src/libudev/libudev-list.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <stddef.h>
   5 #include <stdlib.h>
   6 #include <string.h>
   7
   8 #include "alloc-util.h"
   9 #include "libudev-list-internal.h"
  10 #include "memory-util.h"
  11
  12 /**
  13  * SECTION:libudev-list
  14  * @short_description: list operation
  15  *
  16  * Libudev list operations.
  17  */
  18
  19 /**
  20  * udev_list_entry:
  21  *
  22  * Opaque object representing one entry in a list. An entry contains
  23  * contains a name, and optionally a value.
  24  */
  25 struct udev_list_entry {
  26         struct udev_list_node node;
  27         struct udev_list *list;
  28         char *name;
  29         char *value;
  30         int num;
  31 };
  32
  33 /* the list's head points to itself if empty */
  34 static void udev_list_node_init(struct udev_list_node *list) {
  35         list->next = list;
  36         list->prev = list;
  37 }
  38
  39 static int udev_list_node_is_empty(struct udev_list_node *list) {
  40         return list->next == list;
  41 }
  42
  43 static void udev_list_node_insert_between(struct udev_list_node *new,
  44                                           struct udev_list_node *prev,
  45                                           struct udev_list_node *next) {
  46         next->prev = new;
  47         new->next = next;
  48         new->prev = prev;
  49         prev->next = new;
  50 }
  51
  52 static void udev_list_node_remove(struct udev_list_node *entry) {
  53         struct udev_list_node *prev = entry->prev;
  54         struct udev_list_node *next = entry->next;
  55
  56         next->prev = prev;
  57         prev->next = next;
  58
  59         entry->prev = NULL;
  60         entry->next = NULL;
  61 }
  62
  63 /* return list entry which embeds this node */
  64 static struct udev_list_entry *list_node_to_entry(struct udev_list_node *node) {
  65         return container_of(node, struct udev_list_entry, node);
  66 }
  67
  68 void udev_list_init(struct udev_list *list, bool unique) {
  69         memzero(list, sizeof(struct udev_list));
  70         list->unique = unique;
  71         udev_list_node_init(&list->node);
  72 }
  73
  74 /* insert entry into a list as the last element  */
  75 static void udev_list_entry_append(struct udev_list_entry *new, struct udev_list *list) {
  76         /* inserting before the list head make the node the last node in the list */
  77         udev_list_node_insert_between(&new->node, list->node.prev, &list->node);
  78         new->list = list;
  79 }
  80
  81 /* insert entry into a list, before a given existing entry */
  82 static void udev_list_entry_insert_before(struct udev_list_entry *new, struct udev_list_entry *entry) {
  83         udev_list_node_insert_between(&new->node, entry->node.prev, &entry->node);
  84         new->list = entry->list;
  85 }
  86
  87 /* binary search in sorted array */
  88 static int list_search(struct udev_list *list, const char *name) {
  89         unsigned first, last;
  90
  91         first = 0;
  92         last = list->entries_cur;
  93         while (first < last) {
  94                 unsigned i;
  95                 int cmp;
  96
  97                 i = (first + last)/2;
  98                 cmp = strcmp(name, list->entries[i]->name);
  99                 if (cmp < 0)
 100                         last = i;
 101                 else if (cmp > 0)
 102                         first = i+1;
 103                 else
 104                         return i;
 105         }
 106
 107         /* not found, return negative insertion-index+1 */
 108         return -(first+1);
 109 }
 110
 111 struct udev_list_entry *udev_list_entry_add(struct udev_list *list, const char *name, const char *value) {
 112         struct udev_list_entry *entry;
 113         int i = 0;
 114
 115         if (list->unique) {
 116                 /* lookup existing name or insertion-index */
 117                 i = list_search(list, name);
 118                 if (i >= 0) {
 119                         entry = list->entries[i];
 120
 121                         free(entry->value);
 122                         if (!value) {
 123                                 entry->value = NULL;
 124                                 return entry;
 125                         }
 126                         entry->value = strdup(value);
 127                         if (!entry->value)
 128                                 return NULL;
 129                         return entry;
 130                 }
 131         }
 132
 133         /* add new name */
 134         entry = new0(struct udev_list_entry, 1);
 135         if (!entry)
 136                 return NULL;
 137
 138         entry->name = strdup(name);
 139         if (!entry->name)
 140                 return mfree(entry);
 141
 142         if (value) {
 143                 entry->value = strdup(value);
 144                 if (!entry->value) {
 145                         free(entry->name);
 146                         return mfree(entry);
 147                 }
 148         }
 149
 150         if (list->unique) {
 151                 /* allocate or enlarge sorted array if needed */
 152                 if (list->entries_cur >= list->entries_max) {
 153                         struct udev_list_entry **entries;
 154                         unsigned add;
 155
 156                         add = list->entries_max;
 157                         if (add < 1)
 158                                 add = 64;
 159                         entries = reallocarray(list->entries, list->entries_max + add, sizeof(struct udev_list_entry *));
 160                         if (!entries) {
 161                                 free(entry->name);
 162                                 free(entry->value);
 163                                 return mfree(entry);
 164                         }
 165                         list->entries = entries;
 166                         list->entries_max += add;
 167                 }
 168
 169                 /* the negative i returned the insertion index */
 170                 i = (-i)-1;
 171
 172                 /* insert into sorted list */
 173                 if ((unsigned)i < list->entries_cur)
 174                         udev_list_entry_insert_before(entry, list->entries[i]);
 175                 else
 176                         udev_list_entry_append(entry, list);
 177
 178                 /* insert into sorted array */
 179                 memmove(&list->entries[i+1], &list->entries[i],
 180                         (list->entries_cur - i) * sizeof(struct udev_list_entry *));
 181                 list->entries[i] = entry;
 182                 list->entries_cur++;
 183         } else
 184                 udev_list_entry_append(entry, list);
 185
 186         return entry;
 187 }
 188
 189 static void udev_list_entry_delete(struct udev_list_entry *entry) {
 190         if (entry->list->entries) {
 191                 int i;
 192                 struct udev_list *list = entry->list;
 193
 194                 /* remove entry from sorted array */
 195                 i = list_search(list, entry->name);
 196                 if (i >= 0) {
 197                         memmove(&list->entries[i], &list->entries[i+1],
 198                                 ((list->entries_cur-1) - i) * sizeof(struct udev_list_entry *));
 199                         list->entries_cur--;
 200                 }
 201         }
 202
 203         udev_list_node_remove(&entry->node);
 204         free(entry->name);
 205         free(entry->value);
 206         free(entry);
 207 }
 208
 209 #define udev_list_entry_foreach_safe(entry, tmp, first) \
 210         for (entry = first, tmp = udev_list_entry_get_next(entry); \
 211              entry; \
 212              entry = tmp, tmp = udev_list_entry_get_next(tmp))
 213
 214 void udev_list_cleanup(struct udev_list *list) {
 215         struct udev_list_entry *entry_loop;
 216         struct udev_list_entry *entry_tmp;
 217
 218         list->entries = mfree(list->entries);
 219         list->entries_cur = 0;
 220         list->entries_max = 0;
 221         udev_list_entry_foreach_safe(entry_loop, entry_tmp, udev_list_get_entry(list))
 222                 udev_list_entry_delete(entry_loop);
 223 }
 224
 225 struct udev_list_entry *udev_list_get_entry(struct udev_list *list) {
 226         if (udev_list_node_is_empty(&list->node))
 227                 return NULL;
 228         return list_node_to_entry(list->node.next);
 229 }
 230
 231 /**
 232  * udev_list_entry_get_next:
 233  * @list_entry: current entry
 234  *
 235  * Get the next entry from the list.
 236  *
 237  * Returns: udev_list_entry, #NULL if no more entries are available.
 238  */
 239 _public_ struct udev_list_entry *udev_list_entry_get_next(struct udev_list_entry *list_entry) {
 240         struct udev_list_node *next;
 241
 242         if (!list_entry)
 243                 return NULL;
 244         next = list_entry->node.next;
 245         /* empty list or no more entries */
 246         if (next == &list_entry->list->node)
 247                 return NULL;
 248         return list_node_to_entry(next);
 249 }
 250
 251 /**
 252  * udev_list_entry_get_by_name:
 253  * @list_entry: current entry
 254  * @name: name string to match
 255  *
 256  * Lookup an entry in the list with a certain name.
 257  *
 258  * Returns: udev_list_entry, #NULL if no matching entry is found.
 259  */
 260 _public_ struct udev_list_entry *udev_list_entry_get_by_name(struct udev_list_entry *list_entry, const char *name) {
 261         int i;
 262
 263         if (!list_entry)
 264                 return NULL;
 265
 266         if (!list_entry->list->unique)
 267                 return NULL;
 268
 269         i = list_search(list_entry->list, name);
 270         if (i < 0)
 271                 return NULL;
 272         return list_entry->list->entries[i];
 273 }
 274
 275 /**
 276  * udev_list_entry_get_name:
 277  * @list_entry: current entry
 278  *
 279  * Get the name of a list entry.
 280  *
 281  * Returns: the name string of this entry.
 282  */
 283 _public_ const char *udev_list_entry_get_name(struct udev_list_entry *list_entry) {
 284         if (!list_entry)
 285                 return NULL;
 286         return list_entry->name;
 287 }
 288
 289 /**
 290  * udev_list_entry_get_value:
 291  * @list_entry: current entry
 292  *
 293  * Get the value of list entry.
 294  *
 295  * Returns: the value string of this entry.
 296  */
 297 _public_ const char *udev_list_entry_get_value(struct udev_list_entry *list_entry) {
 298         if (!list_entry)
 299                 return NULL;
 300         return list_entry->value;
 301 }