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
48                by Paul Howarth <paul@city-fan.org>
5 *
6 * $Id: inststr.c,v 1.1.1.1 2008/10/15 03:30:51 james26_jang Exp $
7 */
8
9#include <string.h>
10
11#define PTRSIZE sizeof(void *)
12typedef unsigned long UL;
13
14void
15inststr(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}
75