/*
 * Harmful Brainfuck interpreter.
 *
 * Author:  Bertram Felgenhauer <int-e@gmx.de>
 * License: CC0
 *
 * 2014-12-25 Initial version.
 */
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>

#define SIZE (1<<20)

char code[SIZE];
int  size;
int  data[SIZE];

void interpret()
{
    int ip;
    int p  = 0;
    for (ip = 0; ip >= 0 && ip < size; ip++) {
        switch (code[ip]) {
        case '+':
            data[p]++;
            if (data[p] >= 256) {
                fprintf(stderr, "\nOverflow at %d (tape: %d)\n", ip, p);
                exit(1);
            }
            break;
        case '-':
            data[p]--;
            if (data[p] < -256) {
                fprintf(stderr, "\nUnderflow at %d (tape: %d)\n", ip, p);
                exit(1);
            }
            break;
        case '<':
            p--;
            if (p < 0) {
                fprintf(stderr, "\nFell off tape at %d\n", ip);
                exit(1);
            }
            break;
        case '>':
            p++;
            if (p >= SIZE) {
                fprintf(stderr, "\nRan out of tape at %d\n", ip);
                exit(1);
            }
            break;
        case '*':
            ip += data[p] - 1;
            break;
        case '.':
            putchar(data[p]);
            fflush(stdout);
            break;
        case ',':
        {
            int c = getchar();
            if (c < 0)
                c = 0;
            data[p] = c;
            break;
        }
        }
    }
}

int main(int argc, char **argv)
{
    FILE *f;

    if (argc < 2) {
        fprintf(stderr, "Usage: %s <harmful>\n", argv[0]);
        exit(1);
    }

    f = fopen(argv[1], "r");
    if (!f) {
        fprintf(stderr, "Error opening `%s'\n", argv[1]);
        exit(1);
    }

    size = fread(code, 1, SIZE, f);
    fclose(f);
    interpret();
    exit(0);
}