/***************************************************
                                                   *
    brainfark.c by rattle (awarenetwork.org)       *

    brainfuck interpreter. very naughty recursive 
    implementation of [] loops. If AWKz was here,
 *  he'd hit me with a giant lambda expression.
 *
 ***************************************************/


#include <memory.h>
#include <stdlib.h>
#include <stdio.h>

typedef unsigned char word;
typedef signed long schlong;

FILE *f = NULL;
word *p = NULL;
schlong s = 0x800, j=0;

void die(char* err) {
     printf("\nCRITICAL ERROR: %s\n",err);
     if (f) fclose(f);
     if (p) free(p);
     exit(1); 
}

void blow(int lo) {
    register int ss = s << 1;

    if (p = realloc(p,ss*sizeof(word))) {
        memset(&p[s],0,s*sizeof(word));
        if (lo) {
            j += s;
            memcpy(&p[s],p,s*sizeof(word));
        }
        s = ss;
    } else die("insufficient memory");
}

void inc() { if (++j>s) blow(0); }
void dec() { if (--j<0) blow(1); }

schlong item() {
     
    schlong step;
    schlong skip = 0;

    for(step=1;;step++) {
        if (skip) {
            switch (fgetc(f)) {
                case '[': skip++; break;
                case ']': skip--; break;
                case EOF: die("unexpected EOF");
                default: break;
            } continue;
        } else switch (fgetc(f)) {
            case '>': inc();   break;
            case '<': dec();   break;
            case '+': p[j]++;  break;
            case '-': p[j]--;  break;

            case '.': putchar(p[j]);  break;
            case ',': p[j]=getchar(); break;

            case '[': 
                while (p[j]) 
                    fseek(f,-item(),SEEK_CUR);
                skip++;
                break;

            case ']': case EOF:
                return step;

            default: break;
        }
    }
}

int main(int argc, char** argv) {

    if (!(p=calloc(s,sizeof(word)))) 
    return 1;

    if (argc==1) {
        die("need an input filename");
    } else { 
        if (f = fopen(argv[1],"rb")) { item(); fclose(f); }
        else die("unable to open file");
    }

    free(p);
    return 0;
}