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444 lines
11 KiB
444 lines
11 KiB
package merkle
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import (
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"crypto/sha256"
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)
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const HASH_BYTE_SIZE int = 4+32
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// Immutable AVL Tree (wraps the Node root)
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type IAVLTree struct {
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root *IAVLNode
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}
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func NewIAVLTree() *IAVLTree {
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return &IAVLTree{}
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}
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func (self *IAVLTree) Root() Node {
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return self.root
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}
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func (self *IAVLTree) Size() uint64 {
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return self.root.Size()
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}
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func (self *IAVLTree) Height() uint8 {
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return self.root.Height()
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}
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func (self *IAVLTree) Has(key Key) bool {
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return self.root.Has(nil, key)
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}
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func (self *IAVLTree) Put(key Key, value Value) {
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self.root, _ = self.root.Put(nil, key, value)
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}
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func (self *IAVLTree) Hash() (ByteSlice, uint64) {
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return self.root.Hash()
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}
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func (self *IAVLTree) Get(key Key) (value Value) {
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return self.root.Get(nil, key)
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}
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func (self *IAVLTree) Remove(key Key) (value Value, err error) {
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new_root, value, err := self.root.Remove(nil, key)
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if err != nil {
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return nil, err
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}
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self.root = new_root
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return value, nil
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}
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// Node
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type IAVLNode struct {
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key Key
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value Value
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size uint64
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height uint8
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hash []byte
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left *IAVLNode
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right *IAVLNode
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// volatile
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flags byte
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}
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func (self *IAVLNode) Copy() *IAVLNode {
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if self == nil {
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return nil
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}
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return &IAVLNode{
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key: self.key,
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value: self.value,
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size: self.size,
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height: self.height,
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left: self.left,
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right: self.right,
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hash: nil,
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flags: byte(0),
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}
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}
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func (self *IAVLNode) Key() Key {
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return self.key
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}
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func (self *IAVLNode) Value() Value {
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return self.value
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}
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func (self *IAVLNode) Left(db Db) Node {
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if self.left == nil { return nil }
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return self.leftFilled(db)
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}
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func (self *IAVLNode) Right(db Db) Node {
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if self.right == nil { return nil }
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return self.rightFilled(db)
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}
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func (self *IAVLNode) Size() uint64 {
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if self == nil { return 0 }
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return self.size
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}
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func (self *IAVLNode) Height() uint8 {
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if self == nil { return 0 }
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return self.height
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}
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func (self *IAVLNode) Has(db Db, key Key) (has bool) {
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if self == nil { return false }
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if self.key.Equals(key) {
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return true
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} else if key.Less(self.key) {
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return self.leftFilled(db).Has(db, key)
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} else {
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return self.rightFilled(db).Has(db, key)
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}
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}
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func (self *IAVLNode) Get(db Db, key Key) (value Value) {
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if self == nil { return nil }
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if self.key.Equals(key) {
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return self.value
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} else if key.Less(self.key) {
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return self.leftFilled(db).Get(db, key)
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} else {
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return self.rightFilled(db).Get(db, key)
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}
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}
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func (self *IAVLNode) Hash() (ByteSlice, uint64) {
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if self == nil { return nil, 0 }
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if self.hash != nil {
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return self.hash, 0
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}
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size := self.ByteSize()
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buf := make([]byte, size, size)
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hasher := sha256.New()
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_, hashCount := self.saveToCountHashes(buf)
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hasher.Write(buf)
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self.hash = hasher.Sum(nil)
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return self.hash, hashCount+1
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}
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// TODO: don't clear the hash if the value hasn't changed.
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func (self *IAVLNode) Put(db Db, key Key, value Value) (_ *IAVLNode, updated bool) {
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if self == nil {
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return &IAVLNode{key: key, value: value, height: 1, size: 1, hash: nil}, false
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}
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self = self.Copy()
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if self.key.Equals(key) {
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self.value = value
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return self, true
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}
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if key.Less(self.key) {
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self.left, updated = self.leftFilled(db).Put(db, key, value)
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} else {
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self.right, updated = self.rightFilled(db).Put(db, key, value)
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}
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if updated {
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return self, updated
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} else {
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self.calcHeightAndSize(db)
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return self.balance(db), updated
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}
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}
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func (self *IAVLNode) Remove(db Db, key Key) (newSelf *IAVLNode, value Value, err error) {
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if self == nil { return nil, nil, NotFound(key) }
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if self.key.Equals(key) {
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if self.left != nil && self.right != nil {
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if self.leftFilled(db).Size() < self.rightFilled(db).Size() {
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self, newSelf = self.popNode(db, self.rightFilled(db).lmd(db))
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} else {
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self, newSelf = self.popNode(db, self.leftFilled(db).rmd(db))
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}
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newSelf.left = self.left
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newSelf.right = self.right
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newSelf.calcHeightAndSize(db)
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return newSelf, self.value, nil
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} else if self.left == nil {
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return self.rightFilled(db), self.value, nil
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} else if self.right == nil {
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return self.leftFilled(db), self.value, nil
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} else {
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return nil, self.value, nil
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}
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}
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if key.Less(self.key) {
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if self.left == nil {
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return self, nil, NotFound(key)
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}
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var newLeft *IAVLNode
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newLeft, value, err = self.leftFilled(db).Remove(db, key)
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if newLeft == self.leftFilled(db) { // not found
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return self, nil, err
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} else if err != nil { // some other error
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return self, value, err
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}
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self = self.Copy()
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self.left = newLeft
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} else {
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if self.right == nil {
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return self, nil, NotFound(key)
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}
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var newRight *IAVLNode
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newRight, value, err = self.rightFilled(db).Remove(db, key)
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if newRight == self.rightFilled(db) { // not found
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return self, nil, err
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} else if err != nil { // some other error
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return self, value, err
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}
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self = self.Copy()
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self.right = newRight
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}
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self.calcHeightAndSize(db)
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return self.balance(db), value, err
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}
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func (self *IAVLNode) ByteSize() int {
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// 1 byte node descriptor
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// 1 byte node neight
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// 8 bytes node size
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size := 10
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size += self.key.ByteSize()
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if self.value != nil {
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size += self.value.ByteSize()
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} else {
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size += 1
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}
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if self.left != nil {
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size += HASH_BYTE_SIZE
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}
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if self.right != nil {
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size += HASH_BYTE_SIZE
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}
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return size
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}
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func (self *IAVLNode) SaveTo(buf []byte) int {
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written, _ := self.saveToCountHashes(buf)
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return written
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}
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func (self *IAVLNode) saveToCountHashes(buf []byte) (int, uint64) {
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cur := 0
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hashCount := uint64(0)
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// node descriptor
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nodeDesc := byte(0)
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if self.value != nil { nodeDesc |= 0x01 }
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if self.left != nil { nodeDesc |= 0x02 }
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if self.right != nil { nodeDesc |= 0x04 }
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cur += UInt8(nodeDesc).SaveTo(buf[cur:])
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// node height & size
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cur += UInt8(self.height).SaveTo(buf[cur:])
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cur += UInt64(self.size).SaveTo(buf[cur:])
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// node key
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cur += self.key.SaveTo(buf[cur:])
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// node value
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if self.value != nil {
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cur += self.value.SaveTo(buf[cur:])
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} else {
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cur += UInt8(0).SaveTo(buf[cur:])
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}
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// left child
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if self.left != nil {
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leftHash, leftCount := self.left.Hash()
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hashCount += leftCount
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cur += leftHash.SaveTo(buf[cur:])
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}
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// right child
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if self.right != nil {
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rightHash, rightCount := self.right.Hash()
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hashCount += rightCount
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cur += rightHash.SaveTo(buf[cur:])
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}
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return cur, hashCount
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}
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func (self *IAVLNode) leftFilled(db Db) *IAVLNode {
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// XXX
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return self.left
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}
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func (self *IAVLNode) rightFilled(db Db) *IAVLNode {
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// XXX
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return self.right
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}
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// Returns a new tree (unless node is the root) & a copy of the popped node.
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// Can only pop nodes that have one or no children.
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func (self *IAVLNode) popNode(db Db, node *IAVLNode) (newSelf, new_node *IAVLNode) {
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if self == nil {
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panic("self can't be nil")
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} else if node == nil {
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panic("node can't be nil")
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} else if node.left != nil && node.right != nil {
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panic("node must not have both left and right")
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}
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if self == node {
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var n *IAVLNode
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if node.left != nil {
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n = node.leftFilled(db)
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} else if node.right != nil {
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n = node.rightFilled(db)
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} else {
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n = nil
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}
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node = node.Copy()
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node.left = nil
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node.right = nil
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node.calcHeightAndSize(db)
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return n, node
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} else {
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self = self.Copy()
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if node.key.Less(self.key) {
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self.left, node = self.leftFilled(db).popNode(db, node)
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} else {
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self.right, node = self.rightFilled(db).popNode(db, node)
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}
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self.calcHeightAndSize(db)
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return self, node
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}
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}
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func (self *IAVLNode) rotateRight(db Db) *IAVLNode {
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self = self.Copy()
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sl := self.leftFilled(db).Copy()
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slr := sl.right
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sl.right = self
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self.left = slr
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self.calcHeightAndSize(db)
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sl.calcHeightAndSize(db)
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return sl
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}
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func (self *IAVLNode) rotateLeft(db Db) *IAVLNode {
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self = self.Copy()
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sr := self.rightFilled(db).Copy()
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srl := sr.left
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sr.left = self
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self.right = srl
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self.calcHeightAndSize(db)
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sr.calcHeightAndSize(db)
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return sr
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}
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func (self *IAVLNode) calcHeightAndSize(db Db) {
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self.height = maxUint8(self.leftFilled(db).Height(), self.rightFilled(db).Height()) + 1
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self.size = self.leftFilled(db).Size() + self.rightFilled(db).Size() + 1
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}
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func (self *IAVLNode) calcBalance(db Db) int {
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if self == nil {
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return 0
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}
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return int(self.leftFilled(db).Height()) - int(self.rightFilled(db).Height())
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}
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func (self *IAVLNode) balance(db Db) (newSelf *IAVLNode) {
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balance := self.calcBalance(db)
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if (balance > 1) {
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if (self.leftFilled(db).calcBalance(db) >= 0) {
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// Left Left Case
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return self.rotateRight(db)
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} else {
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// Left Right Case
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self = self.Copy()
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self.left = self.leftFilled(db).rotateLeft(db)
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//self.calcHeightAndSize()
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return self.rotateRight(db)
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}
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}
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if (balance < -1) {
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if (self.rightFilled(db).calcBalance(db) <= 0) {
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// Right Right Case
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return self.rotateLeft(db)
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} else {
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// Right Left Case
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self = self.Copy()
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self.right = self.rightFilled(db).rotateRight(db)
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//self.calcHeightAndSize()
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return self.rotateLeft(db)
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}
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}
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// Nothing changed
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return self
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}
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func (self *IAVLNode) _md(side func(*IAVLNode)*IAVLNode) (*IAVLNode) {
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if self == nil {
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return nil
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} else if side(self) != nil {
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return side(self)._md(side)
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} else {
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return self
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}
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}
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func (self *IAVLNode) lmd(db Db) (*IAVLNode) {
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return self._md(func(node *IAVLNode)*IAVLNode { return node.leftFilled(db) })
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}
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func (self *IAVLNode) rmd(db Db) (*IAVLNode) {
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return self._md(func(node *IAVLNode)*IAVLNode { return node.rightFilled(db) })
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}
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func maxUint8(a, b uint8) uint8 {
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if a > b {
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return a
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}
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return b
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}
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