Arena *arena_alloc(U64 cap)
{
	Arena *arena = 0;

	/* TODO(pryazha): Use OS related memory allocator (like VirtualAlloc on Windows) */
	arena = malloc(sizeof(Arena));
	Assert(arena);

	if (!cap)
		cap = DEFAULT_ALLOC_SIZE;

	arena->mem = malloc(cap);
	Assert(arena->mem);
	arena->cap = cap;
	arena->used = 0;

	return arena;
}

void arena_release(Arena *arena)
{
	free(arena->mem);
	arena->mem = 0;
	arena->cap = 0;
	arena->used = 0;
	free(arena);
}

void *arena_push(Arena *arena, U64 size)
{
	Assert(arena->used+size <= arena->cap);
	void *r = arena->mem+arena->used;
	arena->used += size;
	return r;
}

void arena_pop(Arena *arena, U64 amount)
{
	Assert(arena);
	U64 clamped = ClampTop(amount, arena->used);
	arena->used = arena->used-clamped;
}