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

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/*
 * Copyright 2010-2015 JetBrains s.r.o.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package kotlin

import java.util.AbstractList
import kotlin.platform.platformName

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

    protected fun Int.flipIndex(): Int = if (this in 0..size() - 1) size() - this - 1 else throw IndexOutOfBoundsException("index $this should be in range [${0..size() - 1}]")
    protected fun Int.flipIndexForward(): Int = if (this in 0..size()) size() - this else throw IndexOutOfBoundsException("index $this should be in range [${0..size()}]")
}

private class ReversedList(protected override val delegate: MutableList) : ReversedListReadOnly(delegate) {
    override fun clear() = delegate.clear()
    override fun remove(index: Int): T = delegate.remove(index.flipIndex())

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

/**
 * Returns a reversed read-only view of the original List.
 * All changes made in the original list will be reflected in the reversed one.
 */
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.
 */
platformName("asReversedMutable")
public fun  MutableList.asReversed(): MutableList = ReversedList(this)