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Optimize deepCopy to eliminate repeated allocations for nested structures #126

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Optimize deepCopy to eliminate repeated allocations for nested structures #126

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Copilot Nov 1, 2025
4657e21
refactor: optimize deepCopy to use iterator-based approach
Copilot Nov 1, 2025
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28 changes: 11 additions & 17 deletions ...tlin/dev/slne/surf/cloud/core/common/player/ppdc/PersistentPlayerDataContainerViewImpl.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,6 @@ import dev.slne.surf.cloud.api.common.player.ppdc.PersistentPlayerDataAdapterCon
import dev.slne.surf.cloud.api.common.player.ppdc.PersistentPlayerDataContainerView
import dev.slne.surf.cloud.api.common.player.ppdc.PersistentPlayerDataType
import dev.slne.surf.cloud.api.common.util.toObjectSet
import it.unimi.dsi.fastutil.objects.ObjectArrayList
import it.unimi.dsi.fastutil.objects.ObjectSet
import net.kyori.adventure.key.Key
import net.kyori.adventure.nbt.*
Expand Down Expand Up @@ -148,30 +147,25 @@ abstract class PersistentPlayerDataContainerViewImpl : PersistentPlayerDataConta
* - `Stack` extends `Vector`, which has legacy synchronization overhead
* - `ArrayDeque` is the recommended implementation for stack operations in modern Java/Kotlin
*
* The implementation uses an iterator-based approach to avoid materializing all entries into a list
* for each nested compound tag, which significantly reduces memory allocations for deeply nested structures.
*
* @param root The root `CompoundBinaryTag` to be deep copied.
* @return A deep copy of the specified `CompoundBinaryTag`.
* @throws IllegalStateException if the structure is too deeply nested (exceeds [MAX_NESTING_DEPTH])
*/
private fun deepCopy(root: CompoundBinaryTag): CompoundBinaryTag {
data class Frame(
val entries: List<Pair<String, BinaryTag>>,
var idx: Int,
val iterator: Iterator<Map.Entry<String, out BinaryTag>>,
val builder: CompoundBinaryTag.Builder,
val parent: Frame?,
val parentKey: String?
)

fun entriesOf(tag: CompoundBinaryTag): List<Pair<String, BinaryTag>> {
val list = ObjectArrayList<Pair<String, BinaryTag>>(tag.size())
tag.forEach { (k, v) -> list.add(k to v) }
return list
}

val stack = ArrayDeque<Frame>()
stack.addLast(
Frame(
entries = entriesOf(root),
idx = 0,
iterator = root.iterator(),
builder = CompoundBinaryTag.builder(),
parent = null,
parentKey = null
Expand All @@ -183,17 +177,18 @@ abstract class PersistentPlayerDataContainerViewImpl : PersistentPlayerDataConta
while (stack.isNotEmpty()) {
val top = stack.removeLast()

while (top.idx < top.entries.size) {
val (key, value) = top.entries[top.idx++]
while (top.iterator.hasNext()) {
val entry = top.iterator.next()
val key = entry.key
val value = entry.value

if (value is CompoundBinaryTag) {
PersistentPlayerDataContainerView.ensureValidNestingDepth(stack.size)

stack.addLast(top)
stack.addLast(
Frame(
entries = entriesOf(value),
idx = 0,
iterator = value.iterator(),
builder = CompoundBinaryTag.builder(),
parent = top,
parentKey = key
Expand All @@ -206,8 +201,7 @@ abstract class PersistentPlayerDataContainerViewImpl : PersistentPlayerDataConta
}
}


if (top.idx >= top.entries.size) {
if (!top.iterator.hasNext()) {
val built = top.builder.build()
if (top.parent == null) {
result = built
Expand Down