sort config file variables

libretro-common/file/config_file.c

@@ -68,6 +68,84 @@ struct config_include_list
 static config_file_t *config_file_new_internal(
       const char *path, unsigned depth);
 
+static int config_sort_compare_func(struct config_entry_list *a,
+      struct config_entry_list *b)
+{
+   const char *a_key = a ? a->key : NULL;
+   const char *b_key = b ? b->key : NULL;
+
+   if (!a_key || !b_key)
+      return 0;
+
+   return strcasecmp(a_key, b_key);
+}
+
+/* https://stackoverflow.com/questions/7685/merge-sort-a-linked-list */
+static struct config_entry_list* merge_sort_linked_list(struct config_entry_list *list, int (*compare)(struct config_entry_list *one,struct config_entry_list *two))
+{
+   struct config_entry_list
+         *right  = list,
+         *temp   = list,
+         *last   = list,
+         *result = 0,
+         *next   = 0,
+         *tail   = 0;
+
+   /* Trivial case. */
+   if (!list || !list->next)
+      return list;
+
+   /* Find halfway through the list (by running two pointers, one at twice the speed of the other). */
+   while (temp && temp->next)
+   {
+      last = right;
+      right = right->next;
+      temp = temp->next->next;
+   }
+
+   /* Break the list in two. (prev pointers are broken here, but we fix later) */
+   last->next = 0;
+
+   /* Recurse on the two smaller lists: */
+   list = merge_sort_linked_list(list, compare);
+   right = merge_sort_linked_list(right, compare);
+
+   /* Merge: */
+   while (list || right)
+   {
+      /* Take from empty lists, or compare: */
+      if (!right)
+      {
+         next = list;
+         list = list->next;
+      }
+      else if (!list)
+      {
+         next = right;
+         right = right->next;
+      }
+      else if (compare(list, right) < 0)
+      {
+         next = list;
+         list = list->next;
+      }
+      else
+      {
+         next = right;
+         right = right->next;
+      }
+
+      if (!result)
+         result=next;
+      else
+         tail->next=next;
+
+      tail = next;
+   }
+
+   return result;
+}
+
 static char *strip_comment(char *str)
 {
    /* Remove everything after comment.
@@ -913,6 +991,8 @@ void config_file_dump(config_file_t *conf, FILE *file)
 
    list = (struct config_entry_list*)conf->entries;
 
+   merge_sort_linked_list(list, config_sort_compare_func);
+
    while (list)
    {
       if (!list->readonly && list->key)