94 lines
1.6 KiB
C++
94 lines
1.6 KiB
C++
#include <intcode/Interpreter.hpp>
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namespace intcode {
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BadInstruction::BadInstruction(char const* what)
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: std::runtime_error{what} {}
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auto StepInput(Machine & m, ValueType input) -> void {
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std::get<Input>(Step(m)).input = input;
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}
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auto StepOutput(Machine & m) -> ValueType {
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return std::get<Output>(Step(m)).output;
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}
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auto Step(Machine & m) -> std::variant<Input, Output, Halt> {
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for (;;) {
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auto instruction = m.Next();
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auto modes = instruction / 10;
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auto arg = [&]() -> ValueType & {
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auto &v = m.Next();
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switch ((modes /= 10) % 10) {
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case 0:
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return m.At(v);
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case 1:
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return v;
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case 2:
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return m.Rel(v);
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default:
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throw BadInstruction{"invalid addressing mode"};
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}
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};
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switch (instruction % 100) {
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case 1: {
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arg() = arg() + arg();
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break;
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}
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case 2: {
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arg() = arg() * arg();
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break;
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}
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case 3: {
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return Input{arg()};
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}
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case 4: {
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return Output{arg()};
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}
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case 5: {
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auto a = arg();
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auto b = arg();
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if (a) { m.Goto(b); }
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break;
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}
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case 6: {
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auto a = arg();
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auto b = arg();
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if (!a) { m.Goto(b); }
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break;
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}
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case 7: {
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auto a = arg();
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auto b = arg();
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arg() = a < b; // order matters
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break;
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}
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case 8: {
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arg() = arg() == arg();
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break;
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}
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case 9:
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m.Rebase(arg());
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break;
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case 99:
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return Halt{};
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default:
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throw BadInstruction{"invalid opcode"};
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}
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}
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}
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} // namespace
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