Fast Efficient Fixed-Size Memory Pool: No Loops and No Overhead

pool.c

// https://arxiv.org/abs/2210.16471v1

#include <stdint.h>
#include <stdlib.h>

typedef struct {
   uint8_t* data;
   uint8_t* head;
   uint8_t* last;
   size_t unit;
   size_t free;
} pool_t;

int pool_create(pool_t* pool, size_t size, size_t unit) {
   if (unit < sizeof(void*))
      unit = sizeof(void*);
   if (size < unit)
      size = unit;

   pool->data = (uint8_t*)malloc(size);
   if (pool->data == NULL)
      return -1;

   pool->head = pool->data;
   pool->last = pool->data;
   pool->unit = unit;
   pool->free = size / unit;

   return 0;
}

void pool_destroy(pool_t* pool) {
   free(pool->data);
}

void* pool_alloc(pool_t* pool) {
   if (pool->free == 0)
      return NULL;

   if (pool->head == pool->last)
      pool->last = *(uint8_t**)pool->last = pool->last + pool->unit;

   void* data = pool->head;
   pool->head = *(uint8_t**)pool->head;
   pool->free--;

   return data;
}

void pool_free(pool_t* pool, void* data) {
   if (data != NULL) {
      *(uint8_t**)data = pool->head;
      pool->head = data;
      pool->free++;
   }
}