os: add Executable() (string, error)

// Executable returns the path name for the executable that started
// the current process. There is no guarantee that the path is still
// pointing to the correct executable. If a symlink was used to start
// the process, depending on the operating system, the result might
// be the symlink or the path it pointed to. If a stable result is
// needed, path/filepath.EvalSymlinks might help.
//
// Executable returns an absolute path unless an error occurred.
//
// The main use case is finding resources located relative to an
// executable.
//
// Executable is not supported on nacl or OpenBSD (unless procfs is
// mounted.)
func Executable() (string, error) {
	return executable()
}

Fixes #12773.

Change-Id: I469738d905b12f0b633ea4d88954f8859227a88c
Reviewed-on: https://go-review.googlesource.com/16551
Run-TryBot: Minux Ma <minux@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

1 files changed, 32 insertions, 0 deletions

diff --git a/src/os/executable_windows.go b/src/os/executable_windows.go
new file mode 100644
index 0000000000..fc5cf86005
--- /dev/null
+++ b/src/os/executable_windows.go
@@ -0,0 +1,32 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package os
+
+import (
+	"internal/syscall/windows"
+	"syscall"
+)
+
+func getModuleFileName(handle syscall.Handle) (string, error) {
+	n := uint32(1024)
+	var buf []uint16
+	for {
+		buf = make([]uint16, n)
+		r, err := windows.GetModuleFileName(handle, &buf[0], n)
+		if err != nil {
+			return "", err
+		}
+		if r < n {
+			break
+		}
+		// r == n means n not big enough
+		n += 1024
+	}
+	return syscall.UTF16ToString(buf), nil
+}
+
+func executable() (string, error) {
+	return getModuleFileName(0)
+}