orbum/liborbum/src/Common/Types/Register/SizedWordRegister.hpp

#pragma once

#include <stdexcept>

#include "Common/Types/Primitive.hpp"
#include "Common/Types/Register/WordRegister.hpp"

/// Sized Word register.
class SizedWordRegister : public WordRegister
{
public:
	SizedWordRegister(const uword initial_value = 0, const bool read_only = false) :
		w(initial_value),
		initial_value(initial_value),
		read_only(read_only)
	{
	}

	/// Initialise register.
	void initialise() override
	{
		w = initial_value;
	}

	/// Read/write functions to access the register.
	ubyte read_ubyte(const size_t offset) override
	{
	#if defined(BUILD_DEBUG)
		if (offset >= NUMBER_BYTES_IN_WORD)
			throw std::runtime_error("Tried to access SizedWordRegister with an invalid offset.");
	#endif

		return b[offset];
	}

	void write_ubyte(const size_t offset, const ubyte value) override
	{
	#if defined(BUILD_DEBUG)
		if (offset >= NUMBER_BYTES_IN_WORD)
			throw std::runtime_error("Tried to access SizedWordRegister with an invalid offset.");
	#endif

		if (!read_only)
			b[offset] = value;
	}

	uhword read_uhword(const size_t offset) override
	{
	#if defined(BUILD_DEBUG)
		if (offset >= NUMBER_HWORDS_IN_WORD)
			throw std::runtime_error("Tried to access SizedWordRegister with an invalid offset.");
	#endif

		return h[offset];
	}

	void write_uhword(const size_t offset, const uhword value) override
	{
	#if defined(BUILD_DEBUG)
		if (offset >= NUMBER_HWORDS_IN_WORD)
			throw std::runtime_error("Tried to access SizedWordRegister with an invalid offset.");
	#endif

		if (!read_only)
			h[offset] = value;
	}

	uword read_uword() override
	{
		return w;
	}

	void write_uword(const uword value) override
	{
		if (!read_only)
			w = value;
	}
	
private:
	/// Primitive (sized) storage for register.
	union
	{
        ubyte  b[NUMBER_BYTES_IN_WORD];
		uhword h[NUMBER_HWORDS_IN_WORD];
		uword  w;
	};

	/// Initial value.
	uword initial_value;
	
	/// Read-only flag.
	/// Writes are silently discarded if turned on.
	bool read_only;
};