[release-branch.go1.21] Revert "os: use handle based APIs to read directories on windows"

This reverts CL 452995.

Reason for revert: caused os.File.ReadDir to fail on
filesystems that do not support FILE_ID_BOTH_DIR_INFO.

This is an alternative to a fix-forward change in CL 518196.
Since the original change was mostly a performance improvement,
reverting to the previous implementation seems less risky than
backporting a larger fix.

Fixes #61910
Fixes #61964

Change-Id: I60f1602b9eb6ea353e7eb23429f19f1ffa16b394
Reviewed-on: https://go-review.googlesource.com/c/go/+/520156
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Austin Clements <austin@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Quim Muntal <quimmuntal@gmail.com>

6 files changed, 158 insertions, 197 deletions

diff --git a/src/internal/syscall/windows/syscall_windows.go b/src/internal/syscall/windows/syscall_windows.go
index 53d32a14a0..892b878d16 100644
--- a/src/internal/syscall/windows/syscall_windows.go
+++ b/src/internal/syscall/windows/syscall_windows.go
@@ -375,25 +375,5 @@ func ErrorLoadingGetTempPath2() error {
 
 //sys	RtlGenRandom(buf []byte) (err error) = advapi32.SystemFunction036
 
-type FILE_ID_BOTH_DIR_INFO struct {
-	NextEntryOffset uint32
-	FileIndex       uint32
-	CreationTime    syscall.Filetime
-	LastAccessTime  syscall.Filetime
-	LastWriteTime   syscall.Filetime
-	ChangeTime      syscall.Filetime
-	EndOfFile       uint64
-	AllocationSize  uint64
-	FileAttributes  uint32
-	FileNameLength  uint32
-	EaSize          uint32
-	ShortNameLength uint32
-	ShortName       [12]uint16
-	FileID          uint64
-	FileName        [1]uint16
-}
-
-//sys	GetVolumeInformationByHandle(file syscall.Handle, volumeNameBuffer *uint16, volumeNameSize uint32, volumeNameSerialNumber *uint32, maximumComponentLength *uint32, fileSystemFlags *uint32, fileSystemNameBuffer *uint16, fileSystemNameSize uint32) (err error) = GetVolumeInformationByHandleW
-
 //sys	RtlLookupFunctionEntry(pc uintptr, baseAddress *uintptr, table *byte) (ret uintptr) = kernel32.RtlLookupFunctionEntry
 //sys	RtlVirtualUnwind(handlerType uint32, baseAddress uintptr, pc uintptr, entry uintptr, ctxt uintptr, data *uintptr, frame *uintptr, ctxptrs *byte) (ret uintptr) = kernel32.RtlVirtualUnwind
diff --git a/src/internal/syscall/windows/zsyscall_windows.go b/src/internal/syscall/windows/zsyscall_windows.go
index 32744b00fc..a5c246b773 100644
--- a/src/internal/syscall/windows/zsyscall_windows.go
+++ b/src/internal/syscall/windows/zsyscall_windows.go
@@ -45,43 +45,42 @@ var (
 	moduserenv  = syscall.NewLazyDLL(sysdll.Add("userenv.dll"))
 	modws2_32   = syscall.NewLazyDLL(sysdll.Add("ws2_32.dll"))
 
-	procAdjustTokenPrivileges         = modadvapi32.NewProc("AdjustTokenPrivileges")
-	procDuplicateTokenEx              = modadvapi32.NewProc("DuplicateTokenEx")
-	procImpersonateSelf               = modadvapi32.NewProc("ImpersonateSelf")
-	procLookupPrivilegeValueW         = modadvapi32.NewProc("LookupPrivilegeValueW")
-	procOpenThreadToken               = modadvapi32.NewProc("OpenThreadToken")
-	procRevertToSelf                  = modadvapi32.NewProc("RevertToSelf")
-	procSetTokenInformation           = modadvapi32.NewProc("SetTokenInformation")
-	procSystemFunction036             = modadvapi32.NewProc("SystemFunction036")
-	procGetAdaptersAddresses          = modiphlpapi.NewProc("GetAdaptersAddresses")
-	procCreateEventW                  = modkernel32.NewProc("CreateEventW")
-	procGetACP                        = modkernel32.NewProc("GetACP")
-	procGetComputerNameExW            = modkernel32.NewProc("GetComputerNameExW")
-	procGetConsoleCP                  = modkernel32.NewProc("GetConsoleCP")
-	procGetCurrentThread              = modkernel32.NewProc("GetCurrentThread")
-	procGetFileInformationByHandleEx  = modkernel32.NewProc("GetFileInformationByHandleEx")
-	procGetFinalPathNameByHandleW     = modkernel32.NewProc("GetFinalPathNameByHandleW")
-	procGetModuleFileNameW            = modkernel32.NewProc("GetModuleFileNameW")
-	procGetTempPath2W                 = modkernel32.NewProc("GetTempPath2W")
-	procGetVolumeInformationByHandleW = modkernel32.NewProc("GetVolumeInformationByHandleW")
-	procLockFileEx                    = modkernel32.NewProc("LockFileEx")
-	procModule32FirstW                = modkernel32.NewProc("Module32FirstW")
-	procModule32NextW                 = modkernel32.NewProc("Module32NextW")
-	procMoveFileExW                   = modkernel32.NewProc("MoveFileExW")
-	procMultiByteToWideChar           = modkernel32.NewProc("MultiByteToWideChar")
-	procRtlLookupFunctionEntry        = modkernel32.NewProc("RtlLookupFunctionEntry")
-	procRtlVirtualUnwind              = modkernel32.NewProc("RtlVirtualUnwind")
-	procSetFileInformationByHandle    = modkernel32.NewProc("SetFileInformationByHandle")
-	procUnlockFileEx                  = modkernel32.NewProc("UnlockFileEx")
-	procVirtualQuery                  = modkernel32.NewProc("VirtualQuery")
-	procNetShareAdd                   = modnetapi32.NewProc("NetShareAdd")
-	procNetShareDel                   = modnetapi32.NewProc("NetShareDel")
-	procNetUserGetLocalGroups         = modnetapi32.NewProc("NetUserGetLocalGroups")
-	procGetProcessMemoryInfo          = modpsapi.NewProc("GetProcessMemoryInfo")
-	procCreateEnvironmentBlock        = moduserenv.NewProc("CreateEnvironmentBlock")
-	procDestroyEnvironmentBlock       = moduserenv.NewProc("DestroyEnvironmentBlock")
-	procGetProfilesDirectoryW         = moduserenv.NewProc("GetProfilesDirectoryW")
-	procWSASocketW                    = modws2_32.NewProc("WSASocketW")
+	procAdjustTokenPrivileges        = modadvapi32.NewProc("AdjustTokenPrivileges")
+	procDuplicateTokenEx             = modadvapi32.NewProc("DuplicateTokenEx")
+	procImpersonateSelf              = modadvapi32.NewProc("ImpersonateSelf")
+	procLookupPrivilegeValueW        = modadvapi32.NewProc("LookupPrivilegeValueW")
+	procOpenThreadToken              = modadvapi32.NewProc("OpenThreadToken")
+	procRevertToSelf                 = modadvapi32.NewProc("RevertToSelf")
+	procSetTokenInformation          = modadvapi32.NewProc("SetTokenInformation")
+	procSystemFunction036            = modadvapi32.NewProc("SystemFunction036")
+	procGetAdaptersAddresses         = modiphlpapi.NewProc("GetAdaptersAddresses")
+	procCreateEventW                 = modkernel32.NewProc("CreateEventW")
+	procGetACP                       = modkernel32.NewProc("GetACP")
+	procGetComputerNameExW           = modkernel32.NewProc("GetComputerNameExW")
+	procGetConsoleCP                 = modkernel32.NewProc("GetConsoleCP")
+	procGetCurrentThread             = modkernel32.NewProc("GetCurrentThread")
+	procGetFileInformationByHandleEx = modkernel32.NewProc("GetFileInformationByHandleEx")
+	procGetFinalPathNameByHandleW    = modkernel32.NewProc("GetFinalPathNameByHandleW")
+	procGetModuleFileNameW           = modkernel32.NewProc("GetModuleFileNameW")
+	procGetTempPath2W                = modkernel32.NewProc("GetTempPath2W")
+	procLockFileEx                   = modkernel32.NewProc("LockFileEx")
+	procModule32FirstW               = modkernel32.NewProc("Module32FirstW")
+	procModule32NextW                = modkernel32.NewProc("Module32NextW")
+	procMoveFileExW                  = modkernel32.NewProc("MoveFileExW")
+	procMultiByteToWideChar          = modkernel32.NewProc("MultiByteToWideChar")
+	procRtlLookupFunctionEntry       = modkernel32.NewProc("RtlLookupFunctionEntry")
+	procRtlVirtualUnwind             = modkernel32.NewProc("RtlVirtualUnwind")
+	procSetFileInformationByHandle   = modkernel32.NewProc("SetFileInformationByHandle")
+	procUnlockFileEx                 = modkernel32.NewProc("UnlockFileEx")
+	procVirtualQuery                 = modkernel32.NewProc("VirtualQuery")
+	procNetShareAdd                  = modnetapi32.NewProc("NetShareAdd")
+	procNetShareDel                  = modnetapi32.NewProc("NetShareDel")
+	procNetUserGetLocalGroups        = modnetapi32.NewProc("NetUserGetLocalGroups")
+	procGetProcessMemoryInfo         = modpsapi.NewProc("GetProcessMemoryInfo")
+	procCreateEnvironmentBlock       = moduserenv.NewProc("CreateEnvironmentBlock")
+	procDestroyEnvironmentBlock      = moduserenv.NewProc("DestroyEnvironmentBlock")
+	procGetProfilesDirectoryW        = moduserenv.NewProc("GetProfilesDirectoryW")
+	procWSASocketW                   = modws2_32.NewProc("WSASocketW")
 )
 
 func adjustTokenPrivileges(token syscall.Token, disableAllPrivileges bool, newstate *TOKEN_PRIVILEGES, buflen uint32, prevstate *TOKEN_PRIVILEGES, returnlen *uint32) (ret uint32, err error) {
@@ -242,14 +241,6 @@ func GetTempPath2(buflen uint32, buf *uint16) (n uint32, err error) {
 	return
 }
 
-func GetVolumeInformationByHandle(file syscall.Handle, volumeNameBuffer *uint16, volumeNameSize uint32, volumeNameSerialNumber *uint32, maximumComponentLength *uint32, fileSystemFlags *uint32, fileSystemNameBuffer *uint16, fileSystemNameSize uint32) (err error) {
-	r1, _, e1 := syscall.Syscall9(procGetVolumeInformationByHandleW.Addr(), 8, uintptr(file), uintptr(unsafe.Pointer(volumeNameBuffer)), uintptr(volumeNameSize), uintptr(unsafe.Pointer(volumeNameSerialNumber)), uintptr(unsafe.Pointer(maximumComponentLength)), uintptr(unsafe.Pointer(fileSystemFlags)), uintptr(unsafe.Pointer(fileSystemNameBuffer)), uintptr(fileSystemNameSize), 0)
-	if r1 == 0 {
-		err = errnoErr(e1)
-	}
-	return
-}
-
 func LockFileEx(file syscall.Handle, flags uint32, reserved uint32, bytesLow uint32, bytesHigh uint32, overlapped *syscall.Overlapped) (err error) {
 	r1, _, e1 := syscall.Syscall6(procLockFileEx.Addr(), 6, uintptr(file), uintptr(flags), uintptr(reserved), uintptr(bytesLow), uintptr(bytesHigh), uintptr(unsafe.Pointer(overlapped)))
 	if r1 == 0 {
diff --git a/src/os/dir_windows.go b/src/os/dir_windows.go
index 1724af58d5..9dc2cd7689 100644
--- a/src/os/dir_windows.go
+++ b/src/os/dir_windows.go
@@ -5,138 +5,60 @@
 package os
 
 import (
-	"internal/syscall/windows"
 	"io"
 	"io/fs"
 	"runtime"
-	"sync"
 	"syscall"
-	"unsafe"
 )
 
-// Auxiliary information if the File describes a directory
-type dirInfo struct {
-	// buf is a slice pointer so the slice header
-	// does not escape to the heap when returning
-	// buf to dirBufPool.
-	buf  *[]byte // buffer for directory I/O
-	bufp int     // location of next record in buf
-	vol  uint32
-}
-
-const (
-	// dirBufSize is the size of the dirInfo buffer.
-	// The buffer must be big enough to hold at least a single entry.
-	// The filename alone can be 512 bytes (MAX_PATH*2), and the fixed part of
-	// the FILE_ID_BOTH_DIR_INFO structure is 105 bytes, so dirBufSize
-	// should not be set below 1024 bytes (512+105+safety buffer).
-	// Windows 8.1 and earlier only works with buffer sizes up to 64 kB.
-	dirBufSize = 64 * 1024 // 64kB
-)
-
-var dirBufPool = sync.Pool{
-	New: func() any {
-		// The buffer must be at least a block long.
-		buf := make([]byte, dirBufSize)
-		return &buf
-	},
-}
-
-func (d *dirInfo) close() {
-	if d.buf != nil {
-		dirBufPool.Put(d.buf)
-		d.buf = nil
-	}
-}
-
 func (file *File) readdir(n int, mode readdirMode) (names []string, dirents []DirEntry, infos []FileInfo, err error) {
 	// If this file has no dirinfo, create one.
-	var infoClass uint32 = windows.FileIdBothDirectoryInfo
+	needdata := true
 	if file.dirinfo == nil {
-		// vol is used by os.SameFile.
-		// It is safe to query it once and reuse the value.
-		// Hard links are not allowed to reference files in other volumes.
-		// Junctions and symbolic links can reference files and directories in other volumes,
-		// but the reparse point should still live in the parent volume.
-		var vol uint32
-		err = windows.GetVolumeInformationByHandle(file.pfd.Sysfd, nil, 0, &vol, nil, nil, nil, 0)
-		runtime.KeepAlive(file)
+		needdata = false
+		file.dirinfo, err = openDir(file.name)
 		if err != nil {
 			err = &PathError{Op: "readdir", Path: file.name, Err: err}
 			return
 		}
-		infoClass = windows.FileIdBothDirectoryRestartInfo
-		file.dirinfo = new(dirInfo)
-		file.dirinfo.buf = dirBufPool.Get().(*[]byte)
-		file.dirinfo.vol = vol
 	}
-	d := file.dirinfo
 	wantAll := n <= 0
 	if wantAll {
 		n = -1
 	}
-	for n != 0 {
-		// Refill the buffer if necessary
-		if d.bufp == 0 {
-			err = windows.GetFileInformationByHandleEx(file.pfd.Sysfd, infoClass, (*byte)(unsafe.Pointer(&(*d.buf)[0])), uint32(len(*d.buf)))
+	d := &file.dirinfo.data
+	for n != 0 && !file.dirinfo.isempty {
+		if needdata {
+			e := syscall.FindNextFile(file.dirinfo.h, d)
 			runtime.KeepAlive(file)
-			if err != nil {
-				if err == syscall.ERROR_NO_MORE_FILES {
+			if e != nil {
+				if e == syscall.ERROR_NO_MORE_FILES {
 					break
-				}
-				if infoClass == windows.FileIdBothDirectoryRestartInfo && err == syscall.ERROR_FILE_NOT_FOUND {
-					// GetFileInformationByHandleEx doesn't document the return error codes when the info class is FileIdBothDirectoryRestartInfo,
-					// but MS-FSA 2.1.5.6.3 [1] specifies that the underlying file system driver should return STATUS_NO_SUCH_FILE when
-					// reading an empty root directory, which is mapped to ERROR_FILE_NOT_FOUND by Windows.
-					// Note that some file system drivers may never return this error code, as the spec allows to return the "." and ".."
-					// entries in such cases, making the directory appear non-empty.
-					// The chances of false positive are very low, as we know that the directory exists, else GetVolumeInformationByHandle
-					// would have failed, and that the handle is still valid, as we haven't closed it.
-					// See go.dev/issue/61159.
-					// [1] https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-fsa/fa8194e0-53ec-413b-8315-e8fa85396fd8
-					break
-				}
-				if s, _ := file.Stat(); s != nil && !s.IsDir() {
-					err = &PathError{Op: "readdir", Path: file.name, Err: syscall.ENOTDIR}
 				} else {
-					err = &PathError{Op: "GetFileInformationByHandleEx", Path: file.name, Err: err}
+					err = &PathError{Op: "FindNextFile", Path: file.name, Err: e}
+					return
 				}
-				return
 			}
-			infoClass = windows.FileIdBothDirectoryInfo
 		}
-		// Drain the buffer
-		var islast bool
-		for n != 0 && !islast {
-			info := (*windows.FILE_ID_BOTH_DIR_INFO)(unsafe.Pointer(&(*d.buf)[d.bufp]))
-			d.bufp += int(info.NextEntryOffset)
-			islast = info.NextEntryOffset == 0
-			if islast {
-				d.bufp = 0
-			}
-			nameslice := unsafe.Slice(&info.FileName[0], info.FileNameLength/2)
-			name := syscall.UTF16ToString(nameslice)
-			if name == "." || name == ".." { // Useless names
-				continue
-			}
-			if mode == readdirName {
-				names = append(names, name)
+		needdata = true
+		name := syscall.UTF16ToString(d.FileName[0:])
+		if name == "." || name == ".." { // Useless names
+			continue
+		}
+		if mode == readdirName {
+			names = append(names, name)
+		} else {
+			f := newFileStatFromWin32finddata(d)
+			f.name = name
+			f.path = file.dirinfo.path
+			f.appendNameToPath = true
+			if mode == readdirDirEntry {
+				dirents = append(dirents, dirEntry{f})
 			} else {
-				f := newFileStatFromFileIDBothDirInfo(info)
-				f.name = name
-				f.vol = d.vol
-				// f.path is used by os.SameFile to decide if it needs
-				// to fetch vol, idxhi and idxlo. But these are already set,
-				// so set f.path to "" to prevent os.SameFile doing it again.
-				f.path = ""
-				if mode == readdirDirEntry {
-					dirents = append(dirents, dirEntry{f})
-				} else {
-					infos = append(infos, f)
-				}
+				infos = append(infos, f)
 			}
-			n--
 		}
+		n--
 	}
 	if !wantAll && len(names)+len(dirents)+len(infos) == 0 {
 		return nil, nil, nil, io.EOF
diff --git a/src/os/file_windows.go b/src/os/file_windows.go
index c77d182fae..8d77a63d37 100644
--- a/src/os/file_windows.go
+++ b/src/os/file_windows.go
@@ -87,6 +87,18 @@ func NewFile(fd uintptr, name string) *File {
 	return newFile(h, name, "file")
 }
 
+// Auxiliary information if the File describes a directory
+type dirInfo struct {
+	h       syscall.Handle // search handle created with FindFirstFile
+	data    syscall.Win32finddata
+	path    string
+	isempty bool // set if FindFirstFile returns ERROR_FILE_NOT_FOUND
+}
+
+func (d *dirInfo) close() error {
+	return syscall.FindClose(d.h)
+}
+
 func epipecheck(file *File, e error) {
 }
 
@@ -94,6 +106,63 @@ func epipecheck(file *File, e error) {
 // On Unix-like systems, it is "/dev/null"; on Windows, "NUL".
 const DevNull = "NUL"
 
+func openDir(name string) (d *dirInfo, e error) {
+	var mask string
+
+	path := fixLongPath(name)
+
+	if len(path) == 2 && path[1] == ':' { // it is a drive letter, like C:
+		mask = path + `*`
+	} else if len(path) > 0 {
+		lc := path[len(path)-1]
+		if lc == '/' || lc == '\\' {
+			mask = path + `*`
+		} else {
+			mask = path + `\*`
+		}
+	} else {
+		mask = `\*`
+	}
+	maskp, e := syscall.UTF16PtrFromString(mask)
+	if e != nil {
+		return nil, e
+	}
+	d = new(dirInfo)
+	d.h, e = syscall.FindFirstFile(maskp, &d.data)
+	if e != nil {
+		// FindFirstFile returns ERROR_FILE_NOT_FOUND when
+		// no matching files can be found. Then, if directory
+		// exists, we should proceed.
+		// If FindFirstFile failed because name does not point
+		// to a directory, we should return ENOTDIR.
+		var fa syscall.Win32FileAttributeData
+		pathp, e1 := syscall.UTF16PtrFromString(path)
+		if e1 != nil {
+			return nil, e
+		}
+		e1 = syscall.GetFileAttributesEx(pathp, syscall.GetFileExInfoStandard, (*byte)(unsafe.Pointer(&fa)))
+		if e1 != nil {
+			return nil, e
+		}
+		if fa.FileAttributes&syscall.FILE_ATTRIBUTE_DIRECTORY == 0 {
+			return nil, syscall.ENOTDIR
+		}
+		if e != syscall.ERROR_FILE_NOT_FOUND {
+			return nil, e
+		}
+		d.isempty = true
+	}
+	d.path = path
+	if !isAbs(d.path) {
+		d.path, e = syscall.FullPath(d.path)
+		if e != nil {
+			d.close()
+			return nil, e
+		}
+	}
+	return d, nil
+}
+
 // openFileNolog is the Windows implementation of OpenFile.
 func openFileNolog(name string, flag int, perm FileMode) (*File, error) {
 	if name == "" {
diff --git a/src/os/os_windows_test.go b/src/os/os_windows_test.go
index a0bfd991e3..d6aab18720 100644
--- a/src/os/os_windows_test.go
+++ b/src/os/os_windows_test.go
@@ -1453,3 +1453,15 @@ func TestNewFileInvalid(t *testing.T) {
 		t.Errorf("NewFile(InvalidHandle) got %v want nil", f)
 	}
 }
+
+func TestReadDirPipe(t *testing.T) {
+	dir := `\\.\pipe\`
+	fi, err := os.Stat(dir)
+	if err != nil || !fi.IsDir() {
+		t.Skipf("%s is not a directory", dir)
+	}
+	_, err = os.ReadDir(dir)
+	if err != nil {
+		t.Errorf("ReadDir(%q) = %v", dir, err)
+	}
+}
diff --git a/src/os/types_windows.go b/src/os/types_windows.go
index d1623f7b17..9a3d508783 100644
--- a/src/os/types_windows.go
+++ b/src/os/types_windows.go
@@ -16,7 +16,7 @@ import (
 type fileStat struct {
 	name string
 
-	// from ByHandleFileInformation, Win32FileAttributeData, Win32finddata, and GetFileInformationByHandleEx
+	// from ByHandleFileInformation, Win32FileAttributeData and Win32finddata
 	FileAttributes uint32
 	CreationTime   syscall.Filetime
 	LastAccessTime syscall.Filetime
@@ -24,7 +24,7 @@ type fileStat struct {
 	FileSizeHigh   uint32
 	FileSizeLow    uint32
 
-	// from Win32finddata and GetFileInformationByHandleEx
+	// from Win32finddata
 	ReparseTag uint32
 
 	// what syscall.GetFileType returns
@@ -32,10 +32,11 @@ type fileStat struct {
 
 	// used to implement SameFile
 	sync.Mutex
-	path  string
-	vol   uint32
-	idxhi uint32
-	idxlo uint32
+	path             string
+	vol              uint32
+	idxhi            uint32
+	idxlo            uint32
+	appendNameToPath bool
 }
 
 // newFileStatFromGetFileInformationByHandle calls GetFileInformationByHandle
@@ -79,26 +80,6 @@ func newFileStatFromGetFileInformationByHandle(path string, h syscall.Handle) (f
 	}, nil
 }
 
-// newFileStatFromFileIDBothDirInfo copies all required information
-// from windows.FILE_ID_BOTH_DIR_INFO d into the newly created fileStat.
-func newFileStatFromFileIDBothDirInfo(d *windows.FILE_ID_BOTH_DIR_INFO) *fileStat {
-	// The FILE_ID_BOTH_DIR_INFO MSDN documentations isn't completely correct.
-	// FileAttributes can contain any file attributes that is currently set on the file,
-	// not just the ones documented.
-	// EaSize contains the reparse tag if the file is a reparse point.
-	return &fileStat{
-		FileAttributes: d.FileAttributes,
-		CreationTime:   d.CreationTime,
-		LastAccessTime: d.LastAccessTime,
-		LastWriteTime:  d.LastWriteTime,
-		FileSizeHigh:   uint32(d.EndOfFile >> 32),
-		FileSizeLow:    uint32(d.EndOfFile),
-		ReparseTag:     d.EaSize,
-		idxhi:          uint32(d.FileID >> 32),
-		idxlo:          uint32(d.FileID),
-	}
-}
-
 // newFileStatFromWin32finddata copies all required information
 // from syscall.Win32finddata d into the newly created fileStat.
 func newFileStatFromWin32finddata(d *syscall.Win32finddata) *fileStat {
@@ -188,7 +169,13 @@ func (fs *fileStat) loadFileId() error {
 		// already done
 		return nil
 	}
-	pathp, err := syscall.UTF16PtrFromString(fs.path)
+	var path string
+	if fs.appendNameToPath {
+		path = fs.path + `\` + fs.name
+	} else {
+		path = fs.path
+	}
+	pathp, err := syscall.UTF16PtrFromString(path)
 	if err != nil {
 		return err
 	}