHeap, 0, SIZE_OF_MEMORY_HEADER); PrintAllocations(); MyClass* myClass1 { new MyClass() }; std::cout << "Adding myClass1" << std::endl; PrintAllocations(); AnotherClass* myClass2 { new AnotherClass() }; std::cout << "Adding: myClass2 (anotherClass)" << std::endl; PrintAllocations(); // delete myClass2; /// myClass2 = nullptr; // std::cout << "Removing: myClass2" << std::endl; // PrintAllocations(); MyClass *myClass3 { new MyClass()}; std::cout << "Adding: myClass3" << std::endl; PrintAllocations(); delete myClass2; myClass2 = nullptr; std::cout << "Removing: myClass2" << std::endl; MyClass * myClass4 { new MyClass() }; std::cout << "Adding: myClass4" << std::endl; PrintAllocations(); delete myClass4; myClass4 = nullptr; std::cout << "Removing: myClass4" << std::endl; PrintAllocations(); delete myClass3; myClass3 = nullptr; std::cout << "Removing: myClass3" << std::endl; PrintAllocations(); delete myClass1; myClass1 = nullptr; std::cout << "Removing: myClass1" << std::endl; PrintAllocations(); return EXIT_SUCCESS; }

Memory Manager (basic)