Adding the program counter relative addressing mode

sources/CPU/CPU.cpp

@@ -318,4 +318,11 @@ namespace ComSquare::CPU
 		lng += this->_bus->read(this->_registers.pac++) << 16u;
 		return lng + this->_registers.x;
 	}
+
+	uint24_t CPU::_getProgramCounterRelativeAddr()
+	{
+		uint24_t pc = this->_registers.pac;
+		int8_t mod = this->_bus->read(this->_registers.pac++);
+		return pc + mod;
+	}
 }

sources/CPU/CPU.hpp

@@ -218,6 +218,8 @@ namespace ComSquare::CPU
 		uint24_t _getAbsoluteIndexedByYAddr();
 		//! @brief The effective address is formed by adding the <long exp> with X.
 		uint24_t _getAbsoluteLongIndexedByXAddr();
+		//! @brief The <8-bit signed exp> is added to PC (program counter) to form the new location.
+		uint24_t _getProgramCounterRelativeAddr();
 
 
 		//! @brief Execute a single instruction.

tests/CPU/testAddressingMode.cpp

@@ -162,4 +162,22 @@ Test(AddrMode, AbsoluteLongIndexByX)
 	pair.second.cpu->_registers.x = 0x0005;
 	cr_assert_eq(pair.second.cpu->_getAbsoluteLongIndexedByXAddr(), 0xEFAC15, "Returned address was %x but was expecting 0xEFAC15.", pair.second.cpu->_getAbsoluteLongIndexedByXAddr());
 	cr_assert_eq(pair.second.cpu->_registers.pac, 0x808003);
+}
+
+Test(AddrMode, ProgramCounterRelativePositive)
+{
+	auto pair = Init();
+	pair.second.cpu->_registers.pac = 0x808010;
+	pair.second.cartridge->_data[0x10] = 0x15;
+	cr_assert_eq(pair.second.cpu->_getProgramCounterRelativeAddr(), 0x808025, "Returned address was %x but was expecting 0x808025.", pair.second.cpu->_getProgramCounterRelativeAddr());
+	cr_assert_eq(pair.second.cpu->_registers.pac, 0x808011);
+}
+
+Test(AddrMode, ProgramCounterRelativeNegative)
+{
+	auto pair = Init();
+	pair.second.cpu->_registers.pac = 0x808010;
+	pair.second.cartridge->_data[0x10] = -0x15;
+	cr_assert_eq(pair.second.cpu->_getProgramCounterRelativeAddr(), 0x807FFB, "Returned address was %x but was expecting 0x807FFB.", pair.second.cpu->_getProgramCounterRelativeAddr());
+	cr_assert_eq(pair.second.cpu->_registers.pac, 0x808011);
 }