/*-
 * Copyright (c) 2004 Matthias Schmidt <schmidtm@mathematik.uni-marburg.de>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Simple Brainfuck Interpreter -- written @ 21c3 Berlin 2004
 */

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <sys/types.h>
#include <sys/stat.h>

int
main(int argc, char **argv)
{
	int	memory[32768],
		space[32768];
	int	fd,
		len,
		buf,
		spointer,
		kl = 0,
		mpointer;

	if (argc <= 1) {
		printf("Usage: %s <brainfuck file>\n", argv[0]);
		exit(1);
	}

	/* Open brainfuck file */	
	if ((fd = open(argv[1], O_RDONLY)) < 0)
		exit(1);

	/* Read the file byte by byte */
	len = spointer = 1;
	while (len > 0) {
		len = read(fd, &buf, 1);
		space[spointer] = buf;
		spointer++;
	}

	close(fd);

	for (mpointer = 0; mpointer < 32768; mpointer++)
		memory[mpointer] = 0;

	
	len = spointer;
	spointer = mpointer = 0;
	
	for (spointer = 0; spointer < len; spointer++) {
		switch(space[spointer]) {
		/* Increment pointer value */
		case '+':
			memory[mpointer]++;
			break;
		/* Decrement pointer value */
		case '-':
			memory[mpointer]--;
			break;
		/* Increment pointer */
		case '>':
			mpointer++;
			break;
		/* Decrement pointer */
		case '<':
			mpointer--;
			break;
		/* Print current pointer value */
		case '.':
			putchar(memory[mpointer]);
			break;
		/* Read value and store in current pointer */
		case ',':
			memory[mpointer] = getchar();
			break;
		/* Start loop */
		case '[':
			if (memory[mpointer] == 0) {
				/* Find matching ] */
				spointer++;
				/* If kl == 0 and space[pointer] == ']' we found
				 * the matching brace */
				while (kl > 0 || space[spointer] != ']') {
					if (space[spointer] == '[') kl++;
					if (space[spointer] == ']') kl--;
					/* Go in right direction */
					spointer++;
				}
			}
			break;
		/* End loop */
		case ']':
			if (memory[mpointer] != 0) {
				/* Find matching [ */
				spointer--;
				while (kl > 0 || space[spointer] != '[') {
					if (space[spointer] == '[') kl--;
					if (space[spointer] == ']') kl++;
					/* Go left */
					spointer--;
				}
				spointer--;
			}
			break;
		}
	}

	putchar('\n');
	return (0);
}