Static memory allocator for embedded systems in C++ with auto fragmentation where malloc/new is unwanted

StaticMemoryAllocator.cpp

/*
    Static memory allocator for embedded systems in C++ with auto fragmentation where malloc/new is unwanted
    Author : Eray Ozturk | [email protected]
*/
#include <iostream>
#include <cstddef>

class StaticMemoryAllocator {
public:
    StaticMemoryAllocator(char* buffer, size_t bufferSize) : buffer_(buffer), bufferSize_(bufferSize), head_(nullptr) {
        BlockHeader* initialBlock = reinterpret_cast<BlockHeader*>(buffer_);
        initialBlock->size = bufferSize_ - sizeof(BlockHeader);
        initialBlock->next = nullptr;
        head_ = initialBlock;
    }

    ~StaticMemoryAllocator() {
        // Deallocate all memory blocks when the allocator instance is destroyed
        BlockHeader* curr = head_;
        while (curr) {
            BlockHeader* next = curr->next;
            curr->size = 0;
            curr->next = nullptr;
            curr = next;
        }
    }

    void* allocate(size_t size) {
        if (size == 0 || size > bufferSize_) {
            return nullptr; // Invalid size
        }

        BlockHeader* prev = nullptr;
        BlockHeader* curr = head_;

        while (curr) {
            if (curr->size >= size) {
                // Allocate from the current block
                if (curr->size > size + sizeof(BlockHeader)) {
                    // Split the block
                    BlockHeader* newBlock = reinterpret_cast<BlockHeader*>(reinterpret_cast<char*>(curr) + sizeof(BlockHeader) + size);
                    newBlock->size = curr->size - size - sizeof(BlockHeader);
                    newBlock->next = curr->next;
                    curr->size = size;
                    curr->next = newBlock;
                }

                // Update the free list
                if (prev) {
                    prev->next = curr->next;
                } else {
                    head_ = curr->next;
                }

                return reinterpret_cast<char*>(curr) + sizeof(BlockHeader);
            }

            prev = curr;
            curr = curr->next;
        }

        return nullptr; // Not enough memory
    }

    void deallocate(void* ptr) {
        if (ptr >= buffer_ && ptr < buffer_ + bufferSize_) {
            BlockHeader* block = reinterpret_cast<BlockHeader*>(static_cast<char*>(ptr) - sizeof(BlockHeader));
            block->next = head_;
            head_ = block;
        }
    }

    void print() {
        std::cout << "Memory Blocks:" << std::endl;
        BlockHeader* curr = head_;
        while (curr) {
            std::cout << "Size: " << curr->size << " bytes" << std::endl;
            curr = curr->next;
        }
    }

private:
    struct BlockHeader {
        size_t size;
        BlockHeader* next;
    };

    char* buffer_;
    size_t bufferSize_;
    BlockHeader* head_;
};

int main() {
    constexpr size_t bufferSize = 1024;
    char memoryBuffer[bufferSize];

    StaticMemoryAllocator memoryAllocator(memoryBuffer, bufferSize);

    // Allocate int
    int* intPtr = static_cast<int*>(memoryAllocator.allocate(sizeof(int)));
    if (intPtr) {
        *intPtr = 42;
        std::cout << "Allocated int: " << *intPtr << std::endl;
        memoryAllocator.print();
    } else {
        std::cout << "Memory allocation failed" << std::endl;
    }

    // Allocate a double block
    double* doublePtr = static_cast<double*>(memoryAllocator.allocate(sizeof(double)));
    if (doublePtr) {
        *doublePtr = 3.14;
        std::cout << "Allocated double: " << *doublePtr << std::endl;
        memoryAllocator.print();
    } else {
        std::cout << "Memory allocation failed" << std::endl;
    }

    // Deallocate the int block
    if (intPtr) {
        memoryAllocator.deallocate(intPtr);
        intPtr = nullptr;
        std::cout << "Deallocated int" << std::endl;
        memoryAllocator.print();
    }

    // Allocate a larger block
    char* charPtr = static_cast<char*>(memoryAllocator.allocate(256));
    if (charPtr) {
        std::cout << "Allocated 256 bytes" << std::endl;
        memoryAllocator.print();
    } else {
        std::cout << "Memory allocation failed" << std::endl;
    }

    return 0;
}