convert.cc

#include <cstdint>
#include <utility>

namespace convertor{
	constexpr uint16_t MAX_KEY = 0b00000000'00000011'11111111;	// 1023
	constexpr uint32_t MAX_VAL = 0b00111111'11111111'11111111;	// 4'194'303

	constexpr
	uint16_t val_i16(uint16_t, uint32_t const val){
		return val & 0b11111111'11111111;
	}

	constexpr
	uint16_t key_i16(uint16_t const key, uint32_t const val){
		uint32_t const x = val & 0b00000000'00111111'00000000'00000000;

		return key & 0b00000011'11111111 | (x >> 6);
	}

	constexpr
	uint16_t i16_key(uint16_t const key, uint16_t){
		return key & 0b00000011'11111111;
	}

	constexpr
	uint32_t i16_val(uint16_t const key, uint16_t const val){
		uint32_t x = key & ~0b00000011'11111111;
		return (x << 6) | val;
	}

	static_assert(i16_key(0b00000000'00000001, 0x00'0000) == 0b00000000'00000001, "");
	static_assert(i16_key(0b00000011'11111111, 0x00'0000) == 0b00000011'11111111, "");

	static_assert(i16_val(0b00000000'00000000, 0x00'0001) == 0x00'0001, "");
	static_assert(i16_val(0b00000000'00000000, 0x00'FFFF) == 0x00'FFFF, "");
	static_assert(i16_val(0b00000100'00000000, 0x00'0000) == 0x01'0000, "");
	static_assert(i16_val(0b00001100'00000000, 0x00'0000) == 0x03'0000, "");
	static_assert(i16_val(0b00011100'00000000, 0x00'0000) == 0x07'0000, "");

	static_assert(val_i16(0, 0x00'0001) ==  0x0001, "");
	static_assert(val_i16(0, 0x01'FFFF) ==  0xFFFF, "");

	static_assert(i16_val(0b00000000'00000000, 0x00'0001) == 0x00'0001, "");
	static_assert(i16_val(0b00000000'00000001, 0x00'FFFF) == 0x00'FFFF, "");
	static_assert(i16_val(0b00000100'00000000, 0x00'0000) == 0x01'0000, "");
	static_assert(i16_val(0b00001100'00000000, 0x00'0000) == 0x03'0000, "");
	static_assert(i16_val(0b00011100'00000000, 0x00'0000) == 0x07'0000, "");
};

int main(){
}