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                                 return EXIT_SUCCESS;
  33                         case '>':
  34                                 ++ptr;
  35                                 if(ptr > b+stacksize){
  36                                         offset = ptr-b;
  37                                         b = realloc(b, stacksize *= 2);
  38                                         ptr = b+offset;
  39                                         memset(ptr, 0, stacksize/2);
  40                                 }
  41                                 break;
  42                         case '<':
  43                                 if(ptr == b){
  44                                         fprintf(stderr, "There is no stack position -1...\n");
  45                                         return EXIT_FAILURE;
  46                                 }
  47                                 --ptr;
  48                                 break;
  49                         case '+':
  50                                 ++*ptr;
  51                                 break;
  52                         case '-':
  53                                 --*ptr;
  54                                 break;
  55                         case '.':
  56                                 putchar(*ptr);
  57                                 break;
  58                         case ',':
  59                                 *ptr = getchar();
  60                                 break;
  61                         case '[':
  62                                 if(*ptr){
  63                                         t = callstack;
  64                                         callstack = malloc(sizeof(struct nest));
  65                                         callstack->next = t;
  66                                         if((callstack->pos = ftell(in)) == -1){
  67                                                 perror("ftell");
  68                                                 return EXIT_FAILURE;
  69                                         }
  70                                 } else {
  71                                         while(fgetc(in) != ']');
  72                                 }
  73                                 break;
  74                         case ']':
  75                                 if(fseek(in, callstack->pos-1, SEEK_SET) == -1){
  76                                         perror("fseek");
  77                                         return EXIT_FAILURE;
  78                                 }
  79                                 t = callstack;
  80                                 callstack = callstack->next;
  81                                 free(t);
  82                                 break;
  83                         default:
  84                                 break;
  85                 }
  86         }
  87 }