Implement Rc/Arc conversions for string-like types

Provides the following conversion implementations:

* `From<`{`CString`,`&CStr`}`>` for {`Arc`,`Rc`}`<CStr>`
* `From<`{`OsString`,`&OsStr`}`>` for {`Arc`,`Rc`}`<OsStr>`
* `From<`{`PathBuf`,`&Path`}`>` for {`Arc`,`Rc`}`<Path>`

src/libstd/ffi/c_str.rs

@@ -19,8 +19,10 @@ use memchr;
 use ops;
 use os::raw::c_char;
 use ptr;
+use rc::Rc;
 use slice;
 use str::{self, Utf8Error};
+use sync::Arc;
 use sys;
 
 /// A type representing an owned, C-compatible, nul-terminated string with no nul bytes in the
@@ -704,6 +706,42 @@ impl From<CString> for Box<CStr> {
     }
 }
 
+#[stable(feature = "shared_from_slice2", since = "1.23.0")]
+impl From<CString> for Arc<CStr> {
+    #[inline]
+    fn from(s: CString) -> Arc<CStr> {
+        let arc: Arc<[u8]> = Arc::from(s.into_inner());
+        unsafe { Arc::from_raw(Arc::into_raw(arc) as *const CStr) }
+    }
+}
+
+#[stable(feature = "shared_from_slice2", since = "1.23.0")]
+impl<'a> From<&'a CStr> for Arc<CStr> {
+    #[inline]
+    fn from(s: &CStr) -> Arc<CStr> {
+        let arc: Arc<[u8]> = Arc::from(s.to_bytes_with_nul());
+        unsafe { Arc::from_raw(Arc::into_raw(arc) as *const CStr) }
+    }
+}
+
+#[stable(feature = "shared_from_slice2", since = "1.23.0")]
+impl From<CString> for Rc<CStr> {
+    #[inline]
+    fn from(s: CString) -> Rc<CStr> {
+        let rc: Rc<[u8]> = Rc::from(s.into_inner());
+        unsafe { Rc::from_raw(Rc::into_raw(rc) as *const CStr) }
+    }
+}
+
+#[stable(feature = "shared_from_slice2", since = "1.23.0")]
+impl<'a> From<&'a CStr> for Rc<CStr> {
+    #[inline]
+    fn from(s: &CStr) -> Rc<CStr> {
+        let rc: Rc<[u8]> = Rc::from(s.to_bytes_with_nul());
+        unsafe { Rc::from_raw(Rc::into_raw(rc) as *const CStr) }
+    }
+}
+
 #[stable(feature = "default_box_extra", since = "1.17.0")]
 impl Default for Box<CStr> {
     fn default() -> Box<CStr> {
@@ -1201,6 +1239,8 @@ mod tests {
     use borrow::Cow::{Borrowed, Owned};
     use hash::{Hash, Hasher};
     use collections::hash_map::DefaultHasher;
+    use rc::Rc;
+    use sync::Arc;
 
     #[test]
     fn c_to_rust() {
@@ -1337,4 +1377,21 @@ mod tests {
         let boxed = <Box<CStr>>::default();
         assert_eq!(boxed.to_bytes_with_nul(), &[0]);
     }
+
+    #[test]
+    fn into_rc() {
+        let orig: &[u8] = b"Hello, world!\0";
+        let cstr = CStr::from_bytes_with_nul(orig).unwrap();
+        let rc: Rc<CStr> = Rc::from(cstr);
+        let arc: Arc<CStr> = Arc::from(cstr);
+
+        assert_eq!(&*rc, cstr);
+        assert_eq!(&*arc, cstr);
+
+        let rc2: Rc<CStr> = Rc::from(cstr.to_owned());
+        let arc2: Arc<CStr> = Arc::from(cstr.to_owned());
+
+        assert_eq!(&*rc2, cstr);
+        assert_eq!(&*arc2, cstr);
+    }
 }

src/libstd/ffi/os_str.rs

@@ -13,6 +13,8 @@ use fmt;
 use ops;
 use cmp;
 use hash::{Hash, Hasher};
+use rc::Rc;
+use sync::Arc;
 
 use sys::os_str::{Buf, Slice};
 use sys_common::{AsInner, IntoInner, FromInner};
@@ -592,6 +594,42 @@ impl From<OsString> for Box<OsStr> {
     }
 }
 
+#[stable(feature = "shared_from_slice2", since = "1.23.0")]
+impl From<OsString> for Arc<OsStr> {
+    #[inline]
+    fn from(s: OsString) -> Arc<OsStr> {
+        let arc = s.inner.into_arc();
+        unsafe { Arc::from_raw(Arc::into_raw(arc) as *const OsStr) }
+    }
+}
+
+#[stable(feature = "shared_from_slice2", since = "1.23.0")]
+impl<'a> From<&'a OsStr> for Arc<OsStr> {
+    #[inline]
+    fn from(s: &OsStr) -> Arc<OsStr> {
+        let arc = s.inner.into_arc();
+        unsafe { Arc::from_raw(Arc::into_raw(arc) as *const OsStr) }
+    }
+}
+
+#[stable(feature = "shared_from_slice2", since = "1.23.0")]
+impl From<OsString> for Rc<OsStr> {
+    #[inline]
+    fn from(s: OsString) -> Rc<OsStr> {
+        let rc = s.inner.into_rc();
+        unsafe { Rc::from_raw(Rc::into_raw(rc) as *const OsStr) }
+    }
+}
+
+#[stable(feature = "shared_from_slice2", since = "1.23.0")]
+impl<'a> From<&'a OsStr> for Rc<OsStr> {
+    #[inline]
+    fn from(s: &OsStr) -> Rc<OsStr> {
+        let rc = s.inner.into_rc();
+        unsafe { Rc::from_raw(Rc::into_raw(rc) as *const OsStr) }
+    }
+}
+
 #[stable(feature = "box_default_extra", since = "1.17.0")]
 impl Default for Box<OsStr> {
     fn default() -> Box<OsStr> {
@@ -793,6 +831,9 @@ mod tests {
     use super::*;
     use sys_common::{AsInner, IntoInner};
 
+    use rc::Rc;
+    use sync::Arc;
+
     #[test]
     fn test_os_string_with_capacity() {
         let os_string = OsString::with_capacity(0);
@@ -935,4 +976,21 @@ mod tests {
         assert_eq!(os_str, os_string);
         assert!(os_string.capacity() >= 123);
     }
+
+    #[test]
+    fn into_rc() {
+        let orig = "Hello, world!";
+        let os_str = OsStr::new(orig);
+        let rc: Rc<OsStr> = Rc::from(os_str);
+        let arc: Arc<OsStr> = Arc::from(os_str);
+
+        assert_eq!(&*rc, os_str);
+        assert_eq!(&*arc, os_str);
+
+        let rc2: Rc<OsStr> = Rc::from(os_str.to_owned());
+        let arc2: Arc<OsStr> = Arc::from(os_str.to_owned());
+
+        assert_eq!(&*rc2, os_str);
+        assert_eq!(&*arc2, os_str);
+    }
 }

src/libstd/path.rs

@@ -86,6 +86,8 @@ use hash::{Hash, Hasher};
 use io;
 use iter::{self, FusedIterator};
 use ops::{self, Deref};
+use rc::Rc;
+use sync::Arc;
 
 use ffi::{OsStr, OsString};
 
@@ -1452,6 +1454,42 @@ impl<'a> From<PathBuf> for Cow<'a, Path> {
     }
 }
 
+#[stable(feature = "shared_from_slice2", since = "1.23.0")]
+impl From<PathBuf> for Arc<Path> {
+    #[inline]
+    fn from(s: PathBuf) -> Arc<Path> {
+        let arc: Arc<OsStr> = Arc::from(s.into_os_string());
+        unsafe { Arc::from_raw(Arc::into_raw(arc) as *const Path) }
+    }
+}
+
+#[stable(feature = "shared_from_slice2", since = "1.23.0")]
+impl<'a> From<&'a Path> for Arc<Path> {
+    #[inline]
+    fn from(s: &Path) -> Arc<Path> {
+        let arc: Arc<OsStr> = Arc::from(s.as_os_str());
+        unsafe { Arc::from_raw(Arc::into_raw(arc) as *const Path) }
+    }
+}
+
+#[stable(feature = "shared_from_slice2", since = "1.23.0")]
+impl From<PathBuf> for Rc<Path> {
+    #[inline]
+    fn from(s: PathBuf) -> Rc<Path> {
+        let rc: Rc<OsStr> = Rc::from(s.into_os_string());
+        unsafe { Rc::from_raw(Rc::into_raw(rc) as *const Path) }
+    }
+}
+
+#[stable(feature = "shared_from_slice2", since = "1.23.0")]
+impl<'a> From<&'a Path> for Rc<Path> {
+    #[inline]
+    fn from(s: &Path) -> Rc<Path> {
+        let rc: Rc<OsStr> = Rc::from(s.as_os_str());
+        unsafe { Rc::from_raw(Rc::into_raw(rc) as *const Path) }
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl ToOwned for Path {
     type Owned = PathBuf;
@@ -2568,6 +2606,9 @@ impl Error for StripPrefixError {
 mod tests {
     use super::*;
 
+    use rc::Rc;
+    use sync::Arc;
+
     macro_rules! t(
         ($path:expr, iter: $iter:expr) => (
             {
@@ -3970,4 +4011,21 @@ mod tests {
         assert_eq!(format!("a{:#<5}b", Path::new("").display()), "a#####b");
         assert_eq!(format!("a{:#<5}b", Path::new("a").display()), "aa####b");
     }
+
+    #[test]
+    fn into_rc() {
+        let orig = "hello/world";
+        let path = Path::new(orig);
+        let rc: Rc<Path> = Rc::from(path);
+        let arc: Arc<Path> = Arc::from(path);
+
+        assert_eq!(&*rc, path);
+        assert_eq!(&*arc, path);
+
+        let rc2: Rc<Path> = Rc::from(path.to_owned());
+        let arc2: Arc<Path> = Arc::from(path.to_owned());
+
+        assert_eq!(&*rc2, path);
+        assert_eq!(&*arc2, path);
+    }
 }

src/libstd/sys/redox/os_str.rs

@@ -15,6 +15,8 @@ use borrow::Cow;
 use fmt;
 use str;
 use mem;
+use rc::Rc;
+use sync::Arc;
 use sys_common::{AsInner, IntoInner};
 use std_unicode::lossy::Utf8Lossy;
 
@@ -123,6 +125,16 @@ impl Buf {
         let inner: Box<[u8]> = unsafe { mem::transmute(boxed) };
         Buf { inner: inner.into_vec() }
     }
+
+    #[inline]
+    pub fn into_arc(&self) -> Arc<Slice> {
+        self.as_slice().into_arc()
+    }
+
+    #[inline]
+    pub fn into_rc(&self) -> Rc<Slice> {
+        self.as_slice().into_rc()
+    }
 }
 
 impl Slice {
@@ -156,4 +168,16 @@ impl Slice {
         let boxed: Box<[u8]> = Default::default();
         unsafe { mem::transmute(boxed) }
     }
+
+    #[inline]
+    pub fn into_arc(&self) -> Arc<Slice> {
+        let arc: Arc<[u8]> = Arc::from(&self.inner);
+        unsafe { Arc::from_raw(Arc::into_raw(arc) as *const Slice) }
+    }
+
+    #[inline]
+    pub fn into_rc(&self) -> Rc<Slice> {
+        let rc: Rc<[u8]> = Rc::from(&self.inner);
+        unsafe { Rc::from_raw(Rc::into_raw(rc) as *const Slice) }
+    }
 }

src/libstd/sys/unix/os_str.rs

@@ -15,6 +15,8 @@ use borrow::Cow;
 use fmt;
 use str;
 use mem;
+use rc::Rc;
+use sync::Arc;
 use sys_common::{AsInner, IntoInner};
 use std_unicode::lossy::Utf8Lossy;
 
@@ -123,6 +125,16 @@ impl Buf {
         let inner: Box<[u8]> = unsafe { mem::transmute(boxed) };
         Buf { inner: inner.into_vec() }
     }
+
+    #[inline]
+    pub fn into_arc(&self) -> Arc<Slice> {
+        self.as_slice().into_arc()
+    }
+
+    #[inline]
+    pub fn into_rc(&self) -> Rc<Slice> {
+        self.as_slice().into_rc()
+    }
 }
 
 impl Slice {
@@ -156,4 +168,16 @@ impl Slice {
         let boxed: Box<[u8]> = Default::default();
         unsafe { mem::transmute(boxed) }
     }
+
+    #[inline]
+    pub fn into_arc(&self) -> Arc<Slice> {
+        let arc: Arc<[u8]> = Arc::from(&self.inner);
+        unsafe { Arc::from_raw(Arc::into_raw(arc) as *const Slice) }
+    }
+
+    #[inline]
+    pub fn into_rc(&self) -> Rc<Slice> {
+        let rc: Rc<[u8]> = Rc::from(&self.inner);
+        unsafe { Rc::from_raw(Rc::into_raw(rc) as *const Slice) }
+    }
 }

src/libstd/sys/wasm/os_str.rs

@@ -15,6 +15,8 @@ use borrow::Cow;
 use fmt;
 use str;
 use mem;
+use rc::Rc;
+use sync::Arc;
 use sys_common::{AsInner, IntoInner};
 use std_unicode::lossy::Utf8Lossy;
 
@@ -123,6 +125,16 @@ impl Buf {
         let inner: Box<[u8]> = unsafe { mem::transmute(boxed) };
         Buf { inner: inner.into_vec() }
     }
+
+    #[inline]
+    pub fn into_arc(&self) -> Arc<Slice> {
+        self.as_slice().into_arc()
+    }
+
+    #[inline]
+    pub fn into_rc(&self) -> Rc<Slice> {
+        self.as_slice().into_rc()
+    }
 }
 
 impl Slice {
@@ -156,4 +168,16 @@ impl Slice {
         let boxed: Box<[u8]> = Default::default();
         unsafe { mem::transmute(boxed) }
     }
+
+    #[inline]
+    pub fn into_arc(&self) -> Arc<Slice> {
+        let arc: Arc<[u8]> = Arc::from(&self.inner);
+        unsafe { Arc::from_raw(Arc::into_raw(arc) as *const Slice) }
+    }
+
+    #[inline]
+    pub fn into_rc(&self) -> Rc<Slice> {
+        let rc: Rc<[u8]> = Rc::from(&self.inner);
+        unsafe { Rc::from_raw(Rc::into_raw(rc) as *const Slice) }
+    }
 }