slab.h

#define _GNU_SOURCE

#ifndef SLAB_H
#define SLAB_H 1

#include "ioengine.h"
#include "indexes/btree.h"

struct slab;
struct slab_callback;

/* Header of a slab -- shouldn't contain any pointer as it is persisted on disk.
 */
struct slab {
  struct slab_context *ctx;

  size_t item_size;
  size_t nb_items;  // Number of non freed items
  size_t last_item; // Total number of items, including freed
  size_t nb_max_items;

  int fd;
  size_t size_on_disk;

  size_t nb_free_items, nb_free_items_in_memory;
  struct freelist_entry *freed_items, *freed_items_tail;
  btree_t *freed_items_recovery, *freed_items_pointed_to;
};

/* This is the callback enqueued in the engine.
 * slab_callback->item = item looked for (that needs to be freed)
 * item = page on disk (in the page cache)
 */
typedef void(slab_cb_t)(struct slab_callback *, void *item);
enum slab_action { ADD, UPDATE, DELETE, READ, READ_NO_LOOKUP, ADD_OR_UPDATE };
struct slab_callback {
  slab_cb_t *cb;
  void *payload;
  void *item;

  // Private
  enum slab_action action;
  struct slab *slab;
  union {
    uint64_t slab_idx;
    uint64_t tmp_page_number; // when we add a new item we don't always know
                              // it's idx directly, sometimes we just know which
                              // page it will be placed on
  };
  struct lru *lru_entry;
  io_cb_t *io_cb;
};

struct slab *create_slab(struct slab_context *ctx, int worker_id,
                         size_t item_size, struct slab_callback *callback);
struct slab *resize_slab(struct slab *s);

void *read_item(struct slab *s, size_t idx);
void read_item_async(struct slab_callback *callback);
void add_item_async(struct slab_callback *callback);
void update_item_async(struct slab_callback *callback);
void remove_item_async(struct slab_callback *callback);

off_t item_page_num(struct slab *s, size_t idx);
#endif