Fix swift-system to work on Windows.

Package.swift

@@ -15,7 +15,7 @@ import PackageDescription
 let package = Package(
     name: "swift-system",
     products: [
-        .library(name: "SystemPackage", targets: ["SystemPackage"]),
+      .library(name: "SystemPackage", targets: ["SystemPackage"])
     ],
     dependencies: [],
     targets: [
@@ -40,6 +40,6 @@ let package = Package(
         swiftSettings: [
           .define("SYSTEM_PACKAGE_DARWIN", .when(platforms: [.macOS, .iOS, .watchOS, .tvOS, .visionOS])),
           .define("SYSTEM_PACKAGE")
-        ]),
+        ])
     ]
 )

Sources/System/ErrnoWindows.swift

@@ -0,0 +1,20 @@
+/*
+ This source file is part of the Swift System open source project
+
+ Copyright (c) 2024 Apple Inc. and the Swift System project authors
+ Licensed under Apache License v2.0 with Runtime Library Exception
+
+ See https://swift.org/LICENSE.txt for license information
+*/
+
+#if os(Windows)
+
+import WinSDK
+
+extension Errno {
+  public init(windowsError: DWORD) {
+    self.init(rawValue: _mapWindowsErrorToErrno(windowsError))
+  }
+}
+
+#endif

Sources/System/FileOperations.swift

@@ -135,8 +135,6 @@ extension FileDescriptor {
       if let permissions = permissions {
         return system_open(path, oFlag, permissions.rawValue)
       }
-      precondition(!options.contains(.create),
-        "Create must be given permissions")
       return system_open(path, oFlag)
     }
     return descOrError.map { FileDescriptor(rawValue: $0) }
@@ -436,7 +434,7 @@ extension FileDescriptor {
 }
 #endif
 
-#if !os(Windows) && !os(WASI)
+#if !os(WASI)
 @available(/*System 1.1.0: macOS 12.3, iOS 15.4, watchOS 8.5, tvOS 15.4*/iOS 8, *)
 extension FileDescriptor {
   /// Creates a unidirectional data channel, which can be used for interprocess communication.
@@ -465,7 +463,6 @@ extension FileDescriptor {
 }
 #endif
 
-#if !os(Windows)
 @available(/*System 1.2.0: macOS 9999, iOS 9999, watchOS 9999, tvOS 9999*/iOS 8, *)
 extension FileDescriptor {
   /// Truncates or extends the file referenced by this file descriptor.
@@ -511,4 +508,47 @@ extension FileDescriptor {
     }
   }
 }
-#endif
+
+extension FilePermissions {
+  /// The file creation permission mask (aka "umask").
+  ///
+  /// Permissions set in this mask will be cleared by functions that create
+  /// files or directories.  Note that this mask is process-wide, and that
+  /// *getting* it is not thread safe.
+  @_alwaysEmitIntoClient
+  public static var creationMask: FilePermissions {
+    get {
+      let oldMask = _umask(0o22)
+      _ = _umask(oldMask)
+      return FilePermissions(rawValue: oldMask)
+    }
+    set {
+      _ = _umask(newValue.rawValue)
+    }
+  }
+
+  /// Change the file creation permission mask, run some code, then
+  /// restore it to its original value.
+  ///
+  /// - Parameters:
+  ///   - permissions: The new permission mask.
+  ///
+  /// This is more efficient than reading `creationMask` and restoring it
+  /// afterwards, because of the way reading the creation mask works.
+  @_alwaysEmitIntoClient
+  public static func withCreationMask<R>(
+    _ permissions: FilePermissions,
+    body: () throws -> R
+  ) rethrows -> R {
+    let oldMask = _umask(permissions.rawValue)
+    defer {
+      _ = _umask(oldMask)
+    }
+    return try body()
+  }
+
+  @usableFromInline
+  internal static func _umask(_ mode: CModeT) -> CModeT {
+    return system_umask(mode)
+  }
+}

Sources/System/FilePath/FilePathParsing.swift

@@ -89,6 +89,11 @@ extension SystemString {
       // `_prenormalizeWindowsRoots` and resume.
       readIdx = _prenormalizeWindowsRoots()
       writeIdx = readIdx
+
+      // Skip redundant separators
+      while readIdx < endIndex && isSeparator(self[readIdx]) {
+          self.formIndex(after: &readIdx)
+      }
     } else {
       assert(genericSeparator == platformSeparator)
     }
@@ -330,10 +335,13 @@ extension FilePath {
 // Whether we are providing Windows paths
 @inline(__always)
 internal var _windowsPaths: Bool {
+  if let forceWindowsPaths = forceWindowsPaths {
+    return forceWindowsPaths
+  }
   #if os(Windows)
   return true
   #else
-  return forceWindowsPaths
+  return false
   #endif
 }
 

Sources/System/FilePath/FilePathTemp.swift

@@ -0,0 +1,97 @@
+/*
+ This source file is part of the Swift System open source project
+
+ Copyright (c) 2024 Apple Inc. and the Swift System project authors
+ Licensed under Apache License v2.0 with Runtime Library Exception
+
+ See https://swift.org/LICENSE.txt for license information
+*/
+
+// MARK: - API
+
+/// Create a temporary path for the duration of the closure.
+///
+/// - Parameters:
+///   - basename: The base name for the temporary path.
+///   - body: The closure to execute.
+///
+/// Creates a temporary directory with a name based on the given `basename`,
+/// executes `body`, passing in the path of the created directory, then
+/// deletes the directory and all of its contents before returning.
+public func withTemporaryFilePath<R>(
+  basename: FilePath.Component,
+  _ body: (FilePath) throws -> R
+) throws -> R {
+  let temporaryDir = try createUniqueTemporaryDirectory(basename: basename)
+  defer {
+    try? _recursiveRemove(at: temporaryDir)
+  }
+
+  return try body(temporaryDir)
+}
+
+// MARK: - Internals
+
+fileprivate let base64 = Array<UInt8>(
+  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_".utf8
+)
+
+/// Create a directory that is only accessible to the current user.
+///
+/// - Parameters:
+///   - path: The path of the directory to create.
+/// - Returns: `true` if a new directory was created.
+///
+/// This function will throw if there is an error, except if the error
+/// is that the directory exists, in which case it returns `false`.
+fileprivate func makeLockedDownDirectory(at path: FilePath) throws -> Bool {
+  return try path.withPlatformString {
+    if system_mkdir($0, 0o700) == 0 {
+      return true
+    }
+    let err = system_errno
+    if err == Errno.fileExists.rawValue {
+      return false
+    } else {
+      throw Errno(rawValue: err)
+    }
+  }
+}
+
+/// Generate a random string of base64 filename safe characters.
+///
+/// - Parameters:
+///   - length: The number of characters in the returned string.
+/// - Returns: A random string of length `length`.
+fileprivate func createRandomString(length: Int) -> String {
+  return String(
+    decoding: (0..<length).map{
+      _ in base64[Int.random(in: 0..<64)]
+    },
+    as: UTF8.self
+  )
+}
+
+/// Given a base name, create a uniquely named temporary directory.
+///
+/// - Parameters:
+///   - basename: The base name for the new directory.
+/// - Returns: The path to the new directory.
+///
+/// Creates a directory in the system temporary directory whose name
+/// starts with `basename`, followed by a `.` and then a random
+/// string of characters.
+fileprivate func createUniqueTemporaryDirectory(
+  basename: FilePath.Component
+) throws -> FilePath {
+  var tempDir = try _getTemporaryDirectory()
+  tempDir.append(basename)
+
+  while true {
+    tempDir.extension = createRandomString(length: 16)
+
+    if try makeLockedDownDirectory(at: tempDir) {
+      return tempDir
+    }
+  }
+}

Sources/System/FilePath/FilePathTempPosix.swift

@@ -0,0 +1,153 @@
+/*
+ This source file is part of the Swift System open source project
+
+ Copyright (c) 2024 Apple Inc. and the Swift System project authors
+ Licensed under Apache License v2.0 with Runtime Library Exception
+
+ See https://swift.org/LICENSE.txt for license information
+ */
+
+#if !os(Windows)
+
+/// Get the path to the system temporary directory.
+internal func _getTemporaryDirectory() throws -> FilePath {
+  guard let tmp = system_getenv("TMPDIR") else {
+    return "/tmp"
+  }
+
+  return FilePath(SystemString(platformString: tmp))
+}
+
+/// Delete the entire contents of a directory, including its subdirectories.
+///
+/// - Parameters:
+///   - path: The directory to be deleted.
+///
+/// Removes a directory completely, including all of its contents.
+internal func _recursiveRemove(
+  at path: FilePath
+) throws {
+  let dirfd = try FileDescriptor.open(path, .readOnly, options: .directory)
+  defer {
+    try? dirfd.close()
+  }
+
+  let dot: (CInterop.PlatformChar, CInterop.PlatformChar) = (46, 0)
+  try withUnsafeBytes(of: dot) {
+    try recursiveRemove(
+      in: dirfd.rawValue,
+      name: $0.assumingMemoryBound(to: CInterop.PlatformChar.self).baseAddress!
+    )
+  }
+
+  try path.withPlatformString {
+    if system_rmdir($0) != 0 {
+      throw Errno.current
+    }
+  }
+}
+
+/// Open a directory by reference to its parent and name.
+///
+/// - Parameters:
+///   - dirfd: An open file descriptor for the parent directory.
+///   - name: The name of the directory to open.
+/// - Returns: A pointer to a `DIR` structure.
+///
+/// This is like `opendir()`, but instead of taking a path, it uses a
+/// file descriptor pointing at the parent, thus avoiding path length
+/// limits.
+fileprivate func impl_opendirat(
+  _ dirfd: CInt,
+  _ name: UnsafePointer<CInterop.PlatformChar>
+) -> system_DIRPtr? {
+  let fd = system_openat(dirfd, name,
+                         FileDescriptor.AccessMode.readOnly.rawValue
+                           | FileDescriptor.OpenOptions.directory.rawValue)
+  if fd < 0 {
+    return nil
+  }
+  return system_fdopendir(fd)
+}
+
+/// Invoke a closure for each file within a particular directory.
+///
+/// - Parameters:
+///   - dirfd: The parent of the directory to be enumerated.
+///   - subdir: The subdirectory to be enumerated.
+///   - body: The closure that will be invoked.
+///
+/// We skip the `.` and `..` pseudo-entries.
+fileprivate func forEachFile(
+  in dirfd: CInt,
+  subdir: UnsafePointer<CInterop.PlatformChar>,
+  _ body: (system_dirent) throws -> ()
+) throws {
+  guard let dir = impl_opendirat(dirfd, subdir) else {
+    throw Errno.current
+  }
+  defer {
+    _ = system_closedir(dir)
+  }
+
+  while let dirent = system_readdir(dir) {
+    // Skip . and ..
+    if dirent.pointee.d_name.0 == 46
+         && (dirent.pointee.d_name.1 == 0
+               || (dirent.pointee.d_name.1 == 46
+                     && dirent.pointee.d_name.2 == 0)) {
+      continue
+    }
+
+    try body(dirent.pointee)
+  }
+}
+
+/// Delete the entire contents of a directory, including its subdirectories.
+///
+/// - Parameters:
+///   - dirfd: The parent of the directory to be removed.
+///   - name: The name of the directory to be removed.
+///
+/// Removes a directory completely, including all of its contents.
+fileprivate func recursiveRemove(
+  in dirfd: CInt,
+  name: UnsafePointer<CInterop.PlatformChar>
+) throws {
+  // First, deal with subdirectories
+  try forEachFile(in: dirfd, subdir: name) { dirent in
+    if dirent.d_type == SYSTEM_DT_DIR {
+      try withUnsafeBytes(of: dirent.d_name) {
+        try recursiveRemove(
+          in: dirfd,
+          name: $0.assumingMemoryBound(to: CInterop.PlatformChar.self)
+            .baseAddress!
+        )
+      }
+    }
+  }
+
+  // Now delete the contents of this directory
+  try forEachFile(in: dirfd, subdir: name) { dirent in
+    let flag: CInt
+
+    if dirent.d_type == SYSTEM_DT_DIR {
+      flag = SYSTEM_AT_REMOVE_DIR
+    } else {
+      flag = 0
+    }
+
+    let result = withUnsafeBytes(of: dirent.d_name) {
+      system_unlinkat(dirfd,
+                      $0.assumingMemoryBound(to: CInterop.PlatformChar.self)
+                        .baseAddress!,
+                      flag)
+    }
+
+    if result != 0 {
+      throw Errno.current
+    }
+  }
+}
+
+#endif // !os(Windows)