util/envlist.c

   1 #include "qemu/osdep.h"
   2 #include "qemu/queue.h"
   3 #include "qemu/envlist.h"
   4
   5 struct envlist_entry {
   6     const char *ev_var;            /* actual env value */
   7     QLIST_ENTRY(envlist_entry) ev_link;
   8 };
   9
  10 struct envlist {
  11     QLIST_HEAD(, envlist_entry) el_entries; /* actual entries */
  12     size_t el_count;                        /* number of entries */
  13 };
  14
  15 /*
  16  * Allocates new envlist and returns pointer to it.
  17  */
  18 envlist_t *
  19 envlist_create(void)
  20 {
  21     envlist_t *envlist;
  22
  23     envlist = g_malloc(sizeof(*envlist));
  24
  25     QLIST_INIT(&envlist->el_entries);
  26     envlist->el_count = 0;
  27
  28     return (envlist);
  29 }
  30
  31 /*
  32  * Releases given envlist and its entries.
  33  */
  34 void
  35 envlist_free(envlist_t *envlist)
  36 {
  37     struct envlist_entry *entry;
  38
  39     assert(envlist != NULL);
  40
  41     while (envlist->el_entries.lh_first != NULL) {
  42         entry = envlist->el_entries.lh_first;
  43         QLIST_REMOVE(entry, ev_link);
  44
  45         g_free((char *)entry->ev_var);
  46         g_free(entry);
  47     }
  48     g_free(envlist);
  49 }
  50
  51 /*
  52  * Sets environment value to envlist in similar manner
  53  * than putenv(3).
  54  *
  55  * Returns 0 in success, errno otherwise.
  56  */
  57 int
  58 envlist_setenv(envlist_t *envlist, const char *env)
  59 {
  60     struct envlist_entry *entry = NULL;
  61     const char *eq_sign;
  62     size_t envname_len;
  63
  64     if ((envlist == NULL) || (env == NULL))
  65         return (EINVAL);
  66
  67     /* find out first equals sign in given env */
  68     if ((eq_sign = strchr(env, '=')) == NULL)
  69         return (EINVAL);
  70     envname_len = eq_sign - env + 1;
  71
  72     /*
  73      * If there already exists variable with given name
  74      * we remove and release it before allocating a whole
  75      * new entry.
  76      */
  77     for (entry = envlist->el_entries.lh_first; entry != NULL;
  78         entry = entry->ev_link.le_next) {
  79         if (strncmp(entry->ev_var, env, envname_len) == 0)
  80             break;
  81     }
  82
  83     if (entry != NULL) {
  84         QLIST_REMOVE(entry, ev_link);
  85         g_free((char *)entry->ev_var);
  86         g_free(entry);
  87     } else {
  88         envlist->el_count++;
  89     }
  90
  91     entry = g_malloc(sizeof(*entry));
  92     entry->ev_var = g_strdup(env);
  93     QLIST_INSERT_HEAD(&envlist->el_entries, entry, ev_link);
  94
  95     return (0);
  96 }
  97
  98 /*
  99  * Removes given env value from envlist in similar manner
 100  * than unsetenv(3).  Returns 0 in success, errno otherwise.
 101  */
 102 int
 103 envlist_unsetenv(envlist_t *envlist, const char *env)
 104 {
 105     struct envlist_entry *entry;
 106     size_t envname_len;
 107
 108     if ((envlist == NULL) || (env == NULL))
 109         return (EINVAL);
 110
 111     /* env is not allowed to contain '=' */
 112     if (strchr(env, '=') != NULL)
 113         return (EINVAL);
 114
 115     /*
 116      * Find out the requested entry and remove
 117      * it from the list.
 118      */
 119     envname_len = strlen(env);
 120     for (entry = envlist->el_entries.lh_first; entry != NULL;
 121         entry = entry->ev_link.le_next) {
 122         if (strncmp(entry->ev_var, env, envname_len) == 0)
 123             break;
 124     }
 125     if (entry != NULL) {
 126         QLIST_REMOVE(entry, ev_link);
 127         g_free((char *)entry->ev_var);
 128         g_free(entry);
 129
 130         envlist->el_count--;
 131     }
 132     return (0);
 133 }
 134
 135 /*
 136  * Returns given envlist as array of strings (in same form that
 137  * global variable environ is).  Caller must free returned memory
 138  * by calling g_free for each element and the array.
 139  * Returned array and given envlist are not related (no common
 140  * references).
 141  *
 142  * If caller provides count pointer, number of items in array is
 143  * stored there.
 144  */
 145 char **
 146 envlist_to_environ(const envlist_t *envlist, size_t *count)
 147 {
 148     struct envlist_entry *entry;
 149     char **env, **penv;
 150
 151     penv = env = g_new(char *, envlist->el_count + 1);
 152
 153     for (entry = envlist->el_entries.lh_first; entry != NULL;
 154         entry = entry->ev_link.le_next) {
 155         *(penv++) = g_strdup(entry->ev_var);
 156     }
 157     *penv = NULL; /* NULL terminate the list */
 158
 159     if (count != NULL)
 160         *count = envlist->el_count;
 161
 162     return (env);
 163 }