build: upgrade dependencies and build with go 1.21

vendor/github.com/Microsoft/go-winio/internal/fs/doc.go

@@ -0,0 +1,2 @@
+// This package contains Win32 filesystem functionality.
+package fs

vendor/github.com/Microsoft/go-winio/internal/fs/fs.go

@@ -0,0 +1,202 @@
+//go:build windows
+
+package fs
+
+import (
+	"golang.org/x/sys/windows"
+
+	"github.com/Microsoft/go-winio/internal/stringbuffer"
+)
+
+//go:generate go run github.com/Microsoft/go-winio/tools/mkwinsyscall -output zsyscall_windows.go fs.go
+
+// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilew
+//sys CreateFile(name string, access AccessMask, mode FileShareMode, sa *syscall.SecurityAttributes, createmode FileCreationDisposition, attrs FileFlagOrAttribute, templatefile windows.Handle) (handle windows.Handle, err error) [failretval==windows.InvalidHandle] = CreateFileW
+
+const NullHandle windows.Handle = 0
+
+// AccessMask defines standard, specific, and generic rights.
+//
+//	Bitmask:
+//	 3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1
+//	 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+//	+---------------+---------------+-------------------------------+
+//	|G|G|G|G|Resvd|A| StandardRights|         SpecificRights        |
+//	|R|W|E|A|     |S|               |                               |
+//	+-+-------------+---------------+-------------------------------+
+//
+//	GR     Generic Read
+//	GW     Generic Write
+//	GE     Generic Exectue
+//	GA     Generic All
+//	Resvd  Reserved
+//	AS     Access Security System
+//
+// https://learn.microsoft.com/en-us/windows/win32/secauthz/access-mask
+//
+// https://learn.microsoft.com/en-us/windows/win32/secauthz/generic-access-rights
+//
+// https://learn.microsoft.com/en-us/windows/win32/fileio/file-access-rights-constants
+type AccessMask = windows.ACCESS_MASK
+
+//nolint:revive // SNAKE_CASE is not idiomatic in Go, but aligned with Win32 API.
+const (
+	// Not actually any.
+	//
+	// For CreateFile: "query certain metadata such as file, directory, or device attributes without accessing that file or device"
+	// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilew#parameters
+	FILE_ANY_ACCESS AccessMask = 0
+
+	// Specific Object Access
+	// from ntioapi.h
+
+	FILE_READ_DATA      AccessMask = (0x0001) // file & pipe
+	FILE_LIST_DIRECTORY AccessMask = (0x0001) // directory
+
+	FILE_WRITE_DATA AccessMask = (0x0002) // file & pipe
+	FILE_ADD_FILE   AccessMask = (0x0002) // directory
+
+	FILE_APPEND_DATA          AccessMask = (0x0004) // file
+	FILE_ADD_SUBDIRECTORY     AccessMask = (0x0004) // directory
+	FILE_CREATE_PIPE_INSTANCE AccessMask = (0x0004) // named pipe
+
+	FILE_READ_EA         AccessMask = (0x0008) // file & directory
+	FILE_READ_PROPERTIES AccessMask = FILE_READ_EA
+
+	FILE_WRITE_EA         AccessMask = (0x0010) // file & directory
+	FILE_WRITE_PROPERTIES AccessMask = FILE_WRITE_EA
+
+	FILE_EXECUTE  AccessMask = (0x0020) // file
+	FILE_TRAVERSE AccessMask = (0x0020) // directory
+
+	FILE_DELETE_CHILD AccessMask = (0x0040) // directory
+
+	FILE_READ_ATTRIBUTES AccessMask = (0x0080) // all
+
+	FILE_WRITE_ATTRIBUTES AccessMask = (0x0100) // all
+
+	FILE_ALL_ACCESS      AccessMask = (STANDARD_RIGHTS_REQUIRED | SYNCHRONIZE | 0x1FF)
+	FILE_GENERIC_READ    AccessMask = (STANDARD_RIGHTS_READ | FILE_READ_DATA | FILE_READ_ATTRIBUTES | FILE_READ_EA | SYNCHRONIZE)
+	FILE_GENERIC_WRITE   AccessMask = (STANDARD_RIGHTS_WRITE | FILE_WRITE_DATA | FILE_WRITE_ATTRIBUTES | FILE_WRITE_EA | FILE_APPEND_DATA | SYNCHRONIZE)
+	FILE_GENERIC_EXECUTE AccessMask = (STANDARD_RIGHTS_EXECUTE | FILE_READ_ATTRIBUTES | FILE_EXECUTE | SYNCHRONIZE)
+
+	SPECIFIC_RIGHTS_ALL AccessMask = 0x0000FFFF
+
+	// Standard Access
+	// from ntseapi.h
+
+	DELETE       AccessMask = 0x0001_0000
+	READ_CONTROL AccessMask = 0x0002_0000
+	WRITE_DAC    AccessMask = 0x0004_0000
+	WRITE_OWNER  AccessMask = 0x0008_0000
+	SYNCHRONIZE  AccessMask = 0x0010_0000
+
+	STANDARD_RIGHTS_REQUIRED AccessMask = 0x000F_0000
+
+	STANDARD_RIGHTS_READ    AccessMask = READ_CONTROL
+	STANDARD_RIGHTS_WRITE   AccessMask = READ_CONTROL
+	STANDARD_RIGHTS_EXECUTE AccessMask = READ_CONTROL
+
+	STANDARD_RIGHTS_ALL AccessMask = 0x001F_0000
+)
+
+type FileShareMode uint32
+
+//nolint:revive // SNAKE_CASE is not idiomatic in Go, but aligned with Win32 API.
+const (
+	FILE_SHARE_NONE        FileShareMode = 0x00
+	FILE_SHARE_READ        FileShareMode = 0x01
+	FILE_SHARE_WRITE       FileShareMode = 0x02
+	FILE_SHARE_DELETE      FileShareMode = 0x04
+	FILE_SHARE_VALID_FLAGS FileShareMode = 0x07
+)
+
+type FileCreationDisposition uint32
+
+//nolint:revive // SNAKE_CASE is not idiomatic in Go, but aligned with Win32 API.
+const (
+	// from winbase.h
+
+	CREATE_NEW        FileCreationDisposition = 0x01
+	CREATE_ALWAYS     FileCreationDisposition = 0x02
+	OPEN_EXISTING     FileCreationDisposition = 0x03
+	OPEN_ALWAYS       FileCreationDisposition = 0x04
+	TRUNCATE_EXISTING FileCreationDisposition = 0x05
+)
+
+// CreateFile and co. take flags or attributes together as one parameter.
+// Define alias until we can use generics to allow both
+
+// https://learn.microsoft.com/en-us/windows/win32/fileio/file-attribute-constants
+type FileFlagOrAttribute uint32
+
+//nolint:revive // SNAKE_CASE is not idiomatic in Go, but aligned with Win32 API.
+const ( // from winnt.h
+	FILE_FLAG_WRITE_THROUGH       FileFlagOrAttribute = 0x8000_0000
+	FILE_FLAG_OVERLAPPED          FileFlagOrAttribute = 0x4000_0000
+	FILE_FLAG_NO_BUFFERING        FileFlagOrAttribute = 0x2000_0000
+	FILE_FLAG_RANDOM_ACCESS       FileFlagOrAttribute = 0x1000_0000
+	FILE_FLAG_SEQUENTIAL_SCAN     FileFlagOrAttribute = 0x0800_0000
+	FILE_FLAG_DELETE_ON_CLOSE     FileFlagOrAttribute = 0x0400_0000
+	FILE_FLAG_BACKUP_SEMANTICS    FileFlagOrAttribute = 0x0200_0000
+	FILE_FLAG_POSIX_SEMANTICS     FileFlagOrAttribute = 0x0100_0000
+	FILE_FLAG_OPEN_REPARSE_POINT  FileFlagOrAttribute = 0x0020_0000
+	FILE_FLAG_OPEN_NO_RECALL      FileFlagOrAttribute = 0x0010_0000
+	FILE_FLAG_FIRST_PIPE_INSTANCE FileFlagOrAttribute = 0x0008_0000
+)
+
+type FileSQSFlag = FileFlagOrAttribute
+
+//nolint:revive // SNAKE_CASE is not idiomatic in Go, but aligned with Win32 API.
+const ( // from winbase.h
+	SECURITY_ANONYMOUS      FileSQSFlag = FileSQSFlag(SecurityAnonymous << 16)
+	SECURITY_IDENTIFICATION FileSQSFlag = FileSQSFlag(SecurityIdentification << 16)
+	SECURITY_IMPERSONATION  FileSQSFlag = FileSQSFlag(SecurityImpersonation << 16)
+	SECURITY_DELEGATION     FileSQSFlag = FileSQSFlag(SecurityDelegation << 16)
+
+	SECURITY_SQOS_PRESENT     FileSQSFlag = 0x00100000
+	SECURITY_VALID_SQOS_FLAGS FileSQSFlag = 0x001F0000
+)
+
+// GetFinalPathNameByHandle flags
+//
+// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getfinalpathnamebyhandlew#parameters
+type GetFinalPathFlag uint32
+
+//nolint:revive // SNAKE_CASE is not idiomatic in Go, but aligned with Win32 API.
+const (
+	GetFinalPathDefaultFlag GetFinalPathFlag = 0x0
+
+	FILE_NAME_NORMALIZED GetFinalPathFlag = 0x0
+	FILE_NAME_OPENED     GetFinalPathFlag = 0x8
+
+	VOLUME_NAME_DOS  GetFinalPathFlag = 0x0
+	VOLUME_NAME_GUID GetFinalPathFlag = 0x1
+	VOLUME_NAME_NT   GetFinalPathFlag = 0x2
+	VOLUME_NAME_NONE GetFinalPathFlag = 0x4
+)
+
+// getFinalPathNameByHandle facilitates calling the Windows API GetFinalPathNameByHandle
+// with the given handle and flags. It transparently takes care of creating a buffer of the
+// correct size for the call.
+//
+// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getfinalpathnamebyhandlew
+func GetFinalPathNameByHandle(h windows.Handle, flags GetFinalPathFlag) (string, error) {
+	b := stringbuffer.NewWString()
+	//TODO: can loop infinitely if Win32 keeps returning the same (or a larger) n?
+	for {
+		n, err := windows.GetFinalPathNameByHandle(h, b.Pointer(), b.Cap(), uint32(flags))
+		if err != nil {
+			return "", err
+		}
+		// If the buffer wasn't large enough, n will be the total size needed (including null terminator).
+		// Resize and try again.
+		if n > b.Cap() {
+			b.ResizeTo(n)
+			continue
+		}
+		// If the buffer is large enough, n will be the size not including the null terminator.
+		// Convert to a Go string and return.
+		return b.String(), nil
+	}
+}

vendor/github.com/Microsoft/go-winio/internal/fs/security.go

@@ -0,0 +1,12 @@
+package fs
+
+// https://learn.microsoft.com/en-us/windows/win32/api/winnt/ne-winnt-security_impersonation_level
+type SecurityImpersonationLevel int32 // C default enums underlying type is `int`, which is Go `int32`
+
+// Impersonation levels
+const (
+	SecurityAnonymous      SecurityImpersonationLevel = 0
+	SecurityIdentification SecurityImpersonationLevel = 1
+	SecurityImpersonation  SecurityImpersonationLevel = 2
+	SecurityDelegation     SecurityImpersonationLevel = 3
+)

vendor/github.com/Microsoft/go-winio/internal/fs/zsyscall_windows.go

@@ -0,0 +1,64 @@
+//go:build windows
+
+// Code generated by 'go generate' using "github.com/Microsoft/go-winio/tools/mkwinsyscall"; DO NOT EDIT.
+
+package fs
+
+import (
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+var _ unsafe.Pointer
+
+// Do the interface allocations only once for common
+// Errno values.
+const (
+	errnoERROR_IO_PENDING = 997
+)
+
+var (
+	errERROR_IO_PENDING error = syscall.Errno(errnoERROR_IO_PENDING)
+	errERROR_EINVAL     error = syscall.EINVAL
+)
+
+// errnoErr returns common boxed Errno values, to prevent
+// allocations at runtime.
+func errnoErr(e syscall.Errno) error {
+	switch e {
+	case 0:
+		return errERROR_EINVAL
+	case errnoERROR_IO_PENDING:
+		return errERROR_IO_PENDING
+	}
+	// TODO: add more here, after collecting data on the common
+	// error values see on Windows. (perhaps when running
+	// all.bat?)
+	return e
+}
+
+var (
+	modkernel32 = windows.NewLazySystemDLL("kernel32.dll")
+
+	procCreateFileW = modkernel32.NewProc("CreateFileW")
+)
+
+func CreateFile(name string, access AccessMask, mode FileShareMode, sa *syscall.SecurityAttributes, createmode FileCreationDisposition, attrs FileFlagOrAttribute, templatefile windows.Handle) (handle windows.Handle, err error) {
+	var _p0 *uint16
+	_p0, err = syscall.UTF16PtrFromString(name)
+	if err != nil {
+		return
+	}
+	return _CreateFile(_p0, access, mode, sa, createmode, attrs, templatefile)
+}
+
+func _CreateFile(name *uint16, access AccessMask, mode FileShareMode, sa *syscall.SecurityAttributes, createmode FileCreationDisposition, attrs FileFlagOrAttribute, templatefile windows.Handle) (handle windows.Handle, err error) {
+	r0, _, e1 := syscall.Syscall9(procCreateFileW.Addr(), 7, uintptr(unsafe.Pointer(name)), uintptr(access), uintptr(mode), uintptr(unsafe.Pointer(sa)), uintptr(createmode), uintptr(attrs), uintptr(templatefile), 0, 0)
+	handle = windows.Handle(r0)
+	if handle == windows.InvalidHandle {
+		err = errnoErr(e1)
+	}
+	return
+}

vendor/github.com/Microsoft/go-winio/internal/socket/rawaddr.go

@@ -0,0 +1,20 @@
+package socket
+
+import (
+	"unsafe"
+)
+
+// RawSockaddr allows structs to be used with [Bind] and [ConnectEx]. The
+// struct must meet the Win32 sockaddr requirements specified here:
+// https://docs.microsoft.com/en-us/windows/win32/winsock/sockaddr-2
+//
+// Specifically, the struct size must be least larger than an int16 (unsigned short)
+// for the address family.
+type RawSockaddr interface {
+	// Sockaddr returns a pointer to the RawSockaddr and its struct size, allowing
+	// for the RawSockaddr's data to be overwritten by syscalls (if necessary).
+	//
+	// It is the callers responsibility to validate that the values are valid; invalid
+	// pointers or size can cause a panic.
+	Sockaddr() (unsafe.Pointer, int32, error)
+}

vendor/github.com/Microsoft/go-winio/internal/socket/socket.go

@@ -0,0 +1,179 @@
+//go:build windows
+
+package socket
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"sync"
+	"syscall"
+	"unsafe"
+
+	"github.com/Microsoft/go-winio/pkg/guid"
+	"golang.org/x/sys/windows"
+)
+
+//go:generate go run github.com/Microsoft/go-winio/tools/mkwinsyscall -output zsyscall_windows.go socket.go
+
+//sys getsockname(s windows.Handle, name unsafe.Pointer, namelen *int32) (err error) [failretval==socketError] = ws2_32.getsockname
+//sys getpeername(s windows.Handle, name unsafe.Pointer, namelen *int32) (err error) [failretval==socketError] = ws2_32.getpeername
+//sys bind(s windows.Handle, name unsafe.Pointer, namelen int32) (err error) [failretval==socketError] = ws2_32.bind
+
+const socketError = uintptr(^uint32(0))
+
+var (
+	// todo(helsaawy): create custom error types to store the desired vs actual size and addr family?
+
+	ErrBufferSize     = errors.New("buffer size")
+	ErrAddrFamily     = errors.New("address family")
+	ErrInvalidPointer = errors.New("invalid pointer")
+	ErrSocketClosed   = fmt.Errorf("socket closed: %w", net.ErrClosed)
+)
+
+// todo(helsaawy): replace these with generics, ie: GetSockName[S RawSockaddr](s windows.Handle) (S, error)
+
+// GetSockName writes the local address of socket s to the [RawSockaddr] rsa.
+// If rsa is not large enough, the [windows.WSAEFAULT] is returned.
+func GetSockName(s windows.Handle, rsa RawSockaddr) error {
+	ptr, l, err := rsa.Sockaddr()
+	if err != nil {
+		return fmt.Errorf("could not retrieve socket pointer and size: %w", err)
+	}
+
+	// although getsockname returns WSAEFAULT if the buffer is too small, it does not set
+	// &l to the correct size, so--apart from doubling the buffer repeatedly--there is no remedy
+	return getsockname(s, ptr, &l)
+}
+
+// GetPeerName returns the remote address the socket is connected to.
+//
+// See [GetSockName] for more information.
+func GetPeerName(s windows.Handle, rsa RawSockaddr) error {
+	ptr, l, err := rsa.Sockaddr()
+	if err != nil {
+		return fmt.Errorf("could not retrieve socket pointer and size: %w", err)
+	}
+
+	return getpeername(s, ptr, &l)
+}
+
+func Bind(s windows.Handle, rsa RawSockaddr) (err error) {
+	ptr, l, err := rsa.Sockaddr()
+	if err != nil {
+		return fmt.Errorf("could not retrieve socket pointer and size: %w", err)
+	}
+
+	return bind(s, ptr, l)
+}
+
+// "golang.org/x/sys/windows".ConnectEx and .Bind only accept internal implementations of the
+// their sockaddr interface, so they cannot be used with HvsockAddr
+// Replicate functionality here from
+// https://cs.opensource.google/go/x/sys/+/master:windows/syscall_windows.go
+
+// The function pointers to `AcceptEx`, `ConnectEx` and `GetAcceptExSockaddrs` must be loaded at
+// runtime via a WSAIoctl call:
+// https://docs.microsoft.com/en-us/windows/win32/api/Mswsock/nc-mswsock-lpfn_connectex#remarks
+
+type runtimeFunc struct {
+	id   guid.GUID
+	once sync.Once
+	addr uintptr
+	err  error
+}
+
+func (f *runtimeFunc) Load() error {
+	f.once.Do(func() {
+		var s windows.Handle
+		s, f.err = windows.Socket(windows.AF_INET, windows.SOCK_STREAM, windows.IPPROTO_TCP)
+		if f.err != nil {
+			return
+		}
+		defer windows.CloseHandle(s) //nolint:errcheck
+
+		var n uint32
+		f.err = windows.WSAIoctl(s,
+			windows.SIO_GET_EXTENSION_FUNCTION_POINTER,
+			(*byte)(unsafe.Pointer(&f.id)),
+			uint32(unsafe.Sizeof(f.id)),
+			(*byte)(unsafe.Pointer(&f.addr)),
+			uint32(unsafe.Sizeof(f.addr)),
+			&n,
+			nil, // overlapped
+			0,   // completionRoutine
+		)
+	})
+	return f.err
+}
+
+var (
+	// todo: add `AcceptEx` and `GetAcceptExSockaddrs`
+	WSAID_CONNECTEX = guid.GUID{ //revive:disable-line:var-naming ALL_CAPS
+		Data1: 0x25a207b9,
+		Data2: 0xddf3,
+		Data3: 0x4660,
+		Data4: [8]byte{0x8e, 0xe9, 0x76, 0xe5, 0x8c, 0x74, 0x06, 0x3e},
+	}
+
+	connectExFunc = runtimeFunc{id: WSAID_CONNECTEX}
+)
+
+func ConnectEx(
+	fd windows.Handle,
+	rsa RawSockaddr,
+	sendBuf *byte,
+	sendDataLen uint32,
+	bytesSent *uint32,
+	overlapped *windows.Overlapped,
+) error {
+	if err := connectExFunc.Load(); err != nil {
+		return fmt.Errorf("failed to load ConnectEx function pointer: %w", err)
+	}
+	ptr, n, err := rsa.Sockaddr()
+	if err != nil {
+		return err
+	}
+	return connectEx(fd, ptr, n, sendBuf, sendDataLen, bytesSent, overlapped)
+}
+
+// BOOL LpfnConnectex(
+//   [in]           SOCKET s,
+//   [in]           const sockaddr *name,
+//   [in]           int namelen,
+//   [in, optional] PVOID lpSendBuffer,
+//   [in]           DWORD dwSendDataLength,
+//   [out]          LPDWORD lpdwBytesSent,
+//   [in]           LPOVERLAPPED lpOverlapped
+// )
+
+func connectEx(
+	s windows.Handle,
+	name unsafe.Pointer,
+	namelen int32,
+	sendBuf *byte,
+	sendDataLen uint32,
+	bytesSent *uint32,
+	overlapped *windows.Overlapped,
+) (err error) {
+	// todo: after upgrading to 1.18, switch from syscall.Syscall9 to syscall.SyscallN
+	r1, _, e1 := syscall.Syscall9(connectExFunc.addr,
+		7,
+		uintptr(s),
+		uintptr(name),
+		uintptr(namelen),
+		uintptr(unsafe.Pointer(sendBuf)),
+		uintptr(sendDataLen),
+		uintptr(unsafe.Pointer(bytesSent)),
+		uintptr(unsafe.Pointer(overlapped)),
+		0,
+		0)
+	if r1 == 0 {
+		if e1 != 0 {
+			err = error(e1)
+		} else {
+			err = syscall.EINVAL
+		}
+	}
+	return err
+}

vendor/github.com/Microsoft/go-winio/internal/socket/zsyscall_windows.go

@@ -0,0 +1,72 @@
+//go:build windows
+
+// Code generated by 'go generate' using "github.com/Microsoft/go-winio/tools/mkwinsyscall"; DO NOT EDIT.
+
+package socket
+
+import (
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+var _ unsafe.Pointer
+
+// Do the interface allocations only once for common
+// Errno values.
+const (
+	errnoERROR_IO_PENDING = 997
+)
+
+var (
+	errERROR_IO_PENDING error = syscall.Errno(errnoERROR_IO_PENDING)
+	errERROR_EINVAL     error = syscall.EINVAL
+)
+
+// errnoErr returns common boxed Errno values, to prevent
+// allocations at runtime.
+func errnoErr(e syscall.Errno) error {
+	switch e {
+	case 0:
+		return errERROR_EINVAL
+	case errnoERROR_IO_PENDING:
+		return errERROR_IO_PENDING
+	}
+	// TODO: add more here, after collecting data on the common
+	// error values see on Windows. (perhaps when running
+	// all.bat?)
+	return e
+}
+
+var (
+	modws2_32 = windows.NewLazySystemDLL("ws2_32.dll")
+
+	procbind        = modws2_32.NewProc("bind")
+	procgetpeername = modws2_32.NewProc("getpeername")
+	procgetsockname = modws2_32.NewProc("getsockname")
+)
+
+func bind(s windows.Handle, name unsafe.Pointer, namelen int32) (err error) {
+	r1, _, e1 := syscall.Syscall(procbind.Addr(), 3, uintptr(s), uintptr(name), uintptr(namelen))
+	if r1 == socketError {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+func getpeername(s windows.Handle, name unsafe.Pointer, namelen *int32) (err error) {
+	r1, _, e1 := syscall.Syscall(procgetpeername.Addr(), 3, uintptr(s), uintptr(name), uintptr(unsafe.Pointer(namelen)))
+	if r1 == socketError {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+func getsockname(s windows.Handle, name unsafe.Pointer, namelen *int32) (err error) {
+	r1, _, e1 := syscall.Syscall(procgetsockname.Addr(), 3, uintptr(s), uintptr(name), uintptr(unsafe.Pointer(namelen)))
+	if r1 == socketError {
+		err = errnoErr(e1)
+	}
+	return
+}

vendor/github.com/Microsoft/go-winio/internal/stringbuffer/wstring.go

@@ -0,0 +1,132 @@
+package stringbuffer
+
+import (
+	"sync"
+	"unicode/utf16"
+)
+
+// TODO: worth exporting and using in mkwinsyscall?
+
+// Uint16BufferSize is the buffer size in the pool, chosen somewhat arbitrarily to accommodate
+// large path strings:
+// MAX_PATH (260) + size of volume GUID prefix (49) + null terminator = 310.
+const MinWStringCap = 310
+
+// use *[]uint16 since []uint16 creates an extra allocation where the slice header
+// is copied to heap and then referenced via pointer in the interface header that sync.Pool
+// stores.
+var pathPool = sync.Pool{ // if go1.18+ adds Pool[T], use that to store []uint16 directly
+	New: func() interface{} {
+		b := make([]uint16, MinWStringCap)
+		return &b
+	},
+}
+
+func newBuffer() []uint16 { return *(pathPool.Get().(*[]uint16)) }
+
+// freeBuffer copies the slice header data, and puts a pointer to that in the pool.
+// This avoids taking a pointer to the slice header in WString, which can be set to nil.
+func freeBuffer(b []uint16) { pathPool.Put(&b) }
+
+// WString is a wide string buffer ([]uint16) meant for storing UTF-16 encoded strings
+// for interacting with Win32 APIs.
+// Sizes are specified as uint32 and not int.
+//
+// It is not thread safe.
+type WString struct {
+	// type-def allows casting to []uint16 directly, use struct to prevent that and allow adding fields in the future.
+
+	// raw buffer
+	b []uint16
+}
+
+// NewWString returns a [WString] allocated from a shared pool with an
+// initial capacity of at least [MinWStringCap].
+// Since the buffer may have been previously used, its contents are not guaranteed to be empty.
+//
+// The buffer should be freed via [WString.Free]
+func NewWString() *WString {
+	return &WString{
+		b: newBuffer(),
+	}
+}
+
+func (b *WString) Free() {
+	if b.empty() {
+		return
+	}
+	freeBuffer(b.b)
+	b.b = nil
+}
+
+// ResizeTo grows the buffer to at least c and returns the new capacity, freeing the
+// previous buffer back into pool.
+func (b *WString) ResizeTo(c uint32) uint32 {
+	// allready sufficient (or n is 0)
+	if c <= b.Cap() {
+		return b.Cap()
+	}
+
+	if c <= MinWStringCap {
+		c = MinWStringCap
+	}
+	// allocate at-least double buffer size, as is done in [bytes.Buffer] and other places
+	if c <= 2*b.Cap() {
+		c = 2 * b.Cap()
+	}
+
+	b2 := make([]uint16, c)
+	if !b.empty() {
+		copy(b2, b.b)
+		freeBuffer(b.b)
+	}
+	b.b = b2
+	return c
+}
+
+// Buffer returns the underlying []uint16 buffer.
+func (b *WString) Buffer() []uint16 {
+	if b.empty() {
+		return nil
+	}
+	return b.b
+}
+
+// Pointer returns a pointer to the first uint16 in the buffer.
+// If the [WString.Free] has already been called, the pointer will be nil.
+func (b *WString) Pointer() *uint16 {
+	if b.empty() {
+		return nil
+	}
+	return &b.b[0]
+}
+
+// String returns the returns the UTF-8 encoding of the UTF-16 string in the buffer.
+//
+// It assumes that the data is null-terminated.
+func (b *WString) String() string {
+	// Using [windows.UTF16ToString] would require importing "golang.org/x/sys/windows"
+	// and would make this code Windows-only, which makes no sense.
+	// So copy UTF16ToString code into here.
+	// If other windows-specific code is added, switch to [windows.UTF16ToString]
+
+	s := b.b
+	for i, v := range s {
+		if v == 0 {
+			s = s[:i]
+			break
+		}
+	}
+	return string(utf16.Decode(s))
+}
+
+// Cap returns the underlying buffer capacity.
+func (b *WString) Cap() uint32 {
+	if b.empty() {
+		return 0
+	}
+	return b.cap()
+}
+
+func (b *WString) cap() uint32 { return uint32(cap(b.b)) }
+func (b *WString) empty() bool { return b == nil || b.cap() == 0 }