From 5712a283775e86ec6f2393c3ad853a5709bc3960 Mon Sep 17 00:00:00 2001
From: Michael Ilseman <milseman@apple.com>
Date: Thu, 22 Oct 2020 17:24:51 -0700
Subject: [PATCH 1/2] Windows TLS mocking support

---
 Sources/SystemInternals/Mocking.swift | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/Sources/SystemInternals/Mocking.swift b/Sources/SystemInternals/Mocking.swift
index 725feef1..343372d7 100644
--- a/Sources/SystemInternals/Mocking.swift
+++ b/Sources/SystemInternals/Mocking.swift
@@ -92,7 +92,26 @@ import Glibc
 #endif
 
 // TLS helper functions
-#if !os(Windows)
+#if os(Windows)
+internal typealias TLSKey = DWORD
+internal func makeTLSKey() -> TLSKey {
+  var raw: DWORD = FlsAlloc(nil)
+  if raw == FLS_OUT_OF_INDEXES {
+    fatalError("Unable to create key")
+  }
+  return raw
+}
+internal func setTLS(_ key: TLSKey, _ p: UnsafeMutableRawPointer?) {
+  guard 0 != FlsSetValue(key, p) else {
+    fatalError("Unable to set TLS")
+  }
+}
+internal func getTLS(_ key: TLSKey) -> UnsafeMutableRawPointer? {
+  FlsGetValue(key)
+}
+
+#else
+
 internal typealias TLSKey = pthread_key_t
 internal func makeTLSKey() -> TLSKey {
   var raw = pthread_key_t()
@@ -109,9 +128,6 @@ internal func setTLS(_ key: TLSKey, _ p: UnsafeMutableRawPointer?) {
 internal func getTLS(_ key: TLSKey) -> UnsafeMutableRawPointer? {
   pthread_getspecific(key)
 }
-#else
-// TODO: Windows version...
-#error("Unsupported Platform")
 #endif
 
 private let driverKey: TLSKey = { makeTLSKey() }()

From 1eeeaf72009e4af41b61ee3484db76d156a43018 Mon Sep 17 00:00:00 2001
From: Michael Ilseman <milseman@apple.com>
Date: Thu, 22 Oct 2020 17:17:39 -0700
Subject: [PATCH 2/2] Initial Windows syscall adapters

---
 Sources/SystemInternals/Syscalls.swift        |   4 +-
 .../WindowsSyscallAdapters.swift              | 102 ++++++++++++++++++
 2 files changed, 104 insertions(+), 2 deletions(-)
 create mode 100644 Sources/SystemInternals/WindowsSyscallAdapters.swift

diff --git a/Sources/SystemInternals/Syscalls.swift b/Sources/SystemInternals/Syscalls.swift
index 2deea86f..a78760da 100644
--- a/Sources/SystemInternals/Syscalls.swift
+++ b/Sources/SystemInternals/Syscalls.swift
@@ -35,11 +35,11 @@ private func mockImpl(
   switch driver.forceErrno {
   case .none: break
   case .always(let e):
-    errno = e
+    system_errno = e
     return -1
   case .counted(let e, let count):
     assert(count >= 1)
-    errno = e
+    system_errno = e
     driver.forceErrno = count > 1 ? .counted(errno: e, count: count-1) : .none
     return -1
   }
diff --git a/Sources/SystemInternals/WindowsSyscallAdapters.swift b/Sources/SystemInternals/WindowsSyscallAdapters.swift
new file mode 100644
index 00000000..7a97695f
--- /dev/null
+++ b/Sources/SystemInternals/WindowsSyscallAdapters.swift
@@ -0,0 +1,102 @@
+/*
+ This source file is part of the Swift System open source project
+
+ Copyright (c) 2020 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)
+
+@inline(__always)
+internal func open(_ path: UnsafePointer<CChar>, _ oflag: Int32) {
+  var fh: CInt = -1
+  _ = _sopen_s(&fh, path, oflag, _SH_DENYNO, _S_IREAD | _S_IWRITE)
+  return fh
+}
+
+@inline(__always)
+internal func open(
+  _ path: UnsafePointer<CChar>, _ oflag: Int32, _ mode: mode_t
+) -> CInt {
+  // TODO(compnerd): Apply read/write permissions
+  var fh: CInt = -1
+  _ = _sopen_s(&fh, path, oflag, _SH_DENYNO, _S_IREAD | _S_IWRITE)
+  return fh
+}
+
+@inline(__always)
+internal func close(_ fd: Int32) -> Int32 {
+  _close(fd)
+}
+
+@inline(__always)
+internal func lseek(
+  _ fd: Int32, _ off: off_t, _ whence: Int32
+) -> off_t {
+  _lseek(fd, off, whence)
+}
+
+@inline(__always)
+internal func read(
+  _ fd: Int32, _ buf: UnsafeMutableRawPointer!, _ nbyte: Int
+) -> Int {
+  Int(_read(fd, buf, numericCast(nbyte)))
+}
+
+@inline(__always)
+internal func write(
+  _ fd: Int32, _ buf: UnsafeRawPointer!, _ nbyte: Int
+) -> Int {
+  Int(_write(fd, buf, numericCast(nbyte)))
+}
+
+@inline(__always)
+internal func pread(
+  _ fd: Int32, _ buf: UnsafeMutableRawPointer!, _ nbyte: Int, _ offset: off_t
+) -> Int {
+  let handle: intptr_t = _get_osfhandle(fd)
+  if handle == /* INVALID_HANDLE_VALUE */ -1 { return Int(EBADF) }
+
+  // NOTE: this is a non-owning handle, do *not* call CloseHandle on it
+  let hFile: HANDLE = HANDLE(bitPattern: handle)!
+
+  var ovlOverlapped: OVERLAPPED = OVERLAPPED()
+  ovlOverlapped.OffsetHigh = DWORD(UInt32(offset >> 32) & 0xffffffff)
+  ovlOverlapped.Offset = DWORD(UInt32(offset >> 0) & 0xffffffff)
+
+  var nNumberOfBytesRead: DWORD = 0
+  if !ReadFile(hFile, buf, DWORD(nbyte), &nNumberOfBytesRead, &ovlOverlapped) {
+    let _ = GetLastError()
+    // TODO(compnerd) map windows error to errno
+    return Int(-1)
+  }
+  return Int(nNumberOfBytesRead)
+}
+
+@inline(__always)
+internal func pwrite(
+  _ fd: Int32, _ buf: UnsafeRawPointer!, _ nbyte: Int, _ offset: off_t
+) -> Int {
+  let handle: intptr_t = _get_osfhandle(fd)
+  if handle == /* INVALID_HANDLE_VALUE */ -1 { return Int(EBADF) }
+
+  // NOTE: this is a non-owning handle, do *not* call CloseHandle on it
+  let hFile: HANDLE = HANDLE(bitPattern: handle)!
+
+  var ovlOverlapped: OVERLAPPED = OVERLAPPED()
+  ovlOverlapped.OffsetHigh = DWORD(UInt32(offset >> 32) & 0xffffffff)
+  ovlOverlapped.Offset = DWORD(UInt32(offset >> 0) & 0xffffffff)
+
+  var nNumberOfBytesWritten: DWORD = 0
+  if !WriteFile(hFile, buf, DWORD(nbyte), &nNumberOfBytesWritten,
+                &ovlOverlapped) {
+    let _ = GetLastError()
+    // TODO(compnerd) map windows error to errno
+    return Int(-1)
+  }
+  return Int(nNumberOfBytesWritten)
+}
+
+#endif