RDIC/gui/memory_arena.c

typedef struct Memory_Arena
{
	void *memory;
	size_t size;
	size_t allocation_offset;
} Memory_Arena;

_Static_assert(sizeof(size_t) == sizeof(void*),
	"The Memory_Arena implementation assumes that size_t and pointers are of the same size.");

void *memory_arena_allocate(
	Memory_Arena *arena,
	size_t size,
	size_t alignment)
{
	#if 0
	printf(
		"%s: arena: {.memory=%p, .size=%zu, .allocation_offset=%zu}\n"
		"size: %zu, alignment: %zu\n"
		, __func__
		, arena->memory, arena->size, arena->allocation_offset
		, size, alignment
		);
	#endif
	size_t allocation_offset = arena->allocation_offset;
	allocation_offset = ((allocation_offset + alignment - 1) / alignment) * alignment;
	if(allocation_offset + size > arena->size)
	{
		return NULL;
	}
	void *allocation = ((char*)arena->memory) + allocation_offset;
	arena->allocation_offset = allocation_offset + size;
	return allocation;
}

void memory_arena_reset(
	Memory_Arena *arena)
{
	arena->allocation_offset = 0;
}