hakmem/core/box/smallobject_hotbox_v5_box.h

// smallobject_hotbox_v5_box.h - SmallObject HotBox v5 型定義（Phase v5-0）
//
// この段階では型とインターフェース定義のみ。挙動は変わらない。

#ifndef HAKMEM_SMALLOBJECT_HOTBOX_V5_BOX_H
#define HAKMEM_SMALLOBJECT_HOTBOX_V5_BOX_H

#include <stdint.h>

#define NUM_SMALL_CLASSES_V5 8  // C0–C7

// SmallPageMetaV5: v5 ページメタデータ
// Hot fields (alloc/free 頻繁アクセス) を先頭に集約（L1 cache 最適化）
typedef struct SmallPageMetaV5 {
    // Hot fields (alloc/free 頻繁アクセス)
    void*     free_list;      // フリーリスト先頭 (offset 0)
    uint16_t  used;           // 使用中ブロック数 (offset 8)
    uint16_t  capacity;       // このページの総容量 (offset 10)

    // Metadata（初期化時のみ）
    uint8_t   class_idx;      // size class index (offset 12)
    uint8_t   flags;          // reserved (offset 13)
    uint16_t  page_idx;       // segment 内でのページインデックス (offset 14)
    void*     segment;        // SmallSegmentV5* への backpointer (offset 16)

    // Intrusive list field for current/partial/full lists (Phase v5-2)
    struct SmallPageMetaV5* next;  // next page in list (offset 24)
} SmallPageMetaV5;  // total 32B

// SmallClassHeapV5: サイズクラス毎のホットヒープ状態
typedef struct SmallClassHeapV5 {
    SmallPageMetaV5* current;      // 現在のページ（alloc 中）
    SmallPageMetaV5* partial_head; // partial ページリスト
    SmallPageMetaV5* full_head;    // full ページリスト
    uint32_t         partial_count; // partial ページ数
} SmallClassHeapV5;

// SmallHeapCtxV5: per-thread ホットヒープコンテキスト
typedef struct SmallHeapCtxV5 {
    SmallClassHeapV5 cls[NUM_SMALL_CLASSES_V5];
    uint8_t header_mode;  // Phase v5-4: FULL or LIGHT (cached from ENV)
} SmallHeapCtxV5;

// ============================================================================
// C6 class configuration (Phase v5-3)
// ============================================================================

#define SMALL_HEAP_V5_C6_CLASS_IDX      6
#define SMALL_HEAP_V5_C6_BLOCK_SIZE     512
#define SMALL_HEAP_V5_C6_PARTIAL_LIMIT  1

// Helper function for partial limit (future extensibility)
static inline uint32_t small_heap_v5_partial_limit(uint32_t class_idx) {
    // C6 only in v5-2/v5-3
    return (class_idx == SMALL_HEAP_V5_C6_CLASS_IDX) ? SMALL_HEAP_V5_C6_PARTIAL_LIMIT : 0u;
}

// ============================================================================
// Page list operations (v5-3 refactor)
// ============================================================================

#define SMALL_PAGE_V5_PUSH_PARTIAL(h, page) \
    do { \
        if ((h) && (page)) { \
            (page)->next = (h)->partial_head; \
            (h)->partial_head = (page); \
            (h)->partial_count++; \
        } \
    } while (0)

#define SMALL_PAGE_V5_POP_PARTIAL(h) \
    ({  SmallPageMetaV5* _p = (h) ? (h)->partial_head : NULL; \
        if (_p && (h)) { \
            (h)->partial_head = _p->next; \
            _p->next = NULL; \
            if ((h)->partial_count > 0) { \
                (h)->partial_count--; \
            } \
        } \
        _p; \
    })

#define SMALL_PAGE_V5_PUSH_FULL(h, page) \
    do { \
        if ((h) && (page)) { \
            (page)->next = (h)->full_head; \
            (h)->full_head = (page); \
        } \
    } while (0)

// Page location in heap lists
typedef enum {
    LOC_NONE = 0,
    LOC_CURRENT,
    LOC_PARTIAL,
    LOC_FULL,
} page_loc_t;

#define SMALL_PAGE_V5_UNLINK(h, loc, prev, page) \
    do { \
        if ((h) && (page)) { \
            switch (loc) { \
                case LOC_CURRENT: \
                    (h)->current = NULL; \
                    break; \
                case LOC_PARTIAL: \
                    if (prev) (prev)->next = (page)->next; \
                    else (h)->partial_head = (page)->next; \
                    if ((h)->partial_count > 0) { \
                        (h)->partial_count--; \
                    } \
                    break; \
                case LOC_FULL: \
                    if (prev) (prev)->next = (page)->next; \
                    else (h)->full_head = (page)->next; \
                    break; \
                default: \
                    break; \
            } \
            (page)->next = NULL; \
        } \
    } while (0)

// ============================================================================
// API
// ============================================================================

SmallHeapCtxV5* small_heap_ctx_v5(void);

// Fast path（Phase v5-1: C6-only route stub, v1/pool fallback）
void* small_alloc_fast_v5(size_t size, uint32_t class_idx, SmallHeapCtxV5* ctx);
void  small_free_fast_v5(void* ptr, uint32_t class_idx, SmallHeapCtxV5* ctx);

#endif // HAKMEM_SMALLOBJECT_HOTBOX_V5_BOX_H