bf.c

   1 #include <stdlib.h>
   2 #include <string.h>
   3 #include <stdio.h>
   4 #include <errno.h>
   5
   6 #define die(s, as...) {fprintf(stderr, s, ## as); return EXIT_FAILURE;}
   7 #define check_fail(v, s, f) if((v) == f) die("%s(): %s\n", s, strerror(errno))
   8 #define check_null(v, s) check_fail(v, s, NULL)
   9
  10 #define INITIALBUFSIZE 2
  11
  12 struct nest {
  13         long pos;
  14         struct nest *next;
  15 };
  16
  17 int main(int argc, char *argv[])
  18 {
  19         size_t offset, stacksize, depth;
  20         char *buf, *ptr;
  21         struct nest *temp, *stack;
  22         FILE *in;
  23
  24         if(argc != 2){
  25                 die("Usage: %s PROGRAM\n", argv[0]);
  26         }
  27
  28         check_null(in = fopen(argv[1], "r"), "fopen");
  29         check_null(buf = calloc(stacksize = INITIALBUFSIZE, 1), "calloc");
  30         ptr = buf;
  31
  32         while(1){
  33                 switch(fgetc(in)){
  34                         case EOF:
  35                                 free(buf);
  36                                 check_fail(fclose(in), "fclose", -1);
  37                                 return EXIT_SUCCESS;
  38                         case '>':
  39                                 if(++ptr >= buf+stacksize){
  40                                         offset = ptr-buf;
  41                                         check_null(buf = realloc(buf, stacksize *=2), "realloc");
  42                                         ptr = buf+offset;
  43                                         memset(ptr, 0, stacksize/2);
  44                                 }
  45                                 break;
  46                         case '<':
  47                                 if(ptr-- == buf){
  48                                         die("There is no stack position -1\n");
  49                                 }
  50                                 break;
  51                         case '+':
  52                                 ++*ptr;
  53                                 break;
  54                         case '-':
  55                                 --*ptr;
  56                                 break;
  57                         case '.':
  58                                 putchar(*ptr);
  59                                 break;
  60                         case ',':
  61                                 *ptr = getchar();
  62                                 break;
  63                         case '[':
  64                                 if(*ptr){
  65                                         temp = stack;
  66                                         check_null(stack = malloc(sizeof(struct nest)), "malloc");
  67                                         stack->next = temp;
  68                                         check_fail(stack->pos = ftell(in), "ftell", -1);
  69                                 } else {
  70                                         depth = 1;
  71                                         while(depth > 0){
  72                                                 switch(fgetc(in)){
  73                                                         case ']':
  74                                                                 depth--;
  75                                                                 break;
  76                                                         case '[':
  77                                                                 depth++;
  78                                                 }
  79                                         }
  80                                 }
  81                                 break;
  82                         case ']':
  83                                 check_fail(fseek(in, stack->pos-1, SEEK_SET), "fseek", -1);
  84                                 temp = stack;
  85                                 stack = stack->next;
  86                                 free(temp);
  87                 }
  88         }
  89 }