Merge pull request #16 from Gankro/master

use new Unique/heap APIs

src/destructors.md

@@ -40,8 +40,8 @@ struct Box<T>{ ptr: Unique<T> }
 impl<T> Drop for Box<T> {
     fn drop(&mut self) {
         unsafe {
-            drop_in_place(*self.ptr);
-            heap::deallocate((*self.ptr) as *mut u8,
+            drop_in_place(self.ptr.as_ptr());
+            heap::deallocate(self.ptr.as_ptr() as *mut u8,
                              mem::size_of::<T>(),
                              mem::align_of::<T>());
         }
@@ -71,8 +71,8 @@ struct Box<T>{ ptr: Unique<T> }
 impl<T> Drop for Box<T> {
     fn drop(&mut self) {
         unsafe {
-            drop_in_place(*self.ptr);
-            heap::deallocate((*self.ptr) as *mut u8,
+            drop_in_place(self.ptr.as_ptr());
+            heap::deallocate(self.ptr.as_ptr() as *mut u8,
                              mem::size_of::<T>(),
                              mem::align_of::<T>());
         }
@@ -86,7 +86,7 @@ impl<T> Drop for SuperBox<T> {
         unsafe {
             // Hyper-optimized: deallocate the box's contents for it
             // without `drop`ing the contents
-            heap::deallocate((*self.my_box.ptr) as *mut u8,
+            heap::deallocate(self.my_box.ptr.as_ptr() as *mut u8,
                              mem::size_of::<T>(),
                              mem::align_of::<T>());
         }
@@ -149,8 +149,8 @@ struct Box<T>{ ptr: Unique<T> }
 impl<T> Drop for Box<T> {
     fn drop(&mut self) {
         unsafe {
-            drop_in_place(*self.ptr);
-            heap::deallocate((*self.ptr) as *mut u8,
+            drop_in_place(self.ptr.as_ptr());
+            heap::deallocate(self.ptr.as_ptr() as *mut u8,
                              mem::size_of::<T>(),
                              mem::align_of::<T>());
         }
@@ -166,7 +166,7 @@ impl<T> Drop for SuperBox<T> {
             // without `drop`ing the contents. Need to set the `box`
             // field as `None` to prevent Rust from trying to Drop it.
             let my_box = self.my_box.take().unwrap();
-            heap::deallocate((*my_box.ptr) as *mut u8,
+            heap::deallocate(my_box.ptr.as_ptr() as *mut u8,
                              mem::size_of::<T>(),
                              mem::align_of::<T>());
             mem::forget(my_box);

src/vec-alloc.md

@@ -7,16 +7,12 @@ can't allocate, but also can't put a null pointer in `ptr`, what do we do in
 
 This is perfectly fine because we already have `cap == 0` as our sentinel for no
 allocation. We don't even need to handle it specially in almost any code because
-we usually need to check if `cap > len` or `len > 0` anyway. The traditional
-Rust value to put here is `0x01`. The standard library actually exposes this
-as `alloc::heap::EMPTY`. There are quite a few places where we'll
-want to use `heap::EMPTY` because there's no real allocation to talk about but
+we usually need to check if `cap > len` or `len > 0` anyway. The recommended
+Rust value to put here is `mem::align_of::<T>()`. Unique provides a convenience
+for this: `Unique::empty()`. There are quite a few places where we'll
+want to use `empty` because there's no real allocation to talk about but
 `null` would make the compiler do bad things.
 
-All of the `heap` API is totally unstable under the `heap_api` feature, though.
-We could trivially define `heap::EMPTY` ourselves, but we'll want the rest of
-the `heap` API anyway, so let's just get that dependency over with.
-
 So:
 
 ```rust,ignore
@@ -24,16 +20,10 @@ So:
 
 use std::mem;
 
-use alloc::heap::EMPTY;
-
 impl<T> Vec<T> {
     fn new() -> Self {
         assert!(mem::size_of::<T>() != 0, "We're not ready to handle ZSTs");
-        unsafe {
-            // need to cast EMPTY to the actual ptr type we want, let
-            // inference handle it.
-            Vec { ptr: Unique::new(heap::EMPTY as *mut _), len: 0, cap: 0 }
-        }
+        Vec { ptr: Unique::empty(), len: 0, cap: 0 }
     }
 }
 ```
@@ -202,7 +192,7 @@ fn grow(&mut self) {
                     "capacity overflow");
 
             let new_num_bytes = old_num_bytes * 2;
-            let ptr = heap::reallocate(*self.ptr as *mut _,
+            let ptr = heap::reallocate(self.ptr.as_ptr() as *mut _,
                                         old_num_bytes,
                                         new_num_bytes,
                                         align);

src/vec-dealloc.md

@@ -21,7 +21,7 @@ impl<T> Drop for Vec<T> {
             let elem_size = mem::size_of::<T>();
             let num_bytes = elem_size * self.cap;
             unsafe {
-                heap::deallocate(*self.ptr as *mut _, num_bytes, align);
+                heap::deallocate(self.ptr.as_ptr() as *mut _, num_bytes, align);
             }
         }
     }

src/vec-deref.md

@@ -18,7 +18,7 @@ impl<T> Deref for Vec<T> {
     type Target = [T];
     fn deref(&self) -> &[T] {
         unsafe {
-            ::std::slice::from_raw_parts(*self.ptr, self.len)
+            ::std::slice::from_raw_parts(self.ptr.as_ptr(), self.len)
         }
     }
 }
@@ -32,7 +32,7 @@ use std::ops::DerefMut;
 impl<T> DerefMut for Vec<T> {
     fn deref_mut(&mut self) -> &mut [T] {
         unsafe {
-            ::std::slice::from_raw_parts_mut(*self.ptr, self.len)
+            ::std::slice::from_raw_parts_mut(self.ptr.as_ptr(), self.len)
         }
     }
 }

src/vec-final.md

@@ -20,13 +20,11 @@ struct RawVec<T> {
 
 impl<T> RawVec<T> {
     fn new() -> Self {
-        unsafe {
-            // !0 is usize::MAX. This branch should be stripped at compile time.
-            let cap = if mem::size_of::<T>() == 0 { !0 } else { 0 };
+        // !0 is usize::MAX. This branch should be stripped at compile time.
+        let cap = if mem::size_of::<T>() == 0 { !0 } else { 0 };
 
-            // heap::EMPTY doubles as "unallocated" and "zero-sized allocation"
-            RawVec { ptr: Unique::new(heap::EMPTY as *mut T), cap: cap }
-        }
+        // Unique::empty() doubles as "unallocated" and "zero-sized allocation"
+        RawVec { ptr: Unique::empty(), cap: cap }
     }
 
     fn grow(&mut self) {
@@ -44,7 +42,7 @@ impl<T> RawVec<T> {
                 (1, ptr)
             } else {
                 let new_cap = 2 * self.cap;
-                let ptr = heap::reallocate(*self.ptr as *mut _,
+                let ptr = heap::reallocate(self.ptr.as_ptr() as *mut _,
                                             self.cap * elem_size,
                                             new_cap * elem_size,
                                             align);
@@ -68,7 +66,7 @@ impl<T> Drop for RawVec<T> {
 
             let num_bytes = elem_size * self.cap;
             unsafe {
-                heap::deallocate(*self.ptr as *mut _, num_bytes, align);
+                heap::deallocate(self.ptr.as_ptr() as *mut _, num_bytes, align);
             }
         }
     }
@@ -84,7 +82,7 @@ pub struct Vec<T> {
 }
 
 impl<T> Vec<T> {
-    fn ptr(&self) -> *mut T { *self.buf.ptr }
+    fn ptr(&self) -> *mut T { self.buf.ptr.as_ptr() }
 
     fn cap(&self) -> usize { self.buf.cap }
 

src/vec-into-iter.md

@@ -139,7 +139,7 @@ impl<T> Drop for IntoIter<T> {
             let elem_size = mem::size_of::<T>();
             let num_bytes = elem_size * self.cap;
             unsafe {
-                heap::deallocate(*self.buf as *mut _, num_bytes, align);
+                heap::deallocate(self.buf.as_ptr() as *mut _, num_bytes, align);
             }
         }
     }

src/vec-layout.md

@@ -32,7 +32,6 @@ As a recap, Unique is a wrapper around a raw pointer that declares that:
 * We are variant over `T`
 * We may own a value of type `T` (for drop check)
 * We are Send/Sync if `T` is Send/Sync
-* We deref to `*mut T` (so it largely acts like a `*mut` in our code)
 * Our pointer is never null (so `Option<Vec<T>>` is null-pointer-optimized)
 
 We can implement all of the above requirements except for the last
@@ -53,21 +52,16 @@ struct Unique<T> {
 unsafe impl<T: Send> Send for Unique<T> {}
 unsafe impl<T: Sync> Sync for Unique<T> {}
 
-impl<T> Unique<T> {
+impl<T: ?Sized> Unique<T> {
     pub fn new(ptr: *mut T) -> Self {
         Unique { ptr: ptr, _marker: PhantomData }
     }
-}
 
-impl<T> Deref for Unique<T> {
-    type Target = *mut T;
-    fn deref(&self) -> &*mut T {
-        // There's no way to cast the *const to a *mut
-        // while also taking a reference. So we just
-        // transmute it since it's all "just pointers".
-        unsafe { mem::transmute(&self.ptr) }
+    pub fn as_ptr(&self) -> *mut T {
+        self.ptr as *mut T
     }
 }
+
 # fn main() {}
 ```
 
@@ -92,7 +86,7 @@ pub struct Vec<T> {
 
 If you don't care about the null-pointer optimization, then you can use the
 stable code. However we will be designing the rest of the code around enabling
-the optimization. In particular, `Unique::new` is unsafe to call, because
+this optimization. It should be noted that `Unique::new` is unsafe to call, because
 putting `null` inside of it is Undefined Behavior. Our stable Unique doesn't
 need `new` to be unsafe because it doesn't make any interesting guarantees about
 its contents.

src/vec-raw.md

@@ -1,3 +1,4 @@
+
 # RawVec
 
 We've actually reached an interesting situation here: we've duplicated the logic
@@ -17,9 +18,7 @@ struct RawVec<T> {
 impl<T> RawVec<T> {
     fn new() -> Self {
         assert!(mem::size_of::<T>() != 0, "TODO: implement ZST support");
-        unsafe {
-            RawVec { ptr: Unique::new(heap::EMPTY as *mut T), cap: 0 }
-        }
+        RawVec { ptr: Unique::empty(), cap: 0 }
     }
 
     // unchanged from Vec
@@ -33,7 +32,7 @@ impl<T> RawVec<T> {
                 (1, ptr)
             } else {
                 let new_cap = 2 * self.cap;
-                let ptr = heap::reallocate(*self.ptr as *mut _,
+                let ptr = heap::reallocate(self.ptr.as_ptr() as *mut _,
                                             self.cap * elem_size,
                                             new_cap * elem_size,
                                             align);
@@ -57,7 +56,7 @@ impl<T> Drop for RawVec<T> {
             let elem_size = mem::size_of::<T>();
             let num_bytes = elem_size * self.cap;
             unsafe {
-                heap::deallocate(*self.ptr as *mut _, num_bytes, align);
+                heap::deallocate(self.ptr.as_mut() as *mut _, num_bytes, align);
             }
         }
     }
@@ -73,7 +72,7 @@ pub struct Vec<T> {
 }
 
 impl<T> Vec<T> {
-    fn ptr(&self) -> *mut T { *self.buf.ptr }
+    fn ptr(&self) -> *mut T { self.buf.ptr.as_ptr() }
 
     fn cap(&self) -> usize { self.buf.cap }
 

src/vec-zsts.md

@@ -19,7 +19,7 @@ RawValIter and RawVec respectively. How mysteriously convenient.
 ## Allocating Zero-Sized Types
 
 So if the allocator API doesn't support zero-sized allocations, what on earth
-do we store as our allocation? Why, `heap::EMPTY` of course! Almost every operation
+do we store as our allocation? `Unique::empty()` of course! Almost every operation
 with a ZST is a no-op since ZSTs have exactly one value, and therefore no state needs
 to be considered to store or load them. This actually extends to `ptr::read` and
 `ptr::write`: they won't actually look at the pointer at all. As such we never need
@@ -35,13 +35,11 @@ method of RawVec.
 ```rust,ignore
 impl<T> RawVec<T> {
     fn new() -> Self {
-        unsafe {
-            // !0 is usize::MAX. This branch should be stripped at compile time.
-            let cap = if mem::size_of::<T>() == 0 { !0 } else { 0 };
+        // !0 is usize::MAX. This branch should be stripped at compile time.
+        let cap = if mem::size_of::<T>() == 0 { !0 } else { 0 };
 
-            // heap::EMPTY doubles as "unallocated" and "zero-sized allocation"
-            RawVec { ptr: Unique::new(heap::EMPTY as *mut T), cap: cap }
-        }
+        // Unique::empty() doubles as "unallocated" and "zero-sized allocation"
+        RawVec { ptr: Unique::empty(), cap: cap }
     }
 
     fn grow(&mut self) {
@@ -59,7 +57,7 @@ impl<T> RawVec<T> {
                 (1, ptr)
             } else {
                 let new_cap = 2 * self.cap;
-                let ptr = heap::reallocate(*self.ptr as *mut _,
+                let ptr = heap::reallocate(self.ptr.as_ptr() as *mut _,
                                             self.cap * elem_size,
                                             new_cap * elem_size,
                                             align);
@@ -85,7 +83,7 @@ impl<T> Drop for RawVec<T> {
 
             let num_bytes = elem_size * self.cap;
             unsafe {
-                heap::deallocate(*self.ptr as *mut _, num_bytes, align);
+                heap::deallocate(self.ptr.as_ptr() as *mut _, num_bytes, align);
             }
         }
     }