60 lines
1.8 KiB
C++
60 lines
1.8 KiB
C++
#include "ldx-opcode-handler.h"
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#include <sstream>
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const uint8_t LdxOpcodeHandler::IMMEDIATE;
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const uint8_t LdxOpcodeHandler::ZERO_PAGE;
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const uint8_t LdxOpcodeHandler::ZERO_PAGE_Y;
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const uint8_t LdxOpcodeHandler::ABSOLUTE;
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const uint8_t LdxOpcodeHandler::ABSOLUTE_Y;
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void LdxOpcodeHandler::execute() {
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auto instructionIndex = reg_man->get_program_counter()->get_value();
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auto opcode = program->get_byte_at(instructionIndex);
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auto byte2 = program->get_byte_at(instructionIndex + 1);
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auto x_reg = reg_man->get_x_index();
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switch (opcode) {
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case IMMEDIATE:
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x_reg->set_value(byte2);
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move_program_counter(2);
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break;
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case ZERO_PAGE:
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x_reg->set_value(memory->get_byte_at(byte2));
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move_program_counter(2);
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break;
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case ZERO_PAGE_Y: {
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uint16_t address = byte2 + reg_man->get_y_index()->get_value();
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x_reg->set_value(memory->get_byte_at(address));
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move_program_counter(2);
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break;
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}
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case ABSOLUTE: {
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auto low = byte2;
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auto high = program->get_byte_at(instructionIndex + 2);
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uint16_t address = (high << 8) + low;
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x_reg->set_value(memory->get_byte_at(address));
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move_program_counter(3);
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break;
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}
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case ABSOLUTE_Y: {
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auto low = byte2;
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auto high = program->get_byte_at(instructionIndex + 2);
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uint16_t address = (high << 8) + low + reg_man->get_y_index()->get_value();
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x_reg->set_value(memory->get_byte_at(address));
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move_program_counter(3);
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break;
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}
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default:
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stringstream stream;
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stream << "Unexpected opcode 0x" << hex << opcode;
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throw runtime_error(stream.str());
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}
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} |