@@ -53,3 +53,174 @@ pub async fn symlink_file<P: AsRef<Path>, Q: AsRef<Path>>(src: P, dst: Q) -> io:
5353let dst = dst. as_ref ( ) . to_owned ( ) ;
5454spawn_blocking ( move || std:: os:: windows:: fs:: symlink_file ( & src, & dst) ) . await
5555}
56+
57+ cfg_not_docs ! {
58+ pub use std:: os:: windows:: fs:: { OpenOptionsExt } ;
59+ }
60+
61+ cfg_docs ! {
62+ /// Windows-specific extensions to `OpenOptions`.
63+ pub trait OpenOptionsExt {
64+ /// Overrides the `dwDesiredAccess` argument to the call to [`CreateFile`]
65+ /// with the specified value.
66+ ///
67+ /// This will override the `read`, `write`, and `append` flags on the
68+ /// `OpenOptions` structure. This method provides fine-grained control over
69+ /// the permissions to read, write and append data, attributes (like hidden
70+ /// and system), and extended attributes.
71+ ///
72+ /// # Examples
73+ ///
74+ /// ```no_run
75+ /// use async_std::fs::OpenOptions;
76+ /// use async_std::os::windows::prelude::*;
77+ ///
78+ /// // Open without read and write permission, for example if you only need
79+ /// // to call `stat` on the file
80+ /// let file = OpenOptions::new().access_mode(0).open("foo.txt").await?;
81+ /// ```
82+ ///
83+ /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
84+ fn access_mode( & mut self , access: u32 ) ->& mut Self ;
85+
86+ /// Overrides the `dwShareMode` argument to the call to [`CreateFile`] with
87+ /// the specified value.
88+ ///
89+ /// By default `share_mode` is set to
90+ /// `FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE`. This allows
91+ /// other processes to read, write, and delete/rename the same file
92+ /// while it is open. Removing any of the flags will prevent other
93+ /// processes from performing the corresponding operation until the file
94+ /// handle is closed.
95+ ///
96+ /// # Examples
97+ ///
98+ /// ```no_run
99+ /// use async_std::fs::OpenOptions;
100+ /// use async_std::os::windows::prelude::*;
101+ ///
102+ /// // Do not allow others to read or modify this file while we have it open
103+ /// // for writing.
104+ /// let file = OpenOptions::new()
105+ /// .write(true)
106+ /// .share_mode(0)
107+ /// .open("foo.txt")
108+ /// .await?;
109+ /// ```
110+ ///
111+ /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
112+ fn share_mode( & mut self , val: u32 ) ->& mut Self ;
113+
114+ /// Sets extra flags for the `dwFileFlags` argument to the call to
115+ /// [`CreateFile2`] to the specified value (or combines it with
116+ /// `attributes` and `security_qos_flags` to set the `dwFlagsAndAttributes`
117+ /// for [`CreateFile`]).
118+ ///
119+ /// Custom flags can only set flags, not remove flags set by Rust's options.
120+ /// This option overwrites any previously set custom flags.
121+ ///
122+ /// # Examples
123+ ///
124+ /// ```no_run
125+ /// # #[cfg(for_demonstration_only)]
126+ /// extern crate winapi;
127+ /// # mod winapi { pub const FILE_FLAG_DELETE_ON_CLOSE: u32 = 0x04000000; }
128+ ///
129+ /// use async_std::fs::OpenOptions;
130+ /// use async_std::os::windows::prelude::*;
131+ ///
132+ /// let file = OpenOptions::new()
133+ /// .create(true)
134+ /// .write(true)
135+ /// .custom_flags(winapi::FILE_FLAG_DELETE_ON_CLOSE)
136+ /// .open("foo.txt")
137+ /// .await?;
138+ /// ```
139+ ///
140+ /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
141+ /// [`CreateFile2`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfile2
142+ fn custom_flags( & mut self , flags: u32 ) ->& mut Self ;
143+
144+ /// Sets the `dwFileAttributes` argument to the call to [`CreateFile2`] to
145+ /// the specified value (or combines it with `custom_flags` and
146+ /// `security_qos_flags` to set the `dwFlagsAndAttributes` for
147+ /// [`CreateFile`]).
148+ ///
149+ /// If a _new_ file is created because it does not yet exist and
150+ /// `.create(true)` or `.create_new(true)` are specified, the new file is
151+ /// given the attributes declared with `.attributes()`.
152+ ///
153+ /// If an _existing_ file is opened with `.create(true).truncate(true)`, its
154+ /// existing attributes are preserved and combined with the ones declared
155+ /// with `.attributes()`.
156+ ///
157+ /// In all other cases the attributes get ignored.
158+ ///
159+ /// # Examples
160+ ///
161+ /// ```no_run
162+ /// # #[cfg(for_demonstration_only)]
163+ /// extern crate winapi;
164+ /// # mod winapi { pub const FILE_ATTRIBUTE_HIDDEN: u32 = 2; }
165+ ///
166+ /// use async_std::fs::OpenOptions;
167+ /// use async_std::os::windows::prelude::*;
168+ ///
169+ /// let file = OpenOptions::new()
170+ /// .write(true)
171+ /// .create(true)
172+ /// .attributes(winapi::FILE_ATTRIBUTE_HIDDEN)
173+ /// .open("foo.txt")
174+ /// .await?;
175+ /// ```
176+ ///
177+ /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
178+ /// [`CreateFile2`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfile2
179+ fn attributes( & mut self , val: u32 ) ->& mut Self ;
180+
181+ /// Sets the `dwSecurityQosFlags` argument to the call to [`CreateFile2`] to
182+ /// the specified value (or combines it with `custom_flags` and `attributes`
183+ /// to set the `dwFlagsAndAttributes` for [`CreateFile`]).
184+ ///
185+ /// By default `security_qos_flags` is not set. It should be specified when
186+ /// opening a named pipe, to control to which degree a server process can
187+ /// act on behalf of a client process (security impersonation level).
188+ ///
189+ /// When `security_qos_flags` is not set, a malicious program can gain the
190+ /// elevated privileges of a privileged Rust process when it allows opening
191+ /// user-specified paths, by tricking it into opening a named pipe. So
192+ /// arguably `security_qos_flags` should also be set when opening arbitrary
193+ /// paths. However the bits can then conflict with other flags, specifically
194+ /// `FILE_FLAG_OPEN_NO_RECALL`.
195+ ///
196+ /// For information about possible values, see [Impersonation Levels] on the
197+ /// Windows Dev Center site. The `SECURITY_SQOS_PRESENT` flag is set
198+ /// automatically when using this method.
199+
200+ /// # Examples
201+ ///
202+ /// ```no_run
203+ /// # #[cfg(for_demonstration_only)]
204+ /// extern crate winapi;
205+ /// # mod winapi { pub const SECURITY_IDENTIFICATION: u32 = 0; }
206+ /// use async_std::fs::OpenOptions;
207+ /// use async_std::os::windows::prelude::*;
208+ ///
209+ /// let file = OpenOptions::new()
210+ /// .write(true)
211+ /// .create(true)
212+ ///
213+ /// // Sets the flag value to `SecurityIdentification`.
214+ /// .security_qos_flags(winapi::SECURITY_IDENTIFICATION)
215+ ///
216+ /// .open(r"\\.\pipe\MyPipe")
217+ /// .await?;
218+ /// ```
219+ ///
220+ /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
221+ /// [`CreateFile2`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfile2
222+ /// [Impersonation Levels]:
223+ /// https://docs.microsoft.com/en-us/windows/win32/api/winnt/ne-winnt-security_impersonation_level
224+ fn security_qos_flags( & mut self , flags: u32 ) ->& mut Self ;
225+ }
226+ }