CLK/InstructionSets/M68k/Sequence.hpp

//
//  Sequencer.hpp
//  Clock Signal
//
//  Created by Thomas Harte on 29/04/2022.
//  Copyright © 2022 Thomas Harte. All rights reserved.
//

#ifndef InstructionSets_68k_Sequencer_hpp
#define InstructionSets_68k_Sequencer_hpp

#include "Instruction.hpp"

namespace InstructionSet {
namespace M68k {

/// Indicates the abstract steps necessary to perform an operation,
/// at least as far as that's generic.
class Sequence {
	public:
		Sequence(Operation);

		enum class Step {
			/// No further steps remain.
			Done,
			/// Fetch the value of operand 1.
			FetchOp1,
			/// Fetch the value of operand 2.
			FetchOp2,
			/// Do the logical operation.
			Perform,
			/// A catch-all for bus activity that doesn't fit the pattern
			/// of fetch/stop operand 1/2, e.g. this opaquely covers almost
			/// the entirety of MOVEM.
			///
			/// TODO: list all operations that contain this step,
			/// and to cover what activity.
			SpecificBusActivity,
			/// Store the value of operand 1.
			StoreOp1,
			/// Store the value of operand 2.
			StoreOp2,
		};

		/// @returns The next @c Step to perform, or @c Done
		/// if no further steps remain. This step is removed from the
		/// list of remaining steps.
		Step pop_front() {
			const auto step = Step(steps_ & 7);
			steps_ >>= 3;
			return step;
		}

		/// @returns @c true if no steps other than @c Done remain;
		/// @c false otherwise.
		bool empty() {
			return !steps_;
		}

	private:
		uint16_t steps_ = 0;

		uint16_t steps_for(Operation);
};

static_assert(sizeof(Sequence) == sizeof(uint16_t));

}
}

#endif /* InstructionSets_68k_Sequencer_h */