bf.c

   1 #include <stdlib.h>
   2 #include <string.h>
   3 #include <stdio.h>
   4
   5 struct nest {
   6         long pos;
   7         struct nest *next;
   8 };
   9
  10 int main(int argc, char *argv[])
  11 {
  12         size_t offset, stacksize;
  13         char *buf, *ptr;
  14         struct nest *temp, *stack;
  15         FILE *in;
  16
  17         if(argc != 2){
  18                 fprintf(stderr, "Usage: %s PROGRAM\n", argv[0]);
  19                 return EXIT_FAILURE;
  20         }
  21
  22         if((buf = malloc(stacksize = 1)) == NULL){
  23                 perror("malloc");
  24                 return EXIT_FAILURE;
  25         }
  26         buf[0] = 0;
  27         ptr = buf;
  28
  29         if((in = fopen(argv[1], "r")) == NULL){
  30                 perror("fopen");
  31                 return EXIT_FAILURE;
  32         }
  33
  34         while(1){
  35                 switch(fgetc(in)){
  36                         case EOF:
  37                                 free(buf);
  38                                 return EXIT_SUCCESS;
  39                         case '>':
  40                                 ++ptr;
  41                                 if(ptr >= buf+stacksize){
  42                                         offset = ptr-buf;
  43                                         if((buf = realloc(buf, stacksize *= 2)) == NULL){
  44                                                 perror("realloc");
  45                                                 return EXIT_FAILURE;
  46                                         }
  47                                         ptr = buf+offset;
  48                                         memset(ptr, 0, stacksize/2);
  49                                 }
  50                                 break;
  51                         case '<':
  52                                 if(ptr == buf){
  53                                         fprintf(stderr, "There is no stack position -1...\n");
  54                                         return EXIT_FAILURE;
  55                                 }
  56                                 --ptr;
  57                                 break;
  58                         case '+':
  59                                 ++*ptr;
  60                                 break;
  61                         case '-':
  62                                 --*ptr;
  63                                 break;
  64                         case '.':
  65                                 putchar(*ptr);
  66                                 break;
  67                         case ',':
  68                                 *ptr = getchar();
  69                                 break;
  70                         case '[':
  71                                 if(*ptr){
  72                                         temp = stack;
  73                                         if((stack = malloc(sizeof(struct nest))) == NULL){
  74                                                 perror("realloc");
  75                                                 return EXIT_FAILURE;
  76                                         }
  77                                         stack->next = temp;
  78                                         if((stack->pos = ftell(in)) == -1){
  79                                                 perror("ftell");
  80                                                 return EXIT_FAILURE;
  81                                         }
  82                                 } else {
  83                                         while(fgetc(in) != ']');
  84                                 }
  85                                 break;
  86                         case ']':
  87                                 if(fseek(in, stack->pos-1, SEEK_SET) == -1){
  88                                         perror("fseek");
  89                                         return EXIT_FAILURE;
  90                                 }
  91                                 temp = stack;
  92                                 stack = stack->next;
  93                                 free(temp);
  94                                 break;
  95                         default:
  96                                 break;
  97                 }
  98         }
  99 }