A simple brainfuck interpreter written in C

brainfuck.c

char * brain_fuck(char * code, char * input){
    const int BUFSIZE = 30000;
    int * ptr = (int *) malloc(BUFSIZE * sizeof(int)),
       i_sz = strlen(input), c_sz = strlen(code),
       idx = -1, j = 0, o = 0;
    char cmd, * output = (char *) malloc(BUFSIZE);

    while (idx++ < c_sz){
        cmd = code[idx];
        if (cmd == '.' && *ptr > 0 && *ptr < 256) output[o++] = (char) *ptr;
        else if (cmd == '+') *ptr = ((*ptr | 0) + 1) % 256;
        else if (cmd == '-') *ptr = ((*ptr | 0) - 1), *ptr = *ptr == -1 ? 255 : *ptr;
        else if (cmd == '>') ptr++;
        else if (cmd == '<') ptr--;
        else if (cmd == ',' && j < i_sz) *ptr = input[j++];
        else if (cmd == '['){
            int open = 1, i = idx + 1;
            *ptr = (*ptr | 0);
            if (!*ptr){
                while (open && i++ < c_sz)
                    if (code[i-1] == '[') open += 1;
                    else if(code[i-1] == ']') open -= 1;
                idx = i - 1;
            }
        }
        else if (cmd == ']'){
            int open = 1, i = idx - 1;
            *ptr = (*ptr | 0);
            if (*ptr){
                while (open && i-- >= 0)
                    if (code[i+1] == '[') open -= 1;
                    else if (code[i+1] == ']') open += 1;
                idx = i + 1;
            }
        }
    }
    output[o] = '\0';
    return output;
}

brain_fuck(",[.>,]", "hello"); //=> "hello"

this looks buggy, lol