Add OpenOption extension flags for sync, dsync, rsync, and nofollow. (#292)

This avoids the need to do a `set_fd_flags` afterward, which can be complex
to do due to Windows' need to reopen the file.

Fixes #146.

Author: sunfishcode

cap-fs-ext/src/lib.rs

@@ -17,6 +17,7 @@ mod is_file_read_write;
 mod metadata_ext;
 mod open_options_follow_ext;
 mod open_options_maybe_dir_ext;
+mod open_options_sync_ext;
 mod reopen;
 
 pub use dir_entry_ext::DirEntryExt;
@@ -28,6 +29,7 @@ pub use is_file_read_write::IsFileReadWrite;
 pub use metadata_ext::MetadataExt;
 pub use open_options_follow_ext::OpenOptionsFollowExt;
 pub use open_options_maybe_dir_ext::OpenOptionsMaybeDirExt;
+pub use open_options_sync_ext::OpenOptionsSyncExt;
 pub use reopen::Reopen;
 
 /// Re-export these to allow them to be used with `Reuse`.

cap-fs-ext/src/open_options_sync_ext.rs

@@ -0,0 +1,57 @@
+/// Extension trait for `cap_primitives::fs::OpenOptions` which adds
+/// `sync`, `dsync`, `rsync`, and `nonblock` functions for controlling various
+/// I/O modes for the opened file.
+pub trait OpenOptionsSyncExt {
+    /// Requests write operations complete as defined by synchronized I/O file
+    /// integrity completion.
+    fn sync(&mut self, enable: bool) -> &mut Self;
+
+    /// Requests write operations complete as defined by synchronized I/O data
+    /// integrity completion.
+    fn dsync(&mut self, enable: bool) -> &mut Self;
+
+    /// Requests read operations complete as defined by the level of integrity
+    /// specified by `sync` and `dsync`.
+    fn rsync(&mut self, enable: bool) -> &mut Self;
+
+    /// Requests that I/O operations fail with `std::io::ErrorKind::WouldBlock`
+    /// if they would otherwise block.
+    ///
+    /// This option is commonly not implemented for regular files, so blocking
+    /// may still occur.
+    fn nonblock(&mut self, enable: bool) -> &mut Self;
+}
+
+impl OpenOptionsSyncExt for cap_primitives::fs::OpenOptions {
+    #[inline]
+    fn sync(&mut self, enable: bool) -> &mut Self {
+        // `sync` functionality is implemented within `cap_primitives`;
+        // we're just exposing it here since `OpenOptions` is re-exported by
+        // `cap_std` etc. and `sync` isn't in `std`.
+        self._cap_fs_ext_sync(enable)
+    }
+
+    #[inline]
+    fn dsync(&mut self, enable: bool) -> &mut Self {
+        // `dsync` functionality is implemented within `cap_primitives`;
+        // we're just exposing it here since `OpenOptions` is re-exported by
+        // `cap_std` etc. and `dsync` isn't in `std`.
+        self._cap_fs_ext_dsync(enable)
+    }
+
+    #[inline]
+    fn rsync(&mut self, enable: bool) -> &mut Self {
+        // `rsync` functionality is implemented within `cap_primitives`;
+        // we're just exposing it here since `OpenOptions` is re-exported by
+        // `cap_std` etc. and `rsync` isn't in `std`.
+        self._cap_fs_ext_rsync(enable)
+    }
+
+    #[inline]
+    fn nonblock(&mut self, enable: bool) -> &mut Self {
+        // `nonblock` functionality is implemented within `cap_primitives`;
+        // we're just exposing it here since `OpenOptions` is re-exported by
+        // `cap_std` etc. and `nonblock` isn't in `std`.
+        self._cap_fs_ext_nonblock(enable)
+    }
+}

cap-primitives/src/fs/open_options.rs

@@ -25,6 +25,10 @@ pub struct OpenOptions {
     pub(crate) create_new: bool,
     pub(crate) dir_required: bool,
     pub(crate) maybe_dir: bool,
+    pub(crate) sync: bool,
+    pub(crate) dsync: bool,
+    pub(crate) rsync: bool,
+    pub(crate) nonblock: bool,
     pub(crate) readdir_required: bool,
     pub(crate) follow: FollowSymlinks,
 
@@ -48,6 +52,10 @@ impl OpenOptions {
             create_new: false,
             dir_required: false,
             maybe_dir: false,
+            sync: false,
+            dsync: false,
+            rsync: false,
+            nonblock: false,
             readdir_required: false,
             follow: FollowSymlinks::Yes,
 
@@ -133,6 +141,34 @@ impl OpenOptions {
         self
     }
 
+    /// Sets the option to enable  fixme
+    #[inline]
+    pub(crate) fn sync(&mut self, enable: bool) -> &mut Self {
+        self.sync = enable;
+        self
+    }
+
+    /// Sets the option to enable  fixme
+    #[inline]
+    pub(crate) fn dsync(&mut self, enable: bool) -> &mut Self {
+        self.dsync = enable;
+        self
+    }
+
+    /// Sets the option to enable  fixme
+    #[inline]
+    pub(crate) fn rsync(&mut self, enable: bool) -> &mut Self {
+        self.rsync = enable;
+        self
+    }
+
+    /// Sets the option to enable  fixme
+    #[inline]
+    pub(crate) fn nonblock(&mut self, enable: bool) -> &mut Self {
+        self.nonblock = enable;
+        self
+    }
+
     /// Sets the option to request the ability to read directory entries.
     #[inline]
     pub(crate) fn readdir_required(&mut self, readdir_required: bool) -> &mut Self {
@@ -161,6 +197,50 @@ impl OpenOptions {
     pub fn _cap_fs_ext_maybe_dir(&mut self, maybe_dir: bool) -> &mut Self {
         self.maybe_dir(maybe_dir)
     }
+
+    /// Wrapper to allow `sync` to be exposed by the `cap-fs-ext` crate.
+    ///
+    /// This is hidden from the main API since this functionality isn't present
+    /// in `std`. Use `cap_fs_ext::OpenOptionsSyncExt` instead of
+    /// calling this directly.
+    #[doc(hidden)]
+    #[inline]
+    pub fn _cap_fs_ext_sync(&mut self, enable: bool) -> &mut Self {
+        self.sync(enable)
+    }
+
+    /// Wrapper to allow `dsync` to be exposed by the `cap-fs-ext` crate.
+    ///
+    /// This is hidden from the main API since this functionality isn't present
+    /// in `std`. Use `cap_fs_ext::OpenOptionsSyncExt` instead of
+    /// calling this directly.
+    #[doc(hidden)]
+    #[inline]
+    pub fn _cap_fs_ext_dsync(&mut self, enable: bool) -> &mut Self {
+        self.dsync(enable)
+    }
+
+    /// Wrapper to allow `rsync` to be exposed by the `cap-fs-ext` crate.
+    ///
+    /// This is hidden from the main API since this functionality isn't present
+    /// in `std`. Use `cap_fs_ext::OpenOptionsSyncExt` instead of
+    /// calling this directly.
+    #[doc(hidden)]
+    #[inline]
+    pub fn _cap_fs_ext_rsync(&mut self, enable: bool) -> &mut Self {
+        self.rsync(enable)
+    }
+
+    /// Wrapper to allow `nonblock` to be exposed by the `cap-fs-ext` crate.
+    ///
+    /// This is hidden from the main API since this functionality isn't present
+    /// in `std`. Use `cap_fs_ext::OpenOptionsSyncExt` instead of
+    /// calling this directly.
+    #[doc(hidden)]
+    #[inline]
+    pub fn _cap_fs_ext_nonblock(&mut self, enable: bool) -> &mut Self {
+        self.nonblock(enable)
+    }
 }
 
 #[cfg(unix)]
@@ -292,6 +372,10 @@ impl arbitrary::Arbitrary<'_> for OpenOptions {
             .create_new(<bool as Arbitrary>::arbitrary(u)?)
             .dir_required(<bool as Arbitrary>::arbitrary(u)?)
             .maybe_dir(<bool as Arbitrary>::arbitrary(u)?)
+            .sync(<bool as Arbitrary>::arbitrary(u)?)
+            .dsync(<bool as Arbitrary>::arbitrary(u)?)
+            .rsync(<bool as Arbitrary>::arbitrary(u)?)
+            .nonblock(<bool as Arbitrary>::arbitrary(u)?)
             .readdir_required(<bool as Arbitrary>::arbitrary(u)?)
             .follow(<FollowSymlinks as Arbitrary>::arbitrary(u)?)
             .clone())

cap-primitives/src/rustix/fs/oflags.rs

@@ -9,6 +9,33 @@ pub(in super::super) fn compute_oflags(options: &OpenOptions) -> io::Result<OFla
     if options.follow == FollowSymlinks::No {
         oflags |= OFlags::NOFOLLOW;
     }
+    if options.sync {
+        oflags |= OFlags::SYNC;
+    }
+    if options.dsync {
+        #[cfg(not(any(target_os = "freebsd",)))]
+        {
+            oflags |= OFlags::DSYNC;
+        }
+
+        // Where needed, approximate `DSYNC` with `SYNC`.
+        #[cfg(any(target_os = "freebsd",))]
+        {
+            oflags |= OFlags::SYNC;
+        }
+    }
+    #[cfg(not(any(
+        target_os = "ios",
+        target_os = "macos",
+        target_os = "freebsd",
+        target_os = "fuchsia"
+    )))]
+    if options.rsync {
+        oflags |= OFlags::RSYNC;
+    }
+    if options.nonblock {
+        oflags |= OFlags::NONBLOCK;
+    }
     if options.dir_required {
         oflags |= OFlags::DIRECTORY;
 

cap-primitives/src/windows/fs/oflags.rs

@@ -2,7 +2,8 @@ use crate::fs::{FollowSymlinks, OpenOptions};
 use std::fs;
 use std::os::windows::fs::OpenOptionsExt;
 use windows_sys::Win32::Storage::FileSystem::{
-    FILE_FLAG_BACKUP_SEMANTICS, FILE_FLAG_OPEN_REPARSE_POINT, FILE_SHARE_DELETE,
+    FILE_FLAG_BACKUP_SEMANTICS, FILE_FLAG_OPEN_REPARSE_POINT, FILE_FLAG_WRITE_THROUGH,
+    FILE_SHARE_DELETE,
 };
 
 /// Translate the given `cap_std` into `std` options. Also return a bool
@@ -34,6 +35,11 @@ pub(in super::super) fn open_options_to_std(opts: &OpenOptions) -> (fs::OpenOpti
         // lookups on Windows.
         share_mode &= !FILE_SHARE_DELETE;
     }
+    // This matches system-interface's `set_fd_flags` interpretation of these
+    // flags on Windows.
+    if opts.sync || opts.dsync {
+        custom_flags |= FILE_FLAG_WRITE_THROUGH;
+    }
     let mut std_opts = fs::OpenOptions::new();
     std_opts
         .read(opts.read)

tests/fs_additional.rs

@@ -899,6 +899,33 @@ fn maybe_dir() {
     check!(tmpdir.open_with("dir", OpenOptions::new().read(true).maybe_dir(true)));
 }
 
+#[test]
+fn sync() {
+    use cap_fs_ext::OpenOptionsSyncExt;
+
+    let tmpdir = tmpdir();
+    check!(tmpdir.create("file"));
+
+    check!(tmpdir.open_with("file", OpenOptions::new().write(true).sync(true)));
+    check!(tmpdir.open_with("file", OpenOptions::new().write(true).dsync(true)));
+    check!(tmpdir.open_with(
+        "file",
+        OpenOptions::new()
+            .read(true)
+            .write(true)
+            .sync(true)
+            .rsync(true)
+    ));
+    check!(tmpdir.open_with(
+        "file",
+        OpenOptions::new()
+            .read(true)
+            .write(true)
+            .dsync(true)
+            .rsync(true)
+    ));
+}
+
 #[test]
 #[cfg(not(windows))]
 fn reopen_fd() {