release/src/router/pptp-client/inststr.c

   1 /* inststr.c ... stolen from bdupdate.c, which stole it from perl 4.
   2  *               Theft by C. Scott Ananian <cananian@alumni.princeton.edu>
   3  *               Modified similarly to perl 5.8.3's alignment-checking code
   4 8                by Paul Howarth <paul@city-fan.org>
   5  *
   6  * $Id: inststr.c,v 1.3 2004/06/08 23:40:14 quozl Exp $
   7  */
   8
   9 #include <string.h>
  10
  11 #define PTRSIZE sizeof(void *)
  12 typedef unsigned long UL;
  13
  14 void
  15 inststr(int argc, char **argv, char **environ, char *src)
  16 {
  17     if (strlen(src) <= strlen(argv[0]))
  18     {
  19         char *ptr;
  20
  21         for (ptr = argv[0]; *ptr; *(ptr++) = '\0');
  22
  23         strcpy(argv[0], src);
  24     } else
  25     {
  26         /* Stolen from the source to perl 4.036 (assigning to $0) */
  27         /* Modified to allow for aligned array members, assuming  */
  28         /* no system has something bizarre like the argv[]        */
  29         /* interleaved with some other data. Also allow for argv  */
  30         /* array having higher numbered elements lower in memory  */
  31         /* than lower numbered elements.                          */
  32         char *ptr, *ptr2;
  33         int count;
  34         UL mask = ~(UL)(PTRSIZE == 4 ? 3 : PTRSIZE == 8 ? 7 : PTRSIZE == 16 ? 15 : 0);
  35         int aligned = (mask < ~(UL)0) && (((UL)(argv[0]) & mask) == (UL)(argv[0]));
  36         ptr = argv[0] + strlen(argv[0]);
  37         if (argv[argc - 1] >= argv[1]) {
  38             /* argv pointers in ascending memory order */
  39             for (count = 1; count < argc; count++) {
  40                 if (argv[count] == ptr + 1
  41                     ||
  42                     (aligned && argv[count] > ptr && argv[count] <= (char *)((UL)(ptr + PTRSIZE) & mask))
  43                    ) {
  44                     ptr = argv[count] + strlen(argv[count]);
  45                 }
  46             }
  47         } else
  48         {
  49             /* sometimes the argv pointers go down in memory rather than up */
  50             for (count = argc - 1; count > 0; count--) {
  51                 if (argv[count] == ptr + 1
  52                     ||
  53                     (aligned && argv[count] > ptr && argv[count] <= (char *)((UL)(ptr + PTRSIZE) & mask))
  54                    ) {
  55                     ptr = argv[count] + strlen(argv[count]);
  56                 }
  57             }
  58         }
  59         for (count = 0; environ[count]; count++) {
  60             if (environ[count] == ptr + 1
  61                 ||
  62                 (aligned && environ[count] > ptr && environ[count] <= (char *)((UL)(ptr + PTRSIZE) & mask))
  63                ) {
  64                    ptr = environ[count] + strlen(environ[count]);
  65             }
  66         }
  67         count = 0;
  68         for (ptr2 = argv[0]; ptr2 <= ptr; ptr2++) {
  69             *ptr2 = '\0';
  70             count++;
  71         }
  72         strncpy(argv[0], src, count);
  73     }
  74 }