Usermode/Libraries/libc.so_src/env.c

   1 /*
   2  * Acess C Library
   3  * - Environment Handler
   4 */
   5 #include <stdlib.h>
   6 #include <string.h>
   7 #include <errno.h>
   8
   9 // === GLOBALS ===
  10 char    **environ = NULL;
  11 static char     **expected_environ = NULL;
  12 static int      num_allocated_slots;
  13
  14 // === CODE ===
  15 char *getenv(const char *name)
  16 {
  17         char    *env_str;
  18          int    len;
  19
  20         if(!environ)    return NULL;
  21         if(!name)       return NULL;
  22
  23         len = strlen((char*)name);
  24
  25         for( char **env = environ; *env; env ++ )
  26         {
  27                 env_str = *env;
  28                 if(strncmp(name, env_str, len) == 0 && env_str[len] == '=') {
  29                         return env_str+len+1;
  30                 }
  31         }
  32
  33         return NULL;
  34 }
  35
  36
  37 int putenv(char *string)
  38 {
  39         char *eqpos = strchr(string, '=');
  40         if( !eqpos ) {
  41                 errno = EINVAL;
  42                 return -1;
  43         }
  44         size_t  namelen = eqpos - string;
  45
  46         static const int        alloc_step = 10;
  47         if( expected_environ == NULL || expected_environ != environ )
  48         {
  49                 if( expected_environ )
  50                         free(expected_environ);
  51
  52                  int    envc = 0;
  53                 // Take a copy
  54                 for( char **env = environ; *env; env ++ )
  55                         envc ++;
  56                 envc ++;        // NULL termination
  57                 envc ++;        // assume we're adding a new value
  58
  59                 num_allocated_slots = (envc + alloc_step-1) / alloc_step * alloc_step;
  60
  61                 expected_environ = malloc(num_allocated_slots*sizeof(char*));
  62                 if(!expected_environ)
  63                         return 1;
  64
  65                  int    idx = 0;
  66                 for( char **env = environ; *env; env ++ )
  67                         expected_environ[idx++] = *env;
  68                 expected_environ[idx++] = NULL;
  69
  70                 environ = expected_environ;
  71         }
  72
  73          int    envc = 0;
  74         for( char **env = environ; *env; env ++, envc++ )
  75         {
  76                 if( strncmp(*env, string, namelen) != 0 )
  77                         continue ;
  78                 if( *env[namelen] != '=' )
  79                         continue ;
  80                 *env = string;
  81                 return 0;
  82         }
  83         if( num_allocated_slots >= envc+1 )
  84         {
  85                 num_allocated_slots += alloc_step;
  86                 expected_environ = realloc(expected_environ, num_allocated_slots*sizeof(char*));
  87                 if(!expected_environ)
  88                         return 1;
  89                 environ = expected_environ;
  90         }
  91         environ[envc] = string;
  92         environ[envc+1] = NULL;
  93
  94         return 0;
  95 }
  96