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 = 1;
  13         char *b = malloc(stacksize);
  14         b[0] = 0;
  15         char *ptr = b;
  16         struct nest *t, *callstack = NULL;
  17         FILE *in;
  18
  19         if(argc != 2){
  20                 fprintf(stderr, "Usage: %s PROGRAM\n", argv[0]);
  21                 return EXIT_FAILURE;
  22         }
  23
  24         if((in = fopen(argv[1], "r")) == NULL){
  25                 perror("fopen");
  26                 return EXIT_FAILURE;
  27         }
  28
  29         while(1){
  30                 switch(fgetc(in)){
  31                         case EOF:
  32                                 free(b);
  33                                 return EXIT_SUCCESS;
  34                         case '>':
  35                                 ++ptr;
  36                                 if(ptr >= b+stacksize){
  37                                         offset = ptr-b;
  38                                         b = realloc(b, stacksize *= 2);
  39                                         ptr = b+offset;
  40                                         memset(ptr, 0, stacksize/2);
  41                                 }
  42                                 break;
  43                         case '<':
  44                                 if(ptr == b){
  45                                         fprintf(stderr, "There is no stack position -1...\n");
  46                                         return EXIT_FAILURE;
  47                                 }
  48                                 --ptr;
  49                                 break;
  50                         case '+':
  51                                 ++*ptr;
  52                                 break;
  53                         case '-':
  54                                 --*ptr;
  55                                 break;
  56                         case '.':
  57                                 putchar(*ptr);
  58                                 break;
  59                         case ',':
  60                                 *ptr = getchar();
  61                                 break;
  62                         case '[':
  63                                 if(*ptr){
  64                                         t = callstack;
  65                                         callstack = malloc(sizeof(struct nest));
  66                                         callstack->next = t;
  67                                         if((callstack->pos = ftell(in)) == -1){
  68                                                 perror("ftell");
  69                                                 return EXIT_FAILURE;
  70                                         }
  71                                 } else {
  72                                         while(fgetc(in) != ']');
  73                                 }
  74                                 break;
  75                         case ']':
  76                                 if(fseek(in, callstack->pos-1, SEEK_SET) == -1){
  77                                         perror("fseek");
  78                                         return EXIT_FAILURE;
  79                                 }
  80                                 t = callstack;
  81                                 callstack = callstack->next;
  82                                 free(t);
  83                                 break;
  84                         default:
  85                                 break;
  86                 }
  87         }
  88 }