// smallsegment_v6_box.h - SmallSegment v6 型定義（Phase v6-2）

#ifndef HAKMEM_SMALLSEGMENT_V6_BOX_H
#define HAKMEM_SMALLSEGMENT_V6_BOX_H

#include <stdint.h>

// Segment constants
#define SMALL_SEGMENT_V6_SIZE       (2 * 1024 * 1024)    // 2 MiB
#define SMALL_PAGE_V6_SIZE          (64 * 1024)          // 64 KiB
#define SMALL_PAGES_PER_SEGMENT     (SMALL_SEGMENT_V6_SIZE / SMALL_PAGE_V6_SIZE)  // 32
#define SMALL_SEGMENT_V6_MAGIC      0xC06E56u  // C0(re) v6
#define SMALL_PAGE_V6_SHIFT         16  // log2(64KiB)

// C6 configuration
#define SMALL_V6_C6_CLASS_IDX       6
#define SMALL_V6_C6_BLOCK_SIZE      512

// C5 configuration (Phase v6-5)
#define SMALL_V6_C5_CLASS_IDX       5
#define SMALL_V6_C5_BLOCK_SIZE      256

// C4 configuration (Phase v6-6)
#define SMALL_V6_C4_CLASS_IDX       4
#define SMALL_V6_C4_BLOCK_SIZE      128

// Page index calculation macro (requires 'seg' variable in scope)
#define SMALL_V6_PAGE_IDX(seg, addr)  (((uintptr_t)(addr) - (seg)->base) >> SMALL_PAGE_V6_SHIFT)

// Forward declaration
typedef struct SmallPageMetaV6 SmallPageMetaV6;

// Page metadata
typedef struct SmallPageMetaV6 {
    void*     free_list;   // freelist head (block先頭をnextとして使う)
    uint16_t  used;        // 現在使用中スロット数
    uint16_t  capacity;    // ページ内スロット数
    uint8_t   class_idx;   // サイズクラス
    uint8_t   flags;       // FULL / PARTIAL / REMOTE_PENDING など
    uint16_t  page_idx;    // Segment 内 index
    void*     segment;     // SmallSegmentV6* への backpointer
} SmallPageMetaV6;

// Segment structure
typedef struct SmallSegmentV6 {
    uintptr_t       base;       // Segment base address
    uint32_t        num_pages;  // Number of pages (typically 32)
    uint32_t        owner_tid;  // Owner thread ID
    uint32_t        magic;      // 0xC0REV6 for validation
    SmallPageMetaV6 page_meta[SMALL_PAGES_PER_SEGMENT];
} SmallSegmentV6;

// ============================================================================
// Inline Helper Functions
// ============================================================================

/// Check if page is valid and active
static inline int small_page_v6_valid(SmallPageMetaV6* page) {
    return page != NULL && page->capacity > 0;
}

/// Check if pointer is within segment bounds
static inline int small_ptr_in_segment_v6(SmallSegmentV6* seg, void* ptr) {
    uintptr_t addr = (uintptr_t)ptr;
    return addr >= seg->base && addr < seg->base + SMALL_SEGMENT_V6_SIZE;
}

/// Check if segment is valid and initialized
static inline int small_segment_v6_valid(SmallSegmentV6* seg) {
    return seg != NULL && seg->magic == SMALL_SEGMENT_V6_MAGIC;
}

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

SmallSegmentV6* small_segment_v6_acquire_for_thread(void);
void small_segment_v6_release(SmallSegmentV6* seg);
SmallPageMetaV6* small_page_meta_v6_of(void* ptr);

#endif // HAKMEM_SMALLSEGMENT_V6_BOX_H