org.jetbrains.kotlin.utils.MemoryOptimizedCollectionUtil.kt Maven / Gradle / Ivy

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/*
 * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
 * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
 */

package org.jetbrains.kotlin.utils

import java.util.*
import kotlin.math.min

/**
 * A memory-optimized version of [Iterable.map].
 * @see Iterable.map
 */
inline fun  Collection.memoryOptimizedMap(transform: (T) -> R): List {
    return mapTo(ArrayList(size), transform).compactIfPossible()
}

/**
 * A memory-optimized version of [Iterable.mapIndexed].
 * @see Iterable.mapIndexed
 */
inline fun  Collection.memoryOptimizedMapIndexed(transform: (index: Int, T) -> R): List {
    return mapIndexedTo(ArrayList(size), transform).compactIfPossible()
}

/**
 * A memory-optimized version of [Iterable.mapNotNull].
 * @see Iterable.mapNotNull
 */
inline fun  Collection.memoryOptimizedMapNotNull(transform: (T) -> R?): List {
    return mapNotNullTo(ArrayList(), transform).compactIfPossible()
}

/**
 * A memory-optimized version of [Iterable.flatMap].
 * @see Iterable.flatMap
 */
inline fun  Collection.memoryOptimizedFlatMap(transform: (T) -> Iterable): List {
    return flatMapTo(ArrayList(), transform).compactIfPossible()
}

/**
 * A memory-optimized version of [Iterable.filter].
 * @see Iterable.filter
 */
inline fun  Collection.memoryOptimizedFilter(predicate: (T) -> Boolean): List {
    return filterTo(ArrayList(), predicate).compactIfPossible()
}

/**
 * A memory-optimized version of [Iterable.filterNot].
 * @see Iterable.filterNot
 */
inline fun  Collection.memoryOptimizedFilterNot(predicate: (T) -> Boolean): List {
    return filterNotTo(ArrayList(), predicate).compactIfPossible()
}

/**
 * A memory-optimized version of [Iterable.filterIsInstance].
 * @see Iterable.filterIsInstance
 */
inline fun  Collection<*>.memoryOptimizedFilterIsInstance(): List {
    return filterIsInstanceTo(ArrayList()).compactIfPossible()
}

/**
 * A memory-optimized version of [Iterable.plus].
 * @see Iterable.plus
 */
infix fun  List.memoryOptimizedPlus(elements: List): List =
    when (val resultSize = size + elements.size) {
        0 -> emptyList()
        1 -> Collections.singletonList(if (isEmpty()) elements.first() else first())
        else -> ArrayList(resultSize).also {
            it.addAll(this)
            it.addAll(elements)
        }
    }

/**
 * A memory-optimized version of [Iterable.plus].
 * @see Iterable.plus
 */
infix fun  List.memoryOptimizedPlus(element: T): List =
    when (size) {
        0 -> Collections.singletonList(element)
        else -> ArrayList(size + 1).also {
            it.addAll(this)
            it.add(element)
        }
    }

/**
 * A memory-optimized version of [Iterable.zip].
 * @see Iterable.zip
 */
infix fun  Collection.memoryOptimizedZip(other: Collection): List> {
    return when {
        isEmpty() || other.isEmpty() -> emptyList()
        min(size, other.size) == 1 -> listOf(first() to other.first())
        else -> zip(other) { t1, t2 -> t1 to t2 }
    }
}

/**
 * [Sequence] variant of [org.jetbrains.kotlin.utils.atMostOne]
 *
 * So, when:
 * - there is no element then `null` will be returned
 * - there is a single element then the element will be returned
 * - there is more than one element then the error will be thrown
 * @see org.jetbrains.kotlin.utils.atMostOne
 */
fun  Sequence.atMostOne(): T? {
    val iterator = iterator()

    if (!iterator.hasNext()) return null

    val single = iterator.next()

    if (iterator.hasNext()) {
        throw IllegalArgumentException("Sequence has more than one element.")
    }

    return single
}

/**
 * The variant of [org.jetbrains.kotlin.util.collectionUtils.filterIsInstanceAnd] extension function but to find the first element
 * which is an instance of type [T] and satisfies [predicate] condition
 * @see org.jetbrains.kotlin.util.collectionUtils.filterIsInstanceAnd
 */
inline fun  Iterable<*>.findIsInstanceAnd(predicate: (T) -> Boolean): T? {
    for (element in this) {
        if (element is T && predicate(element)) {
            return element
        }
    }
    return null
}

/**
 * The same as [Collection.toMutableList] extension function, but it returns a SmartList which is better with in sense of memory consumption
 * @see Collection.toMutableList
 */
fun  Collection.toSmartList(): List = SmartList(this)