How to search for an element on a Gtree (glib)?

Question

So I have a Gtree which every node is a struct:

typedef struct user {
    int id;
    char username[256]; 
    int post_count; 
    char short_bio[16384]; 
    int reputation;
}*USER;

And a GTree:

GTree* users;

What I want to do now is, once I have an ID I want to search on my Gtree* users to see if there is an User with the same ID as that I pass, if there is I want to increment the post_count variable and stop searching.

Example:

I pass to the function id=3 and it searches on the GTree for 
a User with id=3 and increments 1 on post_count, using GLIB; 

void increment (GTree* a,int id);

Answer 1

According to the documentation it looks like g_tree_lookup is a function which you need. It would find a value according to the passed gconstpointer key:

g_tree_lookup ()
gpointer
g_tree_lookup (GTree *tree,
               gconstpointer key);

Gets the value corresponding to the given key. Since a GTree is automatically balanced as key/value pairs are added, key lookup is O(log n) (where n is the number of key/value pairs in the tree).

The code would be similar to:

  void increment (GTree* a, int id)
  {
      gpointer ptr = g_tree_lookup (a,  &id);   // search the tree and find the value

      struct user *u = (struct user *) ptr; // cast the `gpointer ` to your pointer to your value 

      if(u){
          u->post_count++;  // increment the post_count
      }
  }

Let me know if this works for you.