hale_stack_memory.cpp

struct ScratchMemory {
	void *base;
	memi capacity;
};

void child(ScratchMemory *memory,...) {
	// do things to memory
}

void parent(ScratchMemory *memory,...) {
	// do things to memory
	child(memory);
	// do things to memory
	// problem: memory is changed by child
}

//
//
//


struct StackMemory {
	void *base;
	void *position;
	memi capacity;
};

void *
stack_allocate(StackMemory *stack, memi capacity)
{
	void *ret;
	memi p = stack->position - stack->base;
	if ((p + capacity) > stack->capacity) {
		stack->base = memory_reallocate(base, p + capacity); // Grow factor?
		ret = stack->base + p;
	} else {
		ret = stack->postition;
	}
	stack->position = ret + capacity;
	return ret;
}

void
stack_release(StackMemory *stack, memi capacity)
{
	stack->position -= capacity;
}

//
//
//

struct StackAllocator {
	StackMemory stack;
	memi capacity;

	StackAllocator(StackMemory *stack) : 
		_stack(stack),
		_capacity(0)
	{}

	~StackAllocator() {
		if (_capacity) {
			stack_release(stack, _capacity);
		}
	}

	inline void *
	allocate(memi capacity) {
		_capacity += capacity;
		memory = stack_allocate(capacity);
	}

	inline void *
	ptr() {
		return stack->position - _capacity;
	}
};

//
//
//

void child1(StackMemory *stack,...) {
	StackAllocator allocator(stack);
	allocator.allocate(stack, 1024);
	// do things to memory
}

void child2(StackMemory *stack,...) {
	// do nothing to memory
}

void parent(StackMemory *stack,...) {
	StackAllocator allocator(stack);
	allocator.allocate(1024);
	// do things to memory
	child1(stack);
	// do things to memory
	child2(stack);
	// do things to memory
}