Add OpenOptions to tokio-fs (#390)

Add an `OpenOptions` struct to `tokio-fs` that mirrors the one found in
`std`. Also provide a conversion from a `std` instance to a Tokio instance.

src/fs.rs

@@ -10,4 +10,5 @@
 pub use tokio_fs::{
     file,
     File,
+    OpenOptions, 
 };

tokio-fs/src/file/mod.rs

@@ -4,9 +4,11 @@
 
 mod create;
 mod open;
+mod open_options;
 
 pub use self::create::CreateFuture;
 pub use self::open::OpenFuture;
+pub use self::open_options::OpenOptions;
 
 use tokio_io::{AsyncRead, AsyncWrite};
 
@@ -36,16 +38,20 @@ pub struct File {
 impl File {
     /// Attempts to open a file in read-only mode.
     ///
+    /// See [`OpenOptions`] for more details.
+    ///
+    /// [`OpenOptions`]: struct.OpenOptions.html
+    ///
     /// # Errors
     ///
     /// `OpenFuture` results in an error if called from outside of the Tokio
     /// runtime or if the underlying [`open`] call results in an error.
     ///
-    /// [`open`]: https://doc.rust-lang.org/std/fs/struct.OpenOptions.html#method.open
+    /// [`open`]: https://doc.rust-lang.org/std/fs/struct.File.html#method.open
     pub fn open<P>(path: P) -> OpenFuture<P>
     where P: AsRef<Path> + Send + 'static,
     {
-        OpenFuture::new(path)
+        OpenOptions::new().read(true).open(path)
     }
 
     /// Opens a file in write-only mode.
@@ -53,6 +59,12 @@ impl File {
     /// This function will create a file if it does not exist, and will truncate
     /// it if it does.
     ///
+    /// See [`OpenOptions`] for more details.
+    ///
+    /// [`OpenOptions`]: struct.OpenOptions.html
+    ///
+    /// # Errors
+    ///
     /// `CreateFuture` results in an error if called from outside of the Tokio
     /// runtime or if the underlying [`create`] call results in an error.
     ///

tokio-fs/src/file/open.rs

@@ -2,21 +2,22 @@ use super::File;
 
 use futures::{Future, Poll};
 
-use std::fs::File as StdFile;
+use std::fs::OpenOptions as StdOpenOptions;
 use std::io;
 use std::path::Path;
 
 /// Future returned by `File::open` and resolves to a `File` instance.
 #[derive(Debug)]
 pub struct OpenFuture<P> {
+    options: StdOpenOptions,
     path: P,
 }
 
 impl<P> OpenFuture<P>
 where P: AsRef<Path> + Send + 'static,
 {
-    pub(crate) fn new(path: P) -> Self {
+    pub(crate) fn new(options: StdOpenOptions, path: P) -> Self {
-        OpenFuture { path }
+        OpenFuture { options, path }
     }
 }
 
@@ -28,7 +29,7 @@ where P: AsRef<Path> + Send + 'static,
 
     fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
         let std = try_ready!(::blocking_io(|| {
-            StdFile::open(&self.path)
+            self.options.open(&self.path)
         }));
 
         let file = File::from_std(std);

tokio-fs/src/file/open_options.rs

@@ -0,0 +1,103 @@
+use super::OpenFuture;
+
+use std::convert::From;
+use std::fs::OpenOptions as StdOpenOptions;
+use std::path::Path;
+
+/// Options and flags which can be used to configure how a file is opened.
+///
+/// This is a specialized version of [`std::fs::OpenOptions`] for usage from
+/// the Tokio runtime.
+///
+/// `From<std::fs::OpenOptions>` is implemented for more advanced configuration
+/// than the methods provided here.
+///
+/// [`std::fs::OpenOptions`]: https://doc.rust-lang.org/std/fs/struct.OpenOptions.html
+#[derive(Clone, Debug)]
+pub struct OpenOptions(StdOpenOptions);
+
+impl OpenOptions {
+    /// Creates a blank new set of options ready for configuration.
+    ///
+    /// All options are initially set to `false`.
+    ///
+    /// # Examples
+    ///
+    /// ```ignore
+    /// use tokio::fs::OpenOptions;
+    ///
+    /// let mut options = OpenOptions::new();
+    /// let future = options.read(true).open("foo.txt");
+    /// ```
+    pub fn new() -> OpenOptions {
+        OpenOptions(StdOpenOptions::new())
+    }
+
+    /// See the underlying [`read`] call for details.
+    ///
+    /// [`read`]: https://doc.rust-lang.org/std/fs/struct.OpenOptions.html#method.read
+    pub fn read(&mut self, read: bool) -> &mut OpenOptions {
+        self.0.read(read);
+        self
+    }
+
+    /// See the underlying [`write`] call for details.
+    ///
+    /// [`write`]: https://doc.rust-lang.org/std/fs/struct.OpenOptions.html#method.write
+    pub fn write(&mut self, write: bool) -> &mut OpenOptions {
+        self.0.write(write);
+        self
+    }
+
+    /// See the underlying [`append`] call for details.
+    ///
+    /// [`append`]: https://doc.rust-lang.org/std/fs/struct.OpenOptions.html#method.append
+    pub fn append(&mut self, append: bool) -> &mut OpenOptions {
+        self.0.append(append);
+        self
+    }
+
+    /// See the underlying [`truncate`] call for details.
+    ///
+    /// [`truncate`]: https://doc.rust-lang.org/std/fs/struct.OpenOptions.html#method.truncate
+    pub fn truncate(&mut self, truncate: bool) -> &mut OpenOptions {
+        self.0.truncate(truncate);
+        self
+    }
+
+    /// See the underlying [`create`] call for details.
+    ///
+    /// [`create`]: https://doc.rust-lang.org/std/fs/struct.OpenOptions.html#method.create
+    pub fn create(&mut self, create: bool) -> &mut OpenOptions {
+        self.0.create(create);
+        self
+    }
+
+    /// See the underlying [`create_new`] call for details.
+    ///
+    /// [`create_new`]: https://doc.rust-lang.org/std/fs/struct.OpenOptions.html#method.create_new
+    pub fn create_new(&mut self, create_new: bool) -> &mut OpenOptions {
+        self.0.create_new(create_new);
+        self
+    }
+
+    /// Opens a file at `path` with the options specified by `self`.
+    ///
+    /// # Errors
+    ///
+    /// `OpenOptionsFuture` results in an error if called from outside of the
+    /// Tokio runtime or if the underlying [`open`] call results in an error.
+    ///
+    /// [`open`]: https://doc.rust-lang.org/std/fs/struct.OpenOptions.html#method.open
+    pub fn open<P>(&self, path: P) -> OpenFuture<P>
+    where P: AsRef<Path> + Send + 'static
+    {
+        OpenFuture::new(self.0.clone(), path)
+    }
+}
+
+impl From<StdOpenOptions> for OpenOptions {
+    fn from(options: StdOpenOptions) -> OpenOptions {
+        OpenOptions(options)
+    }
+}

tokio-fs/src/lib.rs

@@ -23,6 +23,7 @@ mod stdout;
 mod stderr;
 
 pub use file::File;
+pub use file::OpenOptions;
 pub use stdin::{stdin, Stdin};
 pub use stdout::{stdout, Stdout};
 pub use stderr::{stderr, Stderr};