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1276 lines
28 KiB
Go
1276 lines
28 KiB
Go
// Copyright 2020 Joshua J Baker. All rights reserved.
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// Use of this source code is governed by an MIT-style license that can be
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// found in the LICENSE file at https://github.com/tidwall/btree/LICENSE
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///////////////////////////////////////////////////////////////////////////////
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// BEGIN PARAMS
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///////////////////////////////////////////////////////////////////////////////
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package btree
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import "sync"
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// degree is the B-Tree degree, which is equal to maximum number of children
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// pre node times two.
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// The default is 128, which means each node can have 255 items and 256 child
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// nodes.
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const degree = 128
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// kind is the item type.
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// It's important to use the equal symbol, which tells Go to create an alias of
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// the type, rather than creating an entirely new type.
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type kind = interface{}
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// contextKind is the kind of context that can be passed to NewOptions and the
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// less function
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type contextKind = interface{}
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// less returns true if A is less than B.
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// The value of context will be whatever was passed to NewOptions through the
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// Options.Context field, otherwise nil if the field was not set.
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func less(a, b kind, context contextKind) bool {
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return context.(func(a, b contextKind) bool)(a, b)
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}
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// BTree aliases
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// These are aliases to the local bTree types and functions, which are exported
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// to allow for public use at a package level.
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// Rename them if desired, or comment them out to make the library private.
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type BTree = bTree
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type Options = bOptions
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type PathHint = bPathHint
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type Iter = bIter
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func New(less func(a, b kind) bool) *bTree { return bNew() }
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func NewOptions(opts bOptions) *bTree { return bNewOptions(opts) }
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// The functions below, which begin with "test*", are required by the
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// btree_test.go file. If you choose not use include the btree_test.go file in
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// your project then these functions may be omitted.
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// testCustomSeed can be used to generate a custom random seed for testing.
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// Returning false will use time.Now().UnixNano()
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func testCustomSeed() (seed int64, ok bool) {
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return 0, false
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}
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// testMakeItem must return a valid item for testing.
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// It's required that the returned item maintains equal order as the
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// provided int, such that:
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// testMakeItem(0) < testMakeItem(1) < testMakeItem(2) < testMakeItem(10)
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func testMakeItem(x int) (item kind) {
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return x
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}
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// testNewBTree must return an operational btree for testing.
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func testNewBTree() *bTree {
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return bNewOptions(bOptions{
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Context: func(a, b contextKind) bool {
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if a == nil {
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return b != nil
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} else if b == nil {
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return false
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}
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return a.(int) < b.(int)
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},
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})
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}
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///////////////////////////////////////////////////////////////////////////////
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// END PARAMS
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///////////////////////////////////////////////////////////////////////////////
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// Do not edit code below this line.
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const maxItems = degree*2 - 1 // max items per node. max children is +1
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const minItems = maxItems / 2
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type bTree struct {
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mu *sync.RWMutex
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cow *cow
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root *node
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count int
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ctx contextKind
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locks bool
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empty kind
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}
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type node struct {
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cow *cow
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count int
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items []kind
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children *[]*node
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}
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type cow struct {
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_ int // cannot be an empty struct
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}
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func (tr *bTree) newNode(leaf bool) *node {
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n := &node{cow: tr.cow}
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if !leaf {
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n.children = new([]*node)
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}
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return n
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}
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// leaf returns true if the node is a leaf.
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func (n *node) leaf() bool {
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return n.children == nil
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}
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// PathHint is a utility type used with the *Hint() functions. Hints provide
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// faster operations for clustered keys.
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type bPathHint struct {
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used [8]bool
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path [8]uint8
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}
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type bOptions struct {
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NoLocks bool
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Context contextKind
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}
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// New returns a new BTree
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func bNew() *bTree {
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return bNewOptions(bOptions{})
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}
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func bNewOptions(opts bOptions) *bTree {
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tr := new(bTree)
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tr.cow = new(cow)
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tr.mu = new(sync.RWMutex)
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tr.ctx = opts.Context
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tr.locks = !opts.NoLocks
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return tr
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}
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// Less is a convenience function that performs a comparison of two items
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// using the same "less" function provided to New.
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func (tr *bTree) Less(a, b kind) bool {
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return less(a, b, tr.ctx)
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}
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func (tr *bTree) find(n *node, key kind,
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hint *bPathHint, depth int,
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) (index int, found bool) {
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if hint == nil {
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// fast path for no hinting
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low := 0
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high := len(n.items)
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for low < high {
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mid := (low + high) / 2
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if !tr.Less(key, n.items[mid]) {
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low = mid + 1
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} else {
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high = mid
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}
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}
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if low > 0 && !tr.Less(n.items[low-1], key) {
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return low - 1, true
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}
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return low, false
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}
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// Try using hint.
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// Best case finds the exact match, updates the hint and returns.
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// Worst case, updates the low and high bounds to binary search between.
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low := 0
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high := len(n.items) - 1
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if depth < 8 && hint.used[depth] {
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index = int(hint.path[depth])
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if index >= len(n.items) {
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// tail item
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if tr.Less(n.items[len(n.items)-1], key) {
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index = len(n.items)
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goto path_match
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}
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index = len(n.items) - 1
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}
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if tr.Less(key, n.items[index]) {
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if index == 0 || tr.Less(n.items[index-1], key) {
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goto path_match
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}
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high = index - 1
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} else if tr.Less(n.items[index], key) {
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low = index + 1
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} else {
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found = true
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goto path_match
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}
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}
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// Do a binary search between low and high
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// keep on going until low > high, where the guarantee on low is that
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// key >= items[low - 1]
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for low <= high {
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mid := low + ((high+1)-low)/2
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// if key >= n.items[mid], low = mid + 1
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// which implies that key >= everything below low
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if !tr.Less(key, n.items[mid]) {
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low = mid + 1
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} else {
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high = mid - 1
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}
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}
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// if low > 0, n.items[low - 1] >= key,
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// we have from before that key >= n.items[low - 1]
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// therefore key = n.items[low - 1],
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// and we have found the entry for key.
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// Otherwise we must keep searching for the key in index `low`.
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if low > 0 && !tr.Less(n.items[low-1], key) {
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index = low - 1
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found = true
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} else {
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index = low
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found = false
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}
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path_match:
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if depth < 8 {
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hint.used[depth] = true
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var pathIndex uint8
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if n.leaf() && found {
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pathIndex = uint8(index + 1)
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} else {
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pathIndex = uint8(index)
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}
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if pathIndex != hint.path[depth] {
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hint.path[depth] = pathIndex
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for i := depth + 1; i < 8; i++ {
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hint.used[i] = false
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}
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}
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}
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return index, found
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}
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// SetHint sets or replace a value for a key using a path hint
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func (tr *bTree) SetHint(item kind, hint *bPathHint) (prev kind, replaced bool) {
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if tr.lock() {
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defer tr.unlock()
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}
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return tr.setHint(item, hint)
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}
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func (tr *bTree) setHint(item kind, hint *bPathHint) (prev kind, replaced bool) {
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if tr.root == nil {
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tr.root = tr.newNode(true)
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tr.root.items = append([]kind{}, item)
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tr.root.count = 1
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tr.count = 1
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return tr.empty, false
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}
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prev, replaced, split := tr.nodeSet(&tr.root, item, hint, 0)
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if split {
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left := tr.cowLoad(&tr.root)
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right, median := tr.nodeSplit(left)
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tr.root = tr.newNode(false)
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*tr.root.children = make([]*node, 0, maxItems+1)
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*tr.root.children = append([]*node{}, left, right)
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tr.root.items = append([]kind{}, median)
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tr.root.updateCount()
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return tr.setHint(item, hint)
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}
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if replaced {
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return prev, true
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}
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tr.count++
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return tr.empty, false
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}
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// Set or replace a value for a key
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func (tr *bTree) Set(item kind) (kind, bool) {
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return tr.SetHint(item, nil)
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}
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func (tr *bTree) nodeSplit(n *node) (right *node, median kind) {
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i := maxItems / 2
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median = n.items[i]
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// left node
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left := tr.newNode(n.leaf())
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left.items = make([]kind, len(n.items[:i]), maxItems/2)
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copy(left.items, n.items[:i])
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if !n.leaf() {
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*left.children = make([]*node, len((*n.children)[:i+1]), maxItems+1)
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copy(*left.children, (*n.children)[:i+1])
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}
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left.updateCount()
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// right node
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right = tr.newNode(n.leaf())
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right.items = make([]kind, len(n.items[i+1:]), maxItems/2)
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copy(right.items, n.items[i+1:])
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if !n.leaf() {
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*right.children = make([]*node, len((*n.children)[i+1:]), maxItems+1)
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copy(*right.children, (*n.children)[i+1:])
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}
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right.updateCount()
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*n = *left
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return right, median
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}
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func (n *node) updateCount() {
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n.count = len(n.items)
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if !n.leaf() {
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for i := 0; i < len(*n.children); i++ {
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n.count += (*n.children)[i].count
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}
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}
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}
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// This operation should not be inlined because it's expensive and rarely
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// called outside of heavy copy-on-write situations. Marking it "noinline"
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// allows for the parent cowLoad to be inlined.
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// go:noinline
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func (tr *bTree) copy(n *node) *node {
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n2 := new(node)
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n2.cow = tr.cow
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n2.count = n.count
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n2.items = make([]kind, len(n.items), cap(n.items))
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copy(n2.items, n.items)
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if !n.leaf() {
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n2.children = new([]*node)
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*n2.children = make([]*node, len(*n.children), maxItems+1)
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copy(*n2.children, *n.children)
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}
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return n2
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}
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// cowLoad loads the provided node and, if needed, performs a copy-on-write.
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func (tr *bTree) cowLoad(cn **node) *node {
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if (*cn).cow != tr.cow {
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*cn = tr.copy(*cn)
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}
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return *cn
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}
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func (tr *bTree) nodeSet(cn **node, item kind,
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hint *bPathHint, depth int,
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) (prev kind, replaced bool, split bool) {
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n := tr.cowLoad(cn)
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i, found := tr.find(n, item, hint, depth)
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if found {
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prev = n.items[i]
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n.items[i] = item
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return prev, true, false
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}
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if n.leaf() {
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if len(n.items) == maxItems {
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return tr.empty, false, true
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}
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n.items = append(n.items, tr.empty)
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copy(n.items[i+1:], n.items[i:])
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n.items[i] = item
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n.count++
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return tr.empty, false, false
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}
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prev, replaced, split = tr.nodeSet(&(*n.children)[i], item, hint, depth+1)
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if split {
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if len(n.items) == maxItems {
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return tr.empty, false, true
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}
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right, median := tr.nodeSplit((*n.children)[i])
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*n.children = append(*n.children, nil)
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copy((*n.children)[i+1:], (*n.children)[i:])
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(*n.children)[i+1] = right
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n.items = append(n.items, tr.empty)
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copy(n.items[i+1:], n.items[i:])
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n.items[i] = median
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return tr.nodeSet(&n, item, hint, depth)
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}
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if !replaced {
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n.count++
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}
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return prev, replaced, false
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}
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func (tr *bTree) Scan(iter func(item kind) bool) {
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if tr.rlock() {
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defer tr.runlock()
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}
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if tr.root == nil {
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return
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}
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tr.root.scan(iter)
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}
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func (n *node) scan(iter func(item kind) bool) bool {
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if n.leaf() {
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for i := 0; i < len(n.items); i++ {
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if !iter(n.items[i]) {
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return false
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}
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}
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return true
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}
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for i := 0; i < len(n.items); i++ {
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if !(*n.children)[i].scan(iter) {
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return false
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}
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if !iter(n.items[i]) {
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return false
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}
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}
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return (*n.children)[len(*n.children)-1].scan(iter)
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}
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// Get a value for key
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func (tr *bTree) Get(key kind) (kind, bool) {
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return tr.GetHint(key, nil)
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}
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// GetHint gets a value for key using a path hint
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func (tr *bTree) GetHint(key kind, hint *bPathHint) (kind, bool) {
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if tr.rlock() {
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defer tr.runlock()
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}
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if tr.root == nil {
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return tr.empty, false
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}
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n := tr.root
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depth := 0
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for {
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i, found := tr.find(n, key, hint, depth)
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if found {
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return n.items[i], true
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}
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if n.children == nil {
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return tr.empty, false
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}
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n = (*n.children)[i]
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depth++
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}
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}
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// Len returns the number of items in the tree
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func (tr *bTree) Len() int {
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return tr.count
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}
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// Delete a value for a key
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func (tr *bTree) Delete(key kind) (kind, bool) {
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return tr.DeleteHint(key, nil)
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}
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// DeleteHint deletes a value for a key using a path hint
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func (tr *bTree) DeleteHint(key kind, hint *bPathHint) (kind, bool) {
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if tr.lock() {
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defer tr.unlock()
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}
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return tr.deleteHint(key, hint)
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}
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func (tr *bTree) deleteHint(key kind, hint *bPathHint) (kind, bool) {
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if tr.root == nil {
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return tr.empty, false
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}
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prev, deleted := tr.delete(&tr.root, false, key, hint, 0)
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if !deleted {
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return tr.empty, false
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}
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if len(tr.root.items) == 0 && !tr.root.leaf() {
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tr.root = (*tr.root.children)[0]
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}
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tr.count--
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if tr.count == 0 {
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tr.root = nil
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}
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return prev, true
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}
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func (tr *bTree) delete(cn **node, max bool, key kind,
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hint *bPathHint, depth int,
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) (kind, bool) {
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n := tr.cowLoad(cn)
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var i int
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var found bool
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if max {
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i, found = len(n.items)-1, true
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} else {
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i, found = tr.find(n, key, hint, depth)
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}
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if n.leaf() {
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if found {
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// found the items at the leaf, remove it and return.
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prev := n.items[i]
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copy(n.items[i:], n.items[i+1:])
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n.items[len(n.items)-1] = tr.empty
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n.items = n.items[:len(n.items)-1]
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n.count--
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return prev, true
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}
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return tr.empty, false
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}
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var prev kind
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var deleted bool
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if found {
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if max {
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i++
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prev, deleted = tr.delete(&(*n.children)[i], true, tr.empty, nil, 0)
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} else {
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prev = n.items[i]
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maxItem, _ := tr.delete(&(*n.children)[i], true, tr.empty, nil, 0)
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deleted = true
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n.items[i] = maxItem
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}
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} else {
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prev, deleted = tr.delete(&(*n.children)[i], max, key, hint, depth+1)
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}
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if !deleted {
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return tr.empty, false
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}
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n.count--
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if len((*n.children)[i].items) < minItems {
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tr.nodeRebalance(n, i)
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}
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return prev, true
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}
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// nodeRebalance rebalances the child nodes following a delete operation.
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// Provide the index of the child node with the number of items that fell
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// below minItems.
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func (tr *bTree) nodeRebalance(n *node, i int) {
|
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if i == len(n.items) {
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i--
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}
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|
|
// ensure copy-on-write
|
|
left := tr.cowLoad(&(*n.children)[i])
|
|
right := tr.cowLoad(&(*n.children)[i+1])
|
|
|
|
if len(left.items)+len(right.items) < maxItems {
|
|
// Merges the left and right children nodes together as a single node
|
|
// that includes (left,item,right), and places the contents into the
|
|
// existing left node. Delete the right node altogether and move the
|
|
// following items and child nodes to the left by one slot.
|
|
|
|
// merge (left,item,right)
|
|
left.items = append(left.items, n.items[i])
|
|
left.items = append(left.items, right.items...)
|
|
if !left.leaf() {
|
|
*left.children = append(*left.children, *right.children...)
|
|
}
|
|
left.count += right.count + 1
|
|
|
|
// move the items over one slot
|
|
copy(n.items[i:], n.items[i+1:])
|
|
n.items[len(n.items)-1] = tr.empty
|
|
n.items = n.items[:len(n.items)-1]
|
|
|
|
// move the children over one slot
|
|
copy((*n.children)[i+1:], (*n.children)[i+2:])
|
|
(*n.children)[len(*n.children)-1] = nil
|
|
(*n.children) = (*n.children)[:len(*n.children)-1]
|
|
} else if len(left.items) > len(right.items) {
|
|
// move left -> right over one slot
|
|
|
|
// Move the item of the parent node at index into the right-node first
|
|
// slot, and move the left-node last item into the previously moved
|
|
// parent item slot.
|
|
right.items = append(right.items, tr.empty)
|
|
copy(right.items[1:], right.items)
|
|
right.items[0] = n.items[i]
|
|
right.count++
|
|
n.items[i] = left.items[len(left.items)-1]
|
|
left.items[len(left.items)-1] = tr.empty
|
|
left.items = left.items[:len(left.items)-1]
|
|
left.count--
|
|
|
|
if !left.leaf() {
|
|
// move the left-node last child into the right-node first slot
|
|
*right.children = append(*right.children, nil)
|
|
copy((*right.children)[1:], *right.children)
|
|
(*right.children)[0] = (*left.children)[len(*left.children)-1]
|
|
(*left.children)[len(*left.children)-1] = nil
|
|
(*left.children) = (*left.children)[:len(*left.children)-1]
|
|
left.count -= (*right.children)[0].count
|
|
right.count += (*right.children)[0].count
|
|
}
|
|
} else {
|
|
// move left <- right over one slot
|
|
|
|
// Same as above but the other direction
|
|
left.items = append(left.items, n.items[i])
|
|
left.count++
|
|
n.items[i] = right.items[0]
|
|
copy(right.items, right.items[1:])
|
|
right.items[len(right.items)-1] = tr.empty
|
|
right.items = right.items[:len(right.items)-1]
|
|
right.count--
|
|
|
|
if !left.leaf() {
|
|
*left.children = append(*left.children, (*right.children)[0])
|
|
copy(*right.children, (*right.children)[1:])
|
|
(*right.children)[len(*right.children)-1] = nil
|
|
*right.children = (*right.children)[:len(*right.children)-1]
|
|
left.count += (*left.children)[len(*left.children)-1].count
|
|
right.count -= (*left.children)[len(*left.children)-1].count
|
|
}
|
|
}
|
|
}
|
|
|
|
// Ascend the tree within the range [pivot, last]
|
|
// Pass nil for pivot to scan all item in ascending order
|
|
// Return false to stop iterating
|
|
func (tr *bTree) Ascend(pivot kind, iter func(item kind) bool) {
|
|
if tr.rlock() {
|
|
defer tr.runlock()
|
|
}
|
|
if tr.root == nil {
|
|
return
|
|
}
|
|
tr.ascend(tr.root, pivot, nil, 0, iter)
|
|
}
|
|
|
|
// The return value of this function determines whether we should keep iterating
|
|
// upon this functions return.
|
|
func (tr *bTree) ascend(n *node, pivot kind,
|
|
hint *bPathHint, depth int, iter func(item kind) bool,
|
|
) bool {
|
|
i, found := tr.find(n, pivot, hint, depth)
|
|
if !found {
|
|
if !n.leaf() {
|
|
if !tr.ascend((*n.children)[i], pivot, hint, depth+1, iter) {
|
|
return false
|
|
}
|
|
}
|
|
}
|
|
// We are either in the case that
|
|
// - node is found, we should iterate through it starting at `i`,
|
|
// the index it was located at.
|
|
// - node is not found, and TODO: fill in.
|
|
for ; i < len(n.items); i++ {
|
|
if !iter(n.items[i]) {
|
|
return false
|
|
}
|
|
if !n.leaf() {
|
|
if !(*n.children)[i+1].scan(iter) {
|
|
return false
|
|
}
|
|
}
|
|
}
|
|
return true
|
|
}
|
|
|
|
func (tr *bTree) Reverse(iter func(item kind) bool) {
|
|
if tr.rlock() {
|
|
defer tr.runlock()
|
|
}
|
|
if tr.root == nil {
|
|
return
|
|
}
|
|
tr.root.reverse(iter)
|
|
}
|
|
|
|
func (n *node) reverse(iter func(item kind) bool) bool {
|
|
if n.leaf() {
|
|
for i := len(n.items) - 1; i >= 0; i-- {
|
|
if !iter(n.items[i]) {
|
|
return false
|
|
}
|
|
}
|
|
return true
|
|
}
|
|
if !(*n.children)[len(*n.children)-1].reverse(iter) {
|
|
return false
|
|
}
|
|
for i := len(n.items) - 1; i >= 0; i-- {
|
|
if !iter(n.items[i]) {
|
|
return false
|
|
}
|
|
if !(*n.children)[i].reverse(iter) {
|
|
return false
|
|
}
|
|
}
|
|
return true
|
|
}
|
|
|
|
// Descend the tree within the range [pivot, first]
|
|
// Pass nil for pivot to scan all item in descending order
|
|
// Return false to stop iterating
|
|
func (tr *bTree) Descend(pivot kind, iter func(item kind) bool) {
|
|
if tr.rlock() {
|
|
defer tr.runlock()
|
|
}
|
|
if tr.root == nil {
|
|
return
|
|
}
|
|
tr.descend(tr.root, pivot, nil, 0, iter)
|
|
}
|
|
|
|
func (tr *bTree) descend(n *node, pivot kind,
|
|
hint *bPathHint, depth int, iter func(item kind) bool,
|
|
) bool {
|
|
i, found := tr.find(n, pivot, hint, depth)
|
|
if !found {
|
|
if !n.leaf() {
|
|
if !tr.descend((*n.children)[i], pivot, hint, depth+1, iter) {
|
|
return false
|
|
}
|
|
}
|
|
i--
|
|
}
|
|
for ; i >= 0; i-- {
|
|
if !iter(n.items[i]) {
|
|
return false
|
|
}
|
|
if !n.leaf() {
|
|
if !(*n.children)[i].reverse(iter) {
|
|
return false
|
|
}
|
|
}
|
|
}
|
|
return true
|
|
}
|
|
|
|
// Load is for bulk loading pre-sorted items
|
|
func (tr *bTree) Load(item kind) (kind, bool) {
|
|
if tr.lock() {
|
|
defer tr.unlock()
|
|
}
|
|
if tr.root == nil {
|
|
return tr.setHint(item, nil)
|
|
}
|
|
n := tr.cowLoad(&tr.root)
|
|
for {
|
|
n.count++ // optimistically update counts
|
|
if n.leaf() {
|
|
if len(n.items) < maxItems {
|
|
if tr.Less(n.items[len(n.items)-1], item) {
|
|
n.items = append(n.items, item)
|
|
tr.count++
|
|
return tr.empty, false
|
|
}
|
|
}
|
|
break
|
|
}
|
|
n = tr.cowLoad(&(*n.children)[len(*n.children)-1])
|
|
}
|
|
// revert the counts
|
|
n = tr.root
|
|
for {
|
|
n.count--
|
|
if n.leaf() {
|
|
break
|
|
}
|
|
n = (*n.children)[len(*n.children)-1]
|
|
}
|
|
return tr.setHint(item, nil)
|
|
}
|
|
|
|
// Min returns the minimum item in tree.
|
|
// Returns nil if the tree has no items.
|
|
func (tr *bTree) Min() (kind, bool) {
|
|
if tr.rlock() {
|
|
defer tr.runlock()
|
|
}
|
|
if tr.root == nil {
|
|
return tr.empty, false
|
|
}
|
|
n := tr.root
|
|
for {
|
|
if n.leaf() {
|
|
return n.items[0], true
|
|
}
|
|
n = (*n.children)[0]
|
|
}
|
|
}
|
|
|
|
// Max returns the maximum item in tree.
|
|
// Returns nil if the tree has no items.
|
|
func (tr *bTree) Max() (kind, bool) {
|
|
if tr.rlock() {
|
|
defer tr.runlock()
|
|
}
|
|
if tr.root == nil {
|
|
return tr.empty, false
|
|
}
|
|
n := tr.root
|
|
for {
|
|
if n.leaf() {
|
|
return n.items[len(n.items)-1], true
|
|
}
|
|
n = (*n.children)[len(*n.children)-1]
|
|
}
|
|
}
|
|
|
|
// PopMin removes the minimum item in tree and returns it.
|
|
// Returns nil if the tree has no items.
|
|
func (tr *bTree) PopMin() (kind, bool) {
|
|
if tr.lock() {
|
|
defer tr.unlock()
|
|
}
|
|
if tr.root == nil {
|
|
return tr.empty, false
|
|
}
|
|
n := tr.cowLoad(&tr.root)
|
|
var item kind
|
|
for {
|
|
n.count-- // optimistically update counts
|
|
if n.leaf() {
|
|
item = n.items[0]
|
|
if len(n.items) == minItems {
|
|
break
|
|
}
|
|
copy(n.items[:], n.items[1:])
|
|
n.items[len(n.items)-1] = tr.empty
|
|
n.items = n.items[:len(n.items)-1]
|
|
tr.count--
|
|
if tr.count == 0 {
|
|
tr.root = nil
|
|
}
|
|
return item, true
|
|
}
|
|
n = tr.cowLoad(&(*n.children)[0])
|
|
}
|
|
// revert the counts
|
|
n = tr.root
|
|
for {
|
|
n.count++
|
|
if n.leaf() {
|
|
break
|
|
}
|
|
n = (*n.children)[0]
|
|
}
|
|
return tr.deleteHint(item, nil)
|
|
}
|
|
|
|
// PopMax removes the minimum item in tree and returns it.
|
|
// Returns nil if the tree has no items.
|
|
func (tr *bTree) PopMax() (kind, bool) {
|
|
if tr.lock() {
|
|
defer tr.unlock()
|
|
}
|
|
if tr.root == nil {
|
|
return tr.empty, false
|
|
}
|
|
n := tr.cowLoad(&tr.root)
|
|
var item kind
|
|
for {
|
|
n.count-- // optimistically update counts
|
|
if n.leaf() {
|
|
item = n.items[len(n.items)-1]
|
|
if len(n.items) == minItems {
|
|
break
|
|
}
|
|
n.items[len(n.items)-1] = tr.empty
|
|
n.items = n.items[:len(n.items)-1]
|
|
tr.count--
|
|
if tr.count == 0 {
|
|
tr.root = nil
|
|
}
|
|
return item, true
|
|
}
|
|
n = tr.cowLoad(&(*n.children)[len(*n.children)-1])
|
|
}
|
|
// revert the counts
|
|
n = tr.root
|
|
for {
|
|
n.count++
|
|
if n.leaf() {
|
|
break
|
|
}
|
|
n = (*n.children)[len(*n.children)-1]
|
|
}
|
|
return tr.deleteHint(item, nil)
|
|
}
|
|
|
|
// GetAt returns the value at index.
|
|
// Return nil if the tree is empty or the index is out of bounds.
|
|
func (tr *bTree) GetAt(index int) (kind, bool) {
|
|
if tr.rlock() {
|
|
defer tr.runlock()
|
|
}
|
|
if tr.root == nil || index < 0 || index >= tr.count {
|
|
return tr.empty, false
|
|
}
|
|
n := tr.root
|
|
for {
|
|
if n.leaf() {
|
|
return n.items[index], true
|
|
}
|
|
i := 0
|
|
for ; i < len(n.items); i++ {
|
|
if index < (*n.children)[i].count {
|
|
break
|
|
} else if index == (*n.children)[i].count {
|
|
return n.items[i], true
|
|
}
|
|
index -= (*n.children)[i].count + 1
|
|
}
|
|
n = (*n.children)[i]
|
|
}
|
|
}
|
|
|
|
// DeleteAt deletes the item at index.
|
|
// Return nil if the tree is empty or the index is out of bounds.
|
|
func (tr *bTree) DeleteAt(index int) (kind, bool) {
|
|
if tr.lock() {
|
|
defer tr.unlock()
|
|
}
|
|
if tr.root == nil || index < 0 || index >= tr.count {
|
|
return tr.empty, false
|
|
}
|
|
var pathbuf [8]uint8 // track the path
|
|
path := pathbuf[:0]
|
|
var item kind
|
|
n := tr.cowLoad(&tr.root)
|
|
outer:
|
|
for {
|
|
n.count-- // optimistically update counts
|
|
if n.leaf() {
|
|
// the index is the item position
|
|
item = n.items[index]
|
|
if len(n.items) == minItems {
|
|
path = append(path, uint8(index))
|
|
break outer
|
|
}
|
|
copy(n.items[index:], n.items[index+1:])
|
|
n.items[len(n.items)-1] = tr.empty
|
|
n.items = n.items[:len(n.items)-1]
|
|
tr.count--
|
|
if tr.count == 0 {
|
|
tr.root = nil
|
|
}
|
|
return item, true
|
|
}
|
|
i := 0
|
|
for ; i < len(n.items); i++ {
|
|
if index < (*n.children)[i].count {
|
|
break
|
|
} else if index == (*n.children)[i].count {
|
|
item = n.items[i]
|
|
path = append(path, uint8(i))
|
|
break outer
|
|
}
|
|
index -= (*n.children)[i].count + 1
|
|
}
|
|
path = append(path, uint8(i))
|
|
n = tr.cowLoad(&(*n.children)[i])
|
|
}
|
|
// revert the counts
|
|
var hint bPathHint
|
|
n = tr.root
|
|
for i := 0; i < len(path); i++ {
|
|
if i < len(hint.path) {
|
|
hint.path[i] = uint8(path[i])
|
|
hint.used[i] = true
|
|
}
|
|
n.count++
|
|
if !n.leaf() {
|
|
n = (*n.children)[uint8(path[i])]
|
|
}
|
|
}
|
|
return tr.deleteHint(item, &hint)
|
|
}
|
|
|
|
// Height returns the height of the tree.
|
|
// Returns zero if tree has no items.
|
|
func (tr *bTree) Height() int {
|
|
if tr.rlock() {
|
|
defer tr.runlock()
|
|
}
|
|
var height int
|
|
if tr.root != nil {
|
|
n := tr.root
|
|
for {
|
|
height++
|
|
if n.leaf() {
|
|
break
|
|
}
|
|
n = (*n.children)[0]
|
|
}
|
|
}
|
|
return height
|
|
}
|
|
|
|
// Walk iterates over all items in tree, in order.
|
|
// The items param will contain one or more items.
|
|
func (tr *bTree) Walk(iter func(item []kind) bool) {
|
|
if tr.rlock() {
|
|
defer tr.runlock()
|
|
}
|
|
if tr.root != nil {
|
|
tr.root.walk(iter)
|
|
}
|
|
}
|
|
|
|
func (n *node) walk(iter func(item []kind) bool) bool {
|
|
if n.leaf() {
|
|
if !iter(n.items) {
|
|
return false
|
|
}
|
|
} else {
|
|
for i := 0; i < len(n.items); i++ {
|
|
(*n.children)[i].walk(iter)
|
|
if !iter(n.items[i : i+1]) {
|
|
return false
|
|
}
|
|
}
|
|
(*n.children)[len(n.items)].walk(iter)
|
|
}
|
|
return true
|
|
}
|
|
|
|
// Copy the tree. This is a copy-on-write operation and is very fast because
|
|
// it only performs a shadowed copy.
|
|
func (tr *bTree) Copy() *bTree {
|
|
if tr.lock() {
|
|
defer tr.unlock()
|
|
}
|
|
tr.cow = new(cow)
|
|
tr2 := new(bTree)
|
|
*tr2 = *tr
|
|
tr2.mu = new(sync.RWMutex)
|
|
tr2.cow = new(cow)
|
|
return tr2
|
|
}
|
|
|
|
func (tr *bTree) lock() bool {
|
|
if tr.locks {
|
|
tr.mu.Lock()
|
|
}
|
|
return tr.locks
|
|
}
|
|
|
|
func (tr *bTree) unlock() {
|
|
tr.mu.Unlock()
|
|
}
|
|
|
|
func (tr *bTree) rlock() bool {
|
|
if tr.locks {
|
|
tr.mu.RLock()
|
|
}
|
|
return tr.locks
|
|
}
|
|
|
|
func (tr *bTree) runlock() {
|
|
tr.mu.RUnlock()
|
|
}
|
|
|
|
// Iter represents an iterator
|
|
type bIter struct {
|
|
tr *bTree
|
|
locked bool
|
|
seeked bool
|
|
atstart bool
|
|
atend bool
|
|
stack []iterStackItem
|
|
item kind
|
|
}
|
|
|
|
type iterStackItem struct {
|
|
n *node
|
|
i int
|
|
}
|
|
|
|
// Iter returns a read-only iterator.
|
|
// The Release method must be called finished with iterator.
|
|
func (tr *bTree) Iter() bIter {
|
|
var iter bIter
|
|
iter.tr = tr
|
|
iter.locked = tr.rlock()
|
|
return iter
|
|
}
|
|
|
|
// Seek to item greater-or-equal-to key.
|
|
// Returns false if there was no item found.
|
|
func (iter *bIter) Seek(key kind) bool {
|
|
if iter.tr == nil {
|
|
return false
|
|
}
|
|
iter.seeked = true
|
|
iter.stack = iter.stack[:0]
|
|
if iter.tr.root == nil {
|
|
return false
|
|
}
|
|
n := iter.tr.root
|
|
for {
|
|
i, found := iter.tr.find(n, key, nil, 0)
|
|
iter.stack = append(iter.stack, iterStackItem{n, i})
|
|
if found {
|
|
return true
|
|
}
|
|
if n.leaf() {
|
|
if i == len(n.items) {
|
|
iter.stack = iter.stack[:0]
|
|
return false
|
|
}
|
|
return true
|
|
}
|
|
n = (*n.children)[i]
|
|
}
|
|
}
|
|
|
|
// First moves iterator to first item in tree.
|
|
// Returns false if the tree is empty.
|
|
func (iter *bIter) First() bool {
|
|
if iter.tr == nil {
|
|
return false
|
|
}
|
|
iter.atend = false
|
|
iter.atstart = false
|
|
iter.seeked = true
|
|
iter.stack = iter.stack[:0]
|
|
if iter.tr.root == nil {
|
|
return false
|
|
}
|
|
n := iter.tr.root
|
|
for {
|
|
iter.stack = append(iter.stack, iterStackItem{n, 0})
|
|
if n.leaf() {
|
|
break
|
|
}
|
|
n = (*n.children)[0]
|
|
}
|
|
s := &iter.stack[len(iter.stack)-1]
|
|
iter.item = s.n.items[s.i]
|
|
return true
|
|
}
|
|
|
|
// Last moves iterator to last item in tree.
|
|
// Returns false if the tree is empty.
|
|
func (iter *bIter) Last() bool {
|
|
if iter.tr == nil {
|
|
return false
|
|
}
|
|
iter.seeked = true
|
|
iter.stack = iter.stack[:0]
|
|
if iter.tr.root == nil {
|
|
return false
|
|
}
|
|
n := iter.tr.root
|
|
for {
|
|
iter.stack = append(iter.stack, iterStackItem{n, len(n.items)})
|
|
if n.leaf() {
|
|
iter.stack[len(iter.stack)-1].i--
|
|
break
|
|
}
|
|
n = (*n.children)[len(n.items)]
|
|
}
|
|
s := &iter.stack[len(iter.stack)-1]
|
|
iter.item = s.n.items[s.i]
|
|
return true
|
|
}
|
|
|
|
// First moves iterator to first item in tree.
|
|
// Returns false if the tree is empty.
|
|
func (iter *bIter) Release() {
|
|
if iter.tr == nil {
|
|
return
|
|
}
|
|
if iter.locked {
|
|
iter.tr.runlock()
|
|
iter.locked = false
|
|
}
|
|
iter.stack = nil
|
|
iter.tr = nil
|
|
}
|
|
|
|
// Next moves iterator to the next item in iterator.
|
|
// Returns false if the tree is empty or the iterator is at the end of
|
|
// the tree.
|
|
func (iter *bIter) Next() bool {
|
|
if iter.tr == nil {
|
|
return false
|
|
}
|
|
if !iter.seeked {
|
|
return iter.First()
|
|
}
|
|
if len(iter.stack) == 0 {
|
|
if iter.atstart {
|
|
return iter.First() && iter.Next()
|
|
}
|
|
return false
|
|
}
|
|
s := &iter.stack[len(iter.stack)-1]
|
|
s.i++
|
|
if s.n.leaf() {
|
|
if s.i == len(s.n.items) {
|
|
for {
|
|
iter.stack = iter.stack[:len(iter.stack)-1]
|
|
if len(iter.stack) == 0 {
|
|
iter.atend = true
|
|
return false
|
|
}
|
|
s = &iter.stack[len(iter.stack)-1]
|
|
if s.i < len(s.n.items) {
|
|
break
|
|
}
|
|
}
|
|
}
|
|
} else {
|
|
n := (*s.n.children)[s.i]
|
|
for {
|
|
iter.stack = append(iter.stack, iterStackItem{n, 0})
|
|
if n.leaf() {
|
|
break
|
|
}
|
|
n = (*n.children)[0]
|
|
}
|
|
}
|
|
s = &iter.stack[len(iter.stack)-1]
|
|
iter.item = s.n.items[s.i]
|
|
return true
|
|
}
|
|
|
|
// Prev moves iterator to the previous item in iterator.
|
|
// Returns false if the tree is empty or the iterator is at the beginning of
|
|
// the tree.
|
|
func (iter *bIter) Prev() bool {
|
|
if iter.tr == nil {
|
|
return false
|
|
}
|
|
if !iter.seeked {
|
|
return false
|
|
}
|
|
if len(iter.stack) == 0 {
|
|
if iter.atend {
|
|
return iter.Last() && iter.Prev()
|
|
}
|
|
return false
|
|
}
|
|
s := &iter.stack[len(iter.stack)-1]
|
|
if s.n.leaf() {
|
|
s.i--
|
|
if s.i == -1 {
|
|
for {
|
|
iter.stack = iter.stack[:len(iter.stack)-1]
|
|
if len(iter.stack) == 0 {
|
|
iter.atstart = true
|
|
return false
|
|
}
|
|
s = &iter.stack[len(iter.stack)-1]
|
|
s.i--
|
|
if s.i > -1 {
|
|
break
|
|
}
|
|
}
|
|
}
|
|
} else {
|
|
n := (*s.n.children)[s.i]
|
|
for {
|
|
iter.stack = append(iter.stack, iterStackItem{n, len(n.items)})
|
|
if n.leaf() {
|
|
iter.stack[len(iter.stack)-1].i--
|
|
break
|
|
}
|
|
n = (*n.children)[len(n.items)]
|
|
}
|
|
}
|
|
s = &iter.stack[len(iter.stack)-1]
|
|
iter.item = s.n.items[s.i]
|
|
return true
|
|
}
|
|
|
|
// Item returns the current iterator item.
|
|
func (iter *bIter) Item() kind {
|
|
return iter.item
|
|
}
|