io/io.hpp

#pragma once

#include <cstdint>

#include <avr/io.h>
#include <avr/sfr_defs.h>

//////////////////////////////////////////////////////////////////////////
// Preprocessor defines

#if defined(__AVR_ATmega32__) || defined(__AVR_ATmega32A__) || defined(__AVR_ATmega644P__) || \
    defined(__AVR_ATmega1284P__)
#define GPIO_32
#endif

#if defined(__AVR_ATmega8__) || defined(__AVR_ATmega8A__) || defined(__AVR_ATmega168A__) || defined(__AVR_ATmega328P__)
#define GPIO_23
#endif

#if defined(__AVR_ATtiny13A__) || defined(__AVR_ATtiny85__)
#define GPIO_6
#endif

#if defined(__AVR_ATmega644P__) || defined(__AVR_ATmega1284P__) || defined(__AVR_ATmega168A__) || \
    defined(__AVR_ATmega328P__) || defined(__AVR_ATtiny13A__) || defined(__AVR_ATtiny85__)
#define HARDWARE_TOGGLE
#endif

#ifdef GPIO_32
#define PORT_A_AVAILABLE
#endif

#if defined(GPIO_32) || defined(GPIO_23) || defined(GPIO_6)
#define PORT_B_AVAILABLE
#endif

#if defined(GPIO_32) || defined(GPIO_23)
#define PORT_C_AVAILABLE
#define PORT_D_AVAILABLE
#define PIN_B6_AVAILABLE
#define PIN_B7_AVAILABLE
#endif

#if defined(GPIO_32)
#define PIN_C7_AVAILABLE
#endif

//////////////////////////////////////////////////////////////////////////
// Library implementation

namespace io {

enum class Dir { IN, OUT };

enum class P {
#ifdef PORT_A_AVAILABLE
	A0 = 0x00,
	A1 = 0x01,
	A2 = 0x02,
	A3 = 0x03,
	A4 = 0x04,
	A5 = 0x05,
	A6 = 0x06,
	A7 = 0x07,
#endif

#ifdef PORT_B_AVAILABLE
	B0 = 0x10,
	B1 = 0x11,
	B2 = 0x12,
	B3 = 0x13,
	B4 = 0x14,
	B5 = 0x15,
#ifdef PIN_B6_AVAILABLE
	B6 = 0x16,
#endif
#ifdef PIN_B7_AVAILABLE
	B7 = 0x17,
#endif
#endif

#ifdef PORT_C_AVAILABLE
	C0 = 0x20,
	C1 = 0x21,
	C2 = 0x22,
	C3 = 0x23,
	C4 = 0x24,
	C5 = 0x25,
	C6 = 0x26,
#ifdef PIN_C7_AVAILABLE
	C7 = 0x27,
#endif
#endif

#ifdef PORT_D_AVAILABLE
	D0 = 0x30,
	D1 = 0x31,
	D2 = 0x32,
	D3 = 0x33,
	D4 = 0x34,
	D5 = 0x35,
	D6 = 0x36,
	D7 = 0x37,
#endif

	NONE,
};

enum class Bus {
#ifdef PORT_A_AVAILABLE
	A = 0x00,
#endif
#ifdef PORT_B_AVAILABLE
	B = 0x01,
#endif
#ifdef PORT_C_AVAILABLE
	C = 0x02,
#endif
#ifdef PORT_D_AVAILABLE
	D = 0x03,
#endif

	NONE,
};

//////////////////////////////////////////////////////////////////////////
// Implementation details

namespace detail {

/*
The following works in avr-gcc 5.4.0, but is not legal C++, because ptr's are not legal constexpr's:
  constexpr auto *foo = ptr;

Workaround is to store the address of the ptr in a uintptr_t and reinterpret_cast it at call site.
The _SFR_ADDR macro in sfr_defs.h would give the address, but it does that by taking the address of the dereferenced
pointer and casts it to uint16_t, which is still not a legal constexpr.
The workaround therefore is to disable the pointer-cast-and-dereference macro _MMIO_BYTE temporarily.
*/

#pragma push_macro("_MMIO_BYTE")
#undef _MMIO_BYTE
#define _MMIO_BYTE

#ifdef PORT_A_AVAILABLE
static constexpr uintptr_t PORT_A_DIR_REG_ADDR = DDRA;
static constexpr uintptr_t PORT_A_OUTPUT_REG_ADDR = PORTA;
static constexpr uintptr_t PORT_A_INPUT_REG_ADDR = PINA;
#else
static constexpr uintptr_t PORT_A_DIR_REG_ADDR = 0;
static constexpr uintptr_t PORT_A_OUTPUT_REG_ADDR = 0;
static constexpr uintptr_t PORT_A_INPUT_REG_ADDR = 0;
#endif

#ifdef PORT_B_AVAILABLE

static constexpr uintptr_t PORT_B_DIR_REG_ADDR = DDRB;
static constexpr uintptr_t PORT_B_OUTPUT_REG_ADDR = PORTB;
static constexpr uintptr_t PORT_B_INPUT_REG_ADDR = PINB;
#else
static constexpr uintptr_t PORT_B_DIR_REG_ADDR = 0;
static constexpr uintptr_t PORT_B_OUTPUT_REG_ADDR = 0;
static constexpr uintptr_t PORT_B_INPUT_REG_ADDR = 0;
#endif

#ifdef PORT_C_AVAILABLE
static constexpr uintptr_t PORT_C_DIR_REG_ADDR = DDRC;
static constexpr uintptr_t PORT_C_OUTPUT_REG_ADDR = PORTC;
static constexpr uintptr_t PORT_C_INPUT_REG_ADDR = PINC;
#else
static constexpr uintptr_t PORT_C_DIR_REG_ADDR = 0;
static constexpr uintptr_t PORT_C_OUTPUT_REG_ADDR = 0;
static constexpr uintptr_t PORT_C_INPUT_REG_ADDR = 0;
#endif

#ifdef PORT_D_AVAILABLE
static constexpr uintptr_t PORT_D_DIR_REG_ADDR = DDRD;
static constexpr uintptr_t PORT_D_OUTPUT_REG_ADDR = PORTD;
static constexpr uintptr_t PORT_D_INPUT_REG_ADDR = PIND;
#else
static constexpr uintptr_t PORT_D_DIR_REG_ADDR = 0;
static constexpr uintptr_t PORT_D_OUTPUT_REG_ADDR = 0;
static constexpr uintptr_t PORT_D_INPUT_REG_ADDR = 0;
#endif

#pragma pop_macro("_MMIO_BYTE")

static constexpr auto getBus(const P pin)
{
	// Upper 4 bits of pin encode which port this pin is on
	const auto port = static_cast<std::uint8_t>(pin) >> 4 & 0x0F;
	return static_cast<Bus>(port);
}

static constexpr auto getPinBit(const P pin)
{
	// Lower 4 bits of pin encode which pin bit it is
	const auto pinBit = static_cast<std::uint8_t>(pin) & 0x0F;
	return pinBit;
}

static constexpr auto getDDR(const Bus bus)
{
	switch (static_cast<std::uint8_t>(bus)) {
	case 0: // Bus::A
		return PORT_A_DIR_REG_ADDR;
	case 1: // Bus::B
		return PORT_B_DIR_REG_ADDR;
	case 2: // Bus::C
		return PORT_C_DIR_REG_ADDR;
	case 3: // Bus::D
		return PORT_D_DIR_REG_ADDR;
	}
}

static constexpr auto getPORT(const Bus bus)
{
	switch (static_cast<std::uint8_t>(bus)) {
	case 0: // Bus::A
		return PORT_A_OUTPUT_REG_ADDR;
	case 1: // Bus::B
		return PORT_B_OUTPUT_REG_ADDR;
	case 2: // Bus::C
		return PORT_C_OUTPUT_REG_ADDR;
	case 3: // Bus::D
		return PORT_D_OUTPUT_REG_ADDR;
	}
}

static constexpr auto getPIN(const Bus bus)
{
	switch (static_cast<std::uint8_t>(bus)) {
	case 0: // Bus::A
		return PORT_A_INPUT_REG_ADDR;
	case 1: // Bus::B
		return PORT_B_INPUT_REG_ADDR;
	case 2: // Bus::C
		return PORT_C_INPUT_REG_ADDR;
	case 3: // Bus::D
		return PORT_D_INPUT_REG_ADDR;
	}
}

using reg_ptr_t = volatile std::uint8_t *;

template <uintptr_t Address>
static inline reg_ptr_t getRegPtr()
{
	return reinterpret_cast<reg_ptr_t>(Address);
}

template <template <P, std::uint8_t> typename Func, P pin, P... pins>
struct CallHelper {
	template <typename... Args>
	[[gnu::always_inline]] static inline void call(Args... args)
	{
		Func<pin, sizeof...(pins)>::call(args...);
		CallHelper<Func, pins...>::call(args...);
	}
};

template <template <P, std::uint8_t> typename Func, P pin>
struct CallHelper<Func, pin> {
	template <typename... Args>
	[[gnu::always_inline]] static inline void call(Args... args)
	{
		Func<pin, 0>::call(args...);
	}
};

template <template <P> typename Func, P pin, P... pins>
struct ReadCallHelper {
	[[gnu::always_inline]] static inline std::uint8_t call()
	{
		return Func<pin>::call() << sizeof...(pins) | ReadCallHelper<Func, pins...>::call();
	}
};

template <template <P> typename Func, P pin>
struct ReadCallHelper<Func, pin> {
	[[gnu::always_inline]] static inline std::uint8_t call()
	{
		return Func<pin>::call();
	}
};

} // namespace detail

//////////////////////////////////////////////////////////////////////////
// Zero overhead Pin object for pretty code without losing performance

template <P pin>
class Pin {
  public:
	// Pin objects cannot be moved or copied
	Pin(const Pin &) = delete;
	Pin(Pin &&) = delete;
	Pin &operator=(const Pin &) = delete;
	Pin &operator=(Pin &&) = delete;

	// The only valid way to create a Pin object is with the default constructor
	Pin() = default;

	[[gnu::always_inline]] static inline void dir(const Dir dir)
	{
		if constexpr (pin != P::NONE) {
			constexpr auto bus = detail::getBus(pin);
			constexpr auto pinBit = detail::getPinBit(pin);

			auto dirRegPtr = detail::getRegPtr<detail::getDDR(bus)>();

			if (dir == Dir::IN)
				*dirRegPtr = *dirRegPtr & ~(1 << pinBit);
			else if (dir == Dir::OUT)
				*dirRegPtr = *dirRegPtr | (1 << pinBit);
		}
	}

	[[gnu::always_inline]] static inline void pullup(const bool enable)
	{
		if constexpr (pin != P::NONE) {
			constexpr auto bus = detail::getBus(pin);
			constexpr auto pinBit = detail::getPinBit(pin);

			auto portRegPtr = detail::getRegPtr<detail::getPORT(bus)>();

			if (enable)
				*portRegPtr = *portRegPtr | (1 << pinBit);
			else
				*portRegPtr = *portRegPtr & ~(1 << pinBit);
		}
	}

	[[gnu::always_inline]] static inline void write(const bool value)
	{
		if constexpr (pin != P::NONE) {
			constexpr auto bus = detail::getBus(pin);
			constexpr auto pinBit = detail::getPinBit(pin);

			auto portRegPtr = detail::getRegPtr<detail::getPORT(bus)>();

			if (value)
				*portRegPtr = *portRegPtr | (1 << pinBit);
			else
				*portRegPtr = *portRegPtr & ~(1 << pinBit);
		}
	}

	[[gnu::always_inline]] static inline void toggle()
	{
		if constexpr (pin != P::NONE) {
			constexpr auto bus = detail::getBus(pin);
			constexpr auto pinBit = detail::getPinBit(pin);

#ifdef HARDWARE_TOGGLE
			auto pinRegPtr = detail::getRegPtr<detail::getPIN(bus)>();
			*pinRegPtr = *pinRegPtr | (1 << pinBit);
#else
			auto portRegPtr = detail::getRegPtr<detail::getPORT(bus)>();
			*portRegPtr = *portRegPtr ^ (1 << pinBit);
#endif
		}
	}

	[[gnu::always_inline]] static inline bool read()
	{
		if constexpr (pin != P::NONE) {
			constexpr auto bus = detail::getBus(pin);
			constexpr auto pinBit = detail::getPinBit(pin);

			auto pinRegPtr = detail::getRegPtr<detail::getPIN(bus)>();

			if (*pinRegPtr >> pinBit & 1)
				return true;
		}
		return false;
	}

	[[gnu::always_inline]] Pin &operator=(const bool value)
	{
		write(value);
		return *this;
	}

	[[gnu::always_inline]] operator bool() const
	{
		return read();
	}
};

//////////////////////////////////////////////////////////////////////////
// Zero overhead Port object for pretty code without losing performance

template <Bus port>
class Port {
  public:
	// Port objects cannot be moved or copied
	Port(const Port &) = delete;
	Port(Port &&) = delete;
	Port &operator=(const Port &) = delete;
	Port &operator=(Port &&) = delete;

	// The only valid way to create a Port object is with the default constructor
	Port() = default;

	[[gnu::always_inline]] static inline void dir(const Dir dir)
	{
		if constexpr (port != Bus::NONE) {
			auto dirRegPtr = detail::getRegPtr<detail::getDDR(port)>();

			if (dir == Dir::IN)
				*dirRegPtr = 0x00;
			else if (dir == Dir::OUT)
				*dirRegPtr = 0xFF;
		}
	}

	[[gnu::always_inline]] static inline void pullup(const bool enable)
	{
		if constexpr (port != Bus::NONE) {
			auto portRegPtr = detail::getRegPtr<detail::getPORT(port)>();

			if (enable)
				*portRegPtr = 0xFF;
			else
				*portRegPtr = 0x00;
		}
	}

	[[gnu::always_inline]] static inline void write([[maybe_unused]] const std::uint8_t value)
	{
		if constexpr (port != Bus::NONE) {
			auto portRegPtr = detail::getRegPtr<detail::getPORT(port)>();
			*portRegPtr = value;
		}
	}

	[[gnu::always_inline]] static inline void invert()
	{
		if constexpr (port != Bus::NONE) {
#ifdef HARDWARE_TOGGLE
			auto pinRegPtr = detail::getRegPtr<detail::getPIN(port)>();
			*pinRegPtr = 0xFF;
#else
			auto portRegPtr = detail::getRegPtr<detail::getPORT(port)>();
			*portRegPtr = ~(*portRegPtr);
#endif
		}
	}

	[[gnu::always_inline]] static inline std::uint8_t read()
	{
		if constexpr (port != Bus::NONE) {
			auto pinRegPtr = detail::getRegPtr<detail::getPIN(port)>();
			return *pinRegPtr;
		}
		return 0x00;
	}

	[[gnu::always_inline]] inline Port &operator=(const std::uint8_t value)
	{
		write(value);
		return *this;
	}

	[[gnu::always_inline]] inline operator std::uint8_t() const
	{
		return read();
	}
};

//////////////////////////////////////////////////////////////////////////
// Zero overhead Virtual Port object for pretty code without losing performance

namespace detail {

template <P pin, std::uint8_t offset>
struct Callers {
	[[gnu::always_inline]] static void call(const Dir dir)
	{
		Pin<pin>::dir(dir);
	};

	[[gnu::always_inline]] static void call(const bool enable)
	{
		Pin<pin>::pullup(enable);
	};

	[[gnu::always_inline]] static void call(const std::uint8_t value)
	{
		Pin<pin>::write(value >> offset & 1);
	};

	[[gnu::always_inline]] static void call()
	{
		Pin<pin>::toggle();
	};
};

template <P pin>
struct readCaller {
	[[gnu::always_inline]] static bool call()
	{
		return Pin<pin>::read();
	};
};

} // namespace detail

template <P... pins>
class VirtPort {
  public:
	static_assert(sizeof...(pins) <= 8, "A virtual port cannot have more than 8 pins");

	// VirtPort objects cannot be moved or copied
	VirtPort(const VirtPort &) = delete;
	VirtPort(VirtPort &&) = delete;
	VirtPort &operator=(const VirtPort &) = delete;
	VirtPort &operator=(VirtPort &&) = delete;

	// The only valid way to create a VirtPort object is with the default constructor
	VirtPort() = default;

	[[gnu::always_inline]] static inline void dir(const Dir dir)
	{
		detail::CallHelper<detail::Callers, pins...>::call(dir);
	}

	[[gnu::always_inline]] static inline void pullup(const bool enable)
	{
		detail::CallHelper<detail::Callers, pins...>::call(enable);
	}

	[[gnu::always_inline]] static inline void write(const std::uint8_t value)
	{
		detail::CallHelper<detail::Callers, pins...>::call(value);
	}

	[[gnu::always_inline]] static inline void invert()
	{
		detail::CallHelper<detail::Callers, pins...>::call();
	}

	[[gnu::always_inline]] static inline std::uint8_t read()
	{
		return detail::ReadCallHelper<detail::readCaller, pins...>::call();
	}

	[[gnu::always_inline]] inline VirtPort &operator=(const std::uint8_t value)
	{
		write(value);
		return *this;
	}

	[[gnu::always_inline]] inline operator std::uint8_t() const
	{
		return read();
	}
};

} // namespace io

//////////////////////////////////////////////////////////////////////////

#undef GPIO_32
#undef GPIO_23
#undef GPIO_6

#undef PORT_A_AVAILABLE
#undef PORT_B_AVAILABLE
#undef PORT_C_AVAILABLE
#undef PORT_D_AVAILABLE

#undef PIN_B6_AVAILABLE
#undef PIN_B7_AVAILABLE
#undef PIN_C7_AVAILABLE