Introduce "tart import" and "tart export" commands (#386)

* Introduce "tart import" and "tart export" commands

* Use AppleArchive instead of ZIP and simply {ar,un}chive the VM dir

* Fix formatting

* Link to Apple's docs

* Print "importing..." and "exporting..." lines

Sources/tart/Commands/Clone.swift

@@ -39,6 +39,7 @@ struct Clone: AsyncParsableCommand {
     try tmpVMDirLock.lock()
 
     try await withTaskCancellationHandler(operation: {
+      // Acquire a global lock
       let lock = try FileLock(lockURL: Config().tartHomeDir)
       try lock.lock()
 
@@ -52,15 +53,3 @@ struct Clone: AsyncParsableCommand {
     })
   }
 }
-
-fileprivate extension VMDirectory {
-  func macAddress() throws -> String {
-    try VMConfig(fromURL: configURL).macAddress.string
-  }
-}
-
-fileprivate extension VMStorageLocal {
-  func hasVMsWithMACAddress(macAddress: String) throws -> Bool {
-    try list().contains { try $1.macAddress() == macAddress }
-  }
-}

Sources/tart/Commands/Export.swift

@@ -0,0 +1,16 @@
+import ArgumentParser
+
+struct Export: AsyncParsableCommand {
+  static var configuration = CommandConfiguration(abstract: "Export VM to a file")
+
+  @Argument(help: "Source VM name.")
+  var name: String
+
+  @Argument(help: "Path to the destination file.")
+  var path: String
+
+  func run() async throws {
+    print("exporting...")
+    try VMStorageHelper.open(name).exportToArchive(path: path)
+  }
+}

Sources/tart/Commands/Import.swift

@@ -0,0 +1,51 @@
+import ArgumentParser
+import Foundation
+
+struct Import: AsyncParsableCommand {
+  static var configuration = CommandConfiguration(abstract: "Import VM from a file")
+
+  @Argument(help: "Path to a file created with \"tart export\".")
+  var path: String
+
+  @Argument(help: "Destination VM name.")
+  var name: String
+
+  func validate() throws {
+    if name.contains("/") {
+      throw ValidationError("<name> should be a local name")
+    }
+  }
+
+  func run() async throws {
+    let localStorage = VMStorageLocal()
+
+    // Create a temporary VM directory to which we will load the export file
+    let tmpVMDir = try VMDirectory.temporary()
+
+    // Lock the temporary VM directory to prevent it's garbage collection
+    // while we're running
+    let tmpVMDirLock = try FileLock(lockURL: tmpVMDir.baseURL)
+    try tmpVMDirLock.lock()
+
+    // Populate the temporary VM directory with the export file contents
+    print("importing...")
+    try tmpVMDir.importFromArchive(path: path)
+
+    try await withTaskCancellationHandler(operation: {
+      // Acquire a global lock
+      let lock = try FileLock(lockURL: Config().tartHomeDir)
+      try lock.lock()
+
+      // Re-generate the VM's MAC address importing it will result in address collision
+      if try localStorage.hasVMsWithMACAddress(macAddress: tmpVMDir.macAddress()) {
+        try tmpVMDir.regenerateMACAddress()
+      }
+
+      try localStorage.move(name, from: tmpVMDir)
+
+      try lock.unlock()
+    }, onCancel: {
+      try? FileManager.default.removeItem(at: tmpVMDir.baseURL)
+    })
+  }
+}

Sources/tart/Root.swift

@@ -27,6 +27,8 @@ struct Root: AsyncParsableCommand {
       IP.self,
       Pull.self,
       Push.self,
+      Import.self,
+      Export.self,
       Prune.self,
       Rename.self,
       Stop.self,

Sources/tart/VMDirectory+Archive.swift

@@ -0,0 +1,95 @@
+import System
+import AppleArchive
+
+fileprivate let permissions = FilePermissions(rawValue: 0o644)
+
+// Compresses VMDirectory using Apple's proprietary archive format[1] and LZFSE compression,
+// which is recommended on Apple platforms[2].
+//
+// [1]: https://developer.apple.com/documentation/accelerate/compressing_file_system_directories
+// [2]: https://developer.apple.com/documentation/compression/algorithm/lzfse
+extension VMDirectory {
+  func exportToArchive(path: String) throws {
+    guard let fileStream = ArchiveByteStream.fileStream(
+      path: FilePath(path),
+      mode: .writeOnly,
+      options: [.create, .truncate],
+      permissions: permissions
+    ) else {
+      let details = Errno(rawValue: CInt(errno))
+
+      throw RuntimeError.ExportFailed("ArchiveByteStream.fileStream() failed: \(details)")
+    }
+    defer {
+      try? fileStream.close()
+    }
+
+    guard let compressionStream = ArchiveByteStream.compressionStream(
+      using: .lzfse,
+      writingTo: fileStream
+    ) else {
+      let details = Errno(rawValue: CInt(errno))
+
+      throw RuntimeError.ExportFailed("ArchiveByteStream.compressionStream() failed: \(details)")
+    }
+    defer {
+      try? compressionStream.close()
+    }
+
+    guard let encodeStream = ArchiveStream.encodeStream(writingTo: compressionStream) else {
+      let details = Errno(rawValue: CInt(errno))
+
+      throw RuntimeError.ExportFailed("ArchiveStream.encodeStream() failed: \(details)")
+    }
+    defer {
+      try? encodeStream.close()
+    }
+
+    guard let keySet = ArchiveHeader.FieldKeySet("TYP,PAT,LNK,DEV,DAT,UID,GID,MOD,FLG,MTM,BTM,CTM") else {
+      return
+    }
+
+    try encodeStream.writeDirectoryContents(archiveFrom: FilePath(baseURL.path), keySet: keySet)
+  }
+
+  func importFromArchive(path: String) throws {
+    guard let fileStream = ArchiveByteStream.fileStream(path: FilePath(path), mode: .readOnly, options: [],
+                                                        permissions: permissions) else {
+      let details = Errno(rawValue: CInt(errno))
+
+      throw RuntimeError.ImportFailed("ArchiveByteStream.fileStream() failed: \(details)")
+    }
+    defer {
+      try? fileStream.close()
+    }
+
+    guard let decompressionStream = ArchiveByteStream.decompressionStream(readingFrom: fileStream) else {
+      let details = Errno(rawValue: CInt(errno))
+
+      throw RuntimeError.ImportFailed("ArchiveByteStream.decompressionStream() failed: \(details)")
+    }
+    defer {
+      try? decompressionStream.close()
+    }
+
+    guard let decodeStream = ArchiveStream.decodeStream(readingFrom: decompressionStream) else {
+      let details = Errno(rawValue: CInt(errno))
+
+      throw RuntimeError.ImportFailed("ArchiveStream.decodeStream() failed: \(details)")
+    }
+    defer {
+      try? decodeStream.close()
+    }
+
+    guard let extractStream = ArchiveStream.extractStream(extractingTo: FilePath(baseURL.path)) else {
+      let details = Errno(rawValue: CInt(errno))
+
+      throw RuntimeError.ImportFailed("ArchiveStream.extractStream() failed: \(details)")
+    }
+    defer {
+      try? extractStream.close()
+    }
+
+    _ = try ArchiveStream.process(readingFrom: decodeStream, writingTo: extractStream)
+  }
+}

Sources/tart/VMDirectory.swift

@@ -68,11 +68,21 @@ struct VMDirectory: Prunable {
     try FileManager.default.copyItem(at: diskURL, to: to.diskURL)
 
     // Re-generate MAC address
-    var newVMConfig = try VMConfig(fromURL: to.configURL)
     if generateMAC {
-      newVMConfig.macAddress = VZMACAddress.randomLocallyAdministered()
+      try to.regenerateMACAddress()
     }
-    try newVMConfig.save(toURL: to.configURL)
+  }
+
+  func macAddress() throws -> String {
+    try VMConfig(fromURL: configURL).macAddress.string
+  }
+
+  func regenerateMACAddress() throws {
+    var vmConfig = try VMConfig(fromURL: configURL)
+
+    vmConfig.macAddress = VZMACAddress.randomLocallyAdministered()
+
+    try vmConfig.save(toURL: configURL)
   }
 
   func resizeDisk(_ sizeGB: UInt16) throws {

Sources/tart/VMStorageHelper.swift

@@ -53,6 +53,8 @@ enum RuntimeError : Error {
   case VMTerminationFailed(_ message: String)
   case InvalidCredentials(_ message: String)
   case VMDirectoryAlreadyInitialized(_ message: String)
+  case ExportFailed(_ message: String)
+  case ImportFailed(_ message: String)
 }
 
 protocol HasExitCode {
@@ -86,6 +88,10 @@ extension RuntimeError : CustomStringConvertible {
       return message
     case .VMDirectoryAlreadyInitialized(let message):
       return message
+    case .ExportFailed(let message):
+      return "VM export failed: \(message)"
+    case .ImportFailed(let message):
+      return "VM import failed: \(message)"
     }
   }
 }

Sources/tart/VMStorageLocal.swift

@@ -62,4 +62,8 @@ class VMStorageLocal {
       throw error
     }
   }
+
+  func hasVMsWithMACAddress(macAddress: String) throws -> Bool {
+    try list().contains { try $1.macAddress() == macAddress }
+  }
 }