buffer_pool.h

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#pragma once
 
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
// C11 stdatomic.h conflicts with MSVC's C++ <atomic> header on Windows.
#if defined(__cplusplus) && defined(_WIN32)
#include <atomic>
using std::atomic_size_t;
#else
#include <stdatomic.h>
#endif
#include "platform/mutex.h"
 
/* ============================================================================
 * Configuration Constants
 * ============================================================================
 */
 
#define BUFFER_POOL_MAX_BYTES (337 * 1024 * 1024)
 
#define BUFFER_POOL_SHRINK_DELAY_MS 5000
 
#define BUFFER_POOL_MIN_SIZE 64
 
#define BUFFER_POOL_MAX_SINGLE_SIZE (4 * 1024 * 1024)
 
#define BUFFER_POOL_MAGIC 0xBF00B001U
#define BUFFER_POOL_MAGIC_FALLBACK 0xBF00FA11U
 
/* ============================================================================
 * Data Structures
 * ============================================================================
 */
 
typedef struct buffer_node {
  uint32_t magic;                     
  uint32_t _pad;                      
  size_t size;                        
  _Atomic(struct buffer_node *) next; 
  _Atomic(uint64_t) returned_at_ms;   
  struct buffer_pool *pool;           
} buffer_node_t;
 
typedef struct buffer_pool {
  _Atomic(buffer_node_t *) free_list; 
  mutex_t shrink_mutex;               
 
  size_t max_bytes;         
  uint64_t shrink_delay_ms; 
 
  _Atomic(size_t) current_bytes;   
  _Atomic(size_t) used_bytes;      
  _Atomic(size_t) peak_bytes;      
  _Atomic(size_t) peak_pool_bytes; 
 
  _Atomic(uint64_t) hits;             
  _Atomic(uint64_t) allocs;           
  _Atomic(uint64_t) returns;          
  _Atomic(uint64_t) shrink_freed;     
  _Atomic(uint64_t) malloc_fallbacks; 
} buffer_pool_t;
 
/* ============================================================================
 * Buffer Pool API
 * ============================================================================
 */
 
buffer_pool_t *buffer_pool_create(size_t max_bytes, uint64_t shrink_delay_ms);
 
void buffer_pool_destroy(buffer_pool_t *pool);
 
void *buffer_pool_alloc(buffer_pool_t *pool, size_t size);
 
void buffer_pool_free(buffer_pool_t *pool, void *data, size_t size);
 
void buffer_pool_shrink(buffer_pool_t *pool);
 
void buffer_pool_get_stats(buffer_pool_t *pool, size_t *current_bytes, size_t *used_bytes, size_t *free_bytes);
 
void buffer_pool_log_stats(buffer_pool_t *pool, const char *name);
 
/* ============================================================================
 * Global Buffer Pool
 * ============================================================================
 */
 
void buffer_pool_init_global(void);
void buffer_pool_cleanup_global(void);
buffer_pool_t *buffer_pool_get_global(void);
 
/* ============================================================================
 * Convenience Macros
 * ============================================================================
 */
 
#define POOL_ALLOC(size) buffer_pool_alloc(NULL, (size))
#define POOL_FREE(data, size) buffer_pool_free(NULL, (data), (size))