Added recursive free of nodes

exercises/02/vslc/src/tree.c

@@ -0,0 +1,96 @@
+#include <vslc.h>
+
+static void node_print ( node_t *root, int nesting );
+static void node_finalize ( node_t *discard );
+static void destroy_subtree ( node_t *discard );
+
+
+/* External interface */
+void
+destroy_syntax_tree ( void )
+{
+    destroy_subtree ( root );
+}
+
+
+void
+print_syntax_tree ( void )
+{
+    node_print ( root, 0 );
+}
+
+
+void
+node_init (node_t *nd, node_index_t type, void *data, uint64_t n_children, ...)
+{
+    // Copy the type
+    nd->type = type;
+    // Copy n_children
+    nd->n_children = n_children;
+
+    /* 
+    The memory for this data needs to be 
+    allocated somewhere not here, since this 
+    function does not know the type.
+    */
+    nd->data = data;
+
+    // Prepeare the VA list
+    va_list list_children;
+    va_start(list_children, n_children);
+
+    // Create memory region for the children pointers
+    nd->children = malloc(n_children * sizeof(node_t*));
+
+    // Populate the memory with pointers to children
+    for (int i = 0; i < n_children; i++)
+        nd->children[i] = va_arg(list_children, node_t*);
+}
+
+
+static void
+node_print ( node_t *root, int nesting )
+{
+    if ( root != NULL )
+    {
+        printf ( "%*c%s", nesting, ' ', node_string[root->type] );
+        if ( root->type == IDENTIFIER_DATA ||
+             root->type == STRING_DATA ||
+             root->type == EXPRESSION ) 
+            printf ( "(%s)", (char *) root->data );
+        else if ( root->type == NUMBER_DATA )
+            printf ( "(%ld)", *((int64_t *)root->data) );
+        putchar ( '\n' );
+        for ( int64_t i=0; i<root->n_children; i++ )
+            node_print ( root->children[i], nesting+1 );
+    }
+    else
+        printf ( "%*c%p\n", nesting, ' ', root );
+}
+
+// The discard should have zero children here. If not -> MEMORY LEAK
+static void
+node_finalize ( node_t *discard )
+{
+    // Free the data and the children lists.
+    free(discard->data);
+    free(discard->children);
+    free(discard);
+}
+
+
+static void
+destroy_subtree ( node_t *discard )
+{
+    // Don't do anything if discard is nullptr
+    if (discard == NULL)
+        return;
+
+    // This will not run if n_children is zero
+    // If non-zero, destroy all child recursivly
+    while (discard->n_children--)
+        destroy_subtree(discard->children[discard->n_children]);
+    
+    // Finally, destroy yourself
+    node_finalize(discard);
+}