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Added NodeIterator and Stream support
Improvement: added the NodeIterator class, to efficiently traverse a node tree using the Iterator interface. And added Stream Element#stream() and Node#nodeStream() methods, to enable fluent composable stream pipelines of node traversals. NodeIterator only hits nodes once (vs head and tail for NodeTraversor), is restartable, supports modifications of the node it just emitted (e.g. replace, remove), supports type filtering, and emits in document order. Refactored most head-only uses of NodeTraversor to use the NodeIterator or a Stream backed by it.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,123 @@ | ||
| package org.jsoup.nodes; | ||
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| import org.jsoup.helper.Validate; | ||
| import org.jspecify.annotations.Nullable; | ||
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| import java.util.Iterator; | ||
| import java.util.NoSuchElementException; | ||
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| /** | ||
| Iterate through a Node and its tree of descendants, in document order, and returns nodes of the specified type. This | ||
| iterator supports structural changes to the tree during the traversal, such as {@link Node#remove()}, | ||
| {@link Node#replaceWith(Node)}, {@link Node#wrap(String)}, etc. | ||
| <p>See also the {@link org.jsoup.select.NodeTraversor NodeTraversor} if {@code head} and {@code tail} callbacks are | ||
| desired for each node.</p> | ||
| */ | ||
| public class NodeIterator<T extends Node> implements Iterator<T> { | ||
| private Node root; // root / starting node | ||
| private @Nullable T next; // the next node to return | ||
| private Node current; // the current (last emitted) node | ||
| private Node previous; // the previously emitted node; used to recover from structural changes | ||
| private @Nullable Node currentParent; // the current node's parent; used to detect structural changes | ||
| private final Class<T> type; // the desired node class type | ||
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| /** | ||
| Create a NoteIterator that will iterate the supplied node, and all of its descendants. The returned {@link #next} | ||
| type will be filtered to the input type. | ||
| * @param start initial node | ||
| * @param type node type to filter for | ||
| */ | ||
| public NodeIterator(Node start, Class<T> type) { | ||
| Validate.notNull(start); | ||
| Validate.notNull(type); | ||
| this.type = type; | ||
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| restart(start); | ||
| } | ||
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| /** | ||
| Create a NoteIterator that will iterate the supplied node, and all of its descendants. All node types will be | ||
| returned. | ||
| * @param start initial node | ||
| */ | ||
| public static NodeIterator<Node> from(Node start) { | ||
| return new NodeIterator<>(start, Node.class); | ||
| } | ||
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| /** | ||
| Restart this Iterator from the specified start node. Will act as if it were newly constructed. Useful for e.g. to | ||
| save some GC if the iterator is used in a tight loop. | ||
| * @param start the new start node. | ||
| */ | ||
| public void restart(Node start) { | ||
| if (type.isInstance(start)) | ||
| //noinspection unchecked | ||
| next = (T) start; // first next() will be the start node | ||
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| root = previous = current = start; | ||
| currentParent = current.parent(); | ||
| } | ||
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| @Override public boolean hasNext() { | ||
| maybeFindNext(); | ||
| return next != null; | ||
| } | ||
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| @Override public T next() { | ||
| maybeFindNext(); | ||
| if (next == null) throw new NoSuchElementException(); | ||
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| T result = next; | ||
| previous = current; | ||
| current = next; | ||
| currentParent = current.parent(); | ||
| next = null; | ||
| return result; | ||
| } | ||
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| /** | ||
| If next is not null, looks for and sets next. If next is null after this, we have reached the end. | ||
| */ | ||
| private void maybeFindNext() { | ||
| if (next != null) return; | ||
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| // change detected (removed or replaced), redo from previous | ||
| if (currentParent != null && !current.hasParent()) | ||
| current = previous; | ||
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| next = findNextNode(); | ||
| } | ||
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| private @Nullable T findNextNode() { | ||
| Node node = current; | ||
| while (true) { | ||
| if (node.childNodeSize() > 0) | ||
| node = node.childNode(0); // descend children | ||
| else if (root.equals(node)) | ||
| node = null; // complete when all children of root are fully visited | ||
| else if (node.nextSibling() != null) | ||
| node = node.nextSibling(); // in a descendant with no more children; traverse | ||
| else { | ||
| while (true) { | ||
| node = node.parent(); // pop out of descendants | ||
| if (node == null || root.equals(node)) | ||
| return null; // got back to root; complete | ||
| if (node.nextSibling() != null) { | ||
| node = node.nextSibling(); // traverse | ||
| break; | ||
| } | ||
| } | ||
| } | ||
| if (node == null) | ||
| return null; // reached the end | ||
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| if (type.isInstance(node)) | ||
| //noinspection unchecked | ||
| return (T) node; | ||
| } | ||
| } | ||
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| @Override public void remove() { | ||
| current.remove(); | ||
| } | ||
| } |
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