scala.compat.java8.collectionImpl.Accumulator.scala Maven / Gradle / Ivy
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package scala.compat.java8.collectionImpl
/** An `Accumulator` is a low-level collection specialized for gathering
* elements in parallel and then joining them in order by merging Accumulators.
* Accumulators can contain more than `Int.MaxValue` elements.
*/
final class Accumulator[A] extends AccumulatorLike[A, Accumulator[A]] { self =>
private[java8] var current: Array[AnyRef] = Accumulator.emptyAnyRefArray
private[java8] var history: Array[Array[AnyRef]] = Accumulator.emptyAnyRefArrayArray
private[java8] var cumul: Array[Long] = Accumulator.emptyLongArray
private[java8] def cumulative(i: Int) = cumul(i)
private def expand(): Unit = {
if (index > 0) {
if (hIndex >= history.length) hExpand()
history(hIndex) = current
cumul(hIndex) = (if (hIndex > 0) cumulative(hIndex-1) else 0) + index
hIndex += 1
}
current = new Array[AnyRef](nextBlockSize)
index = 0
}
private def hExpand(): Unit = {
if (hIndex == 0) {
history = new Array[Array[AnyRef]](4)
cumul = new Array[Long](4)
}
else {
history = java.util.Arrays.copyOf(history, history.length << 1)
cumul = java.util.Arrays.copyOf(cumul, cumul.length << 1)
}
}
/** Appends an element to this `Accumulator`. */
final def +=(a: A): Unit = {
totalSize += 1
if (index >= current.length) expand()
current(index) = a.asInstanceOf[AnyRef]
index += 1
}
/** Removes all elements from `that` and appends them to this `Accumulator`. */
final def drain[A1 <: A](that: Accumulator[A1]): Unit = {
var h = 0
var prev = 0L
var more = true
while (more && h < that.hIndex) {
val n = (that.cumulative(h) - prev).toInt
if (current.length - index >= n) {
System.arraycopy(that.history(h), 0, current, index, n)
prev = that.cumulative(h)
index += n
h += 1
}
else more = false
}
if (h >= that.hIndex && current.length - index >= that.index) {
if (that.index > 0) System.arraycopy(that.current, 0, current, index, that.index)
index += that.index
}
else {
val slots = (if (index > 0) 1 else 0) + that.hIndex - h
if (hIndex + slots > history.length) {
val n = math.max(4, 1 << (32 - java.lang.Integer.numberOfLeadingZeros(1 + hIndex + slots)))
history = java.util.Arrays.copyOf(history, n)
cumul = java.util.Arrays.copyOf(cumul, n)
}
var pv = (if (hIndex > 0) cumulative(hIndex-1) else 0L)
if (index > 0) {
pv += index
cumul(hIndex) = pv
history(hIndex) = (if (index < (current.length >>> 3) && current.length > 32) java.util.Arrays.copyOf(current, index) else current)
hIndex += 1
}
while (h < that.hIndex) {
pv += that.cumulative(h) - prev
prev = that.cumulative(h)
cumul(hIndex) = pv
history(hIndex) = that.history(h)
h += 1
hIndex += 1
}
index = that.index
current = that.current
}
totalSize += that.totalSize
that.clear
}
override def clear(): Unit = {
super.clear()
current = Accumulator.emptyAnyRefArray
history = Accumulator.emptyAnyRefArrayArray
cumul = Accumulator.emptyLongArray
}
/** Retrieves the `ix`th element. */
final def apply(ix: Long): A = {
if (totalSize - ix <= index || hIndex == 0) current((ix - (totalSize - index)).toInt).asInstanceOf[A]
else {
val w = seekSlot(ix)
history((w >>> 32).toInt)((w & 0xFFFFFFFFL).toInt).asInstanceOf[A]
}
}
/** Retrieves the `ix`th element, using an `Int` index. */
final def apply(i: Int): A = apply(i.toLong)
/** Returns a `Stepper` over the contents of this `Accumulator`*/
final def stepper: AnyStepper[A] = new AccumulatorStepper[A](this)
/** Returns an `Iterator` over the contents of this `Accumulator`. */
final def iterator = stepper.iterator
/** Returns a `java.util.Spliterator` over the contents of this `Accumulator`*/
final def spliterator: java.util.Spliterator[A] = stepper.spliterator
/** Produces a sequential Java 8 Stream over the elements of this `Accumulator`*/
final def seqStream: java.util.stream.Stream[A] = java.util.stream.StreamSupport.stream(spliterator, false)
/** Produces a parallel Java 8 Stream over the elements of this `Accumulator`*/
final def parStream: java.util.stream.Stream[A] = java.util.stream.StreamSupport.stream(spliterator, true)
/** Copies the elements in this `Accumulator` into an `Array` */
final def toArray(implicit tag: reflect.ClassTag[A]) = {
if (totalSize > Int.MaxValue) throw new IllegalArgumentException("Too many elements accumulated for an array: "+totalSize.toString)
val a = new Array[A](totalSize.toInt)
var j = 0
var h = 0
var pv = 0L
while (h < hIndex) {
val x = history(h)
val n = cumulative(h) - pv
pv = cumulative(h)
var i = 0
while (i < n) {
a(j) = x(i).asInstanceOf[A]
i += 1
j += 1
}
h += 1
}
var i = 0
while (i < index) {
a(j) = current(i).asInstanceOf[A]
i += 1
j += 1
}
a
}
/** Copies the elements in this `Accumulator` to a `List` */
final def toList: List[A] = {
var ans: List[A] = Nil
var i = index - 1
while (i >= 0) {
ans = current(i).asInstanceOf[A] :: ans
i -= 1
}
var h = hIndex - 1
while (h >= 0) {
val a = history(h)
i = (cumulative(h) - (if (h == 0) 0L else cumulative(h-1))).toInt - 1
while (i >= 0) {
ans = a(i).asInstanceOf[A] :: ans
i -= 1
}
h -= 1
}
ans
}
/** Copies the elements in this `Accumulator` to a specified collection.
* Usage example: `acc.to[Vector]`
*/
final def to[Coll[_]](implicit cbf: collection.generic.CanBuildFrom[Nothing, A, Coll[A]]): Coll[A] = {
if (totalSize > Int.MaxValue) throw new IllegalArgumentException("Too many elements accumulated for a Scala collection: "+totalSize.toString)
val b = cbf()
b.sizeHint(totalSize.toInt)
var h = 0
var pv = 0L
while (h < hIndex) {
val x = history(h)
val n = cumulative(h) - pv
pv = cumulative(h)
var i = 0
while (i < n) {
b += x(i).asInstanceOf[A]
i += 1
}
h += 1
}
var i = 0
while (i < index) {
b += current(i).asInstanceOf[A]
i += 1
}
b.result
}
}
object Accumulator {
private val emptyAnyRefArray = new Array[AnyRef](0)
private val emptyAnyRefArrayArray = new Array[Array[AnyRef]](0)
private val emptyLongArray = new Array[Long](0)
/** A `Supplier` of `Accumulator`s, suitable for use with `java.util.stream.Stream`'s `collect` method. */
def supplier[A] = new java.util.function.Supplier[Accumulator[A]]{ def get: Accumulator[A] = new Accumulator[A] }
/** A `BiConsumer` that adds an element to an `Accumulator`, suitable for use with `java.util.stream.Stream`'s `collect` method. */
def adder[A] = new java.util.function.BiConsumer[Accumulator[A], A]{ def accept(ac: Accumulator[A], a: A) { ac += a } }
/** A `BiConsumer` that merges `Accumulator`s, suitable for use with `java.util.stream.Stream`'s `collect` method. */
def merger[A] = new java.util.function.BiConsumer[Accumulator[A], Accumulator[A]]{ def accept(a1: Accumulator[A], a2: Accumulator[A]) { a1 drain a2 } }
/** Builds an `Accumulator` from any `TraversableOnce` */
def from[A](source: TraversableOnce[A]) = {
val a = new Accumulator[A]
source.foreach(a += _)
a
}
}
private[java8] class AccumulatorStepper[A](private val acc: Accumulator[A]) extends AnyStepper[A] {
import java.util.Spliterator._
private var h = 0
private var i = 0
private var a = if (acc.hIndex > 0) acc.history(0) else acc.current
private var n = if (acc.hIndex > 0) acc.cumulative(0) else acc.index
private var N = acc.totalSize
private def duplicateSelf(limit: Long = N): AccumulatorStepper[A] = {
val ans = new AccumulatorStepper(acc)
ans.h = h
ans.i = i
ans.a = a
ans.n = n
ans.N = limit
ans
}
private def loadMore(): Unit = {
h += 1
if (h < acc.hIndex) { a = acc.history(h); n = acc.cumulative(h) - acc.cumulative(h-1) }
else { a = acc.current; n = acc.index }
i = 0
}
def characteristics = ORDERED | SIZED | SUBSIZED
def estimateSize = N
def hasNext = N > 0
def next: A =
if (N <= 0) throw new NoSuchElementException("Next in empty Stepper")
else {
if (i >= n) loadMore()
val ans = a(i).asInstanceOf[A]
i += 1
N -= 1
ans
}
// Overidden for efficiency
override def tryStep(f: A => Unit): Boolean =
if (N <= 0) false
else {
if (i >= n) loadMore()
f(a(i).asInstanceOf[A])
i += 1
N -= 1
true
}
// Overidden for efficiency
override def tryAdvance(f: java.util.function.Consumer[_ >: A]): Boolean =
if (N <= 0) false
else {
if (i >= n) loadMore()
f.accept(a(i).asInstanceOf[A])
i += 1
N -= 1
true
}
// Overridden for efficiency
override def foreach(f: A => Unit) {
while (N > 0) {
if (i >= n) loadMore()
val i0 = i
if ((n-i) > N) n = i + N.toInt
while (i < n) {
f(a(i).asInstanceOf[A])
i += 1
}
N -= (n - i0)
}
}
// Overridden for efficiency
override def forEachRemaining(f: java.util.function.Consumer[_ >: A]) {
while (N > 0) {
if (i >= n) loadMore()
val i0 = i
if ((n-i) > N) n = i + N.toInt
while (i < n) {
f.accept(a(i).asInstanceOf[A])
i += 1
}
N -= (n - i0)
}
}
def substep(): AnyStepper[A] =
if (N <= 1) null
else {
val half = (N >> 1)
val M = (if (h <= 0) 0L else acc.cumulative(h-1)) + i
val R = M + half
val ans = duplicateSelf(half)
if (h < acc.hIndex) {
val w = acc.seekSlot(R)
h = (w >>> 32).toInt
if (h < acc.hIndex) {
a = acc.history(h)
n = acc.cumulative(h) - (if (h > 0) acc.cumulative(h-1) else 0)
}
else {
a = acc.current
n = acc.index
}
i = (w & 0xFFFFFFFFL).toInt
}
else i += half.toInt
N -= half
ans
}
override def toString = s"$h $i ${a.mkString("{",",","}")} $n $N"
}
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