tag_alloc

dogtag.c

#define TAG_TYPE            int
#define TAG_SIZE            sizeof(TAG_TYPE)

#define VALID_START_TAG     0xDEADBEEF
#define VALID_END_TAG       0xCAFEBABE
#define TAG_INVALID_VALUE   0xBADC0DE5

#define PTR_START_TAG(memory)   (TAG_TYPE *)(memory->ptr - TAG_SIZE)
#define PTR_END_TAG(memory)     (TAG_TYPE *)(memory->ptr + memory->size)

typedef struct memory {
    void * ptr;
    size_t size;
} memory_t;

bool tag_alloc(memory_t * memory, size_t size) {
    void * ptr = malloc(size + (2 * TAG_SIZE));
    if (ptr == NULL) {
        return false;
    }
    TAG_TYPE * startPtr = ptr;
    *startPtr = VALID_START_TAG;
 
    ptr += TAG_SIZE;
 
    // Advance the first tag and the remainder of the buffer
    TAG_TYPE * endPtr = ptr + size;
    *endPtr = VALID_END_TAG;
    
    memory->ptr = ptr;
    memory->size = size;
    return true;
}