View source for r7.1.1:Macro LFDS711 BTREE AU GET VALUE FROM ELEMENT

{{DISPLAYTITLE:macro LFDS711_BTREE_AU_GET_VALUE_FROM_ELEMENT}}
==Source File==
 └───liblfds711
     └───inc
         └───liblfds711
                 lfds711_btree_addonly_unbalanced.h

==Opaque Structures==
 struct [[r7.1.1:struct lfds711_btree_au_element|lfds711_btree_au_element]];

==Macro==
 #define LFDS711_BTREE_AU_GET_VALUE_FROM_ELEMENT( btree_au_element )

==Parameters==
''btree_au_element''
: A ''struct lfds711_btree_au_element''.  Not a pointer to it - the struct itself.

==Return Value==
Returns a void pointer, the value from the element.

==Notes==
The value in an element is set atomically by ''LFDS711_BTREE_AU_SET_VALUE_IN_ELEMENT'' and this macro performs the necessary matching read-side work to ensure that it correctly reads the set value, the upshot being that the value can be safely and correctly read at any time, on any element, inside or outside of the btree.

As with all ''liblfds'' macros, the macro operates on the structure itself, not a pointer to it.

==Example==
 #include <stdio.h>
 #include "liblfds711.h"
 
 struct test_data
 {
   int long long unsigned
     unique_id;
 
   char
     payload[64];
 
   struct lfds711_btree_au_element
     buae;
 };
 
 int key_compare_function( void const *new_key, void const *existing_key )
 {
   int
     cr = 0;
 
   int long long unsigned
     *new_key = (int long long unsigned *) new_key,
     *existing_key  = (int long long unsigned *) existing_key;
 
   if( *new_key > *existing_key )
     cr = 1;
 
   if( *new_key < *existing_key )
     cr = -1;
 
   return( cr );
 }
 
 int main()
 {
   struct lfds711_btree_au_element
     *buae;
 
   struct lfds711_btree_au_state
     baus;
 
   struct lfds711_misc_prng_state
     ps;
 
   struct test_data
     td = { 15, "Germanium-76" },
     *temp_td;
 
   lfds711_misc_library_init_valid_on_current_logical_core();
 
   lfds711_misc_prng_init( &ps );
 
   lfds711_btree_au_init_valid_on_current_logical_core( &baus, key_compare_function, LFDS711_BTREE_AU_EXISTING_KEY_FAIL, NULL );
 
   LFDS711_BTREE_AU_SET_KEY_IN_ELEMENT( td.baue, &td.unique_id );
   LFDS711_BTREE_AU_SET_VALUE_IN_ELEMENT( td.baue, &td );
   lfds711_btree_au_link( baus, &td.baue, NULL, &ps );
 
   lfds711_btree_au_get_by_position( &baus, &baue, LFDS711_BTREE_AU_ROOT );
 
   temp_td = LFDS711_BTREE_AU_GET_VALUE_FROM_ELEMENT( *baue );
 
   printf( "payload in element is \"%s\"\n", temp_td->payload );
 
   lfds711_btree_au_cleanup( &baus );
 
   lfds711_misc_library_cleanup();
 
   return( EXIT_SUCCESS );
 }

==See Also==
* [[r7.1.1:Binary Tree (add-only, unbalanced)|Binary Tree (add-only, unbalanced)]]