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

StaticMemoryAllocator.c

/*
    Static memory allocator for embedded systems in C with auto fragmentation where malloc is unwanted
    Author : Eray Ozturk | [email protected]
*/
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>

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

typedef struct {
    char* buffer;
    size_t bufferSize;
    struct BlockHeader* head;
} StaticMemoryAllocator;

void initializeAllocator(StaticMemoryAllocator* allocator, char* buffer, size_t bufferSize) {
    allocator->buffer = buffer;
    allocator->bufferSize = bufferSize;
    allocator->head = (struct BlockHeader*)buffer;
    allocator->head->size = bufferSize - sizeof(struct BlockHeader);
    allocator->head->next = NULL;
}

void* allocate(StaticMemoryAllocator* allocator, size_t size) {
    if (size == 0 || size > allocator->bufferSize) {
        return NULL; // Invalid size
    }

    struct BlockHeader* prev = NULL;
    struct BlockHeader* curr = allocator->head;

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

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

            return (char*)curr + sizeof(struct BlockHeader);
        }

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

    return NULL; // Not enough memory
}

void deallocate(StaticMemoryAllocator* allocator, void* ptr) {
    if (ptr >= allocator->buffer && ptr < allocator->buffer + allocator->bufferSize) {
        struct BlockHeader* block = (struct BlockHeader*)((char*)ptr - sizeof(struct BlockHeader));
        block->next = allocator->head;
        allocator->head = block;
    }
}

void cleanupAllocator(StaticMemoryAllocator* allocator) {
    struct BlockHeader* curr = allocator->head;
    while (curr) {
        curr->size = 0;
        curr->next = NULL;
        curr = curr->next;
    }
}

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

    StaticMemoryAllocator memoryAllocator;
    initializeAllocator(&memoryAllocator, memoryBuffer, bufferSize);

    // Allocate an int
    int* intPtr = (int*)allocate(&memoryAllocator, sizeof(int));
    if (intPtr) {
        *intPtr = 42;
        printf("Allocated int: %d\n", *intPtr);
    } else {
        printf("Memory allocation failed\n");
    }

    // Allocate a double block
    double* doublePtr = (double*)allocate(&memoryAllocator, sizeof(double));
    if (doublePtr) {
        *doublePtr = 3.14;
        printf("Allocated double: %.2lf\n", *doublePtr);
    } else {
        printf("Memory allocation failed\n");
    }

    // Deallocate the int block
    if (intPtr) {
        deallocate(&memoryAllocator, intPtr);
        intPtr = NULL;
        printf("Deallocated int\n");
    }

    // Allocate a larger block
    char* charPtr = (char*)allocate(&memoryAllocator, 256);
    if (charPtr) {
        printf("Allocated 256 bytes\n");
    } else {
        printf("Memory allocation failed\n");
    }

    // Clean up the allocator (release all memory)
    cleanupAllocator(&memoryAllocator);

    return 0;
}