fs.rs.html -- source
Description: Source to the Rust file `src/libstd/sys/windows/ext/fs.rs`.
Keywords: rust, rustlang, rust-lang

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    //! Windows-specific extensions for the primitives in the `std::fs` module.

    #![stable(feature = "rust1", since = "1.0.0")]

    use crate::fs::{self, Metadata, OpenOptions};
    use crate::io;
    use crate::path::Path;
    use crate::sys;
    use crate::sys_common::{AsInner, AsInnerMut};

    /// Windows-specific extensions to [`File`].
    ///
    /// [`File`]: ../../../fs/struct.File.html
    #[stable(feature = "file_offset", since = "1.15.0")]
    pub trait FileExt {
        /// Seeks to a given position and reads a number of bytes.
        ///
        /// Returns the number of bytes read.
        ///
        /// The offset is relative to the start of the file and thus independent
        /// from the current cursor. The current cursor **is** affected by this
        /// function, it is set to the end of the read.
        ///
        /// Reading beyond the end of the file will always return with a length of
        /// 0\.
        ///
        /// Note that similar to `File::read`, it is not an error to return with a
        /// short read. When returning from such a short read, the file pointer is
        /// still updated.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::io;
        /// use std::fs::File;
        /// use std::os::windows::prelude::*;
        ///
        /// fn main() -> io::Result<()> {
        ///     let mut file = File::open("foo.txt")?;
        ///     let mut buffer = [0; 10];
        ///
        ///     // Read 10 bytes, starting 72 bytes from the
        ///     // start of the file.
        ///     file.seek_read(&mut buffer[..], 72)?;
        ///     Ok(())
        /// }
        /// ```
        #[stable(feature = "file_offset", since = "1.15.0")]
        fn seek_read(&self, buf: &mut [u8], offset: u64) -> io::Result<usize>;

        /// Seeks to a given position and writes a number of bytes.
        ///
        /// Returns the number of bytes written.
        ///
        /// The offset is relative to the start of the file and thus independent
        /// from the current cursor. The current cursor **is** affected by this
        /// function, it is set to the end of the write.
        ///
        /// When writing beyond the end of the file, the file is appropriately
        /// extended and the intermediate bytes are left uninitialized.
        ///
        /// Note that similar to `File::write`, it is not an error to return a
        /// short write. When returning from such a short write, the file pointer
        /// is still updated.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::fs::File;
        /// use std::os::windows::prelude::*;
        ///
        /// fn main() -> std::io::Result<()> {
        ///     let mut buffer = File::create("foo.txt")?;
        ///
        ///     // Write a byte string starting 72 bytes from
        ///     // the start of the file.
        ///     buffer.seek_write(b"some bytes", 72)?;
        ///     Ok(())
        /// }
        /// ```
        #[stable(feature = "file_offset", since = "1.15.0")]
        fn seek_write(&self, buf: &[u8], offset: u64) -> io::Result<usize>;
    }

    #[stable(feature = "file_offset", since = "1.15.0")]
    impl FileExt for fs::File {
        fn seek_read(&self, buf: &mut [u8], offset: u64) -> io::Result<usize> {
            self.as_inner().read_at(buf, offset)
        }

        fn seek_write(&self, buf: &[u8], offset: u64) -> io::Result<usize> {
            self.as_inner().write_at(buf, offset)
        }
    }

    /// Windows-specific extensions to [`fs::OpenOptions`].
    ///
    /// [`fs::OpenOptions`]: ../../../../std/fs/struct.OpenOptions.html
    #[stable(feature = "open_options_ext", since = "1.10.0")]
    pub trait OpenOptionsExt {
        /// Overrides the `dwDesiredAccess` argument to the call to [`CreateFile`]
        /// with the specified value.
        ///
        /// This will override the `read`, `write`, and `append` flags on the
        /// `OpenOptions` structure. This method provides fine-grained control over
        /// the permissions to read, write and append data, attributes (like hidden
        /// and system), and extended attributes.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::fs::OpenOptions;
        /// use std::os::windows::prelude::*;
        ///
        /// // Open without read and write permission, for example if you only need
        /// // to call `stat` on the file
        /// let file = OpenOptions::new().access_mode(0).open("foo.txt");
        /// ```
        ///
        /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
        #[stable(feature = "open_options_ext", since = "1.10.0")]
        fn access_mode(&mut self, access: u32) -> &mut Self;

        /// Overrides the `dwShareMode` argument to the call to [`CreateFile`] with
        /// the specified value.
        ///
        /// By default `share_mode` is set to
        /// `FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE`. This allows
        /// other processes to read, write, and delete/rename the same file
        /// while it is open. Removing any of the flags will prevent other
        /// processes from performing the corresponding operation until the file
        /// handle is closed.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::fs::OpenOptions;
        /// use std::os::windows::prelude::*;
        ///
        /// // Do not allow others to read or modify this file while we have it open
        /// // for writing.
        /// let file = OpenOptions::new()
        ///     .write(true)
        ///     .share_mode(0)
        ///     .open("foo.txt");
        /// ```
        ///
        /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
        #[stable(feature = "open_options_ext", since = "1.10.0")]
        fn share_mode(&mut self, val: u32) -> &mut Self;

        /// Sets extra flags for the `dwFileFlags` argument to the call to
        /// [`CreateFile2`] to the specified value (or combines it with
        /// `attributes` and `security_qos_flags` to set the `dwFlagsAndAttributes`
        /// for [`CreateFile`]).
        ///
        /// Custom flags can only set flags, not remove flags set by Rust's options.
        /// This option overwrites any previously set custom flags.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// # #[cfg(for_demonstration_only)]
        /// extern crate winapi;
        /// # mod winapi { pub const FILE_FLAG_DELETE_ON_CLOSE: u32 = 0x04000000; }
        ///
        /// use std::fs::OpenOptions;
        /// use std::os::windows::prelude::*;
        ///
        /// let file = OpenOptions::new()
        ///     .create(true)
        ///     .write(true)
        ///     .custom_flags(winapi::FILE_FLAG_DELETE_ON_CLOSE)
        ///     .open("foo.txt");
        /// ```
        ///
        /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
        /// [`CreateFile2`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfile2
        #[stable(feature = "open_options_ext", since = "1.10.0")]
        fn custom_flags(&mut self, flags: u32) -> &mut Self;

        /// Sets the `dwFileAttributes` argument to the call to [`CreateFile2`] to
        /// the specified value (or combines it with `custom_flags` and
        /// `security_qos_flags` to set the `dwFlagsAndAttributes` for
        /// [`CreateFile`]).
        ///
        /// If a _new_ file is created because it does not yet exist and
        /// `.create(true)` or `.create_new(true)` are specified, the new file is
        /// given the attributes declared with `.attributes()`.
        ///
        /// If an _existing_ file is opened with `.create(true).truncate(true)`, its
        /// existing attributes are preserved and combined with the ones declared
        /// with `.attributes()`.
        ///
        /// In all other cases the attributes get ignored.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// # #[cfg(for_demonstration_only)]
        /// extern crate winapi;
        /// # mod winapi { pub const FILE_ATTRIBUTE_HIDDEN: u32 = 2; }
        ///
        /// use std::fs::OpenOptions;
        /// use std::os::windows::prelude::*;
        ///
        /// let file = OpenOptions::new()
        ///     .write(true)
        ///     .create(true)
        ///     .attributes(winapi::FILE_ATTRIBUTE_HIDDEN)
        ///     .open("foo.txt");
        /// ```
        ///
        /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
        /// [`CreateFile2`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfile2
        #[stable(feature = "open_options_ext", since = "1.10.0")]
        fn attributes(&mut self, val: u32) -> &mut Self;

        /// Sets the `dwSecurityQosFlags` argument to the call to [`CreateFile2`] to
        /// the specified value (or combines it with `custom_flags` and `attributes`
        /// to set the `dwFlagsAndAttributes` for [`CreateFile`]).
        ///
        /// By default `security_qos_flags` is not set. It should be specified when
        /// opening a named pipe, to control to which degree a server process can
        /// act on behalf of a client process (security impersonation level).
        ///
        /// When `security_qos_flags` is not set, a malicious program can gain the
        /// elevated privileges of a privileged Rust process when it allows opening
        /// user-specified paths, by tricking it into opening a named pipe. So
        /// arguably `security_qos_flags` should also be set when opening arbitrary
        /// paths. However the bits can then conflict with other flags, specifically
        /// `FILE_FLAG_OPEN_NO_RECALL`.
        ///
        /// For information about possible values, see [Impersonation Levels] on the
        /// Windows Dev Center site. The `SECURITY_SQOS_PRESENT` flag is set
        /// automatically when using this method.

        /// # Examples
        ///
        /// ```no_run
        /// # #[cfg(for_demonstration_only)]
        /// extern crate winapi;
        /// # mod winapi { pub const SECURITY_IDENTIFICATION: u32 = 0; }
        /// use std::fs::OpenOptions;
        /// use std::os::windows::prelude::*;
        ///
        /// let file = OpenOptions::new()
        ///     .write(true)
        ///     .create(true)
        ///
        ///     // Sets the flag value to `SecurityIdentification`.
        ///     .security_qos_flags(winapi::SECURITY_IDENTIFICATION)
        ///
        ///     .open(r"\\.\pipe\MyPipe");
        /// ```
        ///
        /// [`CreateFile`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea
        /// [`CreateFile2`]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfile2
        /// [Impersonation Levels]:
        ///     https://docs.microsoft.com/en-us/windows/win32/api/winnt/ne-winnt-security_impersonation_level
        #[stable(feature = "open_options_ext", since = "1.10.0")]
        fn security_qos_flags(&mut self, flags: u32) -> &mut Self;
    }

    #[stable(feature = "open_options_ext", since = "1.10.0")]
    impl OpenOptionsExt for OpenOptions {
        fn access_mode(&mut self, access: u32) -> &mut OpenOptions {
            self.as_inner_mut().access_mode(access);
            self
        }

        fn share_mode(&mut self, share: u32) -> &mut OpenOptions {
            self.as_inner_mut().share_mode(share);
            self
        }

        fn custom_flags(&mut self, flags: u32) -> &mut OpenOptions {
            self.as_inner_mut().custom_flags(flags);
            self
        }

        fn attributes(&mut self, attributes: u32) -> &mut OpenOptions {
            self.as_inner_mut().attributes(attributes);
            self
        }

        fn security_qos_flags(&mut self, flags: u32) -> &mut OpenOptions {
            self.as_inner_mut().security_qos_flags(flags);
            self
        }
    }

    /// Windows-specific extensions to [`fs::Metadata`].
    ///
    /// The data members that this trait exposes correspond to the members
    /// of the [`BY_HANDLE_FILE_INFORMATION`] structure.
    ///
    /// [`fs::Metadata`]: ../../../../std/fs/struct.Metadata.html
    /// [`BY_HANDLE_FILE_INFORMATION`]:
    ///     https://docs.microsoft.com/en-us/windows/win32/api/fileapi/ns-fileapi-by_handle_file_information
    #[stable(feature = "metadata_ext", since = "1.1.0")]
    pub trait MetadataExt {
        /// Returns the value of the `dwFileAttributes` field of this metadata.
        ///
        /// This field contains the file system attribute information for a file
        /// or directory. For possible values and their descriptions, see
        /// [File Attribute Constants] in the Windows Dev Center.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::io;
        /// use std::fs;
        /// use std::os::windows::prelude::*;
        ///
        /// fn main() -> io::Result<()> {
        ///     let metadata = fs::metadata("foo.txt")?;
        ///     let attributes = metadata.file_attributes();
        ///     Ok(())
        /// }
        /// ```
        ///
        /// [File Attribute Constants]:
        ///     https://docs.microsoft.com/en-us/windows/win32/fileio/file-attribute-constants
        #[stable(feature = "metadata_ext", since = "1.1.0")]
        fn file_attributes(&self) -> u32;

        /// Returns the value of the `ftCreationTime` field of this metadata.
        ///
        /// The returned 64-bit value is equivalent to a [`FILETIME`] struct,
        /// which represents the number of 100-nanosecond intervals since
        /// January 1, 1601 (UTC). The struct is automatically
        /// converted to a `u64` value, as that is the recommended way
        /// to use it.
        ///
        /// If the underlying filesystem does not support creation time, the
        /// returned value is 0.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::io;
        /// use std::fs;
        /// use std::os::windows::prelude::*;
        ///
        /// fn main() -> io::Result<()> {
        ///     let metadata = fs::metadata("foo.txt")?;
        ///     let creation_time = metadata.creation_time();
        ///     Ok(())
        /// }
        /// ```
        ///
        /// [`FILETIME`]: https://docs.microsoft.com/en-us/windows/win32/api/minwinbase/ns-minwinbase-filetime
        #[stable(feature = "metadata_ext", since = "1.1.0")]
        fn creation_time(&self) -> u64;

        /// Returns the value of the `ftLastAccessTime` field of this metadata.
        ///
        /// The returned 64-bit value is equivalent to a [`FILETIME`] struct,
        /// which represents the number of 100-nanosecond intervals since
        /// January 1, 1601 (UTC). The struct is automatically
        /// converted to a `u64` value, as that is the recommended way
        /// to use it.
        ///
        /// For a file, the value specifies the last time that a file was read
        /// from or written to. For a directory, the value specifies when
        /// the directory was created. For both files and directories, the
        /// specified date is correct, but the time of day is always set to
        /// midnight.
        ///
        /// If the underlying filesystem does not support last access time, the
        /// returned value is 0.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::io;
        /// use std::fs;
        /// use std::os::windows::prelude::*;
        ///
        /// fn main() -> io::Result<()> {
        ///     let metadata = fs::metadata("foo.txt")?;
        ///     let last_access_time = metadata.last_access_time();
        ///     Ok(())
        /// }
        /// ```
        ///
        /// [`FILETIME`]: https://docs.microsoft.com/en-us/windows/win32/api/minwinbase/ns-minwinbase-filetime
        #[stable(feature = "metadata_ext", since = "1.1.0")]
        fn last_access_time(&self) -> u64;

        /// Returns the value of the `ftLastWriteTime` field of this metadata.
        ///
        /// The returned 64-bit value is equivalent to a [`FILETIME`] struct,
        /// which represents the number of 100-nanosecond intervals since
        /// January 1, 1601 (UTC). The struct is automatically
        /// converted to a `u64` value, as that is the recommended way
        /// to use it.
        ///
        /// For a file, the value specifies the last time that a file was written
        /// to. For a directory, the structure specifies when the directory was
        /// created.
        ///
        /// If the underlying filesystem does not support the last write time,
        /// the returned value is 0.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::io;
        /// use std::fs;
        /// use std::os::windows::prelude::*;
        ///
        /// fn main() -> io::Result<()> {
        ///     let metadata = fs::metadata("foo.txt")?;
        ///     let last_write_time = metadata.last_write_time();
        ///     Ok(())
        /// }
        /// ```
        ///
        /// [`FILETIME`]: https://docs.microsoft.com/en-us/windows/win32/api/minwinbase/ns-minwinbase-filetime
        #[stable(feature = "metadata_ext", since = "1.1.0")]
        fn last_write_time(&self) -> u64;

        /// Returns the value of the `nFileSize{High,Low}` fields of this
        /// metadata.
        ///
        /// The returned value does not have meaning for directories.
        ///
        /// # Examples
        ///
        /// ```no_run
        /// use std::io;
        /// use std::fs;
        /// use std::os::windows::prelude::*;
        ///
        /// fn main() -> io::Result<()> {
        ///     let metadata = fs::metadata("foo.txt")?;
        ///     let file_size = metadata.file_size();
        ///     Ok(())
        /// }
        /// ```
        #[stable(feature = "metadata_ext", since = "1.1.0")]
        fn file_size(&self) -> u64;

        /// Returns the value of the `dwVolumeSerialNumber` field of this
        /// metadata.
        ///
        /// This will return `None` if the `Metadata` instance was created from a
        /// call to `DirEntry::metadata`. If this `Metadata` was created by using
        /// `fs::metadata` or `File::metadata`, then this will return `Some`.
        #[unstable(feature = "windows_by_handle", issue = "63010")]
        fn volume_serial_number(&self) -> Option<u32>;

        /// Returns the value of the `nNumberOfLinks` field of this
        /// metadata.
        ///
        /// This will return `None` if the `Metadata` instance was created from a
        /// call to `DirEntry::metadata`. If this `Metadata` was created by using
        /// `fs::metadata` or `File::metadata`, then this will return `Some`.
        #[unstable(feature = "windows_by_handle", issue = "63010")]
        fn number_of_links(&self) -> Option<u32>;

        /// Returns the value of the `nFileIndex{Low,High}` fields of this
        /// metadata.
        ///
        /// This will return `None` if the `Metadata` instance was created from a
        /// call to `DirEntry::metadata`. If this `Metadata` was created by using
        /// `fs::metadata` or `File::metadata`, then this will return `Some`.
        #[unstable(feature = "windows_by_handle", issue = "63010")]
        fn file_index(&self) -> Option<u64>;
    }

    #[stable(feature = "metadata_ext", since = "1.1.0")]
    impl MetadataExt for Metadata {
        fn file_attributes(&self) -> u32 {
            self.as_inner().attrs()
        }
        fn creation_time(&self) -> u64 {
            self.as_inner().created_u64()
        }
        fn last_access_time(&self) -> u64 {
            self.as_inner().accessed_u64()
        }
        fn last_write_time(&self) -> u64 {
            self.as_inner().modified_u64()
        }
        fn file_size(&self) -> u64 {
            self.as_inner().size()
        }
        fn volume_serial_number(&self) -> Option<u32> {
            self.as_inner().volume_serial_number()
        }
        fn number_of_links(&self) -> Option<u32> {
            self.as_inner().number_of_links()
        }
        fn file_index(&self) -> Option<u64> {
            self.as_inner().file_index()
        }
    }

    /// Windows-specific extensions to [`FileType`].
    ///
    /// On Windows, a symbolic link knows whether it is a file or directory.
    ///
    /// [`FileType`]: ../../../../std/fs/struct.FileType.html
    #[unstable(feature = "windows_file_type_ext", issue = "none")]
    pub trait FileTypeExt {
        /// Returns `true` if this file type is a symbolic link that is also a directory.
        #[unstable(feature = "windows_file_type_ext", issue = "none")]
        fn is_symlink_dir(&self) -> bool;
        /// Returns `true` if this file type is a symbolic link that is also a file.
        #[unstable(feature = "windows_file_type_ext", issue = "none")]
        fn is_symlink_file(&self) -> bool;
    }

    #[unstable(feature = "windows_file_type_ext", issue = "none")]
    impl FileTypeExt for fs::FileType {
        fn is_symlink_dir(&self) -> bool {
            self.as_inner().is_symlink_dir()
        }
        fn is_symlink_file(&self) -> bool {
            self.as_inner().is_symlink_file()
        }
    }

    /// Creates a new file symbolic link on the filesystem.
    ///
    /// The `dst` path will be a file symbolic link pointing to the `src`
    /// path.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// use std::os::windows::fs;
    ///
    /// fn main() -> std::io::Result<()> {
    ///     fs::symlink_file("a.txt", "b.txt")?;
    ///     Ok(())
    /// }
    /// ```
    #[stable(feature = "symlink", since = "1.1.0")]
    pub fn symlink_file<P: AsRef<Path>, Q: AsRef<Path>>(src: P, dst: Q) -> io::Result<()> {
        sys::fs::symlink_inner(src.as_ref(), dst.as_ref(), false)
    }

    /// Creates a new directory symlink on the filesystem.
    ///
    /// The `dst` path will be a directory symbolic link pointing to the `src`
    /// path.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// use std::os::windows::fs;
    ///
    /// fn main() -> std::io::Result<()> {
    ///     fs::symlink_dir("a", "b")?;
    ///     Ok(())
    /// }
    /// ```
    #[stable(feature = "symlink", since = "1.1.0")]
    pub fn symlink_dir<P: AsRef<Path>, Q: AsRef<Path>>(src: P, dst: Q) -> io::Result<()> {
        sys::fs::symlink_inner(src.as_ref(), dst.as_ref(), true)
    }