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perf: index EXT4 FileTree children by name to avoid O(n^2) unpack #793

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perf: index EXT4 FileTree children by name to avoid O(n^2) unpack #793

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31 changes: 19 additions & 12 deletions Sources/ContainerizationEXT4/EXT4+FileTree.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,9 @@ extension EXT4 {
class FileTreeNode {
let inode: InodeNumber
let name: String
var children: [Ptr<FileTreeNode>] = []
private(set) var children: [Ptr<FileTreeNode>] = []
// Name index of `children` for O(1) lookup, maintained by addChild/removeChild.
private(set) var childIndex: [String: Ptr<FileTreeNode>] = [:]
var blocks: (start: UInt32, end: UInt32)?
var additionalBlocks: [(start: UInt32, end: UInt32)]?
var link: InodeNumber?
Expand All @@ -39,16 +41,19 @@ extension EXT4 {
) {
self.inode = inode
self.name = name
self.children = children
self.blocks = blocks
self.additionalBlocks = additionalBlocks
self.link = link
self.parent = parent
for child in children {
self.addChild(child)
}
}

deinit {
self.children.removeAll()
self.children = []
self.childIndex.removeAll()
self.blocks = nil
self.additionalBlocks = nil
self.link = nil
Expand All @@ -64,6 +69,16 @@ extension EXT4 {
let path = components.reversed().joined(separator: "/")
return FilePath(path).lexicallyNormalized()
}

func addChild(_ child: Ptr<FileTreeNode>) {
children.append(child)
childIndex[child.pointee.name] = child
}

func removeChild(named name: String) {
children.removeAll { $0.pointee.name == name }
childIndex[name] = nil
}
}

var root: Ptr<FileTreeNode>
Expand All @@ -82,18 +97,10 @@ extension EXT4 {
return node
}
for component in components {
var found = false
for childPtr in node.pointee.children {
let child = childPtr.pointee
if child.name == component {
node = childPtr
found = true
break
}
}
guard found else {
guard let childPtr = node.pointee.childIndex[component] else {
return nil
}
node = childPtr
}
return node
}
Expand Down
8 changes: 3 additions & 5 deletions Sources/ContainerizationEXT4/EXT4+Formatter.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -186,7 +186,7 @@ extension EXT4 {
blocks: nil,
link: targetNode.inode
))
parentTreeNode.children.append(linkTreeNodePtr)
parentTreeNode.addChild(linkTreeNodePtr)
parentTreeNodePtr.pointee = parentTreeNode
}

Expand Down Expand Up @@ -254,9 +254,7 @@ extension EXT4 {
}
}
parentInodePtr.pointee = parentInode
parentNode.children.removeAll { childPtr in
childPtr.pointee.name == pathComponent
}
parentNode.removeChild(named: pathComponent)
parentNodePtr.pointee = parentNode

if let hardlink = pathNode.link {
Expand Down Expand Up @@ -412,7 +410,7 @@ extension EXT4 {
children: [],
blocks: (startBlock, endBlock)
))
parentTreeNode.children.append(childTreeNodePtr)
parentTreeNode.addChild(childTreeNodePtr)
parentTreeNodePtr.pointee = parentTreeNode
}
childInode.mode = mode
Expand Down
2 changes: 1 addition & 1 deletion Sources/ContainerizationEXT4/EXT4+Reader.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -102,7 +102,7 @@ extension EXT4 {
itemTreeNode.blocks = blocks.first
}
let itemTreeNodePtr = Ptr(itemTreeNode)
root.children.append(itemTreeNodePtr)
root.addChild(itemTreeNodePtr)
itemPtr.pointee = root
let itemInode = try self.getInode(number: itemInodeNum)
if itemInode.mode.isDir() {
Expand Down
10 changes: 5 additions & 5 deletions Tests/ContainerizationEXT4Tests/TestEXT4Reader+IO.swift
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Expand Up @@ -617,10 +617,10 @@ struct EXT4PathIOTests {
let tree = EXT4.FileTree(EXT4.RootInode, "/")

let dirPtr = EXT4.Ptr(EXT4.FileTree.FileTreeNode(inode: 3, name: "dir", parent: tree.root))
tree.root.pointee.children.append(dirPtr)
tree.root.pointee.addChild(dirPtr)

let filePtr = EXT4.Ptr(EXT4.FileTree.FileTreeNode(inode: 4, name: "file", parent: dirPtr))
dirPtr.pointee.children.append(filePtr)
dirPtr.pointee.addChild(filePtr)

#expect(dirPtr.pointee.path == FilePath("/dir"))
#expect(filePtr.pointee.path == FilePath("/dir/file"))
Expand All @@ -631,10 +631,10 @@ struct EXT4PathIOTests {
let tree = EXT4.FileTree(EXT4.RootInode, ".")

let dirPtr = EXT4.Ptr(EXT4.FileTree.FileTreeNode(inode: 3, name: "dir", parent: tree.root))
tree.root.pointee.children.append(dirPtr)
tree.root.pointee.addChild(dirPtr)

let filePtr = EXT4.Ptr(EXT4.FileTree.FileTreeNode(inode: 4, name: "file", parent: dirPtr))
dirPtr.pointee.children.append(filePtr)
dirPtr.pointee.addChild(filePtr)

#expect(dirPtr.pointee.path == FilePath("dir"))
#expect(filePtr.pointee.path == FilePath("dir/file"))
Expand All @@ -645,7 +645,7 @@ struct EXT4PathIOTests {
let tree = EXT4.FileTree(EXT4.RootInode, "dir")

let filePtr = EXT4.Ptr(EXT4.FileTree.FileTreeNode(inode: 3, name: "file", parent: tree.root))
tree.root.pointee.children.append(filePtr)
tree.root.pointee.addChild(filePtr)

#expect(filePtr.pointee.path == FilePath("dir/file"))
}
Expand Down