// hakmem_sizeclass_dist.h - Size Class Distribution Signature
// Purpose: Detect workload changes via L1 distance
//
// License: MIT
// Date: 2025-10-21

#ifndef HAKMEM_SIZECLASS_DIST_H
#define HAKMEM_SIZECLASS_DIST_H

#include <stdint.h>
#include <stddef.h>

// ============================================================================
// Size Class Distribution (4 classes: 1MB, 2MB, 4MB, 8MB)
// ============================================================================

#define SIZECLASS_NUM_CLASSES 4

typedef struct {
    uint32_t freq[SIZECLASS_NUM_CLASSES];  // Frequency of each class
    uint64_t total;                        // Total allocations recorded
} hak_sizeclass_dist_t;

// ============================================================================
// Public API
// ============================================================================

// Initialize distribution
void hak_sizeclass_dist_init(hak_sizeclass_dist_t* dist);

// Record an allocation size (will classify into size class)
void hak_sizeclass_dist_record(hak_sizeclass_dist_t* dist, size_t size);

// Calculate L1 distance between two distributions
// Returns: 0.0 (identical) to 2.0 (completely different)
double hak_sizeclass_dist_l1(const hak_sizeclass_dist_t* a,
                             const hak_sizeclass_dist_t* b);

// Copy distribution
void hak_sizeclass_dist_copy(hak_sizeclass_dist_t* dst,
                             const hak_sizeclass_dist_t* src);

// Reset distribution (start new window)
void hak_sizeclass_dist_reset(hak_sizeclass_dist_t* dist);

// Get total allocations
uint64_t hak_sizeclass_dist_total(const hak_sizeclass_dist_t* dist);

// Print distribution (for debugging)
void hak_sizeclass_dist_print(const hak_sizeclass_dist_t* dist, const char* label);

#endif // HAKMEM_SIZECLASS_DIST_H