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/*
* Scala (https://www.scala-lang.org)
*
* Copyright EPFL and Lightbend, Inc.
*
* Licensed under Apache License 2.0
* (http://www.apache.org/licenses/LICENSE-2.0).
*
* See the NOTICE file distributed with this work for
* additional information regarding copyright ownership.
*/
package scala
package collection
import scala.annotation.unchecked.uncheckedVariance
import scala.runtime.Statics
/**
* Trait that overrides iterable operations to take advantage of strict builders.
*
* @tparam A Elements type
* @tparam CC Collection type constructor
* @tparam C Collection type
*/
trait StrictOptimizedIterableOps[+A, +CC[_], +C]
extends Any
with IterableOps[A, CC, C] {
// Optimized, push-based version of `partition`
override def partition(p: A => Boolean): (C, C) = {
val l, r = newSpecificBuilder
iterator.foreach(x => (if (p(x)) l else r) += x)
(l.result(), r.result())
}
override def span(p: A => Boolean): (C, C) = {
val first = newSpecificBuilder
val second = newSpecificBuilder
val it = iterator
var inFirst = true
while (it.hasNext && inFirst) {
val a = it.next()
if (p(a)) {
first += a
} else {
second += a
inFirst = false
}
}
while (it.hasNext) {
second += it.next()
}
(first.result(), second.result())
}
override def unzip[A1, A2](implicit asPair: A => (A1, A2)): (CC[A1], CC[A2]) = {
val first = iterableFactory.newBuilder[A1]
val second = iterableFactory.newBuilder[A2]
foreach { a =>
val pair = asPair(a)
first += pair._1
second += pair._2
}
(first.result(), second.result())
}
override def unzip3[A1, A2, A3](implicit asTriple: A => (A1, A2, A3)): (CC[A1], CC[A2], CC[A3]) = {
val b1 = iterableFactory.newBuilder[A1]
val b2 = iterableFactory.newBuilder[A2]
val b3 = iterableFactory.newBuilder[A3]
foreach { xyz =>
val triple = asTriple(xyz)
b1 += triple._1
b2 += triple._2
b3 += triple._3
}
(b1.result(), b2.result(), b3.result())
}
// The implementations of the following operations are not fundamentally different from
// the view-based implementations, but they turn out to be slightly faster because
// a couple of indirection levels are removed
override def map[B](f: A => B): CC[B] =
strictOptimizedMap(iterableFactory.newBuilder, f)
/**
* @param b Builder to use to build the resulting collection
* @param f Element transformation function
* @tparam B Type of elements of the resulting collection (e.g. `String`)
* @tparam C2 Type of the resulting collection (e.g. `List[String]`)
* @return The resulting collection
*/
@inline protected[this] final def strictOptimizedMap[B, C2](b: mutable.Builder[B, C2], f: A => B): C2 = {
val it = iterator
while (it.hasNext) {
b += f(it.next())
}
b.result()
}
override def flatMap[B](f: A => IterableOnce[B]): CC[B] =
strictOptimizedFlatMap(iterableFactory.newBuilder, f)
/**
* @param b Builder to use to build the resulting collection
* @param f Element transformation function
* @tparam B Type of elements of the resulting collection (e.g. `String`)
* @tparam C2 Type of the resulting collection (e.g. `List[String]`)
* @return The resulting collection
*/
@inline protected[this] final def strictOptimizedFlatMap[B, C2](b: mutable.Builder[B, C2], f: A => IterableOnce[B]): C2 = {
val it = iterator
while (it.hasNext) {
b ++= f(it.next())
}
b.result()
}
/**
* @param that Elements to concatenate to this collection
* @param b Builder to use to build the resulting collection
* @tparam B Type of elements of the resulting collections (e.g. `Int`)
* @tparam C2 Type of the resulting collection (e.g. `List[Int]`)
* @return The resulting collection
*/
@inline protected[this] final def strictOptimizedConcat[B >: A, C2](that: IterableOnce[B], b: mutable.Builder[B, C2]): C2 = {
b ++= this
b ++= that
b.result()
}
override def collect[B](pf: PartialFunction[A, B]): CC[B] =
strictOptimizedCollect(iterableFactory.newBuilder, pf)
/**
* @param b Builder to use to build the resulting collection
* @param pf Element transformation partial function
* @tparam B Type of elements of the resulting collection (e.g. `String`)
* @tparam C2 Type of the resulting collection (e.g. `List[String]`)
* @return The resulting collection
*/
@inline protected[this] final def strictOptimizedCollect[B, C2](b: mutable.Builder[B, C2], pf: PartialFunction[A, B]): C2 = {
val marker = Statics.pfMarker
val it = iterator
while (it.hasNext) {
val elem = it.next()
val v = pf.applyOrElse(elem, ((x: A) => marker).asInstanceOf[Function[A, B]])
if (marker ne v.asInstanceOf[AnyRef]) b += v
}
b.result()
}
override def flatten[B](implicit toIterableOnce: A => IterableOnce[B]): CC[B] =
strictOptimizedFlatten(iterableFactory.newBuilder)
/**
* @param b Builder to use to build the resulting collection
* @param toIterableOnce Evidence that `A` can be seen as an `IterableOnce[B]`
* @tparam B Type of elements of the resulting collection (e.g. `Int`)
* @tparam C2 Type of the resulting collection (e.g. `List[Int]`)
* @return The resulting collection
*/
@inline protected[this] final def strictOptimizedFlatten[B, C2](b: mutable.Builder[B, C2])(implicit toIterableOnce: A => IterableOnce[B]): C2 = {
val it = iterator
while (it.hasNext) {
b ++= toIterableOnce(it.next())
}
b.result()
}
override def zip[B](that: IterableOnce[B]): CC[(A @uncheckedVariance, B)] =
strictOptimizedZip(that, iterableFactory.newBuilder[(A, B)])
/**
* @param that Collection to zip with this collection
* @param b Builder to use to build the resulting collection
* @tparam B Type of elements of the second collection (e.g. `String`)
* @tparam C2 Type of the resulting collection (e.g. `List[(Int, String)]`)
* @return The resulting collection
*/
@inline protected[this] final def strictOptimizedZip[B, C2](that: IterableOnce[B], b: mutable.Builder[(A, B), C2]): C2 = {
val it1 = iterator
val it2 = that.iterator
while (it1.hasNext && it2.hasNext) {
b += ((it1.next(), it2.next()))
}
b.result()
}
override def zipWithIndex: CC[(A @uncheckedVariance, Int)] = {
val b = iterableFactory.newBuilder[(A, Int)]
var i = 0
val it = iterator
while (it.hasNext) {
b += ((it.next(), i))
i += 1
}
b.result()
}
override def scanLeft[B](z: B)(op: (B, A) => B): CC[B] = {
val b = iterableFactory.newBuilder[B]
b.sizeHint(toIterable, delta = 0)
var acc = z
b += acc
val it = iterator
while (it.hasNext) {
acc = op(acc, it.next())
b += acc
}
b.result()
}
override def filter(pred: A => Boolean): C = filterImpl(pred, isFlipped = false)
override def filterNot(pred: A => Boolean): C = filterImpl(pred, isFlipped = true)
protected[collection] def filterImpl(pred: A => Boolean, isFlipped: Boolean): C = {
val b = newSpecificBuilder
val it = iterator
while (it.hasNext) {
val elem = it.next()
if (pred(elem) != isFlipped) {
b += elem
}
}
b.result()
}
// Optimized, push-based version of `partitionMap`
override def partitionMap[A1, A2](f: A => Either[A1, A2]): (CC[A1], CC[A2]) = {
val l = iterableFactory.newBuilder[A1]
val r = iterableFactory.newBuilder[A2]
foreach { x =>
f(x) match {
case Left(x1) => l += x1
case Right(x2) => r += x2
}
}
(l.result(), r.result())
}
// Optimization avoids creation of second collection
override def tapEach[U](f: A => U): C = {
foreach(f)
coll
}
/** A collection containing the last `n` elements of this collection.
* $willForceEvaluation
*/
override def takeRight(n: Int): C = {
val b = newSpecificBuilder
b.sizeHintBounded(n, toIterable)
val lead = iterator drop n
val it = iterator
while (lead.hasNext) {
lead.next()
it.next()
}
while (it.hasNext) b += it.next()
b.result()
}
/** The rest of the collection without its `n` last elements. For
* linear, immutable collections this should avoid making a copy.
* $willForceEvaluation
*/
override def dropRight(n: Int): C = {
val b = newSpecificBuilder
if (n >= 0) b.sizeHint(toIterable, delta = -n)
val lead = iterator drop n
val it = iterator
while (lead.hasNext) {
b += it.next()
lead.next()
}
b.result()
}
}
