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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 subtracting<Value2>(
_ level: _HashLevel,
_ other: _HashNode<Key, Value2>
) -> _HashNode? {
assert(level.isAtRoot)
let builder = _subtracting(level, other)
guard let builder = builder else { return nil }
let root = builder.finalize(.top)
root._fullInvariantCheck()
return root
}
@inlinable
internal func _subtracting<Value2>(
_ level: _HashLevel,
_ other: _HashNode<Key, Value2>
) -> Builder? {
if self.raw.storage === other.raw.storage { return .empty(level) }
if self.isCollisionNode || other.isCollisionNode {
return _subtracting_slow(level, other)
}
return self.read { l in
other.read { r in
var result: Builder = .empty(level)
var removing = false
for (bucket, lslot) in l.itemMap {
let lp = l.itemPtr(at: lslot)
let include: Bool
if r.itemMap.contains(bucket) {
let rslot = r.itemMap.slot(of: bucket)
include = (lp.pointee.key != r[item: rslot].key)
}
else if r.childMap.contains(bucket) {
let rslot = r.childMap.slot(of: bucket)
let h = _Hash(lp.pointee.key)
include = !r[child: rslot]
.containsKey(level.descend(), lp.pointee.key, h)
}
else {
include = true
}
if include, removing {
result.addNewItem(level, lp.pointee, at: bucket)
}
else if !include, !removing {
removing = true
result.copyItems(level, from: l, upTo: bucket)
}
}
for (bucket, lslot) in l.childMap {
var done = false
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 child = l[child: lslot]
.removing(level.descend(), rp.pointee.key, h)?.replacement
if let child = child {
assert(child.count < self.count)
if !removing {
removing = true
result.copyItemsAndChildren(level, from: l, upTo: bucket)
}
result.addNewChildBranch(level, child, at: bucket)
done = true
}
}
else if r.childMap.contains(bucket) {
let rslot = r.childMap.slot(of: bucket)
let child = l[child: lslot]
._subtracting(level.descend(), r[child: rslot])
if let child = child {
assert(child.count < self.count)
if !removing {
removing = true
result.copyItemsAndChildren(level, from: l, upTo: bucket)
}
result.addNewChildBranch(level, child, at: bucket)
done = true
}
}
if !done, removing {
result.addNewChildNode(level, l[child: lslot], at: bucket)
}
}
guard removing else { return nil }
return result
}
}
}
@inlinable @inline(never)
internal func _subtracting_slow<Value2>(
_ level: _HashLevel,
_ other: _HashNode<Key, Value2>
) -> Builder? {
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 {
return nil
}
var result: Builder = .empty(level)
var removing = false
let ritems = r.reverseItems
for lslot: _HashSlot in stride(from: .zero, to: l.itemsEndSlot, by: 1) {
let lp = l.itemPtr(at: lslot)
let include = !ritems.contains { $0.key == lp.pointee.key }
if include, removing {
result.addNewCollision(level, lp.pointee, l.collisionHash)
}
else if !include, !removing {
removing = true
result.copyCollisions(from: l, upTo: lslot)
}
}
guard removing else { return nil }
assert(result.count < self.count)
return result
}
}
}
// 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 ritem = r.itemPtr(at: rslot)
let h = _Hash(ritem.pointee.key)
let res = l.find(level, ritem.pointee.key, h)
guard let res = res else { return nil }
return self._removingItemFromLeaf(level, at: bucket, res.slot)
.replacement
}
else if r.childMap.contains(bucket) {
let rslot = r.childMap.slot(of: bucket)
return _subtracting(level.descend(), r[child: rslot])
.map { .childBranch(level, $0, at: bucket) }
}
return nil
}
}
}
assert(rc)
// `other` is a collision node on a compressed path.
return read { l in
other.read { r in
let bucket = r.collisionHash[level]
if l.itemMap.contains(bucket) {
let lslot = l.itemMap.slot(of: bucket)
let litem = l.itemPtr(at: lslot)
let h = _Hash(litem.pointee.key)
let res = r.find(level, litem.pointee.key, h)
if res == nil { return nil }
return self._removingItemFromLeaf(level, at: bucket, lslot)
.replacement
}
if l.childMap.contains(bucket) {
let lslot = l.childMap.slot(of: bucket)
let branch = l[child: lslot]._subtracting(level.descend(), other)
guard let branch = branch else { return nil }
var result = self._removingChild(level, at: bucket, lslot)
result.addNewChildBranch(level, branch, at: bucket)
return result
}
return nil
}
}
}
}
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