POSIX sapi_memory backend: a single fixed-size static byte arena with a per-pool intrusive free list carved out of it at sapi_mem_pool_create() time (ADR-018 section 2.3). More...

#include "safeapi/posix_backend/sapi_posix_backend.h"
#include "safeapi/utils/cast/sapi_cast.h"
#include <stdint.h>
#include "safeapi/oal/memory/sapi_mem_util.h"

Include dependency graph for sapi_posix_backend_memory.c:

Data Structures
struct	posix_mem_pool_state_t

Macros
#define	SAPI_POSIX_MEM_ARENA_SIZE (1024U * 1024U)

Typedefs
typedef char	posix_mem_pool_storage_fits_[(sizeof(posix_mem_pool_state_t)<=sizeof(sapi_mem_pool_storage_t)) ? 1 :-1]

Functions
static sapi_status_t	backend_create (sapi_mem_pool_storage_t storage, const sapi_mem_pool_config_t config, sapi_mem_pool_handle_t *out_handle)
static sapi_status_t	backend_acquire (sapi_mem_pool_handle_t handle, void **out_block)
static bool	block_belongs_to_pool (const posix_mem_pool_state_t state, const void block)
static sapi_status_t	backend_release (sapi_mem_pool_handle_t handle, void *block)
static sapi_status_t	backend_stats (sapi_mem_pool_handle_t handle, size_t out_free_blocks, size_t out_used_blocks)
const sapi_mem_pool_backend_t *	sapi_posix_backend_memory (void)
	The POSIX sapi_memory backend (static arena, no malloc).

Variables
static uint8_t	g_arena [SAPI_POSIX_MEM_ARENA_SIZE]
static size_t	g_arena_used = 0U
static const sapi_mem_pool_backend_t	s_posix_memory_backend

Detailed Description

POSIX sapi_memory backend: a single fixed-size static byte arena with a per-pool intrusive free list carved out of it at sapi_mem_pool_create() time (ADR-018 section 2.3).

This is static partitioning, not malloc()/free(): the arena's total size (SAPI_POSIX_MEM_ARENA_SIZE, default 1 MiB) is a compile-time constant, every pool's claim against it is a one-way bump allocation checked against remaining arena space (SAPI_STATUS_RESOURCE_EXHAUSTED rather than growing anything), and no memory is ever returned to the arena once a pool claims it - only individual blocks are recycled within their own pool's free list. Matches REQ-OAL-MEM-001: pools are expected to be reserved during system initialization.

Known constraint: the free list is intrusive (a free block's first sizeof(void*) bytes store the pointer to the next free block in the same pool), so block_size must be >= sizeof(void*). A pool requesting a smaller block_size is rejected with SAPI_STATUS_INVALID_PARAM rather than silently corrupting adjacent memory.

Known simplification: the global arena cursor (g_arena_used) and each pool's free-list head are not protected by a lock. REQ-OAL-MEM-001 frames pool reservation as an initialization-time activity (a single thread, before concurrent operation begins), so backend_create() being unsynchronized matches that expectation; acquire()/release() on an already-created pool being called concurrently from multiple threads is NOT safe with this backend and is a documented limitation, not an oversight - a production backend needing concurrent acquire/release would need a lock or a lock-free free-list (e.g. compare-and-swap), deliberately left out of this first cut.

Definition in file sapi_posix_backend_memory.c.