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KT-77646 - Optimize copyOf(newSize) function for primitive arrays #5455

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KT-77646 - Optimize copyOf(newSize) function for primitive arrays #5455

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55 changes: 49 additions & 6 deletions libraries/stdlib/js/src/generated/_ArraysJs.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -940,7 +940,14 @@ public fun <T> Array<out T>.copyOf(newSize: Int): Array<T?> {
*/
public actual fun ByteArray.copyOf(newSize: Int): ByteArray {
require(newSize >= 0) { "Invalid new array size: $newSize." }
return fillFrom(this, ByteArray(newSize))
val size = this.size
return when {
newSize < 16 || size < 16 -> fillFrom(this, ByteArray(newSize))
newSize > size -> ByteArray(newSize).also { copy ->
copy.asDynamic().set(this, 0)
}
else -> this.asDynamic().slice(0, newSize)
}
}

/**
Expand All @@ -954,7 +961,14 @@ public actual fun ByteArray.copyOf(newSize: Int): ByteArray {
*/
public actual fun ShortArray.copyOf(newSize: Int): ShortArray {
require(newSize >= 0) { "Invalid new array size: $newSize." }
return fillFrom(this, ShortArray(newSize))
val size = this.size
return when {
newSize < 16 || size < 16 -> fillFrom(this, ShortArray(newSize))
newSize > size -> ShortArray(newSize).also { copy ->
copy.asDynamic().set(this, 0)
}
else -> this.asDynamic().slice(0, newSize)
}
}

/**
Expand All @@ -968,7 +982,14 @@ public actual fun ShortArray.copyOf(newSize: Int): ShortArray {
*/
public actual fun IntArray.copyOf(newSize: Int): IntArray {
require(newSize >= 0) { "Invalid new array size: $newSize." }
return fillFrom(this, IntArray(newSize))
val size = this.size
return when {
newSize < 16 || size < 16 -> fillFrom(this, IntArray(newSize))
newSize > size -> IntArray(newSize).also { copy ->
copy.asDynamic().set(this, 0)
}
else -> this.asDynamic().slice(0, newSize)
}
}

/**
Expand Down Expand Up @@ -996,7 +1017,14 @@ public actual fun LongArray.copyOf(newSize: Int): LongArray {
*/
public actual fun FloatArray.copyOf(newSize: Int): FloatArray {
require(newSize >= 0) { "Invalid new array size: $newSize." }
return fillFrom(this, FloatArray(newSize))
val size = this.size
return when {
newSize < 16 || size < 16 -> fillFrom(this, FloatArray(newSize))
newSize > size -> FloatArray(newSize).also { copy ->
copy.asDynamic().set(this, 0)
}
else -> this.asDynamic().slice(0, newSize)
}
}

/**
Expand All @@ -1010,7 +1038,14 @@ public actual fun FloatArray.copyOf(newSize: Int): FloatArray {
*/
public actual fun DoubleArray.copyOf(newSize: Int): DoubleArray {
require(newSize >= 0) { "Invalid new array size: $newSize." }
return fillFrom(this, DoubleArray(newSize))
val size = this.size
return when {
newSize < 16 || size < 16 -> fillFrom(this, DoubleArray(newSize))
newSize > size -> DoubleArray(newSize).also { copy ->
copy.asDynamic().set(this, 0)
}
else -> this.asDynamic().slice(0, newSize)
}
}

/**
Expand Down Expand Up @@ -1038,7 +1073,15 @@ public actual fun BooleanArray.copyOf(newSize: Int): BooleanArray {
*/
public actual fun CharArray.copyOf(newSize: Int): CharArray {
require(newSize >= 0) { "Invalid new array size: $newSize." }
return withType("CharArray", fillFrom(this, CharArray(newSize)))
val size = this.size
val copy = when {
newSize < 16 || size < 16 -> fillFrom(this, CharArray(newSize))
newSize > size -> CharArray(newSize).also { copy ->
copy.asDynamic().set(this, 0)
}
else -> this.asDynamic().slice(0, newSize)
}
return withType("CharArray", copy)
}

/**
Expand Down
43 changes: 35 additions & 8 deletions libraries/tools/kotlin-stdlib-gen/src/templates/Arrays.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -1076,14 +1076,41 @@ object ArrayOps : TemplateGroupBase() {
returns("SELF")
on(Platform.JS) {
when (primitive!!) {
PrimitiveType.Boolean ->
body { "return withType(\"BooleanArray\", arrayCopyResize(this, newSize, false))" }
PrimitiveType.Char ->
body { "return withType(\"CharArray\", fillFrom(this, ${primitive}Array(newSize)))" }
PrimitiveType.Long ->
body { "return withType(\"LongArray\", arrayCopyResize(this, newSize, ${primitive!!.zero()}))" }
else ->
body { "return fillFrom(this, ${primitive}Array(newSize))" }
PrimitiveType.Long -> body {
"return withType(\"LongArray\", arrayCopyResize(this, newSize, ${primitive!!.zero()}))"
}
PrimitiveType.Boolean -> body {
"return withType(\"BooleanArray\", arrayCopyResize(this, newSize, false))"
}
// Benchmarking showed that when copying a small number of elements (typically < 20),
// a simple loop is consistently faster than calling TypedArray.set or TypedArray.slice
// across JS engines. We chose 16 as an arbitrary threshold based on those results.
PrimitiveType.Char -> body {
"""
val size = this.size
val copy = when {
newSize < 16 || size < 16 -> fillFrom(this, CharArray(newSize))
newSize > size -> CharArray(newSize).also { copy ->
copy.asDynamic().set(this, 0)
}
else -> this.asDynamic().slice(0, newSize)
}

return withType("CharArray", copy)
""".trimIndent()
}
else -> body {
"""
val size = this.size
return when {
newSize < 16 || size < 16 -> fillFrom(this, ${primitive}Array(newSize))
newSize > size -> ${primitive}Array(newSize).also { copy ->
copy.asDynamic().set(this, 0)
}
else -> this.asDynamic().slice(0, newSize)
}
""".trimIndent()
}
}
body { newSizeCheck + "\n" + body }
}
Expand Down