--- /dev/null
+// Copyright 2024 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 windows
+
+import (
+ "syscall"
+)
+
+// Openat flags not supported by syscall.Open.
+//
+// These are invented values.
+//
+// When adding a new flag here, add an unexported version to
+// the set of invented O_ values in syscall/types_windows.go
+// to avoid overlap.
+const (
+ O_DIRECTORY = 0x100000 // target must be a directory
+ O_NOFOLLOW_ANY = 0x20000000 // disallow symlinks anywhere in the path
+)
+
+func Openat(dirfd syscall.Handle, name string, flag int, perm uint32) (_ syscall.Handle, e1 error) {
+ if len(name) == 0 {
+ return syscall.InvalidHandle, syscall.ERROR_FILE_NOT_FOUND
+ }
+
+ var access, options uint32
+ switch flag & (syscall.O_RDONLY | syscall.O_WRONLY | syscall.O_RDWR) {
+ case syscall.O_RDONLY:
+ // FILE_GENERIC_READ includes FILE_LIST_DIRECTORY.
+ access = FILE_GENERIC_READ
+ case syscall.O_WRONLY:
+ access = FILE_GENERIC_WRITE
+ options |= FILE_NON_DIRECTORY_FILE
+ case syscall.O_RDWR:
+ access = FILE_GENERIC_READ | FILE_GENERIC_WRITE
+ options |= FILE_NON_DIRECTORY_FILE
+ }
+ if flag&syscall.O_CREAT != 0 {
+ access |= FILE_GENERIC_WRITE
+ }
+ if flag&syscall.O_APPEND != 0 {
+ access &^= FILE_WRITE_DATA
+ access |= FILE_APPEND_DATA
+ }
+ if flag&O_DIRECTORY != 0 {
+ options |= FILE_DIRECTORY_FILE
+ access |= FILE_LIST_DIRECTORY
+ }
+ if flag&syscall.O_SYNC != 0 {
+ options |= FILE_WRITE_THROUGH
+ }
+ // Allow File.Stat.
+ access |= STANDARD_RIGHTS_READ | FILE_READ_ATTRIBUTES | FILE_READ_EA
+
+ objAttrs := &OBJECT_ATTRIBUTES{}
+ if flag&O_NOFOLLOW_ANY != 0 {
+ objAttrs.Attributes |= OBJ_DONT_REPARSE
+ }
+ if flag&syscall.O_CLOEXEC == 0 {
+ objAttrs.Attributes |= OBJ_INHERIT
+ }
+ if err := objAttrs.init(dirfd, name); err != nil {
+ return syscall.InvalidHandle, err
+ }
+
+ // We don't use FILE_OVERWRITE/FILE_OVERWRITE_IF, because when opening
+ // a file with FILE_ATTRIBUTE_READONLY these will replace an existing
+ // file with a new, read-only one.
+ //
+ // Instead, we ftruncate the file after opening when O_TRUNC is set.
+ var disposition uint32
+ switch {
+ case flag&(syscall.O_CREAT|syscall.O_EXCL) == (syscall.O_CREAT | syscall.O_EXCL):
+ disposition = FILE_CREATE
+ case flag&syscall.O_CREAT == syscall.O_CREAT:
+ disposition = FILE_OPEN_IF
+ default:
+ disposition = FILE_OPEN
+ }
+
+ fileAttrs := uint32(FILE_ATTRIBUTE_NORMAL)
+ if perm&syscall.S_IWRITE == 0 {
+ fileAttrs = FILE_ATTRIBUTE_READONLY
+ }
+
+ var h syscall.Handle
+ err := NtCreateFile(
+ &h,
+ SYNCHRONIZE|access,
+ objAttrs,
+ &IO_STATUS_BLOCK{},
+ nil,
+ fileAttrs,
+ FILE_SHARE_READ|FILE_SHARE_WRITE|FILE_SHARE_DELETE,
+ disposition,
+ FILE_SYNCHRONOUS_IO_NONALERT|options,
+ 0,
+ 0,
+ )
+ if err != nil {
+ return h, ntCreateFileError(err, flag)
+ }
+
+ if flag&syscall.O_TRUNC != 0 {
+ err = syscall.Ftruncate(h, 0)
+ if err != nil {
+ syscall.CloseHandle(h)
+ return syscall.InvalidHandle, err
+ }
+ }
+
+ return h, nil
+}
+
+// ntCreateFileError maps error returns from NTCreateFile to user-visible errors.
+func ntCreateFileError(err error, flag int) error {
+ s, ok := err.(NTStatus)
+ if !ok {
+ // Shouldn't really be possible, NtCreateFile always returns NTStatus.
+ return err
+ }
+ switch s {
+ case STATUS_REPARSE_POINT_ENCOUNTERED:
+ return syscall.ELOOP
+ case STATUS_NOT_A_DIRECTORY:
+ // ENOTDIR is the errno returned by open when O_DIRECTORY is specified
+ // and the target is not a directory.
+ //
+ // NtCreateFile can return STATUS_NOT_A_DIRECTORY under other circumstances,
+ // such as when opening "file/" where "file" is not a directory.
+ // (This might be Windows version dependent.)
+ //
+ // Only map STATUS_NOT_A_DIRECTORY to ENOTDIR when O_DIRECTORY is specified.
+ if flag&O_DIRECTORY != 0 {
+ return syscall.ENOTDIR
+ }
+ case STATUS_FILE_IS_A_DIRECTORY:
+ return syscall.EISDIR
+ }
+ return s.Errno()
+}
+
+func Mkdirat(dirfd syscall.Handle, name string, mode uint32) error {
+ objAttrs := &OBJECT_ATTRIBUTES{}
+ if err := objAttrs.init(dirfd, name); err != nil {
+ return err
+ }
+ var h syscall.Handle
+ err := NtCreateFile(
+ &h,
+ FILE_GENERIC_READ,
+ objAttrs,
+ &IO_STATUS_BLOCK{},
+ nil,
+ syscall.FILE_ATTRIBUTE_NORMAL,
+ syscall.FILE_SHARE_READ|syscall.FILE_SHARE_WRITE|syscall.FILE_SHARE_DELETE,
+ FILE_CREATE,
+ FILE_DIRECTORY_FILE,
+ 0,
+ 0,
+ )
+ if err != nil {
+ return ntCreateFileError(err, 0)
+ }
+ return nil
+}