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* move traverse into CPS * add iterator * add ascending * fix iter.valid * fix test * gofmt * simplify logicl, add comments * rm using iterator inside iavl * add detailed comments * add comments per review * modify to closure independent * apply review, add docs, separate iterator.go * fix lint * fix fix lint * add more docs Co-authored-by: Marko <marbar3778@yahoo.com>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,228 @@ | ||
| package iavl | ||
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| // NOTE: This file favors int64 as opposed to int for size/counts. | ||
| // The Tree on the other hand favors int. This is intentional. | ||
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| import ( | ||
| "bytes" | ||
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| dbm "github.com/tendermint/tm-db" | ||
| ) | ||
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| type traversal struct { | ||
| tree *ImmutableTree | ||
| start, end []byte // iteration domain | ||
| ascending bool // ascending traversal | ||
| inclusive bool // end key inclusiveness | ||
| post bool // postorder traversal | ||
| delayedNodes *delayedNodes // delayed nodes to be traversed | ||
| } | ||
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| func (node *Node) newTraversal(tree *ImmutableTree, start, end []byte, ascending bool, inclusive bool, post bool) *traversal { | ||
| return &traversal{ | ||
| tree: tree, | ||
| start: start, | ||
| end: end, | ||
| ascending: ascending, | ||
| inclusive: inclusive, | ||
| post: post, | ||
| delayedNodes: &delayedNodes{{node, true}}, // set initial traverse to the node | ||
| } | ||
| } | ||
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| // delayedNode represents the delayed iteration on the nodes. | ||
| // When delayed is set to true, the delayedNode should be expanded, and their | ||
| // children should be traversed. When delayed is set to false, the delayedNode is | ||
| // already have expanded, and it could be immediately returned. | ||
| type delayedNode struct { | ||
| node *Node | ||
| delayed bool | ||
| } | ||
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| type delayedNodes []delayedNode | ||
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| func (nodes *delayedNodes) pop() (*Node, bool) { | ||
| node := (*nodes)[len(*nodes)-1] | ||
| *nodes = (*nodes)[:len(*nodes)-1] | ||
| return node.node, node.delayed | ||
| } | ||
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| func (nodes *delayedNodes) push(node *Node, delayed bool) { | ||
| *nodes = append(*nodes, delayedNode{node, delayed}) | ||
| } | ||
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| func (nodes *delayedNodes) length() int { | ||
| return len(*nodes) | ||
| } | ||
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| // `traversal` returns the delayed execution of recursive traversal on a tree. | ||
| // | ||
| // `traversal` will traverse the tree in a depth-first manner. To handle locating | ||
| // the next element, and to handle unwinding, the traversal maintains its future | ||
| // iteration under `delayedNodes`. At each call of `next()`, it will retrieve the | ||
| // next element from the `delayedNodes` and acts accordingly. The `next()` itself | ||
| // defines how to unwind the delayed nodes stack. The caller can either call the | ||
| // next traversal to proceed, or simply discard the `traversal` struct to stop iteration. | ||
| // | ||
| // At the each step of `next`, the `delayedNodes` can have one of the three states: | ||
| // 1. It has length of 0, meaning that their is no more traversable nodes. | ||
| // 2. It has length of 1, meaning that the traverse is being started from the initial node. | ||
| // 3. It has length of 2>=, meaning that there are delayed nodes to be traversed. | ||
| // | ||
| // When the `delayedNodes` are not empty, `next` retrieves the first `delayedNode` and initially check: | ||
| // 1. If it is not an delayed node (node.delayed == false) it immediately returns it. | ||
| // | ||
| // A. If the `node` is a branch node: | ||
| // 1. If the traversal is postorder, then append the current node to the t.delayedNodes, | ||
| // with `delayed` set to false. This makes the current node returned *after* all the children | ||
| // are traversed, without being expanded. | ||
| // 2. Append the traversable children nodes into the `delayedNodes`, with `delayed` set to true. This | ||
| // makes the children nodes to be traversed, and expanded with their respective children. | ||
| // 3. If the traversal is preorder, (with the children to be traversed already pushed to the | ||
| // `delayedNodes`), returns the current node. | ||
| // 4. Call `traversal.next()` to further traverse through the `delayedNodes`. | ||
| // | ||
| // B. If the `node` is a leaf node, it will be returned without expand, by the following process: | ||
| // 1. If the traversal is postorder, the current node will be append to the `delayedNodes` with `delayed` | ||
| // set to false, and immediately returned at the subsequent call of `traversal.next()` at the last line. | ||
| // 2. If the traversal is preorder, the current node will be returned. | ||
| func (t *traversal) next() *Node { | ||
| // End of traversal. | ||
| if t.delayedNodes.length() == 0 { | ||
| return nil | ||
| } | ||
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| node, delayed := t.delayedNodes.pop() | ||
|
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| // Already expanded, immediately return. | ||
| if !delayed || node == nil { | ||
| return node | ||
| } | ||
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| afterStart := t.start == nil || bytes.Compare(t.start, node.key) < 0 | ||
| startOrAfter := afterStart || bytes.Equal(t.start, node.key) | ||
| beforeEnd := t.end == nil || bytes.Compare(node.key, t.end) < 0 | ||
| if t.inclusive { | ||
| beforeEnd = beforeEnd || bytes.Equal(node.key, t.end) | ||
| } | ||
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| // case of postorder. A-1 and B-1 | ||
| // Recursively process left sub-tree, then right-subtree, then node itself. | ||
| if t.post && (!node.isLeaf() || (startOrAfter && beforeEnd)) { | ||
| t.delayedNodes.push(node, false) | ||
| } | ||
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| // case of branch node, traversing children. A-2. | ||
| if !node.isLeaf() { | ||
| // if node is a branch node and the order is ascending, | ||
| // We traverse through the left subtree, then the right subtree. | ||
| if t.ascending { | ||
| if beforeEnd { | ||
| // push the delayed traversal for the right nodes, | ||
| t.delayedNodes.push(node.getRightNode(t.tree), true) | ||
| } | ||
| if afterStart { | ||
| // push the delayed traversal for the left nodes, | ||
| t.delayedNodes.push(node.getLeftNode(t.tree), true) | ||
| } | ||
| } else { | ||
| // if node is a branch node and the order is not ascending | ||
| // We traverse through the right subtree, then the left subtree. | ||
| if afterStart { | ||
| // push the delayed traversal for the left nodes, | ||
| t.delayedNodes.push(node.getLeftNode(t.tree), true) | ||
| } | ||
| if beforeEnd { | ||
| // push the delayed traversal for the right nodes, | ||
| t.delayedNodes.push(node.getRightNode(t.tree), true) | ||
| } | ||
| } | ||
| } | ||
|
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| // case of preorder traversal. A-3 and B-2. | ||
| // Process root then (recursively) processing left child, then process right child | ||
| if !t.post && (!node.isLeaf() || (startOrAfter && beforeEnd)) { | ||
| return node | ||
| } | ||
|
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| // Keep traversing and expanding the remaning delayed nodes. A-4. | ||
| return t.next() | ||
| } | ||
|
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| // Iterator is a dbm.Iterator for ImmutableTree | ||
| type Iterator struct { | ||
| start, end []byte | ||
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| key, value []byte | ||
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| valid bool | ||
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| t *traversal | ||
| } | ||
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| func (t *ImmutableTree) Iterator(start, end []byte, ascending bool) *Iterator { | ||
| iter := &Iterator{ | ||
| start: start, | ||
| end: end, | ||
| valid: true, | ||
| t: t.root.newTraversal(t, start, end, ascending, false, false), | ||
| } | ||
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| iter.Next() | ||
| return iter | ||
| } | ||
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| var _ dbm.Iterator = &Iterator{} | ||
|
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| // Domain implements dbm.Iterator. | ||
| func (iter *Iterator) Domain() ([]byte, []byte) { | ||
| return iter.start, iter.end | ||
| } | ||
|
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| // Valid implements dbm.Iterator. | ||
| func (iter *Iterator) Valid() bool { | ||
| return iter.valid | ||
| } | ||
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| // Key implements dbm.Iterator | ||
| func (iter *Iterator) Key() []byte { | ||
| return iter.key | ||
| } | ||
|
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| // Value implements dbm.Iterator | ||
| func (iter *Iterator) Value() []byte { | ||
| return iter.value | ||
| } | ||
|
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| // Next implements dbm.Iterator | ||
| func (iter *Iterator) Next() { | ||
| if iter.t == nil { | ||
| return | ||
| } | ||
|
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| node := iter.t.next() | ||
| if node == nil { | ||
| iter.t = nil | ||
| iter.valid = false | ||
| return | ||
| } | ||
|
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| if node.height == 0 { | ||
| iter.key, iter.value = node.key, node.value | ||
| return | ||
| } | ||
|
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| iter.Next() | ||
| } | ||
|
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| // Close implements dbm.Iterator | ||
| func (iter *Iterator) Close() error { | ||
| iter.t = nil | ||
| iter.valid = false | ||
| return nil | ||
| } | ||
|
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| // Error implements dbm.Iterator | ||
| func (iter *Iterator) Error() error { | ||
| return nil | ||
| } |
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