From 29775ff8a83c37815e5aaef9f664258e30eb43b5 Mon Sep 17 00:00:00 2001
From: Dominic Della Valle <ddvpublic@gmail.com>
Date: Wed, 14 Mar 2018 15:27:20 -0400
Subject: [PATCH] Add Windows native support

Change-Id: I7c536cce60fe127290db9399891df73daa099374
---
 lock/helpers_windows.go | 26 +++++++++++++++
 lock/lock_windows.go    | 73 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 99 insertions(+)
 create mode 100644 lock/helpers_windows.go
 create mode 100644 lock/lock_windows.go

diff --git a/lock/helpers_windows.go b/lock/helpers_windows.go
new file mode 100644
index 0000000..a620bea
--- /dev/null
+++ b/lock/helpers_windows.go
@@ -0,0 +1,26 @@
+package lock
+
+import (
+	"golang.org/x/sys/windows"
+)
+
+func loadSystemDLL(name string) (*windows.DLL, error) {
+	const LOAD_LIBRARY_SEARCH_SYSTEM32 = 0x00000800
+	modHandle, err := windows.LoadLibraryEx(name, 0, LOAD_LIBRARY_SEARCH_SYSTEM32)
+	if err != nil {
+		return nil, err
+	}
+	return &windows.DLL{Name: "kernel32", Handle: modHandle}, nil
+}
+
+func winCreateEphemeral(name string) (windows.Handle, error) {
+	const FILE_ATTRIBUTE_TEMPORARY = 0x100
+	const FILE_FLAG_DELETE_ON_CLOSE = 0x04000000
+
+	handle, err := windows.CreateFile(windows.StringToUTF16Ptr(name), windows.GENERIC_WRITE, windows.FILE_SHARE_DELETE|windows.FILE_SHARE_READ, nil, windows.OPEN_ALWAYS, FILE_ATTRIBUTE_TEMPORARY|FILE_FLAG_DELETE_ON_CLOSE, 0)
+	if err != nil {
+
+		return 0, err
+	}
+	return handle, nil
+}
diff --git a/lock/lock_windows.go b/lock/lock_windows.go
new file mode 100644
index 0000000..11e946c
--- /dev/null
+++ b/lock/lock_windows.go
@@ -0,0 +1,73 @@
+/*
+Copyright 2013 The Go Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package lock
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"sync"
+
+	"golang.org/x/sys/windows"
+)
+
+func init() {
+	lockFn = lockWindows
+}
+
+type winUnlocker struct {
+	h   windows.Handle
+	abs string
+	// once guards the close method call.
+	once sync.Once
+	// err holds the error returned by Close.
+	err error
+}
+
+func (u *winUnlocker) Close() error {
+	u.once.Do(u.close)
+	return u.err
+}
+
+func (u *winUnlocker) close() {
+	lockmu.Lock()
+	defer lockmu.Unlock()
+	delete(locked, u.abs)
+
+	u.err = windows.CloseHandle(u.h)
+}
+
+func lockWindows(name string) (io.Closer, error) {
+	fi, err := os.Stat(name)
+	if err == nil && fi.Size() > 0 {
+		return nil, fmt.Errorf("can't lock file %q: %s", name, "has non-zero size")
+	}
+
+	handle, err := winCreateEphemeral(name)
+	if err != nil {
+		return nil, fmt.Errorf("creation of lock %s failed: %v", name, err)
+	}
+
+	absPath, err := filepath.Abs(name)
+	if err != nil {
+		windows.CloseHandle(handle)
+		return nil, fmt.Errorf("can't lock file %q, unable to determine full path: %s", name, err)
+	}
+
+	return &winUnlocker{h: handle, abs: absPath}, nil
+}