From c5630a890652f7251aa63c3342813194cbf8b986 Mon Sep 17 00:00:00 2001
From: mpl <mathieu.lonjaret@gmail.com>
Date: Mon, 18 Aug 2014 18:16:46 +0200
Subject: [PATCH] osutil: selfpath for windows, and make it public.

Change-Id: Ic3e8de6e75651921cb29e3b5e91cdb9f5159896a
---
 pkg/osutil/restart_stub.go    | 14 +++++++--
 pkg/osutil/restart_unix.go    | 17 +++++++----
 pkg/osutil/restart_windows.go | 54 +++++++++++++++++++++++++++++++++++
 3 files changed, 77 insertions(+), 8 deletions(-)
 create mode 100644 pkg/osutil/restart_windows.go

diff --git a/pkg/osutil/restart_stub.go b/pkg/osutil/restart_stub.go
index 28d46ab8a..cfb51a6af 100644
--- a/pkg/osutil/restart_stub.go
+++ b/pkg/osutil/restart_stub.go
@@ -1,4 +1,4 @@
-// +build windows appengine
+// +build appengine
 
 /*
 Copyright 2012 The Camlistore Authors.
@@ -19,13 +19,21 @@ limitations under the License.
 package osutil
 
 import (
+	"errors"
 	"log"
+	"runtime"
 )
 
-// restartProcess returns an error if things couldn't be
+// SelfPath returns the path of the executable for the currently running
+// process.
+func SelfPath() (string, error) {
+	return "", errors.New("SelfPath not implemented on App Engine.")
+}
+
+// RestartProcess returns an error if things couldn't be
 // restarted.  On success, this function never returns
 // because the process becomes the new process.
 func RestartProcess() error {
-	log.Print("RestartProcess not implemented on windows")
+	log.Print("RestartProcess not implemented on this platform.")
 	return nil
 }
diff --git a/pkg/osutil/restart_unix.go b/pkg/osutil/restart_unix.go
index 61ad64cc9..3fba01f8e 100644
--- a/pkg/osutil/restart_unix.go
+++ b/pkg/osutil/restart_unix.go
@@ -21,6 +21,7 @@ package osutil
 
 import (
 	"errors"
+	"fmt"
 	"os"
 	"runtime"
 	"syscall"
@@ -29,7 +30,13 @@ import (
 // if non-nil, osSelfPath is used from selfPath.
 var osSelfPath func() (string, error)
 
-func selfPath() (string, error) {
+// TODO(mpl): document the symlink behaviour in SelfPath for the BSDs when
+// I know for sure.
+
+// SelfPath returns the path of the executable for the currently running
+// process. At least on linux, the returned path is a symlink to the actual
+// executable.
+func SelfPath() (string, error) {
 	if f := osSelfPath; f != nil {
 		return f()
 	}
@@ -45,16 +52,16 @@ func selfPath() (string, error) {
 		// See https://codereview.appspot.com/6736069/
 		return os.Args[0], nil
 	}
-	return "", errors.New("No restart because selfPath() not implemented for " + runtime.GOOS)
+	return "", errors.New("SelfPath not implemented for " + runtime.GOOS)
 }
 
-// restartProcess returns an error if things couldn't be
+// RestartProcess returns an error if things couldn't be
 // restarted.  On success, this function never returns
 // because the process becomes the new process.
 func RestartProcess() error {
-	path, err := selfPath()
+	path, err := SelfPath()
 	if err != nil {
-		return err
+		return fmt.Errorf("RestartProcess failed: %v", err)
 	}
 	return syscall.Exec(path, os.Args, os.Environ())
 }
diff --git a/pkg/osutil/restart_windows.go b/pkg/osutil/restart_windows.go
new file mode 100644
index 000000000..3363ad07f
--- /dev/null
+++ b/pkg/osutil/restart_windows.go
@@ -0,0 +1,54 @@
+// +build windows
+
+/*
+Copyright 2014 The Camlistore 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 osutil
+
+import (
+	"log"
+	"syscall"
+	"unicode/utf16"
+	"unsafe"
+)
+
+// SelfPath returns the path of the executable for the currently running
+// process.
+func SelfPath() (string, error) {
+	kernel32, err := syscall.LoadDLL("kernel32.dll")
+	if err != nil {
+		return "", err
+	}
+	sysproc, err := kernel32.FindProc("GetModuleFileNameW")
+	if err != nil {
+		return "", err
+	}
+	b := make([]uint16, syscall.MAX_PATH)
+	r, _, err := sysproc.Call(0, uintptr(unsafe.Pointer(&b[0])), uintptr(len(b)))
+	n := uint32(r)
+	if n == 0 {
+		return "", err
+	}
+	return string(utf16.Decode(b[0:n])), nil
+}
+
+// RestartProcess returns an error if things couldn't be
+// restarted.  On success, this function never returns
+// because the process becomes the new process.
+func RestartProcess() error {
+	log.Print("RestartProcess not implemented on this platform.")
+	return nil
+}