use clipboard package to handle clipboard stuff

vendor/github.com/atotto/clipboard/clipboard_windows.go

@@ -0,0 +1,128 @@
+// Copyright 2013 @atotto. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build windows
+
+package clipboard
+
+import (
+	"syscall"
+	"time"
+	"unsafe"
+)
+
+const (
+	cfUnicodetext = 13
+	gmemMoveable  = 0x0002
+)
+
+var (
+	user32           = syscall.MustLoadDLL("user32")
+	openClipboard    = user32.MustFindProc("OpenClipboard")
+	closeClipboard   = user32.MustFindProc("CloseClipboard")
+	emptyClipboard   = user32.MustFindProc("EmptyClipboard")
+	getClipboardData = user32.MustFindProc("GetClipboardData")
+	setClipboardData = user32.MustFindProc("SetClipboardData")
+
+	kernel32     = syscall.NewLazyDLL("kernel32")
+	globalAlloc  = kernel32.NewProc("GlobalAlloc")
+	globalFree   = kernel32.NewProc("GlobalFree")
+	globalLock   = kernel32.NewProc("GlobalLock")
+	globalUnlock = kernel32.NewProc("GlobalUnlock")
+	lstrcpy      = kernel32.NewProc("lstrcpyW")
+)
+
+// waitOpenClipboard opens the clipboard, waiting for up to a second to do so.
+func waitOpenClipboard() error {
+	started := time.Now()
+	limit := started.Add(time.Second)
+	var r uintptr
+	var err error
+	for time.Now().Before(limit) {
+		r, _, err = openClipboard.Call(0)
+		if r != 0 {
+			return nil
+		}
+		time.Sleep(time.Millisecond)
+	}
+	return err
+}
+
+func readAll() (string, error) {
+	err := waitOpenClipboard()
+	if err != nil {
+		return "", err
+	}
+	defer closeClipboard.Call()
+
+	h, _, err := getClipboardData.Call(cfUnicodetext)
+	if h == 0 {
+		return "", err
+	}
+
+	l, _, err := globalLock.Call(h)
+	if l == 0 {
+		return "", err
+	}
+
+	text := syscall.UTF16ToString((*[1 << 20]uint16)(unsafe.Pointer(l))[:])
+
+	r, _, err := globalUnlock.Call(h)
+	if r == 0 {
+		return "", err
+	}
+
+	return text, nil
+}
+
+func writeAll(text string) error {
+	err := waitOpenClipboard()
+	if err != nil {
+		return err
+	}
+	defer closeClipboard.Call()
+
+	r, _, err := emptyClipboard.Call(0)
+	if r == 0 {
+		return err
+	}
+
+	data := syscall.StringToUTF16(text)
+
+	// "If the hMem parameter identifies a memory object, the object must have
+	// been allocated using the function with the GMEM_MOVEABLE flag."
+	h, _, err := globalAlloc.Call(gmemMoveable, uintptr(len(data)*int(unsafe.Sizeof(data[0]))))
+	if h == 0 {
+		return err
+	}
+	defer func() {
+		if h != 0 {
+			globalFree.Call(h)
+		}
+	}()
+
+	l, _, err := globalLock.Call(h)
+	if l == 0 {
+		return err
+	}
+
+	r, _, err = lstrcpy.Call(l, uintptr(unsafe.Pointer(&data[0])))
+	if r == 0 {
+		return err
+	}
+
+	r, _, err = globalUnlock.Call(h)
+	if r == 0 {
+		if err.(syscall.Errno) != 0 {
+			return err
+		}
+	}
+
+	r, _, err = setClipboardData.Call(cfUnicodetext, h)
+	if r == 0 {
+		return err
+	}
+	h = 0 // suppress deferred cleanup
+	return nil
+}