elf/eval.c

   1 /* You don't really want to know what this hack is for.
   2 Copyright (C) 1996 Free Software Foundation, Inc.
   3 This file is part of the GNU C Library.
   4
   5 The GNU C Library is free software; you can redistribute it and/or
   6 modify it under the terms of the GNU Library General Public License as
   7 published by the Free Software Foundation; either version 2 of the
   8 License, or (at your option) any later version.
   9
  10 The GNU C Library is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 Library General Public License for more details.
  14
  15 You should have received a copy of the GNU Library General Public
  16 License along with the GNU C Library; see the file COPYING.LIB.  If
  17 not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18 Boston, MA 02111-1307, USA.  */
  19
  20 #include <stdio.h>
  21 #include <ctype.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25 #include <dlfcn.h>
  26
  27 static void *funcall (char **stringp);
  28 static void *eval (char **stringp);
  29
  30 static void *
  31 funcall (char **stringp)
  32 {
  33   void *args[strlen (*stringp)], **ap = args;
  34   void *argcookie = &args[1];
  35
  36   do
  37     {
  38       /* Evaluate the next token.  */
  39       *ap++ = eval (stringp);
  40
  41       /* Whitespace is irrelevant.  */
  42       while (isspace (**stringp))
  43         ++*stringp;
  44
  45       /* Terminate at closing paren or end of line.  */
  46     } while (**stringp != '\0' && **stringp != ')');
  47   if (**stringp != '\0')
  48     /* Swallow closing paren.  */
  49     ++*stringp;
  50
  51   if (args[0] == NULL)
  52     {
  53       static const char unknown[] = "Unknown function\n";
  54       write (1, unknown, sizeof unknown - 1);
  55       return NULL;
  56     }
  57
  58   /* Do it to it.  */
  59   __builtin_return (__builtin_apply (args[0],
  60                                      &argcookie,
  61                                      (char *) ap - (char *) &args[1]));
  62 }
  63
  64 static void *
  65 eval (char **stringp)
  66 {
  67   void *value;
  68   char *p = *stringp, c;
  69
  70   /* Whitespace is irrelevant.  */
  71   while (isspace (*p))
  72     ++p;
  73
  74   switch (*p)
  75     {
  76     case '"':
  77       /* String constant.  */
  78       value = ++p;
  79       do
  80         if (*p == '\\')
  81           {
  82             switch (*strcpy (p, p + 1))
  83               {
  84               case 't':
  85                 *p = '\t';
  86                 break;
  87               case 'n':
  88                 *p = '\n';
  89                 break;
  90               }
  91             ++p;
  92           }
  93       while (*p != '\0' && *p++ != '"');
  94       if (p[-1] == '"')
  95         p[-1] = '\0';
  96       break;
  97
  98     case '(':
  99       *stringp = ++p;
 100       return funcall (stringp);
 101
 102     default:
 103       /* Try to parse it as a number.  */
 104       value = (void *) strtol (p, stringp, 0);
 105       if (*stringp != p)
 106         return value;
 107
 108       /* Anything else is a symbol that produces its address.  */
 109       value = p;
 110       do
 111         ++p;
 112       while (*p != '\0' && !isspace (*p) && (!ispunct (*p) || *p == '_'));
 113       c = *p;
 114       *p = '\0';
 115       value = dlsym (NULL, value);
 116       *p = c;
 117       break;
 118     }
 119
 120   *stringp = p;
 121   return value;
 122 }
 123
 124
 125 void
 126 _start (void)
 127 {
 128   char *buf = NULL;
 129   size_t bufsz = 0;
 130
 131   while (getline (&buf, &bufsz, stdin) > 0)
 132     {
 133       char *p = buf;
 134       eval (&p);
 135     }
 136
 137   exit (0);
 138 }