kotlin.collections.ReversedViews.kt Maven / Gradle / Ivy

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Kotlin Common Standard Library

There is a newer version: 2.0.0-RC3

/*
 * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
 * that can be found in the license/LICENSE.txt file.
 */
@file:kotlin.jvm.JvmMultifileClass
@file:kotlin.jvm.JvmName("CollectionsKt")

package kotlin.collections

import kotlin.*


private open class ReversedListReadOnly(private val delegate: List) : AbstractList() {
    override val size: Int get() = delegate.size
    override fun get(index: Int): T = delegate[reverseElementIndex(index)]
}

private class ReversedList(private val delegate: MutableList) : AbstractMutableList() {
    override val size: Int get() = delegate.size
    override fun get(index: Int): T = delegate[reverseElementIndex(index)]

    override fun clear() = delegate.clear()
    override fun removeAt(index: Int): T = delegate.removeAt(reverseElementIndex(index))

    override fun set(index: Int, element: T): T = delegate.set(reverseElementIndex(index), element)
    override fun add(index: Int, element: T) {
        delegate.add(reversePositionIndex(index), element)
    }
}

private fun List<*>.reverseElementIndex(index: Int) =
    if (index in 0..lastIndex) lastIndex - index else throw IndexOutOfBoundsException("Element index $index must be in range [${0..lastIndex}].")

private fun List<*>.reversePositionIndex(index: Int) =
    if (index in 0..size) size - index else throw IndexOutOfBoundsException("Position index $index must be in range [${0..size}].")


/**
 * Returns a reversed read-only view of the original List.
 * All changes made in the original list will be reflected in the reversed one.
 * @sample samples.collections.ReversedViews.asReversedList
 */
public fun  List.asReversed(): List = ReversedListReadOnly(this)

/**
 * Returns a reversed mutable view of the original mutable List.
 * All changes made in the original list will be reflected in the reversed one and vice versa.
 * @sample samples.collections.ReversedViews.asReversedMutableList
 */
@kotlin.jvm.JvmName("asReversedMutable")
public fun  MutableList.asReversed(): MutableList = ReversedList(this)