Init-time bump-arena implementation (Layer 0, #147). More...

#include "ra8_arena.h"
#include <stdint.h>
#include "ra8_attributes.h"
#include "ra8_check.h"
#include "ra8_err.h"

Include dependency graph for ra8_arena.c:

Functions
static bool	internal_is_pow2 (uint32_t v)
	Test whether `v` is a power of two.
ra8_err_t	ra8_arena_init (ra8_arena_t arena, void base, uint32_t size)
	Bind a bump arena over a caller-owned tier region.
ra8_err_t	ra8_arena_carve (ra8_arena_t arena, uint32_t bytes, uint32_t align, void *out_ptr)
	Carve an aligned sub-block from the arena (bump; no free).
ra8_err_t	ra8_arena_remaining (const ra8_arena_t arena, uint32_t out_remaining)
	Report the bytes still available in the arena.

Variables
static const char *const	s_tag = "ra8_arena"
	Module log tag.

Detailed Description

Init-time bump-arena implementation (Layer 0, #147).

Tag: [Ring 2 / Core] {World: NS}

Bump-only allocation with power-of-two alignment. Fit checks use uintptr_t subtraction against the region end so they never overflow.

Copyright: Copyright (c) 2026 Brighton Sikarskie SPDX-License-Identifier: MIT

Definition in file ra8_arena.c.

Function Documentation

◆ internal_is_pow2()

bool internal_is_pow2 ( uint32_t v )

static

Test whether v is a power of two.

A power of two has exactly one set bit, so v & (v - 1) is zero; zero is rejected by the leading v != 0 term.

Parameters

[in] v Value to test.

Returns: true if v is a non-zero power of two, else false.

Return values

true	`v` is a non-zero power of two.
false	`v` is zero or has more than one set bit.

Precondition: None.; v fits in a uint32_t.

Postcondition: No state is modified.; The result depends only on v.

Note: Pure; thread-safe.

Since: 0.1.0

Definition at line 48 of file ra8_arena.c.

References RA8_INTERNAL.

Referenced by ra8_arena_carve().

◆ ra8_arena_carve()

ra8_err_t ra8_arena_carve	(	ra8_arena_t *	arena,
		uint32_t	bytes,
		uint32_t	align,
		void **	out_ptr )

nodiscard

Carve an aligned sub-block from the arena (bump; no free).

Parameters

[in]	arena	Initialised arena.
[in]	bytes	Block size to carve (> 0).
[in]	align	Required alignment in bytes (a power of two, >= 1).
[out]	out_ptr	Receives the aligned block pointer on success.

Returns: ra8_err_t Error code.

Return values

k_ra8_ok	Block carved; *out_ptr set.
k_ra8_err_null_ptr	arena or out_ptr was NULL.
k_ra8_err_invalid_size	bytes was zero.
k_ra8_err_invalid_arg	align was zero or not a power of two.
k_ra8_err_no_mem	The aligned block does not fit the remainder.

Precondition: arena was populated by ra8_arena_init.; align is a power of two.

Postcondition: On success *out_ptr is align-aligned with bytes of storage, and arena->used advanced past it.; On any non-ok return the arena is unchanged.

Note: Not thread-safe; init-time use only (there is no matching free).

Since: 0.1.0

Definition at line 69 of file ra8_arena.c.

References ra8_arena_t::base, internal_is_pow2(), k_ra8_err_invalid_arg, k_ra8_err_invalid_size, k_ra8_err_no_mem, k_ra8_ok, RA8_CHECK_NULL_PTR, s_tag, ra8_arena_t::size, and ra8_arena_t::used.

Referenced by mem_run_arena().

◆ ra8_arena_init()

ra8_err_t ra8_arena_init	(	ra8_arena_t *	arena,
		void *	base,
		uint32_t	size )

nodiscard

Bind a bump arena over a caller-owned tier region.

Parameters

[out]	arena	Arena state to populate (zero-initialised by caller).
[in]	base	First byte of the region (out-lives the arena).
[in]	size	Region length in bytes.

Returns: ra8_err_t Error code.

Return values

k_ra8_ok	Arena ready (empty).
k_ra8_err_null_ptr	arena or base was NULL.
k_ra8_err_invalid_size	size was zero.

Precondition: base addresses at least size writable bytes.; arena does not alias base.

Postcondition: On success arena->used == 0 and the whole region is available.; On any non-ok return arena is left unbound.

Note: Not thread-safe.

Since: 0.1.0

Definition at line 56 of file ra8_arena.c.

References ra8_arena_t::base, k_ra8_err_invalid_size, k_ra8_ok, RA8_CHECK_NULL_PTR, s_tag, ra8_arena_t::size, and ra8_arena_t::used.

Referenced by mem_run_arena().

◆ ra8_arena_remaining()

ra8_err_t ra8_arena_remaining	(	const ra8_arena_t *	arena,
		uint32_t *	out_remaining )

nodiscard

Report the bytes still available in the arena.

Parameters

[in]	arena	Initialised arena.
[out]	out_remaining	Receives size - used.

Returns: ra8_err_t Error code.

Return values

k_ra8_ok	Remaining bytes reported.
k_ra8_err_null_ptr	arena or out_remaining was NULL.

Precondition: arena was populated by ra8_arena_init.; out_remaining is writable.

Postcondition: *out_remaining == arena->size - arena->used.; No arena state is mutated.

Note: Thread-safe with respect to a quiescent arena (pure read).

Since: 0.1.0

Definition at line 94 of file ra8_arena.c.

References k_ra8_ok, RA8_CHECK_NULL_PTR, s_tag, ra8_arena_t::size, and ra8_arena_t::used.

Referenced by mem_run_arena().

Variable Documentation

◆ s_tag

const char* const s_tag = "ra8_arena"

static

Module log tag.

Definition at line 25 of file ra8_arena.c.

Functions

Variables

Detailed Description

Function Documentation

◆ internal_is_pow2()

◆ ra8_arena_carve()

◆ ra8_arena_init()

◆ ra8_arena_remaining()

Variable Documentation

◆ s_tag