brainfuck.c

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

#define MEM_SIZE 30000

char mem[MEM_SIZE] = {0};
char *memp = mem;

void bf_eval(char *code, int len, FILE *in, FILE *out)
{
    int ip = 0;

    while (ip < len) {
        switch (code[ip]) {
            case '+':
                ++*memp;
                break;

            case '-':
                --*memp;
                break;

            case '>':
                if (memp == (mem+MEM_SIZE)) {
                    printf("err: mem pointer reached upper limit\n");
                    return;
                }

                memp++;
                break;

            case '<':
                if (memp == mem) {
                    printf("err: mem pointer reached lower limit\n");
                    return;
                }

                memp--;
                break;

            case '.':
                putc(*(int *)memp, out);
                break;

            case ',':
                *memp = getc(in);
                break;

            case '[':
                if (*memp == 0) {
                    int depth = 1;
                    while (depth != 0) {
                        ip++;
                        if (code[ip] == '[') {
                            depth++;
                        } else if (code[ip] == ']') {
                            depth--;
                        }
                    }
                }
                break;

            case ']':
                if (*memp != 0) {
                    int depth = 1;
                    while (depth != 0) {
                        ip--;
                        if (code[ip] == ']') {
                            depth++;
                        } else if (code[ip] == '[') {
                            depth--;
                        }
                    }
                }
                break;

        }

        ip++;
    }
}

char *tests[] = {
    // prints "Brainfuck in C!\n"
    "++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>+++++"
    "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++"
    "++++++++++++++++++++++++++++++++++++.>+++++++++++++++++++++++++++++++++++"
    "++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>+++++++++"
    "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++"
    "+++++++++++++++++++++++.>++++++++++++++++++++++++++++++++++++++++++++++++"
    "++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>+++++++++"
    "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++"
    "++++++++++++++++++++.>+++++++++++++++++++++++++++++++++++++++++++++++++++"
    "++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>+++++"
    "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++"
    "+++++++++++++++++++++.>++++++++++++++++++++++++++++++++++++++++++++++++++"
    "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>++++++++++++++"
    "++++++++++++++++++.>+++++++++++++++++++++++++++++++++++++++++++++++++++++"
    "++++++++++++++++++++++++++++++++++++++++++++++++++++.>+++++++++++++++++++"
    "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++"
    "++++++++++++++++++.>++++++++++++++++++++++++++++++++.>+++++++++++++++++++"
    "++++++++++++++++++++++++++++++++++++++++++++++++.>+++++++++++++++++++++++"
    "++++++++++.>++++++++++.",

    // prints "Hello World!\n"
    "++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>."
    "<-.<.+++.------.--------.>>+.>++.",

    // prints Sierpinski triangle
    "                                >"
    "                               + +"
    "                              +   +"
    "                             [ < + +"
    "                            +       +"
    "                           + +     + +"
    "                          >   -   ]   >"
    "                         + + + + + + + +"
    "                        [               >"
    "                       + +             + +"
    "                      <   -           ]   >"
    "                     > + + >         > > + >"
    "                    >       >       +       <"
    "                   < <     < <     < <     < <"
    "                  <   [   -   [   -   >   +   <"
    "                 ] > [ - < + > > > . < < ] > > >"
    "                [                               ["
    "               - >                             + +"
    "              +   +                           +   +"
    "             + + [ >                         + + + +"
    "            <       -                       ]       >"
    "           . <     < [                     - >     + <"
    "          ]   +   >   [                   -   >   +   +"
    "         + + + + + + + +                 < < + > ] > . ["
    "        -               ]               >               ]"
    "       ] +             < <             < [             - ["
    "      -   >           +   <           ]   +           >   ["
    "     - < + >         > > - [         - > + <         ] + + >"
    "    [       -       <       -       >       ]       <       <"
    "   < ]     < <     < <     ] +     + +     + +     + +     + +"
    "  +   .   +   +   +   .   [   -   ]   <   ]   +   +   +   +   +"
    " * * * * * M a d e * B y : * N Y Y R I K K I * 2 0 0 2 * * * * *",
};

int main(int argc, char *argv[])
{
    int len = sizeof(tests)/sizeof(char *);

    for (int i = 0; i < len; i++) {
        // reset memory pointer and memory
        memp = mem;
        memset(mem, 0, MEM_SIZE);
        // evaluate program
        bf_eval(tests[i], strlen(tests[i]), stdin, stdout);
    }

    return 0;
}