namespace factor
{

// Context object count and identifiers must be kept in sync with:
//   core/kernel/kernel.factor

static const cell context_object_count = 10;

enum context_object {
	OBJ_NAMESTACK,
	OBJ_CATCHSTACK,
	OBJ_CONTEXT,
	OBJ_IN_CALLBACK_P,
};

static const cell stack_reserved = 1024;

struct context {

	// First 4 fields accessed directly by compiler. See basis/vm/vm.factor

	/* Factor callstack pointers */
	void *callstack_top;
	void *callstack_bottom;

	/* current datastack top pointer */
	cell datastack;

	/* current retain stack top pointer */
	cell retainstack;

	/* C callstack pointer */
	cell callstack_save;

	segment *datastack_seg;
	segment *retainstack_seg;
	segment *callstack_seg;

	/* context-specific special objects, accessed by context-object and
	set-context-object primitives */
	cell context_objects[context_object_count];

	context(cell datastack_size, cell retainstack_size, cell callstack_size);
	~context();

	void reset_datastack();
	void reset_retainstack();
	void reset_callstack();
	void reset_context_objects();
	void reset();
	void fix_stacks();
	void scrub_stacks(gc_info *info, cell index);

	cell peek()
	{
		return *(cell *)datastack;
	}

	void replace(cell tagged)
	{
		*(cell *)datastack = tagged;
	}

	cell pop()
	{
		cell value = peek();
		datastack -= sizeof(cell);
		return value;
	}

	void push(cell tagged)
	{
		datastack += sizeof(cell);
		replace(tagged);
	}
};

VM_C_API context *new_context(factor_vm *parent);
VM_C_API void delete_context(factor_vm *parent, context *old_context);
VM_C_API void reset_context(factor_vm *parent, context *ctx);
VM_C_API cell begin_callback(factor_vm *parent, cell quot);
VM_C_API void end_callback(factor_vm *parent);

}