brainfuck.c

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

#define MEM_MAX 2024
#define PROG_MAX 16384
#define NAME_MAX 256

void getprog(char *prg, char fname[NAME_MAX]) {
	FILE *fp;
	fp = fopen(fname, "r");
	if (fp == NULL) {
		printf("Couldn't open file %s", fname);
		exit(1);
	}
	char c;
	int i = 0;
	while ( (c = fgetc(fp)) != EOF ) {
		if (c == '+' || c == '-' || c == '<' || c == '>' || c == '[' || c == ']' || c == '.' || c == ',') {
			*(prg+i) = c;
			i++;
		}
	}
	fclose(fp);
}

void printarr(int *arr, int len) {
	printf("\n");
	for (int i = 0; i < len; i++) {
		printf("%d, ", *(arr+i));
	}
	printf("\n");
}

void eval(char **inst, int **cell) {
	switch (**inst) {
		case '+': {
			(**cell)++;
		} break;

		case '-': {
			(**cell)--;
		} break;

		case '>': {
			(*cell)++;
		} break;

		case '<': {
			(*cell)--;
		} break;

		case '.': {
			printf("%c", **cell);
		} break;

		case ',': {
			printf(",");
		} break;

		case '[': {
			if (**cell == 0) { 
				int open = 0;
				for (int i = 1; i < PROG_MAX; i++) {
					if ( (*(*inst+i)) == '[' ) {
						open++;
					} else if ( (*(*inst+i)) == ']' ) {
						open--;
						if (open == -1) {
							(*inst) += (i);
							break;
						}
					}
				}
			}
		} break;

		case ']': {
			if (**cell != 0) {
				int closed = 0;
				for (int i = 1; i < PROG_MAX; i++) {
					if ( (*(*inst-i)) == ']' ) {
						closed++;
					} else if ( (*(*inst-i)) == '[' ) {
						closed--;
						if (closed == -1) {
							(*inst) -= (i);
							break;
						}
					}
				}
			}
		} break;

		default: break;
	}
}

int main(int argc, char *argv[]) {
	if (argc < 2) {
		printf("Please specify the file to run\n");
		printf("./brainfuck FILENAME...");
		exit(1);
	}

	int mem[MEM_MAX] = {0};
	char prog[PROG_MAX];

	if ( strcmp(argv[1], "-i") == 0) {
		memset(prog, '\0', sizeof(prog));
		strcpy(prog, argv[2]);
	} else {
		getprog(prog, argv[1]);
	}

	char *ip = prog; /* instruction pointer */
	int *mp = mem; /* memory pointer */

	for (;;) {
		eval(&ip, &mp);
		// printarr(mem, 10);
		if ( *(++ip) == '\0') break;
	}

	// printarr(mem, 10);

	return 0;
}