2018/Day21/Day21A.cpp

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <inttypes.h>
#include <assert.h>
#include <string.h>
#include <locale.h>
#include <climits>
#include <unordered_set>

typedef struct {
    uint8_t opcode;
    int32_t a, b, c;
} Instruction;

Instruction instructions[1024];

enum {
    ADDR, ADDI, MULR, MULI, BANR, BANI, BORR, BORI,
    SETR, SETI, GTIR, GTRI, GTRR, EQIR, EQRI, EQRR,
    IP,
};

const char *names[] = {
    "addr", "addi", "mulr", "muli", "banr", "bani", "borr", "bori",
    "setr", "seti", "gtir", "gtri", "gtrr", "eqir", "eqri", "eqrr",
    "#ip",
};

int instruction_read(Instruction *i, FILE *file) {
    char mnemonic[64] = {0};
    size_t count = fscanf(file, "%s %u %u %u", mnemonic, &i->a, &i->b, &i->c);
    if (count != 4 && count != 2)
        return 0;

    for (int opcode = 0; opcode <= IP; opcode++) {
        if (strcmp(names[opcode], mnemonic) == 0) {
            i->opcode = opcode;
            return 1;
        }
    }
    printf("Unknown mnemonic '%s'\n", mnemonic);
    return 0;
}

void instruction_execute(const Instruction *i, int32_t *r, int32_t *ip, int32_t *ip_r) {
    if (*ip_r != -1)
        r[*ip_r] = *ip;

    switch (i->opcode) {
    // Addition
    case ADDR: r[i->c] = r[i->a] + r[i->b];    break;
    case ADDI: r[i->c] = r[i->a] + i->b;       break;

    // Multiplication
    case MULR: r[i->c] = r[i->a] * r[i->b];    break;
    case MULI: r[i->c] = r[i->a] * i->b;       break;

    // Bitwise AND
    case BANR: r[i->c] = (r[i->a] & r[i->b]);  break;
    case BANI: r[i->c] = (r[i->a] & i->b);     break;

    // Bitwise OR
    case BORR: r[i->c] = (r[i->a] | r[i->b]);  break;
    case BORI: r[i->c] = (r[i->a] | i->b);     break;

    // Assignment
    case SETR: r[i->c] = r[i->a];              break;
    case SETI: r[i->c] = i->a;                 break;

    // Greater-than testing
    case GTIR: r[i->c] = (i->a > r[i->b]);     break;
    case GTRI: r[i->c] = (r[i->a] > i->b);     break;
    case GTRR: r[i->c] = (r[i->a] > r[i->b]);  break;

    // Equality testing
    case EQIR: r[i->c] = (i->a == r[i->b]);    break;
    case EQRI: r[i->c] = (r[i->a] == i->b);    break;
    case EQRR: r[i->c] = (r[i->a] == r[i->b]); break;

    case IP:   *ip_r = i->a; *ip -= 1;         break;

    default: assert(0);
    }

    if (*ip_r != -1)
        *ip = r[*ip_r];

    *ip += 1;
}

int main(int argc, char **argv) {
    setlocale(LC_NUMERIC, "");
    if (argc != 2) {
        printf("Usage: %s [input]\n", argv[0]);
        return EXIT_FAILURE;
    }

    FILE *file = fopen(argv[1], "r");

    int32_t jump_regs[6] = {-1};
    int32_t registers[6] = {INT_MAX, 0};
    int32_t ip_reg = -1;
    size_t instr_count = 0;
    for (instr_count = 0; instr_count < 1024 && instruction_read(&instructions[instr_count], file); instr_count++) {
        if (instructions[instr_count].opcode == IP) {
            ip_reg = instructions[instr_count].a;
            instr_count -= 1;
            continue;
        }

        printf("[%2zu] %s %d %d %d\n", instr_count, names[instructions[instr_count].opcode],
               instructions[instr_count].a, instructions[instr_count].b,
               instructions[instr_count].c);
    }
    printf("\n");

    std::unordered_set<size_t> breakpoints;
    bool stepping = true;

    uint64_t instructions_executed = 0;
    for (int32_t i = 0; i < instr_count;) {
        Instruction instruction = instructions[i];

        if (breakpoints.find(i) != breakpoints.end())
            stepping = true;

        if (stepping) {
            const char *name = names[instruction.opcode];
            printf("[%2d] \033[33m%s %d %d %d\033[0m\r", i,
                   name, instruction.a, instruction.b, instruction.c);
        }
        instruction_execute(&instruction, registers, &i, &ip_reg);
        if (stepping) {
            printf("\033[30C[%d, %d, %d, %d, %d, %d]\n", registers[0], registers[1],
                   registers[2], registers[3], registers[4], registers[5]);

        read:
            printf("> ");
            char c;
            scanf(" %c", &c);
            switch (c) {
            case 0:
                printf("q\n");
                [[fallthrough]];

            case 'q':
                i = instr_count;
                break;

            case 'c':
                stepping = false;
                break;

            case 'b':
                breakpoints.insert(i);
                break;

            case 's':
                break;

            case '\n':
                goto read;

            default:
                printf("Unknown command '%c'\n", c);
                goto read;
            }
        }

        instructions_executed += 1;
        if (!stepping && instructions_executed % (1 << 20) == 0) {
            printf("%'lu %d ", instructions_executed, i);
            printf("[%'d, %'d, %'d, %'d, %'d, %'d]\033[K\r", registers[0], registers[1],
                registers[2], registers[3], registers[4], registers[5]);
        }
    }
    printf("instructions: %lu\n", instructions_executed);

    fclose(file);

    printf("%d\n", registers[0]);
    return EXIT_SUCCESS;
}