#ifndef UC_SPOOL_H_
#define UC_SPOOL_H_

#include <stddef.h>
#include <stdint.h>
#ifdef __cplusplus
extern "C" {
#endif

typedef union UCPoolBlock UCPoolBlock;
union UCPoolBlock {
    UCPoolBlock *next;      // next free block (when not allocated)
    unsigned char data[0];  // data when allocated
};
/** @file
 * Static pool allocator.
 *
 *  An UCPool allocates fixed size memory chunks from a provided buffer,
 *  and memory allocations can be free'd in any order.
 *
 * The backing array should be suitable aligned to the types
 * that will be allocated from it. Use .e.g
 * @code
 * _Alignas(16) char mem[1024];
 * @endcode
 * as the backing buffer.
 *
 */
typedef struct UCPool UCPool;
struct UCPool {
    UCPoolBlock *free_list;  // free list
    size_t block_size;       // aligned size of each block
    size_t capacity;         // number of blocks
    size_t align;            // alignment
    UCPoolBlock *start;      // start of user buffer
    UCPoolBlock *end;        // one past end of user buffer
};

/** Initialize the pool.
 *
 * Block size will be rounded up by alignment, or to size of a pointer
 *
 * @param buffer      backing buffer for the pool
 * @param buffer_size size of @buffer
 * @param block_size  size of each allocation.
 * @param alignment   alignment of each block (must be power of 2)
 */
void uc_pool_init(UCPool *pool, void *buffer, size_t buffer_size, size_t block_size, size_t alignment);

// Allocate a block from the pool. Returns NULL if no more space
[[gnu::assume_aligned(_Alignof(UCPoolBlock))]]
void *uc_pool_alloc(UCPool *pool);

// Free @p . Returns memory to the pool
void uc_pool_free(UCPool *pool, void *p);
void uc_pool_reset(UCPool *pool);

#ifdef __cplusplus
}
#endif

#endif