<util/arena.h>

Bump allocator over a caller-provided buffer.

Allocations only move a cursor forward; nothing is freed individually. ArenaReset() releases everything at once.

#include <util/arena.h>

Structures

Arena

An arena: a buffer and how much of it is used. The heap's reservation and current break.

Field	Type	Description
base	uint8_t *	Start of the buffer.
size	size_t	Buffer size in bytes.
offset	size_t	Bytes handed out so far.
base	VirtAddr	Start of the reservation.
brk	VirtAddr	Current break.
mapped	VirtAddr	End of the reservation.

Functions

ArenaInit

void ArenaInit(Arena *a, void *buf, size_t size);

Sets up an arena over buf.

The arena does not own the buffer.

Parameter	Direction	Description
a	out	Arena to initialise.
buf	in	Backing buffer.
size	in	Size of buf in bytes.

ArenaAlloc

void * ArenaAlloc(Arena *a, size_t size);

Takes size bytes from the arena, with no alignment.

Parameter	Direction	Description
a	inout	Arena to allocate from.
size	in	Bytes wanted.

Returns: The memory, or NULL if fewer than size bytes are left.

ArenaAllocAligned

void * ArenaAllocAligned(Arena *a, size_t size, size_t align);

Takes size bytes from the arena, aligned to align.

Skips padding bytes as needed to reach the alignment.

Parameter	Direction	Description
a	inout	Arena to allocate from.
size	in	Bytes wanted.
align	in	Alignment in bytes; must be a power of two.

Returns: The memory, or NULL if padding plus size does not fit.

ArenaReset

void ArenaReset(Arena *a);

Releases every allocation at once; the buffer is kept for reuse.

Parameter	Direction	Description
a	inout	Arena to reset.

ArenaDestroy

void ArenaDestroy(Arena *a);

Forgets the buffer and zeroes the arena.

The buffer itself is not freed.

Parameter	Direction	Description
a	out	Arena to clear.