hakmem/core/hakmem_shared_pool.h

#pragma once

#include <stdint.h>
#include <pthread.h>
#include <stdatomic.h>
#include "superslab/superslab_types.h"

// Shared SuperSlab Pool (Phase 12-2 skeleton)
// Multiple tiny size classes share a global set of SuperSlab instances.
// This header exposes the minimal API used by refill/free hot paths in Phase 12.

#ifdef __cplusplus
extern "C" {
#endif

typedef struct SharedSuperSlabPool {
    SuperSlab** slabs;          // Dynamic array of SuperSlab*
    uint32_t    capacity;       // Allocated entries in slabs[]
    uint32_t    total_count;    // Total SuperSlabs ever allocated (<= capacity)
    uint32_t    active_count;   // SuperSlabs that have >0 active slabs

    pthread_mutex_t alloc_lock; // Protects pool metadata and grow/scan operations

    // Per-class hints: last known SuperSlab with a free slab for that class.
    // Read lock-free (best-effort), updated under alloc_lock.
    SuperSlab*  class_hints[TINY_NUM_CLASSES_SS];

    // LRU cache integration hooks (Phase 9/12, optional for now)
    SuperSlab*  lru_head;
    SuperSlab*  lru_tail;
    uint32_t    lru_count;
} SharedSuperSlabPool;

// Global singleton
extern SharedSuperSlabPool g_shared_pool;

// Initialize shared pool (idempotent, thread-safe wrt multiple callers on startup paths)
void shared_pool_init(void);

// Get/allocate a SuperSlab registered in the pool.
// Returns non-NULL on success, NULL on failure.
SuperSlab* shared_pool_acquire_superslab(void);

// Acquire a slab for class_idx from shared pool.
// On success:
//   *ss_out        = SuperSlab containing slab
//   *slab_idx_out  = slab index [0, SLABS_PER_SUPERSLAB_MAX)
// Returns 0 on success, non-zero on failure.
int shared_pool_acquire_slab(int class_idx, SuperSlab** ss_out, int* slab_idx_out);

 // Release an empty slab back to pool (mark as unassigned).
 // Caller must ensure TinySlabMeta.used == 0.
void shared_pool_release_slab(SuperSlab* ss, int slab_idx);

#ifdef __cplusplus
}
#endif