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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift Collections open source project
//
// Copyright (c) 2022 - 2024 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
//
//===----------------------------------------------------------------------===//
extension _HashNode {
@inlinable
internal func union<Value2>(
_ level: _HashLevel,
_ other: _HashNode<Key, Value2>
) -> (copied: Bool, node: _HashNode<Key, Void>) {
guard self.count > 0 else { return (true, other.mapValuesToVoid()) }
guard other.count > 0 else { return (false, self.mapValuesToVoid()) }
if level.isAtRoot, self.hasSingletonItem {
// In this special case, the root node may turn into a collision node
// during the merge process. Prevent this from causing issues below by
// handling it up front.
return self.read { l in
let lp = l.itemPtr(at: .zero)
var copy = other.mapValuesToVoid(copy: true)
let r = copy.updateValue(
level, forKey: lp.pointee.key, _Hash(lp.pointee.key)
) {
$0.initialize(to: (lp.pointee.key, ()))
}
if !r.inserted {
UnsafeHandle.update(r.leaf) {
$0[item: r.slot] = lp.pointee
}
}
return (true, copy)
}
}
return _union(level, other)
}
@inlinable
internal func _union<Value2>(
_ level: _HashLevel,
_ other: _HashNode<Key, Value2>
) -> (copied: Bool, node: _HashNode<Key, Void>) {
if self.raw.storage === other.raw.storage {
return (false, self.mapValuesToVoid())
}
if self.isCollisionNode || other.isCollisionNode {
return _union_slow(level, other)
}
return self.read { l in
other.read { r in
var node = self.mapValuesToVoid()
var copied = false
for (bucket, lslot) in l.itemMap {
assert(!node.isCollisionNode)
if r.itemMap.contains(bucket) {
let rslot = r.itemMap.slot(of: bucket)
let lp = l.itemPtr(at: lslot)
let rp = r.itemPtr(at: rslot)
if lp.pointee.key != rp.pointee.key {
let slot = (
copied
? node.read { $0.itemMap.slot(of: bucket) }
: lslot)
_ = node.ensureUniqueAndSpawnChild(
isUnique: copied,
level: level,
replacing: bucket,
itemSlot: slot,
newHash: _Hash(rp.pointee.key),
{ $0.initialize(to: (rp.pointee.key, ())) })
// If we hadn't handled the singleton root node case above,
// then this call would sometimes turn `node` into a collision
// node on a compressed path, causing mischief.
assert(!node.isCollisionNode)
copied = true
}
}
else if r.childMap.contains(bucket) {
let rslot = r.childMap.slot(of: bucket)
let rp = r.childPtr(at: rslot)
node.ensureUnique(
isUnique: copied, withFreeSpace: _HashNode.spaceForSpawningChild)
let item = node.removeItem(at: bucket)
let r = rp.pointee.mapValuesToVoid()
.inserting(level.descend(), (item.key, ()), _Hash(item.key))
node.insertChild(r.node, bucket)
copied = true
}
}
for (bucket, lslot) in l.childMap {
assert(!node.isCollisionNode)
if r.itemMap.contains(bucket) {
let rslot = r.itemMap.slot(of: bucket)
let rp = r.itemPtr(at: rslot)
let h = _Hash(rp.pointee.key)
let r = l[child: lslot].mapValuesToVoid()
.inserting(level.descend(), (rp.pointee.key, ()), h)
guard r.inserted else {
// Nothing to do
continue
}
node.ensureUnique(isUnique: copied)
let delta = node.replaceChild(at: bucket, with: r.node)
assert(delta == 1)
copied = true
}
else if r.childMap.contains(bucket) {
let rslot = r.childMap.slot(of: bucket)
let child = l[child: lslot]._union(level.descend(), r[child: rslot])
guard child.copied else {
// Nothing to do
continue
}
node.ensureUnique(isUnique: copied)
let delta = node.replaceChild(at: bucket, with: child.node)
assert(delta > 0) // If we didn't add an item, why did we copy?
copied = true
}
}
assert(!node.isCollisionNode)
/// Add buckets in `other` that we haven't processed above.
let seen = l.itemMap.union(l.childMap)
for (bucket, _) in r.itemMap.subtracting(seen) {
let rslot = r.itemMap.slot(of: bucket)
node.ensureUniqueAndInsertItem(
isUnique: copied, (r[item: rslot].key, ()), at: bucket)
copied = true
}
for (bucket, _) in r.childMap.subtracting(seen) {
let rslot = r.childMap.slot(of: bucket)
node.ensureUnique(
isUnique: copied, withFreeSpace: _HashNode.spaceForNewChild)
copied = true
node.insertChild(r[child: rslot].mapValuesToVoid(), bucket)
}
return (copied, node)
}
}
}
@inlinable @inline(never)
internal func _union_slow<Value2>(
_ level: _HashLevel,
_ other: _HashNode<Key, Value2>
) -> (copied: Bool, node: _HashNode<Key, Void>) {
let lc = self.isCollisionNode
let rc = other.isCollisionNode
if lc && rc {
return read { l in
other.read { r in
guard l.collisionHash == r.collisionHash else {
let node = _HashNode<Key, Void>.build(
level: level,
child1: self.mapValuesToVoid(), l.collisionHash,
child2: other.mapValuesToVoid(), r.collisionHash)
return (true, node)
}
var copied = false
var node = self.mapValuesToVoid()
let litems = l.reverseItems
for rs: _HashSlot in stride(from: .zero, to: r.itemsEndSlot, by: 1) {
let p = r.itemPtr(at: rs)
if !litems.contains(where: { $0.key == p.pointee.key }) {
_ = node.ensureUniqueAndAppendCollision(
isUnique: copied, (p.pointee.key, ()))
copied = true
}
}
return (copied, node)
}
}
}
// One of the nodes must be on a compressed path.
assert(!level.isAtBottom)
if lc {
// `self` is a collision node on a compressed path. The other tree might
// have the same set of collisions, just expanded a bit deeper.
return read { l in
other.read { r in
let bucket = l.collisionHash[level]
if r.itemMap.contains(bucket) {
let rslot = r.itemMap.slot(of: bucket)
let rp = r.itemPtr(at: rslot)
if
r.hasSingletonItem
&& l.reverseItems.contains(where: { $0.key == rp.pointee.key })
{
return (false, self.mapValuesToVoid())
}
let node = other.mapValuesToVoid().copyNodeAndPushItemIntoNewChild(
level: level, self.mapValuesToVoid(), at: bucket, itemSlot: rslot)
return (true, node)
}
if r.childMap.contains(bucket) {
let rslot = r.childMap.slot(of: bucket)
let res = self._union(level.descend(), r[child: rslot])
var node = other.mapValuesToVoid(copy: true)
let delta = node.replaceChild(at: bucket, rslot, with: res.node)
assert(delta >= 0)
return (true, node)
}
var node = other.mapValuesToVoid(
copy: true, extraBytes: _HashNode<Key, Void>.spaceForNewChild)
node.insertChild(self.mapValuesToVoid(), bucket)
return (true, node)
}
}
}
assert(rc)
// `other` is a collision node on a compressed path.
return read { l -> (copied: Bool, node: _HashNode<Key, Void>) in
other.read { r -> (copied: Bool, node: _HashNode<Key, Void>) in
let bucket = r.collisionHash[level]
if l.itemMap.contains(bucket) {
let lslot = l.itemMap.slot(of: bucket)
assert(!l.hasSingletonItem) // Handled up front above
let node = self.mapValuesToVoid().copyNodeAndPushItemIntoNewChild(
level: level, other.mapValuesToVoid(), at: bucket, itemSlot: lslot)
return (true, node)
}
if l.childMap.contains(bucket) {
let lslot = l.childMap.slot(of: bucket)
let child = l[child: lslot]._union(level.descend(), other)
guard child.copied else { return (false, self.mapValuesToVoid()) }
var node = self.mapValuesToVoid(copy: true)
let delta = node.replaceChild(at: bucket, lslot, with: child.node)
assert(delta > 0) // If we didn't add an item, why did we copy?
return (true, node)
}
var node = self.mapValuesToVoid(
copy: true, extraBytes: _HashNode.spaceForNewChild)
node.insertChild(other.mapValuesToVoid(), bucket)
return (true, node)
}
}
}
}
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