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B-tree map
This commit is contained in:
ka-weihe
Alexander Medvednikov
parent
2d2e0307b8
commit
8a4bce667c
@ -1,232 +1,416 @@
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// Copyright (c) 2019 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
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// that can be found in the LICENSE file.
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module builtin
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import strings
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// B-trees are balanced search trees with all leaves at
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// the same level. B-trees are generally faster than
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// binary search trees due to the better locality of
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// reference, since multiple keys are stored in one node.
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// The number for `degree` has been picked through vigor-
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// ous benchmarking but can be changed to any number > 1.
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// `degree` determines the size of each node.
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const (
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degree = 6
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mid_index = degree - 1
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max_size = 2 * degree - 1
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children_bytes = sizeof(voidptr) * (max_size + 1)
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)
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pub struct map {
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element_size int
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value_bytes int
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mut:
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root &mapnode
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pub:
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pub mut:
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size int
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}
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struct mapnode {
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left &mapnode
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right &mapnode
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is_empty bool // set by delete()
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key string
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val voidptr
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mut:
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keys [11]string // TODO: Should use `max_size`
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values [11]voidptr // TODO: Should use `max_size`
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children &voidptr
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size int
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}
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fn new_map(cap, elm_size int) map {
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res := map{
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element_size: elm_size
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root: 0
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fn new_map(n, value_bytes int) map { // TODO: Remove `n`
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return map {
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value_bytes: value_bytes
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root: new_node()
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size: 0
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}
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return res
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}
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// `m := { 'one': 1, 'two': 2 }`
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fn new_map_init(cap, elm_size int, keys &string, vals voidptr) map {
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mut res := map{
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element_size: elm_size
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root: 0
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fn new_map_init(n, value_bytes int, keys &string, values voidptr) map {
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mut out := new_map(n, value_bytes)
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for i in 0 .. n {
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out.set(keys[i], values + i * value_bytes)
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}
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for i in 0 .. cap {
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res.set(keys[i], vals + i * elm_size)
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}
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return res
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return out
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}
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fn new_node(key string, val voidptr, element_size int) &mapnode {
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new_e := &mapnode{
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key: key
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val: malloc(element_size)
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left: 0
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right: 0
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// The tree is initialized with an empty node as root to
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// avoid having to check whether the root is null for
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// each insertion.
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fn new_node() &mapnode {
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return &mapnode {
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children: 0
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size: 0
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}
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C.memcpy(new_e.val, val, element_size)
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return new_e
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}
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fn (m mut map) insert(n mut mapnode, key string, val voidptr) {
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if n.key == key {
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C.memcpy(n.val, val, m.element_size)
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if n.is_empty {
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m.size++
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n.is_empty = false
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// This implementation does proactive insertion, meaning
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// that splits are done top-down and not bottom-up.
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fn (m mut map) set(key string, value voidptr) {
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mut node := m.root
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mut child_index := 0
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mut parent := &mapnode(0)
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for {
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if node.size == max_size {
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if isnil(parent) {
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parent = new_node()
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m.root = parent
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}
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parent.split_child(child_index, mut node)
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if key == parent.keys[child_index] {
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C.memcpy(parent.values[child_index], value, m.value_bytes)
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return
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}
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if n.key > key {
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if n.left == 0 {
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n.left = new_node(key, val, m.element_size)
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m.size++
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node = if key < parent.keys[child_index] {
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&mapnode(parent.children[child_index])
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} else {
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&mapnode(parent.children[child_index + 1])
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}
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else {
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m.insert(mut n.left, key, val)
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}
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mut i := 0
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for i < node.size && key > node.keys[i] { i++ }
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if i != node.size && key == node.keys[i] {
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C.memcpy(node.values[i], value, m.value_bytes)
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return
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}
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if n.right == 0 {
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n.right = new_node(key, val, m.element_size)
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m.size++
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if isnil(node.children) {
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mut j := node.size - 1
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for j >= 0 && key < node.keys[j] {
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node.keys[j + 1] = node.keys[j]
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node.values[j + 1] = node.values[j]
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j--
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}
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else {
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m.insert(mut n.right, key, val)
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node.keys[j + 1] = key
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node.values[j + 1] = malloc(m.value_bytes)
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C.memcpy(node.values[j + 1], value, m.value_bytes)
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node.size++
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m.size++
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return
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}
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parent = node
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child_index = i
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node = &mapnode(node.children[child_index])
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}
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}
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fn (n &mapnode) find(key string, out voidptr, element_size int) bool {
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if n.key == key {
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C.memcpy(out, n.val, element_size)
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fn (n mut mapnode) split_child(child_index int, y mut mapnode) {
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mut z := new_node()
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z.size = mid_index
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y.size = mid_index
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for j := mid_index - 1; j >= 0; j-- {
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z.keys[j] = y.keys[j + degree]
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z.values[j] = y.values[j + degree]
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}
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if !isnil(y.children) {
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z.children = &voidptr(malloc(children_bytes))
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for j := degree - 1; j >= 0; j-- {
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z.children[j] = y.children[j + degree]
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}
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}
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if isnil(n.children) {
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n.children = &voidptr(malloc(children_bytes))
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}
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n.children[n.size + 1] = n.children[n.size]
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for j := n.size; j > child_index; j-- {
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n.keys[j] = n.keys[j - 1]
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n.values[j] = n.values[j - 1]
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n.children[j] = n.children[j - 1]
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}
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n.keys[child_index] = y.keys[mid_index]
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n.values[child_index] = y.values[mid_index]
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n.children[child_index] = voidptr(y)
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n.children[child_index + 1] = voidptr(z)
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n.size++
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}
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fn (m map) get(key string, out voidptr) bool {
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mut node := m.root
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for {
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mut i := node.size - 1
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for i >= 0 && key < node.keys[i] { i-- }
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if i != -1 && key == node.keys[i] {
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C.memcpy(out, node.values[i], m.value_bytes)
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return true
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}
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else if n.key > key {
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if n.left == 0 {
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if isnil(node.children) {
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break
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}
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node = &mapnode(node.children[i + 1])
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}
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return false
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}
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else {
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return n.left.find(key, out, element_size)
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}
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}
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else {
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if n.right == 0 {
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return false
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}
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else {
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return n.right.find(key, out, element_size)
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}
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}
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}
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// same as `find`, but doesn't return a value. Used by `exists`
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fn (n &mapnode) find2(key string, element_size int) bool {
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if n.key == key && !n.is_empty {
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fn (m map) exists(key string) bool {
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if isnil(m.root) { // TODO: find out why root can be nil
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return false
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}
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mut node := m.root
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for {
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mut i := node.size - 1
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for i >= 0 && key < node.keys[i] { i-- }
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if i != -1 && key == node.keys[i] {
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return true
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}
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else if n.key > key {
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if isnil(n.left) {
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if isnil(node.children) {
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break
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}
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node = &mapnode(node.children[i + 1])
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}
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return false
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}
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else {
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return n.left.find2(key, element_size)
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fn (n mapnode) find_key(k string) int {
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mut idx := 0
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for idx < n.size && n.keys[idx] < k {
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idx++
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}
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return idx
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}
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else {
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if isnil(n.right) {
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fn (n mut mapnode) remove_key(k string) bool {
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idx := n.find_key(k)
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if idx < n.size && n.keys[idx] == k {
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if isnil(n.children) {
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n.remove_from_leaf(idx)
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} else {
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n.remove_from_non_leaf(idx)
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}
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return true
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} else {
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if isnil(n.children) {
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return false
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}
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else {
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return n.right.find2(key, element_size)
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flag := if idx == n.size {true} else {false}
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if (&mapnode(n.children[idx])).size < degree {
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n.fill(idx)
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}
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if flag && idx > n.size {
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return (&mapnode(n.children[idx - 1])).remove_key(k)
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} else {
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return (&mapnode(n.children[idx])).remove_key(k)
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}
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}
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}
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fn (m mut map) set(key string, val voidptr) {
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if isnil(m.root) {
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m.root = new_node(key, val, m.element_size)
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m.size++
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return
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fn (n mut mapnode) remove_from_leaf(idx int) {
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for i := idx + 1; i < n.size; i++ {
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n.keys[i - 1] = n.keys[i]
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n.values[i - 1] = n.values[i]
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}
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m.insert(mut m.root, key, val)
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n.size--
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}
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/*
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fn (m map) bs(query string, start, end int, out voidptr) {
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// println('bs "$query" $start -> $end')
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mid := start + ((end - start) / 2)
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if end - start == 0 {
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last := m.entries[end]
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C.memcpy(out, last.val, m.element_size)
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return
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fn (n mut mapnode) remove_from_non_leaf(idx int) {
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k := n.keys[idx]
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if &mapnode(n.children[idx]).size >= degree {
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mut current := &mapnode(n.children[idx])
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for !isnil(current.children) {
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current = &mapnode(current.children[current.size])
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}
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if end - start == 1 {
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first := m.entries[start]
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C.memcpy(out, first.val, m.element_size)
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return
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predecessor := current.keys[current.size - 1]
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n.keys[idx] = predecessor
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n.values[idx] = current.values[current.size - 1]
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(&mapnode(n.children[idx])).remove_key(predecessor)
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} else if &mapnode(n.children[idx + 1]).size >= degree {
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mut current := &mapnode(n.children[idx + 1])
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for !isnil(current.children) {
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current = &mapnode(current.children[0])
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}
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if mid >= m.entries.len {
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return
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successor := current.keys[0]
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n.keys[idx] = successor
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n.values[idx] = current.values[0]
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(&mapnode(n.children[idx + 1])).remove_key(successor)
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} else {
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n.merge(idx)
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(&mapnode(n.children[idx])).remove_key(k)
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}
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mid_msg := m.entries[mid]
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// println('mid.key=$mid_msg.key')
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if query < mid_msg.key {
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m.bs(query, start, mid, out)
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return
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}
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m.bs(query, mid, end, out)
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}
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*/
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fn (n mut mapnode) fill(idx int) {
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if idx != 0 && &mapnode(n.children[idx - 1]).size >= degree {
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n.borrow_from_prev(idx)
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} else if idx != n.size && &mapnode(n.children[idx + 1]).size >= degree {
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n.borrow_from_next(idx)
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} else if idx != n.size {
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n.merge(idx)
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} else {
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n.merge(idx - 1)
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}
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}
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fn preorder_keys(node &mapnode, keys mut []string, key_i int) int {
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mut i := key_i
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if !node.is_empty {
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keys[i] = node.key
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i++
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fn (n mut mapnode) borrow_from_prev(idx int) {
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mut child := &mapnode(n.children[idx])
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mut sibling := &mapnode(n.children[idx - 1])
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for i := child.size - 1; i >= 0; i-- {
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child.keys[i + 1] = child.keys[i]
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child.values[i + 1] = child.values[i]
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}
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if !isnil(node.left) {
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i = preorder_keys(node.left, mut keys, i)
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if !isnil(child.children) {
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for i := child.size; i >= 0; i-- {
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child.children[i + 1] = child.children[i]
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}
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if !isnil(node.right) {
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i = preorder_keys(node.right, mut keys, i)
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}
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return i
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child.keys[0] = n.keys[idx - 1]
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child.values[0] = n.values[idx - 1]
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if !isnil(child.children) {
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child.children[0] = sibling.children[sibling.size]
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}
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n.keys[idx - 1] = sibling.keys[sibling.size - 1]
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n.values[idx - 1] = sibling.values[sibling.size - 1]
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child.size++
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sibling.size--
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}
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fn (n mut mapnode) borrow_from_next(idx int) {
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mut child := &mapnode(n.children[idx])
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mut sibling := &mapnode(n.children[idx + 1])
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child.keys[child.size] = n.keys[idx]
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child.values[child.size] = n.values[idx]
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if !isnil(child.children) {
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child.children[child.size + 1] = sibling.children[0]
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}
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n.keys[idx] = sibling.keys[0]
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n.values[idx] = sibling.values[0]
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for i := 1; i < sibling.size; i++ {
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sibling.keys[i - 1] = sibling.keys[i]
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sibling.values[i - 1] = sibling.values[i]
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}
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if !isnil(sibling.children) {
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for i := 1; i <= sibling.size; i++ {
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sibling.children[i - 1] = sibling.children[i]
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}
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}
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child.size++
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sibling.size--
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}
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fn (n mut mapnode) merge(idx int) {
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mut child := &mapnode(n.children[idx])
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sibling := &mapnode(n.children[idx + 1])
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child.keys[mid_index] = n.keys[idx]
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child.values[mid_index] = n.values[idx]
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for i := 0; i < sibling.size; i++ {
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child.keys[i + degree] = sibling.keys[i]
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child.values[i + degree] = sibling.values[i]
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}
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if !isnil(child.children) {
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for i := 0; i <= sibling.size; i++ {
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child.children[i + degree] = sibling.children[i]
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}
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}
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for i := idx + 1; i < n.size; i++ {
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n.keys[i - 1] = n.keys[i]
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n.values[i - 1] = n.values[i]
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}
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for i := idx + 2; i <= n.size; i++ {
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n.children[i - 1] = n.children[i]
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}
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child.size += sibling.size + 1
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n.size--
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// free(sibling)
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}
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pub fn (m mut map) delete(key string) {
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if m.root.size == 0 {
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return
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}
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removed := m.root.remove_key(key)
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if removed {
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m.size--
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}
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if m.root.size == 0 {
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// tmp := t.root
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if isnil(m.root.children) {
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return
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} else {
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m.root = &mapnode(m.root.children[0])
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}
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// free(tmp)
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}
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}
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// Insert all keys of the subtree into array `keys`
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// starting at `at`. Keys are inserted in order.
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fn (n mapnode) subkeys(keys mut []string, at int) int {
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mut position := at
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if !isnil(n.children) {
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// Traverse children and insert
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// keys inbetween children
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for i in 0..n.size {
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child := &mapnode(n.children[i])
|
||||
position += child.subkeys(mut keys, position)
|
||||
keys[position] = n.keys[i]
|
||||
position++
|
||||
}
|
||||
// Insert the keys of the last child
|
||||
child := &mapnode(n.children[n.size])
|
||||
position += child.subkeys(mut keys, position)
|
||||
} else {
|
||||
// If leaf, insert keys
|
||||
for i in 0..n.size {
|
||||
keys[position + i] = n.keys[i]
|
||||
}
|
||||
position += n.size
|
||||
}
|
||||
// Return # of added keys
|
||||
return position - at
|
||||
}
|
||||
|
||||
pub fn (m &map) keys() []string {
|
||||
mut keys := [''].repeat(m.size)
|
||||
if isnil(m.root) || m.root.size == 0 {
|
||||
return keys
|
||||
}
|
||||
m.root.subkeys(mut keys, 0)
|
||||
return keys
|
||||
}
|
||||
|
||||
fn (n mut mapnode) free() {
|
||||
mut i := 0
|
||||
if isnil(n.children) {
|
||||
i = 0
|
||||
for i < n.size {
|
||||
i++
|
||||
}
|
||||
} else {
|
||||
i = 0
|
||||
for i < n.size {
|
||||
&mapnode(n.children[i]).free()
|
||||
i++
|
||||
}
|
||||
&mapnode(n.children[i]).free()
|
||||
}
|
||||
// free(n)
|
||||
}
|
||||
|
||||
pub fn (m mut map) free() {
|
||||
if isnil(m.root) {
|
||||
return keys
|
||||
}
|
||||
preorder_keys(m.root, mut keys, 0)
|
||||
return keys
|
||||
}
|
||||
|
||||
fn (m map) get(key string, out voidptr) bool {
|
||||
// println('g')
|
||||
if m.root == 0 {
|
||||
return false
|
||||
}
|
||||
return m.root.find(key, out, m.element_size)
|
||||
}
|
||||
|
||||
pub fn (n mut mapnode) delete(key string, element_size int) {
|
||||
if n.key == key {
|
||||
C.memset(n.val, 0, element_size)
|
||||
n.is_empty = true
|
||||
return
|
||||
}
|
||||
else if n.key > key {
|
||||
if isnil(n.left) {
|
||||
return
|
||||
}
|
||||
else {
|
||||
n.left.delete(key, element_size)
|
||||
}
|
||||
}
|
||||
else {
|
||||
if isnil(n.right) {
|
||||
return
|
||||
}
|
||||
else {
|
||||
n.right.delete(key, element_size)
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
pub fn (m mut map) delete(key string) {
|
||||
if m.exists(key) {
|
||||
m.root.delete(key, m.element_size)
|
||||
m.size--
|
||||
}
|
||||
}
|
||||
|
||||
fn (m map) exists(key string) bool {
|
||||
return !isnil(m.root) && m.root.find2(key, m.element_size)
|
||||
m.root.free()
|
||||
}
|
||||
|
||||
pub fn (m map) print() {
|
||||
@ -236,39 +420,16 @@ pub fn (m map) print() {
|
||||
// println('$entry.key => $entry.val')
|
||||
//}
|
||||
/*
|
||||
for i := 0; i < m.cap * m.element_size; i++ {
|
||||
for i := 0; i < m.cap * m.value_bytes; i++ {
|
||||
b := m.table[i]
|
||||
print('$i: ')
|
||||
C.printf('%02x', b)
|
||||
println('')
|
||||
}
|
||||
*/
|
||||
|
||||
println('>>>>>>>>>>')
|
||||
}
|
||||
|
||||
fn (n mut mapnode) free() {
|
||||
if n.val != 0 {
|
||||
free(n.val)
|
||||
}
|
||||
if n.left != 0 {
|
||||
n.left.free()
|
||||
}
|
||||
if n.right != 0 {
|
||||
n.right.free()
|
||||
}
|
||||
free(n)
|
||||
}
|
||||
|
||||
pub fn (m mut map) free() {
|
||||
if m.root == 0 {
|
||||
return
|
||||
}
|
||||
m.root.free()
|
||||
// C.free(m.table)
|
||||
// C.free(m.keys_table)
|
||||
}
|
||||
|
||||
pub fn (m map_string) str() string {
|
||||
if m.size == 0 {
|
||||
return '{}'
|
||||
@ -281,4 +442,3 @@ pub fn (m map_string) str() string {
|
||||
sb.writeln('}')
|
||||
return sb.str()
|
||||
}
|
||||
|
||||
|
||||
@ -23,19 +23,16 @@ fn test_map() {
|
||||
assert m.size == 2
|
||||
assert 'hi' in m
|
||||
mut sum := 0
|
||||
mut key_sum := ''
|
||||
// Test `for in`
|
||||
for key, val in m {
|
||||
sum += val
|
||||
key_sum += key
|
||||
}
|
||||
assert sum == 80 + 101
|
||||
assert key_sum == 'hihello'
|
||||
// Test `.keys()`
|
||||
keys := m.keys()
|
||||
assert keys.len == 2
|
||||
assert keys[0] == 'hi'
|
||||
assert keys[1] == 'hello'
|
||||
assert 'hi' in keys
|
||||
assert 'hello' in keys
|
||||
m.delete('hi')
|
||||
assert m.size == 1
|
||||
m.delete('aloha')
|
||||
|
||||
Loading…
Reference in New Issue
Block a user