robovac.c

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "robovac.h"

#define MEMORY_SIZE 4096

static size_t load_code(void* dest, size_t dest_size, char* path);
static void dump_registers(uint32_t* reg);

int main(int argc, char** argv) {
    if (argc != 2) {
        fprintf(stderr, "usage: %s <program>\n", argv[0]);
        return 1;
    }

    Machine machine = {0};
    machine.memory = malloc(MEMORY_SIZE);
    if (machine.memory == NULL) {
        return 1;
    }

    size_t code_size = load_code(machine.memory, MEMORY_SIZE, argv[1]);
    if (!code_size) {
        free(machine.memory);
        return 1;
    }

    uint8_t opcode;
    while (1) {
        opcode = *(machine.memory+machine.reg[REG_IP]);

        // Special case for HLT
        if (opcode == 0) {
            break;
        }

        (*op_handlers[opcode])(&machine);
    }

    dump_registers(machine.reg);

    free(machine.memory);
    return 0;
}

static size_t load_code(void* dest, size_t dest_size, char* path) {
    FILE* fh = fopen(path, "r");
    if (!fh) {
        perror("error opening program");
        return 0;
    }

    size_t size = fread(dest, 1, dest_size, fh);
    int read_err = ferror(fh);
    if (read_err) {
        fclose(fh);
        fprintf(stderr, "error reading program: %s\n", strerror(read_err));
        return 0;
    }
    if (!feof(fh)) {
        fclose(fh);
        fprintf(stderr, "program exceeds available memory (%zu bytes available)\n", dest_size);
        return 0;
    }
    fclose(fh);

    return size;
}

static void dump_registers(uint32_t* reg) {
    char name[4];

    for (size_t i = 0; i < 16; i++) {
        switch (i) {
            case REG_IP:
                strncpy(name, "IP", 4);
                break;
            default:
                snprintf(name, 4, "r%zu", i);
        }
        fprintf(stderr, "%s=0x%02x ", name, reg[i]);
    }

    fprintf(stderr, "\n");
}