From 59019ff22b1676bf44fbece0fcc5e00b494dcd93 Mon Sep 17 00:00:00 2001
From: YR Chen <stevapple@icloud.com>
Date: Sat, 19 Dec 2020 12:26:26 +0800
Subject: [PATCH] Implement `commandLineFitsWithinSystemLimits` and
 `tokenizeResponseFile` for Windows

---
 Sources/SwiftDriver/Driver/Driver.swift    |  2 +-
 Sources/SwiftDriver/Utilities/System.swift | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/Sources/SwiftDriver/Driver/Driver.swift b/Sources/SwiftDriver/Driver/Driver.swift
index e832a353b..93f5750f4 100644
--- a/Sources/SwiftDriver/Driver/Driver.swift
+++ b/Sources/SwiftDriver/Driver/Driver.swift
@@ -744,7 +744,7 @@ extension Driver {
   ///
   /// - Parameter content: response file's content to be tokenized.
   private static func tokenizeResponseFile(_ content: String) -> [String] {
-    #if !os(macOS) && !os(Linux) && !os(Android)
+    #if !os(macOS) && !os(Linux) && !os(Android) && !os(Windows)
       #warning("Response file tokenization unimplemented for platform; behavior may be incorrect")
     #endif
     return content.split { $0 == "\n" || $0 == "\r\n" }
diff --git a/Sources/SwiftDriver/Utilities/System.swift b/Sources/SwiftDriver/Utilities/System.swift
index dc2159272..5738c440a 100644
--- a/Sources/SwiftDriver/Utilities/System.swift
+++ b/Sources/SwiftDriver/Utilities/System.swift
@@ -12,6 +12,8 @@
 
 #if os(macOS)
 import Darwin
+#elseif os(Windows)
+import WinSDK.core.file
 #elseif canImport(Glibc)
 import Glibc
 #endif
@@ -46,6 +48,25 @@ func commandLineFitsWithinSystemLimits(path: String, args: [String]) -> Bool {
   }
   return commandLineLength < effectiveArgMax
 }
+#elseif os(Windows)
+// See: https://docs.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation
+func commandLineFitsWithinSystemLimits(path: String, args: [String]) -> Bool {
+  // Known limit for all CreateProcess APIs.
+  guard path.utf8.count + args.map(\.count).reduce(0, +) < 32_767 else {
+    return false
+  }
+
+  // Path component length limit for Unicode APIs.
+  var length: UInt32 = 0
+  withUnsafeMutablePointer(to: &length) { ptr -> Void in
+    GetVolumeInformationA(nil, nil, 0, nil, ptr, nil, nil, 0)
+  }
+  guard path.split(separator: "\\").reduce(true, { result, component in
+      result && component.utf8.count < length
+    }) else { return false }
+
+  return true
+}
 #else
 func commandLineFitsWithinSystemLimits(path: String, args: [String]) -> Bool {
   #warning("missing implementation for current platform")