From 3c29434a79f5af9ce668f699105778f36417a5d6 Mon Sep 17 00:00:00 2001
From: Simon Rozman <simon@rozman.si>
Date: Wed, 6 Feb 2019 20:15:40 +0100
Subject: [PATCH] setupapi: Make toUTF16() public and add UTF16ToBuf()
 counterpart

Signed-off-by: Simon Rozman <simon@rozman.si>
---
 setupapi/setupapi_windows.go      | 19 +++++++++++++++----
 setupapi/setupapi_windows_test.go | 13 +++++++++++++
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/setupapi/setupapi_windows.go b/setupapi/setupapi_windows.go
index 84d324d..740b81b 100644
--- a/setupapi/setupapi_windows.go
+++ b/setupapi/setupapi_windows.go
@@ -264,9 +264,9 @@ func SetupDiGetDeviceRegistryProperty(DeviceInfoSet DevInfo, DeviceInfoData *SP_
 func getRegistryValue(buf []byte, dataType uint32) (interface{}, error) {
 	switch dataType {
 	case windows.REG_SZ:
-		return windows.UTF16ToString(toUTF16(buf)), nil
+		return windows.UTF16ToString(BufToUTF16(buf)), nil
 	case windows.REG_EXPAND_SZ:
-		return registry.ExpandString(windows.UTF16ToString(toUTF16(buf)))
+		return registry.ExpandString(windows.UTF16ToString(BufToUTF16(buf)))
 	case windows.REG_BINARY:
 		return buf, nil
 	case windows.REG_DWORD_LITTLE_ENDIAN:
@@ -274,7 +274,7 @@ func getRegistryValue(buf []byte, dataType uint32) (interface{}, error) {
 	case windows.REG_DWORD_BIG_ENDIAN:
 		return binary.BigEndian.Uint32(buf), nil
 	case windows.REG_MULTI_SZ:
-		bufW := toUTF16(buf)
+		bufW := BufToUTF16(buf)
 		a := []string{}
 		for i := 0; i < len(bufW); {
 			j := i + wcslen(bufW[i:])
@@ -291,7 +291,8 @@ func getRegistryValue(buf []byte, dataType uint32) (interface{}, error) {
 	}
 }
 
-func toUTF16(buf []byte) []uint16 {
+// BufToUTF16 function reinterprets []byte buffer as []uint16
+func BufToUTF16(buf []byte) []uint16 {
 	sl := struct {
 		addr *uint16
 		len  int
@@ -300,6 +301,16 @@ func toUTF16(buf []byte) []uint16 {
 	return *(*[]uint16)(unsafe.Pointer(&sl))
 }
 
+// UTF16ToBuf function reinterprets []uint16 as []byte
+func UTF16ToBuf(buf []uint16) []byte {
+	sl := struct {
+		addr *byte
+		len  int
+		cap  int
+	}{(*byte)(unsafe.Pointer(&buf[0])), len(buf) * 2, cap(buf) * 2}
+	return *(*[]byte)(unsafe.Pointer(&sl))
+}
+
 func wcslen(str []uint16) int {
 	for i := 0; i < len(str); i++ {
 		if str[i] == 0 {
diff --git a/setupapi/setupapi_windows_test.go b/setupapi/setupapi_windows_test.go
index 12b5fe1..3d9abd6 100644
--- a/setupapi/setupapi_windows_test.go
+++ b/setupapi/setupapi_windows_test.go
@@ -403,3 +403,16 @@ func TestSetupDiGetSelectedDevice(t *testing.T) {
 		}
 	}
 }
+
+func TestUTF16ToBuf(t *testing.T) {
+	buf := []uint16{0x0123, 0x4567, 0x89ab, 0xcdef}
+	buf2 := UTF16ToBuf(buf)
+	if len(buf)*2 != len(buf2) ||
+		cap(buf)*2 != cap(buf2) ||
+		buf2[0] != 0x23 || buf2[1] != 0x01 ||
+		buf2[2] != 0x67 || buf2[3] != 0x45 ||
+		buf2[4] != 0xab || buf2[5] != 0x89 ||
+		buf2[6] != 0xef || buf2[7] != 0xcd {
+		t.Errorf("SetupDiSetSelectedDevice(nil) should fail with ERROR_INVALID_USER_BUFFER")
+	}
+}