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99 lines
3.0 KiB
C++
99 lines
3.0 KiB
C++
//
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// Parser.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 1/16/21.
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// Copyright © 2021 Thomas Harte. All rights reserved.
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//
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#ifndef InstructionSets_M50740_Parser_hpp
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#define InstructionSets_M50740_Parser_hpp
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#include <cstdint>
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#include "Decoder.hpp"
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namespace InstructionSet {
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namespace M50740 {
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template<typename Target> struct Parser {
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void parse(Target &target, const uint8_t *storage, uint16_t start, uint16_t closing_bound) {
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Decoder decoder;
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while(start != closing_bound) {
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const auto next = decoder.decode(&storage[start], closing_bound - start);
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if(next.first <= 0) {
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// If there weren't enough bytes left before the closing bound to complete
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// an instruction, but implicitly there were some bytes left, announce overflow
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// and terminate.
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target.announce_overflow(start);
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return;
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} else {
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// Pass on the instruction.
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target.announce_instruction(start, next.second);
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// Check for end of stream and potential new entry points.
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switch(next.second.operation) {
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// Terminating instructions.
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case Operation::RTS: case Operation::RTI: case Operation::BRK:
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return;
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// Terminating operations with implied additional entry point.
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case Operation::JMP:
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target.add_entry(storage[start + 1] | (storage[start + 2] << 8));
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return;
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case Operation::BRA:
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target.add_entry(start + 2 + int8_t(storage[start + 1]));
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return;
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// Instructions that suggest another entry point but don't terminate parsing.
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case Operation::BBS: case Operation::BBC:
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case Operation::BCC: case Operation::BCS:
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case Operation::BVC: case Operation::BVS:
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case Operation::BMI: case Operation::BPL:
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case Operation::BNE: case Operation::BEQ:
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target.add_entry(start + 2 + int8_t(storage[start + 1]));
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break;
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case Operation::JSR:
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target.add_entry(storage[start + 1] | (storage[start + 2] << 8));
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break;
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default: break;
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}
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// Provide any fixed address accesses.
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switch(next.second.addressing_mode) {
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case AddressingMode::Absolute:
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target.add_access(storage[start + 1] | (storage[start + 2] << 8));
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break;
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case AddressingMode::ZeroPage:
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case AddressingMode::Bit0ZeroPage: case AddressingMode::Bit1ZeroPage:
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case AddressingMode::Bit2ZeroPage: case AddressingMode::Bit3ZeroPage:
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case AddressingMode::Bit4ZeroPage: case AddressingMode::Bit5ZeroPage:
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case AddressingMode::Bit6ZeroPage: case AddressingMode::Bit7ZeroPage:
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target.add_access(storage[start + 1]);
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break;
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case AddressingMode::SpecialPage:
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target.add_access(storage[start + 1] | 0x1f00);
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break;
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case AddressingMode::ImmediateZeroPage:
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target.add_access(storage[start + 2]);
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break;
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case AddressingMode::Bit0AccumulatorRelative:
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target.add_access(start + 2 + int8_t(storage[start + 1]));
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break;
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default: break;
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}
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// Advance.
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start += next.first;
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}
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}
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}
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};
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}
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}
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#endif /* InstructionSets_M50740_Parser_hpp */
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