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/*
* Copyright © 2017-2023 WireGuard LLC. All Rights Reserved.
* SPDX-License-Identifier: Apache-2.0
*/
package com.wireguard.android.databinding
import java.util.AbstractList
import java.util.Collections
import java.util.Comparator
import java.util.Spliterator
/**
* KeyedArrayList that enforces uniqueness and sorted order across the set of keys. This class uses
* binary search to improve lookup and replacement times to O(log(n)). However, due to the
* array-based nature of this class, insertion and removal of elements with anything but the largest
* key still require O(n) time.
*/
class ObservableSortedKeyedArrayList<K, E : Keyed<out K>>(private val comparator: Comparator<in K>) : ObservableKeyedArrayList<K, E>() {
@Transient
private val keyList = KeyList(this)
override fun add(element: E): Boolean {
val insertionPoint = getInsertionPoint(element)
if (insertionPoint < 0) {
// Skipping insertion is non-destructive if the new and existing objects are the same.
if (element === get(-insertionPoint - 1)) return false
throw IllegalArgumentException("Element with same key already exists in list")
}
super.add(insertionPoint, element)
return true
}
override fun add(index: Int, element: E) {
val insertionPoint = getInsertionPoint(element)
require(insertionPoint >= 0) { "Element with same key already exists in list" }
if (insertionPoint != index) throw IndexOutOfBoundsException("Wrong index given for element")
super.add(index, element)
}
override fun addAll(elements: Collection<E>): Boolean {
var didChange = false
for (e in elements) {
if (add(e))
didChange = true
}
return didChange
}
override fun addAll(index: Int, elements: Collection<E>): Boolean {
var i = index
for (e in elements)
add(i++, e)
return true
}
private fun getInsertionPoint(e: E) = -Collections.binarySearch(keyList, e.key, comparator) - 1
override fun indexOfKey(key: K): Int {
val index = Collections.binarySearch(keyList, key, comparator)
return if (index >= 0) index else -1
}
override fun set(index: Int, element: E): E {
val order = comparator.compare(element.key, get(index).key)
if (order != 0) {
// Allow replacement if the new key would be inserted adjacent to the replaced element.
val insertionPoint = getInsertionPoint(element)
if (insertionPoint < index || insertionPoint > index + 1)
throw IndexOutOfBoundsException("Wrong index given for element")
}
return super.set(index, element)
}
private class KeyList<K, E : Keyed<out K>>(private val list: ObservableSortedKeyedArrayList<K, E>) : AbstractList<K>(), Set<K> {
override fun get(index: Int): K = list[index].key
override val size
get() = list.size
override fun spliterator(): Spliterator<K> = super<AbstractList>.spliterator()
}
}
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