#[cfg(test)]
use std::boxed::Box;
+use core::any::Any;
use core::borrow;
use core::cell::Cell;
use core::cmp::Ordering;
use core::intrinsics::abort;
use core::marker;
use core::marker::Unsize;
-use core::mem::{self, forget, size_of, size_of_val, uninitialized};
+use core::mem::{self, align_of_val, forget, size_of_val, uninitialized};
use core::ops::Deref;
use core::ops::CoerceUnsized;
use core::ptr::{self, Shared};
use core::convert::From;
use heap::{Heap, Alloc, Layout, box_free};
-use raw_vec::RawVec;
+use string::String;
+use vec::Vec;
struct RcBox<T: ?Sized> {
strong: Cell<usize>,
ptr: Shared::from(Box::into_unique(box RcBox {
strong: Cell::new(1),
weak: Cell::new(1),
- value: value,
+ value,
})),
}
}
Err(this)
}
}
+}
+impl<T: ?Sized> Rc<T> {
/// Consumes the `Rc`, returning the wrapped pointer.
///
/// To avoid a memory leak the pointer must be converted back to an `Rc` using
/// ```
#[stable(feature = "rc_raw", since = "1.17.0")]
pub unsafe fn from_raw(ptr: *const T) -> Self {
- // To find the corresponding pointer to the `RcBox` we need to subtract the offset of the
- // `value` field from the pointer.
-
- let ptr = (ptr as *const u8).offset(-offset_of!(RcBox<T>, value));
- Rc {
- ptr: Shared::new_unchecked(ptr as *mut u8 as *mut _)
- }
- }
-}
+ // Align the unsized value to the end of the RcBox.
+ // Because it is ?Sized, it will always be the last field in memory.
+ let align = align_of_val(&*ptr);
+ let layout = Layout::new::<RcBox<()>>();
+ let offset = (layout.size() + layout.padding_needed_for(align)) as isize;
-impl Rc<str> {
- /// Constructs a new `Rc<str>` from a string slice.
- #[doc(hidden)]
- #[unstable(feature = "rustc_private",
- reason = "for internal use in rustc",
- issue = "27812")]
- pub fn __from_str(value: &str) -> Rc<str> {
- unsafe {
- // Allocate enough space for `RcBox<str>`.
- let aligned_len = 2 + (value.len() + size_of::<usize>() - 1) / size_of::<usize>();
- let vec = RawVec::<usize>::with_capacity(aligned_len);
- let ptr = vec.ptr();
- forget(vec);
- // Initialize fields of `RcBox<str>`.
- *ptr.offset(0) = 1; // strong: Cell::new(1)
- *ptr.offset(1) = 1; // weak: Cell::new(1)
- ptr::copy_nonoverlapping(value.as_ptr(), ptr.offset(2) as *mut u8, value.len());
- // Combine the allocation address and the string length into a fat pointer to `RcBox`.
- let rcbox_ptr: *mut RcBox<str> = mem::transmute([ptr as usize, value.len()]);
- assert!(aligned_len * size_of::<usize>() == size_of_val(&*rcbox_ptr));
- Rc { ptr: Shared::new_unchecked(rcbox_ptr) }
- }
- }
-}
+ // Reverse the offset to find the original RcBox.
+ let fake_ptr = ptr as *mut RcBox<T>;
+ let rc_ptr = set_data_ptr(fake_ptr, (ptr as *mut u8).offset(-offset));
-impl<T> Rc<[T]> {
- /// Constructs a new `Rc<[T]>` from a `Box<[T]>`.
- #[doc(hidden)]
- #[unstable(feature = "rustc_private",
- reason = "for internal use in rustc",
- issue = "27812")]
- pub fn __from_array(value: Box<[T]>) -> Rc<[T]> {
- unsafe {
- let ptr: *mut RcBox<[T]> =
- mem::transmute([mem::align_of::<RcBox<[T; 1]>>(), value.len()]);
- // FIXME(custom-DST): creating this invalid &[T] is dubiously defined,
- // we should have a better way of getting the size/align
- // of a DST from its unsized part.
- let ptr = Heap.alloc(Layout::for_value(&*ptr))
- .unwrap_or_else(|e| Heap.oom(e));
- let ptr: *mut RcBox<[T]> = mem::transmute([ptr as usize, value.len()]);
-
- // Initialize the new RcBox.
- ptr::write(&mut (*ptr).strong, Cell::new(1));
- ptr::write(&mut (*ptr).weak, Cell::new(1));
- ptr::copy_nonoverlapping(
- value.as_ptr(),
- &mut (*ptr).value as *mut [T] as *mut T,
- value.len());
-
- // Free the original allocation without freeing its (moved) contents.
- box_free(Box::into_raw(value));
-
- Rc { ptr: Shared::new_unchecked(ptr as *mut _) }
+ Rc {
+ ptr: Shared::new_unchecked(rc_ptr),
}
}
-}
-impl<T: ?Sized> Rc<T> {
/// Creates a new [`Weak`][weak] pointer to this value.
///
/// [weak]: struct.Weak.html
}
}
+impl Rc<Any> {
+ #[inline]
+ #[unstable(feature = "rc_downcast", issue = "44608")]
+ /// Attempt to downcast the `Rc<Any>` to a concrete type.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(rc_downcast)]
+ /// use std::any::Any;
+ /// use std::rc::Rc;
+ ///
+ /// fn print_if_string(value: Rc<Any>) {
+ /// if let Ok(string) = value.downcast::<String>() {
+ /// println!("String ({}): {}", string.len(), string);
+ /// }
+ /// }
+ ///
+ /// fn main() {
+ /// let my_string = "Hello World".to_string();
+ /// print_if_string(Rc::new(my_string));
+ /// print_if_string(Rc::new(0i8));
+ /// }
+ /// ```
+ pub fn downcast<T: Any>(self) -> Result<Rc<T>, Rc<Any>> {
+ if (*self).is::<T>() {
+ // avoid the pointer arithmetic in from_raw
+ unsafe {
+ let raw: *const RcBox<Any> = self.ptr.as_ptr();
+ forget(self);
+ Ok(Rc {
+ ptr: Shared::new_unchecked(raw as *const RcBox<T> as *mut _),
+ })
+ }
+ } else {
+ Err(self)
+ }
+ }
+}
+
+impl<T: ?Sized> Rc<T> {
+ // Allocates an `RcBox<T>` with sufficient space for an unsized value
+ unsafe fn allocate_for_ptr(ptr: *const T) -> *mut RcBox<T> {
+ // Create a fake RcBox to find allocation size and alignment
+ let fake_ptr = ptr as *mut RcBox<T>;
+
+ let layout = Layout::for_value(&*fake_ptr);
+
+ let mem = Heap.alloc(layout)
+ .unwrap_or_else(|e| Heap.oom(e));
+
+ // Initialize the real RcBox
+ let inner = set_data_ptr(ptr as *mut T, mem) as *mut RcBox<T>;
+
+ ptr::write(&mut (*inner).strong, Cell::new(1));
+ ptr::write(&mut (*inner).weak, Cell::new(1));
+
+ inner
+ }
+
+ fn from_box(v: Box<T>) -> Rc<T> {
+ unsafe {
+ let bptr = Box::into_raw(v);
+
+ let value_size = size_of_val(&*bptr);
+ let ptr = Self::allocate_for_ptr(bptr);
+
+ // Copy value as bytes
+ ptr::copy_nonoverlapping(
+ bptr as *const T as *const u8,
+ &mut (*ptr).value as *mut _ as *mut u8,
+ value_size);
+
+ // Free the allocation without dropping its contents
+ box_free(bptr);
+
+ Rc { ptr: Shared::new_unchecked(ptr) }
+ }
+ }
+}
+
+// Sets the data pointer of a `?Sized` raw pointer.
+//
+// For a slice/trait object, this sets the `data` field and leaves the rest
+// unchanged. For a sized raw pointer, this simply sets the pointer.
+unsafe fn set_data_ptr<T: ?Sized, U>(mut ptr: *mut T, data: *mut U) -> *mut T {
+ ptr::write(&mut ptr as *mut _ as *mut *mut u8, data as *mut u8);
+ ptr
+}
+
+impl<T> Rc<[T]> {
+ // Copy elements from slice into newly allocated Rc<[T]>
+ //
+ // Unsafe because the caller must either take ownership or bind `T: Copy`
+ unsafe fn copy_from_slice(v: &[T]) -> Rc<[T]> {
+ let v_ptr = v as *const [T];
+ let ptr = Self::allocate_for_ptr(v_ptr);
+
+ ptr::copy_nonoverlapping(
+ v.as_ptr(),
+ &mut (*ptr).value as *mut [T] as *mut T,
+ v.len());
+
+ Rc { ptr: Shared::new_unchecked(ptr) }
+ }
+}
+
+trait RcFromSlice<T> {
+ fn from_slice(slice: &[T]) -> Self;
+}
+
+impl<T: Clone> RcFromSlice<T> for Rc<[T]> {
+ #[inline]
+ default fn from_slice(v: &[T]) -> Self {
+ // Panic guard while cloning T elements.
+ // In the event of a panic, elements that have been written
+ // into the new RcBox will be dropped, then the memory freed.
+ struct Guard<T> {
+ mem: *mut u8,
+ elems: *mut T,
+ layout: Layout,
+ n_elems: usize,
+ }
+
+ impl<T> Drop for Guard<T> {
+ fn drop(&mut self) {
+ use core::slice::from_raw_parts_mut;
+
+ unsafe {
+ let slice = from_raw_parts_mut(self.elems, self.n_elems);
+ ptr::drop_in_place(slice);
+
+ Heap.dealloc(self.mem, self.layout.clone());
+ }
+ }
+ }
+
+ unsafe {
+ let v_ptr = v as *const [T];
+ let ptr = Self::allocate_for_ptr(v_ptr);
+
+ let mem = ptr as *mut _ as *mut u8;
+ let layout = Layout::for_value(&*ptr);
+
+ // Pointer to first element
+ let elems = &mut (*ptr).value as *mut [T] as *mut T;
+
+ let mut guard = Guard{
+ mem: mem,
+ elems: elems,
+ layout: layout,
+ n_elems: 0,
+ };
+
+ for (i, item) in v.iter().enumerate() {
+ ptr::write(elems.offset(i as isize), item.clone());
+ guard.n_elems += 1;
+ }
+
+ // All clear. Forget the guard so it doesn't free the new RcBox.
+ forget(guard);
+
+ Rc { ptr: Shared::new_unchecked(ptr) }
+ }
+ }
+}
+
+impl<T: Copy> RcFromSlice<T> for Rc<[T]> {
+ #[inline]
+ fn from_slice(v: &[T]) -> Self {
+ unsafe { Rc::copy_from_slice(v) }
+ }
+}
+
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: ?Sized> Deref for Rc<T> {
type Target = T;
}
}
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<'a, T: Clone> From<&'a [T]> for Rc<[T]> {
+ #[inline]
+ fn from(v: &[T]) -> Rc<[T]> {
+ <Self as RcFromSlice<T>>::from_slice(v)
+ }
+}
+
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<'a> From<&'a str> for Rc<str> {
+ #[inline]
+ fn from(v: &str) -> Rc<str> {
+ unsafe { mem::transmute(<Rc<[u8]>>::from(v.as_bytes())) }
+ }
+}
+
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl From<String> for Rc<str> {
+ #[inline]
+ fn from(v: String) -> Rc<str> {
+ Rc::from(&v[..])
+ }
+}
+
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<T: ?Sized> From<Box<T>> for Rc<T> {
+ #[inline]
+ fn from(v: Box<T>) -> Rc<T> {
+ Rc::from_box(v)
+ }
+}
+
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<T> From<Vec<T>> for Rc<[T]> {
+ #[inline]
+ fn from(mut v: Vec<T>) -> Rc<[T]> {
+ unsafe {
+ let rc = Rc::copy_from_slice(&v);
+
+ // Allow the Vec to free its memory, but not destroy its contents
+ v.set_len(0);
+
+ rc
+ }
+ }
+}
+
/// `Weak` is a version of [`Rc`] that holds a non-owning reference to the
/// managed value. The value is accessed by calling [`upgrade`] on the `Weak`
/// pointer, which returns an [`Option`]`<`[`Rc`]`<T>>`.
}
}
+ #[test]
+ fn test_into_from_raw_unsized() {
+ use std::fmt::Display;
+ use std::string::ToString;
+
+ let rc: Rc<str> = Rc::from("foo");
+
+ let ptr = Rc::into_raw(rc.clone());
+ let rc2 = unsafe { Rc::from_raw(ptr) };
+
+ assert_eq!(unsafe { &*ptr }, "foo");
+ assert_eq!(rc, rc2);
+
+ let rc: Rc<Display> = Rc::new(123);
+
+ let ptr = Rc::into_raw(rc.clone());
+ let rc2 = unsafe { Rc::from_raw(ptr) };
+
+ assert_eq!(unsafe { &*ptr }.to_string(), "123");
+ assert_eq!(rc2.to_string(), "123");
+ }
+
#[test]
fn get_mut() {
let mut x = Rc::new(3);
assert!(Rc::ptr_eq(&five, &same_five));
assert!(!Rc::ptr_eq(&five, &other_five));
}
+
+ #[test]
+ fn test_from_str() {
+ let r: Rc<str> = Rc::from("foo");
+
+ assert_eq!(&r[..], "foo");
+ }
+
+ #[test]
+ fn test_copy_from_slice() {
+ let s: &[u32] = &[1, 2, 3];
+ let r: Rc<[u32]> = Rc::from(s);
+
+ assert_eq!(&r[..], [1, 2, 3]);
+ }
+
+ #[test]
+ fn test_clone_from_slice() {
+ #[derive(Clone, Debug, Eq, PartialEq)]
+ struct X(u32);
+
+ let s: &[X] = &[X(1), X(2), X(3)];
+ let r: Rc<[X]> = Rc::from(s);
+
+ assert_eq!(&r[..], s);
+ }
+
+ #[test]
+ #[should_panic]
+ fn test_clone_from_slice_panic() {
+ use std::string::{String, ToString};
+
+ struct Fail(u32, String);
+
+ impl Clone for Fail {
+ fn clone(&self) -> Fail {
+ if self.0 == 2 {
+ panic!();
+ }
+ Fail(self.0, self.1.clone())
+ }
+ }
+
+ let s: &[Fail] = &[
+ Fail(0, "foo".to_string()),
+ Fail(1, "bar".to_string()),
+ Fail(2, "baz".to_string()),
+ ];
+
+ // Should panic, but not cause memory corruption
+ let _r: Rc<[Fail]> = Rc::from(s);
+ }
+
+ #[test]
+ fn test_from_box() {
+ let b: Box<u32> = box 123;
+ let r: Rc<u32> = Rc::from(b);
+
+ assert_eq!(*r, 123);
+ }
+
+ #[test]
+ fn test_from_box_str() {
+ use std::string::String;
+
+ let s = String::from("foo").into_boxed_str();
+ let r: Rc<str> = Rc::from(s);
+
+ assert_eq!(&r[..], "foo");
+ }
+
+ #[test]
+ fn test_from_box_slice() {
+ let s = vec![1, 2, 3].into_boxed_slice();
+ let r: Rc<[u32]> = Rc::from(s);
+
+ assert_eq!(&r[..], [1, 2, 3]);
+ }
+
+ #[test]
+ fn test_from_box_trait() {
+ use std::fmt::Display;
+ use std::string::ToString;
+
+ let b: Box<Display> = box 123;
+ let r: Rc<Display> = Rc::from(b);
+
+ assert_eq!(r.to_string(), "123");
+ }
+
+ #[test]
+ fn test_from_box_trait_zero_sized() {
+ use std::fmt::Debug;
+
+ let b: Box<Debug> = box ();
+ let r: Rc<Debug> = Rc::from(b);
+
+ assert_eq!(format!("{:?}", r), "()");
+ }
+
+ #[test]
+ fn test_from_vec() {
+ let v = vec![1, 2, 3];
+ let r: Rc<[u32]> = Rc::from(v);
+
+ assert_eq!(&r[..], [1, 2, 3]);
+ }
+
+ #[test]
+ fn test_downcast() {
+ use std::any::Any;
+
+ let r1: Rc<Any> = Rc::new(i32::max_value());
+ let r2: Rc<Any> = Rc::new("abc");
+
+ assert!(r1.clone().downcast::<u32>().is_err());
+
+ let r1i32 = r1.downcast::<i32>();
+ assert!(r1i32.is_ok());
+ assert_eq!(r1i32.unwrap(), Rc::new(i32::max_value()));
+
+ assert!(r2.clone().downcast::<i32>().is_err());
+
+ let r2str = r2.downcast::<&'static str>();
+ assert!(r2str.is_ok());
+ assert_eq!(r2str.unwrap(), Rc::new("abc"));
+ }
}
#[stable(feature = "rust1", since = "1.0.0")]
projects / rust.git / blobdiff