elf/eval.c

   1 #include <stdio.h>
   2 #include <ctype.h>
   3 #include <stdlib.h>
   4 #include <dlfcn.h>
   5
   6 static void *funcall (char **stringp);
   7 static void *eval (char **stringp);
   8
   9 static void *
  10 funcall (char **stringp)
  11 {
  12   void *args[strlen (*stringp)], **ap = args;
  13   void *argcookie = &args[1];
  14
  15   do
  16     {
  17       /* Evaluate the next token.  */
  18       *ap++ = eval (stringp);
  19
  20       /* Whitespace is irrelevant.  */
  21       while (isspace (**stringp))
  22         ++*stringp;
  23
  24       /* Terminate at closing paren or end of line.  */
  25     } while (**stringp != '\0' && **stringp != ')');
  26   if (**stringp != '\0')
  27     /* Swallow closing paren.  */
  28     ++*stringp;
  29
  30   /* Do it to it.  */
  31   __builtin_return (__builtin_apply (args[0],
  32                                      &argcookie,
  33                                      (char *) ap - (char *) &args[1]));
  34 }
  35
  36 static void *
  37 eval (char **stringp)
  38 {
  39   void *value;
  40   char *p = *stringp, c;
  41
  42   /* Whitespace is irrelevant.  */
  43   while (isspace (*p))
  44     ++p;
  45
  46   switch (*p)
  47     {
  48     case '"':
  49       /* String constant.  */
  50       value = ++p;
  51       do
  52         if (*p == '\\')
  53           {
  54             switch (*strcpy (p, p + 1))
  55               {
  56               case 't':
  57                 *p = '\t';
  58                 break;
  59               case 'n':
  60                 *p = '\n';
  61                 break;
  62               }
  63             ++p;
  64           }
  65       while (*p != '\0' && *p++ != '"');
  66       if (p[-1] == '"')
  67         p[-1] = '\0';
  68       break;
  69
  70     case '(':
  71       *stringp = ++p;
  72       return funcall (stringp);
  73
  74     default:
  75       /* Try to parse it as a number.  */
  76       value = (void *) strtol (p, stringp, 0);
  77       if (*stringp != p)
  78         return value;
  79
  80       /* Anything else is a symbol that produces its address.  */
  81       value = p;
  82       do
  83         ++p;
  84       while (*p != '\0' && !isspace (*p) && !ispunct (*p));
  85       c = *p;
  86       *p = '\0';
  87       value = dlsym (NULL, value);
  88       *p = c;
  89       break;
  90     }
  91
  92   *stringp = p;
  93   return value;
  94 }
  95
  96
  97 void
  98 _start (void)
  99 {
 100   char *buf = NULL;
 101   size_t bufsz = 0;
 102
 103   while (getline (&buf, &bufsz, stdin) > 0)
 104     {
 105       char *p = buf;
 106       eval (&p);
 107     }
 108
 109   exit (0);
 110 }