lang/cem/libcc.ansi/misc/putenv.c

   1 /*
   2  * (c) copyright 1989 by the Vrije Universiteit, Amsterdam, The Netherlands.
   3  * See the copyright notice in the ACK home directory, in the file "Copyright".
   4  */
   5 /* $Id: putenv.c,v 1.6 1994/06/24 11:45:38 ceriel Exp $ */
   6
   7 #include        <stdlib.h>
   8 #include        <string.h>
   9
  10 #define ENTRY_INC       10
  11 #define rounded(x)      (((x / ENTRY_INC) + 1) * ENTRY_INC)
  12
  13 extern const char **_penvp;
  14 extern const char **environ;    /* environ is a shadow name for _penvp */
  15
  16 int
  17 putenv(char *name)
  18 {
  19         register const char **v = _penvp;
  20         register char *r;
  21         static int size = 0;
  22         /* When size != 0, it contains the number of entries in the
  23          * table (including the final NULL pointer). This means that the
  24          * last non-null entry  is _penvp[size - 2].
  25          */
  26
  27         if (!name) return 0;
  28         if (r = strchr(name, '=')) {
  29                 register const char *p, *q;
  30
  31                 *r = '\0';
  32
  33                 if (v != NULL) {
  34                         while ((p = *v) != NULL) {
  35                                 q = name;
  36                                 while (*q && (*q++ == *p++))
  37                                         /* EMPTY */ ;
  38                                 if (*q || (*p != '=')) {
  39                                         v++;
  40                                 } else {
  41                                         /* The name was already in the
  42                                          * environment.
  43                                          */
  44                                         *r = '=';
  45                                         *v = name;
  46                                         return 0;
  47                                 }
  48                         }
  49                 }
  50                 *r = '=';
  51                 v = _penvp;
  52         }
  53
  54         if (!size) {
  55                 register const char **p;
  56                 register int i = 0;
  57
  58                 if (v)
  59                         do {
  60                                 i++;
  61                         } while (*v++);
  62                 if (!(v = malloc(rounded(i) * sizeof(char **))))
  63                         return 1;
  64                 size = i;
  65                 p = _penvp;
  66                 _penvp = v;
  67                 while (*v++ = *p++);            /* copy the environment */
  68                 v = _penvp;
  69         } else if (!(size % ENTRY_INC)) {
  70                 if (!(v = realloc(_penvp, rounded(size) * sizeof(char **))))
  71                         return 1;
  72                 _penvp = v;
  73         }
  74         v[size - 1] = name;
  75         v[size] = NULL;
  76         size++;
  77         environ = _penvp;
  78         return 0;
  79 }