/** Bind this frame to a tree node. Called with exclusive latch held. */
void bind(Node node, int nodePos) {
mNode = node;
mNodePos = nodePos;
TreeCursorFrame last = node.mLastCursorFrame;
if (last != null) {
mPrevCousin = last;
last.mNextCousin = this;
}
node.mLastCursorFrame = this;
}
/** Unbind this frame from a tree node. Called with exclusive latch held. */
void unbind() {
TreeCursorFrame prev = mPrevCousin;
TreeCursorFrame next = mNextCousin;
if (prev != null) {
prev.mNextCousin = next;
mPrevCousin = null;
}
if (next != null) {
next.mPrevCousin = prev;
mNextCousin = null;
} else {
mNode.mLastCursorFrame = prev;
}
}
/**
* Copy this frame and all parent frames.
*
* @param dest new frame instance to receive copy
*/
void copyInto(TreeCursorFrame dest) {
Node node = acquireExclusive();
TreeCursorFrame parent = mParentFrame;
if (parent != null) {
node.releaseExclusive();
TreeCursorFrame parentCopy = new TreeCursorFrame();
while (true) {
// Need to check if parent is null, when looping back.
if (parent != null) {
parent.copyInto(parentCopy);
}
// Parent can change when tree height is concurrently changing.
node = acquireExclusive();
final TreeCursorFrame actualParent = mParentFrame;
if (actualParent == parent) {
// Parent frame hasn't changed, so use the copy.
if (parent != null) {
dest.mParentFrame = parentCopy;
}
break;
}
// Get rid of the stale copy and do over, which should be rare.
node.releaseExclusive();
popAll(parentCopy);
parent = actualParent;
}
}
dest.mNotFoundKey = mNotFoundKey;
dest.bind(node, mNodePos);
node.releaseExclusive();
}
/** Pop given non-null frame and all parent frames. */
static void popAll(TreeCursorFrame frame) {
outer:
do {
Node node = frame.mNode;
while (true) {
if (node == null) {
// Frame was not bound properly, suggesting that cursor is
// being cleaned up in response to an exception. Frame
// cannot be latched, so just go to the parent.
frame = frame.mParentFrame;
continue outer;
}
node.acquireExclusive();
Node actualNode = frame.mNode;
if (actualNode == node) {
frame = frame.pop();
node.releaseExclusive();
continue outer;
}
node.releaseExclusive();
node = actualNode;
}
} while (frame != null);
}