/** Transform ^(nil x) to x
*/
static pANTLR3_BASE_TREE
rulePostProcessing (pANTLR3_BASE_TREE_ADAPTOR adaptor, pANTLR3_BASE_TREE root)
{
if (root != NULL && root->isNil(root) && root->getChildCount(root) == 1)
{
root = root->getChild(root, 0);
}
return root;
}
/** If oldRoot is a nil root, just copy or move the children to newRoot.
* If not a nil root, make oldRoot a child of newRoot.
*
* old=^(nil a b c), new=r yields ^(r a b c)
* old=^(a b c), new=r yields ^(r ^(a b c))
*
* If newRoot is a nil-rooted single child tree, use the single
* child as the new root node.
*
* old=^(nil a b c), new=^(nil r) yields ^(r a b c)
* old=^(a b c), new=^(nil r) yields ^(r ^(a b c))
*
* If oldRoot was null, it's ok, just return newRoot (even if isNil).
*
* old=null, new=r yields r
* old=null, new=^(nil r) yields ^(nil r)
*
* Return newRoot. Throw an exception if newRoot is not a
* simple node or nil root with a single child node--it must be a root
* node. If newRoot is ^(nil x) return x as newRoot.
*
* Be advised that it's ok for newRoot to point at oldRoot's
* children; i.e., you don't have to copy the list. We are
* constructing these nodes so we should have this control for
* efficiency.
*/
static pANTLR3_BASE_TREE
becomeRoot (pANTLR3_BASE_TREE_ADAPTOR adaptor, pANTLR3_BASE_TREE newRootTree, pANTLR3_BASE_TREE oldRootTree)
{
/* Protect against tree rewrites if we are in some sort of error
* state, but have tried to recover. In C we can end up with a null pointer
* for a tree that was not produced.
*/
if (newRootTree == NULL)
{
return oldRootTree;
}
/* root is just the new tree as is if there is no
* current root tree.
*/
if (oldRootTree == NULL)
{
return newRootTree;
}
/* Produce ^(nil real-node)
*/
if (newRootTree->isNil(newRootTree))
{
if (newRootTree->getChildCount(newRootTree) > 1)
{
/* TODO: Handle tree exceptions
*/
fprintf(stderr, "More than one node as root! TODO: Create tree exception hndling\n");
return newRootTree;
}
/* The new root is the first child
*/
newRootTree = newRootTree->getChild(newRootTree, 0);
}
/* Add old root into new root. addChild takes care of the case where oldRoot
* is a flat list (nill rooted tree). All children of oldroot are added to
* new root.
*/
newRootTree->addChild(newRootTree, oldRootTree);
/* Always returns new root structure
*/
return newRootTree;
}
