//!
//! [arc]: struct.Arc.html
-use boxed::Box;
-
use core::sync::atomic;
use core::sync::atomic::Ordering::{Acquire, Relaxed, Release, SeqCst};
use core::borrow;
use core::fmt;
use core::cmp::Ordering;
use core::intrinsics::abort;
-use core::mem;
-use core::mem::uninitialized;
+use core::mem::{self, align_of_val, size_of_val, uninitialized};
use core::ops::Deref;
use core::ops::CoerceUnsized;
use core::ptr::{self, Shared};
use core::{isize, usize};
use core::convert::From;
-use heap::{Heap, Alloc, Layout};
+use heap::{Heap, Alloc, Layout, box_free};
+use boxed::Box;
+use string::String;
+use vec::Vec;
/// A soft limit on the amount of references that may be made to an `Arc`.
///
Ok(elem)
}
}
+}
+impl<T: ?Sized> Arc<T> {
/// Consumes the `Arc`, returning the wrapped pointer.
///
/// To avoid a memory leak the pointer must be converted back to an `Arc` 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 `ArcInner` we need to subtract the offset of the
- // `data` field from the pointer.
- let ptr = (ptr as *const u8).offset(-offset_of!(ArcInner<T>, data));
+ // Align the unsized value to the end of the ArcInner.
+ // Because it is ?Sized, it will always be the last field in memory.
+ let align = align_of_val(&*ptr);
+ let layout = Layout::new::<ArcInner<()>>();
+ let offset = (layout.size() + layout.padding_needed_for(align)) as isize;
+
+ // Reverse the offset to find the original ArcInner.
+ let fake_ptr = ptr as *mut ArcInner<T>;
+ let arc_ptr = set_data_ptr(fake_ptr, (ptr as *mut u8).offset(-offset));
+
Arc {
- ptr: Shared::new_unchecked(ptr as *mut u8 as *mut _),
+ ptr: Shared::new_unchecked(arc_ptr),
}
}
-}
-impl<T: ?Sized> Arc<T> {
/// Creates a new [`Weak`][weak] pointer to this value.
///
/// [weak]: struct.Weak.html
}
}
+impl<T: ?Sized> Arc<T> {
+ // Allocates an `ArcInner<T>` with sufficient space for an unsized value
+ unsafe fn allocate_for_ptr(ptr: *const T) -> *mut ArcInner<T> {
+ // Create a fake ArcInner to find allocation size and alignment
+ let fake_ptr = ptr as *mut ArcInner<T>;
+
+ let layout = Layout::for_value(&*fake_ptr);
+
+ let mem = Heap.alloc(layout)
+ .unwrap_or_else(|e| Heap.oom(e));
+
+ // Initialize the real ArcInner
+ let inner = set_data_ptr(ptr as *mut T, mem) as *mut ArcInner<T>;
+
+ ptr::write(&mut (*inner).strong, atomic::AtomicUsize::new(1));
+ ptr::write(&mut (*inner).weak, atomic::AtomicUsize::new(1));
+
+ inner
+ }
+
+ fn from_box(v: Box<T>) -> Arc<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).data as *mut _ as *mut u8,
+ value_size);
+
+ // Free the allocation without dropping its contents
+ box_free(bptr);
+
+ Arc { 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> Arc<[T]> {
+ // Copy elements from slice into newly allocated Arc<[T]>
+ //
+ // Unsafe because the caller must either take ownership or bind `T: Copy`
+ unsafe fn copy_from_slice(v: &[T]) -> Arc<[T]> {
+ let v_ptr = v as *const [T];
+ let ptr = Self::allocate_for_ptr(v_ptr);
+
+ ptr::copy_nonoverlapping(
+ v.as_ptr(),
+ &mut (*ptr).data as *mut [T] as *mut T,
+ v.len());
+
+ Arc { ptr: Shared::new_unchecked(ptr) }
+ }
+}
+
+// Specialization trait used for From<&[T]>
+trait ArcFromSlice<T> {
+ fn from_slice(slice: &[T]) -> Self;
+}
+
+impl<T: Clone> ArcFromSlice<T> for Arc<[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 ArcInner 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).data 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 ArcInner.
+ mem::forget(guard);
+
+ Arc { ptr: Shared::new_unchecked(ptr) }
+ }
+ }
+}
+
+impl<T: Copy> ArcFromSlice<T> for Arc<[T]> {
+ #[inline]
+ fn from_slice(v: &[T]) -> Self {
+ unsafe { Arc::copy_from_slice(v) }
+ }
+}
+
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: ?Sized> Clone for Arc<T> {
/// Makes a clone of the `Arc` pointer.
}
}
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<'a, T: Clone> From<&'a [T]> for Arc<[T]> {
+ #[inline]
+ fn from(v: &[T]) -> Arc<[T]> {
+ <Self as ArcFromSlice<T>>::from_slice(v)
+ }
+}
+
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<'a> From<&'a str> for Arc<str> {
+ #[inline]
+ fn from(v: &str) -> Arc<str> {
+ unsafe { mem::transmute(<Arc<[u8]>>::from(v.as_bytes())) }
+ }
+}
+
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl From<String> for Arc<str> {
+ #[inline]
+ fn from(v: String) -> Arc<str> {
+ Arc::from(&v[..])
+ }
+}
+
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<T: ?Sized> From<Box<T>> for Arc<T> {
+ #[inline]
+ fn from(v: Box<T>) -> Arc<T> {
+ Arc::from_box(v)
+ }
+}
+
+#[stable(feature = "shared_from_slice", since = "1.21.0")]
+impl<T> From<Vec<T>> for Arc<[T]> {
+ #[inline]
+ fn from(mut v: Vec<T>) -> Arc<[T]> {
+ unsafe {
+ let arc = Arc::copy_from_slice(&v);
+
+ // Allow the Vec to free its memory, but not destroy its contents
+ v.set_len(0);
+
+ arc
+ }
+ }
+}
+
#[cfg(test)]
mod tests {
+ use std::boxed::Box;
use std::clone::Clone;
use std::sync::mpsc::channel;
use std::mem::drop;
}
}
+ #[test]
+ fn test_into_from_raw_unsized() {
+ use std::fmt::Display;
+ use std::string::ToString;
+
+ let arc: Arc<str> = Arc::from("foo");
+
+ let ptr = Arc::into_raw(arc.clone());
+ let arc2 = unsafe { Arc::from_raw(ptr) };
+
+ assert_eq!(unsafe { &*ptr }, "foo");
+ assert_eq!(arc, arc2);
+
+ let arc: Arc<Display> = Arc::new(123);
+
+ let ptr = Arc::into_raw(arc.clone());
+ let arc2 = unsafe { Arc::from_raw(ptr) };
+
+ assert_eq!(unsafe { &*ptr }.to_string(), "123");
+ assert_eq!(arc2.to_string(), "123");
+ }
+
#[test]
fn test_cowarc_clone_make_mut() {
let mut cow0 = Arc::new(75);
}
t.join().unwrap();
}
+
+ #[test]
+ fn test_from_str() {
+ let r: Arc<str> = Arc::from("foo");
+
+ assert_eq!(&r[..], "foo");
+ }
+
+ #[test]
+ fn test_copy_from_slice() {
+ let s: &[u32] = &[1, 2, 3];
+ let r: Arc<[u32]> = Arc::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: Arc<[X]> = Arc::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: Arc<[Fail]> = Arc::from(s);
+ }
+
+ #[test]
+ fn test_from_box() {
+ let b: Box<u32> = box 123;
+ let r: Arc<u32> = Arc::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: Arc<str> = Arc::from(s);
+
+ assert_eq!(&r[..], "foo");
+ }
+
+ #[test]
+ fn test_from_box_slice() {
+ let s = vec![1, 2, 3].into_boxed_slice();
+ let r: Arc<[u32]> = Arc::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: Arc<Display> = Arc::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: Arc<Debug> = Arc::from(b);
+
+ assert_eq!(format!("{:?}", r), "()");
+ }
+
+ #[test]
+ fn test_from_vec() {
+ let v = vec![1, 2, 3];
+ let r: Arc<[u32]> = Arc::from(v);
+
+ assert_eq!(&r[..], [1, 2, 3]);
+ }
}
#[stable(feature = "rust1", since = "1.0.0")]
projects / rust.git / blobdiff