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@ -1,11 +1,11 @@
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% Example: Implementing Vec
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% Example: Implementing Vec
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TODO: audit for non-ZST offsets from heap::empty
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To bring everything together, we're going to write `std::Vec` from scratch.
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To bring everything together, we're going to write `std::Vec` from scratch.
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Because the all the best tools for writing unsafe code are unstable, this
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Because the all the best tools for writing unsafe code are unstable, this
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project will only work on nightly (as of Rust 1.2.0).
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project will only work on nightly (as of Rust 1.2.0).
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# Layout
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# Layout
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First off, we need to come up with the struct layout. Naively we want this
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First off, we need to come up with the struct layout. Naively we want this
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@ -63,16 +63,19 @@ as `std::rt::heap::EMPTY`. There are quite a few places where we'll want to use
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`heap::EMPTY` because there's no real allocation to talk about but `null` would
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`heap::EMPTY` because there's no real allocation to talk about but `null` would
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make the compiler angry.
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make the compiler angry.
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All of the `heap` API is totally unstable under the `alloc` feature, though.
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All of the `heap` API is totally unstable under the `heap_api` feature, though.
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We could trivially define `heap::EMPTY` ourselves, but we'll want the rest of
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We could trivially define `heap::EMPTY` ourselves, but we'll want the rest of
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the `heap` API anyway, so let's just get that dependency over with.
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the `heap` API anyway, so let's just get that dependency over with.
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# Allocating Memory
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# Allocating Memory
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So:
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So:
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```rust
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```rust
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#![feature(alloc)]
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#![feature(heap_api)]
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use std::rt::heap::EMPTY;
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use std::rt::heap::EMPTY;
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use std::mem;
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use std::mem;
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@ -184,6 +187,10 @@ fn grow(&mut self) {
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Nothing particularly tricky here. Just computing sizes and alignments and doing
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Nothing particularly tricky here. Just computing sizes and alignments and doing
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some careful multiplication checks.
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some careful multiplication checks.
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# Push and Pop
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# Push and Pop
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Alright. We can initialize. We can allocate. Let's actually implement some
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Alright. We can initialize. We can allocate. Let's actually implement some
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@ -240,6 +247,10 @@ pub fn pop(&mut self) -> Option<T> {
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}
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}
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```
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```
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# Deallocating
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# Deallocating
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Next we should implement Drop so that we don't massively leaks tons of resources.
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Next we should implement Drop so that we don't massively leaks tons of resources.
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@ -270,6 +281,10 @@ impl<T> Drop for Vec<T> {
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}
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}
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```
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```
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# Deref
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# Deref
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Alright! We've got a decent minimal ArrayStack implemented. We can push, we can
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Alright! We've got a decent minimal ArrayStack implemented. We can push, we can
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@ -311,6 +326,10 @@ impl<T> DerefMut for Vec<T> {
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Now we have `len`, `first`, `last`, indexing, slicing, sorting, `iter`, `iter_mut`,
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Now we have `len`, `first`, `last`, indexing, slicing, sorting, `iter`, `iter_mut`,
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and all other sorts of bells and whistles provided by slice. Sweet!
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and all other sorts of bells and whistles provided by slice. Sweet!
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# Insert and Remove
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# Insert and Remove
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Something *not* provided but slice is `insert` and `remove`, so let's do those next.
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Something *not* provided but slice is `insert` and `remove`, so let's do those next.
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@ -362,6 +381,10 @@ pub fn remove(&mut self, index: usize) -> T {
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}
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}
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```
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```
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# IntoIter
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# IntoIter
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Let's move on to writing iterators. `iter` and `iter_mut` have already been
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Let's move on to writing iterators. `iter` and `iter_mut` have already been
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@ -410,7 +433,22 @@ struct IntoIter<T> {
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}
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}
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```
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```
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And initialize it like this:
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One last subtle detail: if our Vec is empty, we want to produce an empty iterator.
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This will actually technically fall out doing the naive thing of:
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```text
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start = ptr
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end = ptr.offset(len)
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```
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However because `offset` is marked as a GEP inbounds instruction, this will tell
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llVM that ptr is allocated and won't alias other allocated memory. This is fine
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for zero-sized types, as they can't alias anything. However if we're using
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heap::EMPTY as a sentinel for a non-allocation for a *non-zero-sized* type,
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this can cause undefined behaviour. Alas, we must therefore special case either
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cap or len being 0 to not do the offset.
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So this is what we end up with for initialization:
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```rust
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```rust
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impl<T> Vec<T> {
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impl<T> Vec<T> {
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@ -428,7 +466,12 @@ impl<T> Vec<T> {
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buf: ptr,
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buf: ptr,
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cap: cap,
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cap: cap,
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start: *ptr,
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start: *ptr,
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end: ptr.offset(len as isize),
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end: if cap == 0 {
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// can't offset off this pointer, it's not allocated!
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*ptr
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} else {
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ptr.offset(len as isize)
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}
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}
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}
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}
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}
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}
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}
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@ -635,6 +678,10 @@ impl<T> Vec<T> {
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Much better.
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Much better.
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# Drain
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# Drain
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Let's move on to Drain. Drain is largely the same as IntoIter, except that
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Let's move on to Drain. Drain is largely the same as IntoIter, except that
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@ -674,7 +721,11 @@ impl<T> RawValIter<T> {
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unsafe fn new(slice: &[T]) -> Self {
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unsafe fn new(slice: &[T]) -> Self {
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RawValIter {
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RawValIter {
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start: slice.as_ptr(),
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start: slice.as_ptr(),
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end: slice.as_ptr().offset(slice.len() as isize),
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end: if slice.len() == 0 {
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slice.as_ptr()
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} else {
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slice.as_ptr().offset(slice.len() as isize)
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}
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}
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}
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}
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}
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}
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}
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@ -771,6 +822,8 @@ impl<T> Vec<T> {
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```
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```
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# Handling Zero-Sized Types
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# Handling Zero-Sized Types
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It's time. We're going to fight the spectre that is zero-sized types. Safe Rust
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It's time. We're going to fight the spectre that is zero-sized types. Safe Rust
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@ -781,13 +834,14 @@ zero-sized types. We need to be careful of two things:
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* The raw allocator API has undefined behaviour if you pass in 0 for an
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* The raw allocator API has undefined behaviour if you pass in 0 for an
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allocation size.
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allocation size.
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* raw pointer offsets are no-ops for zero-sized types, which will break our
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* raw pointer offsets are no-ops for zero-sized types, which will break our
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C-style pointer iterator
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C-style pointer iterator.
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Thankfully we abstracted out pointer-iterators and allocating handling into
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Thankfully we abstracted out pointer-iterators and allocating handling into
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RawValIter and RawVec respectively. How mysteriously convenient.
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RawValIter and RawVec respectively. How mysteriously convenient.
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## Allocating Zero-Sized Types
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## Allocating Zero-Sized Types
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So if the allocator API doesn't support zero-sized allocations, what on earth
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So if the allocator API doesn't support zero-sized allocations, what on earth
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@ -797,13 +851,457 @@ to be considered to store or load them. This actually extends to `ptr::read` and
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`ptr::write`: they won't actually look at the pointer at all. As such we *never* need
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`ptr::write`: they won't actually look at the pointer at all. As such we *never* need
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to change the pointer.
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to change the pointer.
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TODO
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Note however that our previous reliance on running out of memory before overflow is
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no longer valid with zero-sized types. We must explicitly guard against capacity
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overflow for zero-sized types.
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Due to our current architecture, all this means is writing 3 guards, one in each
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method of RawVec.
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```rust
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impl<T> RawVec<T> {
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fn new() -> Self {
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unsafe {
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// -1 is usize::MAX. This branch should be stripped at compile time.
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let cap = if mem::size_of::<T>() == 0 { -1 } else { 0 };
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// heap::EMPTY doubles as "unallocated" and "zero-sized allocation"
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RawVec { ptr: Unique::new(heap::EMPTY as *mut T), cap: cap }
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}
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}
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fn grow(&mut self) {
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unsafe {
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let elem_size = mem::size_of::<T>();
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// since we set the capacity to usize::MAX when elem_size is
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// 0, getting to here necessarily means the Vec is overfull.
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assert!(elem_size != 0, "capacity overflow");
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let align = mem::min_align_of::<T>();
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let (new_cap, ptr) = if self.cap == 0 {
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let ptr = heap::allocate(elem_size, align);
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(1, ptr)
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} else {
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let new_cap = 2 * self.cap;
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let ptr = heap::reallocate(*self.ptr as *mut _,
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self.cap * elem_size,
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new_cap * elem_size,
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align);
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(new_cap, ptr)
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};
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// If allocate or reallocate fail, we'll get `null` back
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if ptr.is_null() { oom() }
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self.ptr = Unique::new(ptr as *mut _);
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self.cap = new_cap;
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}
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}
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}
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impl<T> Drop for RawVec<T> {
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fn drop(&mut self) {
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let elem_size = mem::size_of::<T>();
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// don't free zero-sized allocations, as they were never allocated.
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if self.cap != 0 && elem_size != 0 {
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let align = mem::min_align_of::<T>();
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let num_bytes = elem_size * self.cap;
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unsafe {
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|
heap::deallocate(*self.ptr as *mut _, num_bytes, align);
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
That's it. We support pushing and popping zero-sized types now. Our iterators
|
|
|
|
|
|
|
|
(that aren't provided by slice Deref) are still busted, though.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
## Iterating Zero-Sized Types
|
|
|
|
## Iterating Zero-Sized Types
|
|
|
|
|
|
|
|
|
|
|
|
TODO
|
|
|
|
Zero-sized offsets are no-ops. This means that our current design will always
|
|
|
|
|
|
|
|
initialize `start` and `end` as the same value, and our iterators will yield
|
|
|
|
|
|
|
|
nothing. The current solution to this is to cast the pointers to integers,
|
|
|
|
|
|
|
|
increment, and then cast them back:
|
|
|
|
|
|
|
|
|
|
|
|
## Advanced Drain
|
|
|
|
```
|
|
|
|
|
|
|
|
impl<T> RawValIter<T> {
|
|
|
|
|
|
|
|
unsafe fn new(slice: &[T]) -> Self {
|
|
|
|
|
|
|
|
RawValIter {
|
|
|
|
|
|
|
|
start: slice.as_ptr(),
|
|
|
|
|
|
|
|
end: if mem::size_of::<T>() == 0 {
|
|
|
|
|
|
|
|
((slice.as_ptr() as usize) + slice.len()) as *const _
|
|
|
|
|
|
|
|
} else if slice.len() == 0 {
|
|
|
|
|
|
|
|
slice.as_ptr()
|
|
|
|
|
|
|
|
} else {
|
|
|
|
|
|
|
|
slice.as_ptr().offset(slice.len() as isize)
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Now we have a different bug. Instead of our iterators not running at all, our
|
|
|
|
|
|
|
|
iterators now run *forever*. We need to do the same trick in our iterator impls:
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
impl<T> Iterator for RawValIter<T> {
|
|
|
|
|
|
|
|
type Item = T;
|
|
|
|
|
|
|
|
fn next(&mut self) -> Option<T> {
|
|
|
|
|
|
|
|
if self.start == self.end {
|
|
|
|
|
|
|
|
None
|
|
|
|
|
|
|
|
} else {
|
|
|
|
|
|
|
|
unsafe {
|
|
|
|
|
|
|
|
let result = ptr::read(self.start);
|
|
|
|
|
|
|
|
self.start = if mem::size_of::<T>() == 0 {
|
|
|
|
|
|
|
|
(self.start as usize + 1) as *const _
|
|
|
|
|
|
|
|
} else {
|
|
|
|
|
|
|
|
self.start.offset(1);
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
Some(result)
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
|
|
|
|
|
|
|
let len = self.end as usize - self.start as usize;
|
|
|
|
|
|
|
|
(len, Some(len))
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
impl<T> DoubleEndedIterator for RawValIter<T> {
|
|
|
|
|
|
|
|
fn next_back(&mut self) -> Option<T> {
|
|
|
|
|
|
|
|
if self.start == self.end {
|
|
|
|
|
|
|
|
None
|
|
|
|
|
|
|
|
} else {
|
|
|
|
|
|
|
|
unsafe {
|
|
|
|
|
|
|
|
self.end = if mem::size_of::<T>() == 0 {
|
|
|
|
|
|
|
|
(self.end as usize - 1) as *const _
|
|
|
|
|
|
|
|
} else {
|
|
|
|
|
|
|
|
self.end.offset(-1);
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
Some(ptr::read(self.end))
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
And that's it. Iteration works!
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
# Advanced Drain
|
|
|
|
|
|
|
|
|
|
|
|
TODO? Not clear if informative
|
|
|
|
TODO? Not clear if informative
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
# The Final Code
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
```rust
|
|
|
|
|
|
|
|
#![feature(unique)]
|
|
|
|
|
|
|
|
#![feature(heap_api)]
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
use std::ptr::{Unique, self};
|
|
|
|
|
|
|
|
use std::rt::heap;
|
|
|
|
|
|
|
|
use std::mem;
|
|
|
|
|
|
|
|
use std::ops::{Deref, DerefMut};
|
|
|
|
|
|
|
|
use std::marker::PhantomData;
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
struct RawVec<T> {
|
|
|
|
|
|
|
|
ptr: Unique<T>,
|
|
|
|
|
|
|
|
cap: usize,
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
impl<T> RawVec<T> {
|
|
|
|
|
|
|
|
fn new() -> Self {
|
|
|
|
|
|
|
|
unsafe {
|
|
|
|
|
|
|
|
// -1 is usize::MAX. This branch should be stripped at compile time.
|
|
|
|
|
|
|
|
let cap = if mem::size_of::<T>() == 0 { -1 } else { 0 };
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
// heap::EMPTY doubles as "unallocated" and "zero-sized allocation"
|
|
|
|
|
|
|
|
RawVec { ptr: Unique::new(heap::EMPTY as *mut T), cap: cap }
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
fn grow(&mut self) {
|
|
|
|
|
|
|
|
unsafe {
|
|
|
|
|
|
|
|
let elem_size = mem::size_of::<T>();
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
// since we set the capacity to usize::MAX when elem_size is
|
|
|
|
|
|
|
|
// 0, getting to here necessarily means the Vec is overfull.
|
|
|
|
|
|
|
|
assert!(elem_size != 0, "capacity overflow");
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
let align = mem::min_align_of::<T>();
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
let (new_cap, ptr) = if self.cap == 0 {
|
|
|
|
|
|
|
|
let ptr = heap::allocate(elem_size, align);
|
|
|
|
|
|
|
|
(1, ptr)
|
|
|
|
|
|
|
|
} else {
|
|
|
|
|
|
|
|
let new_cap = 2 * self.cap;
|
|
|
|
|
|
|
|
let ptr = heap::reallocate(*self.ptr as *mut _,
|
|
|
|
|
|
|
|
self.cap * elem_size,
|
|
|
|
|
|
|
|
new_cap * elem_size,
|
|
|
|
|
|
|
|
align);
|
|
|
|
|
|
|
|
(new_cap, ptr)
|
|
|
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
// If allocate or reallocate fail, we'll get `null` back
|
|
|
|
|
|
|
|
if ptr.is_null() { oom() }
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
self.ptr = Unique::new(ptr as *mut _);
|
|
|
|
|
|
|
|
self.cap = new_cap;
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
impl<T> Drop for RawVec<T> {
|
|
|
|
|
|
|
|
fn drop(&mut self) {
|
|
|
|
|
|
|
|
let elem_size = mem::size_of::<T>();
|
|
|
|
|
|
|
|
if self.cap != 0 && elem_size != 0 {
|
|
|
|
|
|
|
|
let align = mem::min_align_of::<T>();
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
let num_bytes = elem_size * self.cap;
|
|
|
|
|
|
|
|
unsafe {
|
|
|
|
|
|
|
|
heap::deallocate(*self.ptr as *mut _, num_bytes, align);
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
pub struct Vec<T> {
|
|
|
|
|
|
|
|
buf: RawVec<T>,
|
|
|
|
|
|
|
|
len: usize,
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
impl<T> Vec<T> {
|
|
|
|
|
|
|
|
fn ptr(&self) -> *mut T { *self.buf.ptr }
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
fn cap(&self) -> usize { self.buf.cap }
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
pub fn new() -> Self {
|
|
|
|
|
|
|
|
Vec { buf: RawVec::new(), len: 0 }
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
pub fn push(&mut self, elem: T) {
|
|
|
|
|
|
|
|
if self.len == self.cap() { self.buf.grow(); }
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
unsafe {
|
|
|
|
|
|
|
|
ptr::write(self.ptr().offset(self.len as isize), elem);
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
// Can't fail, we'll OOM first.
|
|
|
|
|
|
|
|
self.len += 1;
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
pub fn pop(&mut self) -> Option<T> {
|
|
|
|
|
|
|
|
if self.len == 0 {
|
|
|
|
|
|
|
|
None
|
|
|
|
|
|
|
|
} else {
|
|
|
|
|
|
|
|
self.len -= 1;
|
|
|
|
|
|
|
|
unsafe {
|
|
|
|
|
|
|
|
Some(ptr::read(self.ptr().offset(self.len as isize)))
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
pub fn insert(&mut self, index: usize, elem: T) {
|
|
|
|
|
|
|
|
assert!(index <= self.len, "index out of bounds");
|
|
|
|
|
|
|
|
if self.cap() == self.len { self.buf.grow(); }
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
unsafe {
|
|
|
|
|
|
|
|
if index < self.len {
|
|
|
|
|
|
|
|
ptr::copy(self.ptr().offset(index as isize),
|
|
|
|
|
|
|
|
self.ptr().offset(index as isize + 1),
|
|
|
|
|
|
|
|
self.len - index);
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
ptr::write(self.ptr().offset(index as isize), elem);
|
|
|
|
|
|
|
|
self.len += 1;
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
pub fn remove(&mut self, index: usize) -> T {
|
|
|
|
|
|
|
|
assert!(index < self.len, "index out of bounds");
|
|
|
|
|
|
|
|
unsafe {
|
|
|
|
|
|
|
|
self.len -= 1;
|
|
|
|
|
|
|
|
let result = ptr::read(self.ptr().offset(index as isize));
|
|
|
|
|
|
|
|
ptr::copy(self.ptr().offset(index as isize + 1),
|
|
|
|
|
|
|
|
self.ptr().offset(index as isize),
|
|
|
|
|
|
|
|
self.len - index);
|
|
|
|
|
|
|
|
result
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
pub fn into_iter(self) -> IntoIter<T> {
|
|
|
|
|
|
|
|
unsafe {
|
|
|
|
|
|
|
|
let iter = RawValIter::new(&self);
|
|
|
|
|
|
|
|
let buf = ptr::read(&self.buf);
|
|
|
|
|
|
|
|
mem::forget(self);
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
IntoIter {
|
|
|
|
|
|
|
|
iter: iter,
|
|
|
|
|
|
|
|
_buf: buf,
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
pub fn drain(&mut self) -> Drain<T> {
|
|
|
|
|
|
|
|
// this is a mem::forget safety thing. If this is forgotten, we just
|
|
|
|
|
|
|
|
// leak the whole Vec's contents. Also we need to do this *eventually*
|
|
|
|
|
|
|
|
// anyway, so why not do it now?
|
|
|
|
|
|
|
|
self.len = 0;
|
|
|
|
|
|
|
|
unsafe {
|
|
|
|
|
|
|
|
Drain {
|
|
|
|
|
|
|
|
iter: RawValIter::new(&self),
|
|
|
|
|
|
|
|
vec: PhantomData,
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
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impl<T> Drop for Vec<T> {
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fn drop(&mut self) {
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while let Some(_) = self.pop() {}
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// allocation is handled by RawVec
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}
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}
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impl<T> Deref for Vec<T> {
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type Target = [T];
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fn deref(&self) -> &[T] {
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unsafe {
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::std::slice::from_raw_parts(self.ptr(), self.len)
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}
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}
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}
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impl<T> DerefMut for Vec<T> {
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fn deref_mut(&mut self) -> &mut [T] {
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unsafe {
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::std::slice::from_raw_parts_mut(self.ptr(), self.len)
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}
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}
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}
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struct RawValIter<T> {
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start: *const T,
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end: *const T,
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}
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impl<T> RawValIter<T> {
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unsafe fn new(slice: &[T]) -> Self {
|
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|
RawValIter {
|
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|
|
|
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|
start: slice.as_ptr(),
|
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|
|
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|
|
end: if mem::size_of::<T>() == 0 {
|
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|
|
((slice.as_ptr() as usize) + slice.len()) as *const _
|
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|
} else if slice.len() == 0 {
|
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|
slice.as_ptr()
|
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|
} else {
|
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|
|
slice.as_ptr().offset(slice.len() as isize)
|
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|
}
|
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}
|
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|
}
|
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|
}
|
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|
|
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|
|
impl<T> Iterator for RawValIter<T> {
|
|
|
|
|
|
|
|
type Item = T;
|
|
|
|
|
|
|
|
fn next(&mut self) -> Option<T> {
|
|
|
|
|
|
|
|
if self.start == self.end {
|
|
|
|
|
|
|
|
None
|
|
|
|
|
|
|
|
} else {
|
|
|
|
|
|
|
|
unsafe {
|
|
|
|
|
|
|
|
let result = ptr::read(self.start);
|
|
|
|
|
|
|
|
self.start = self.start.offset(1);
|
|
|
|
|
|
|
|
Some(result)
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
|
|
|
|
|
|
|
let len = self.end as usize - self.start as usize;
|
|
|
|
|
|
|
|
(len, Some(len))
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
impl<T> DoubleEndedIterator for RawValIter<T> {
|
|
|
|
|
|
|
|
fn next_back(&mut self) -> Option<T> {
|
|
|
|
|
|
|
|
if self.start == self.end {
|
|
|
|
|
|
|
|
None
|
|
|
|
|
|
|
|
} else {
|
|
|
|
|
|
|
|
unsafe {
|
|
|
|
|
|
|
|
self.end = self.end.offset(-1);
|
|
|
|
|
|
|
|
Some(ptr::read(self.end))
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
pub struct IntoIter<T> {
|
|
|
|
|
|
|
|
_buf: RawVec<T>, // we don't actually care about this. Just need it to live.
|
|
|
|
|
|
|
|
iter: RawValIter<T>,
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
impl<T> Iterator for IntoIter<T> {
|
|
|
|
|
|
|
|
type Item = T;
|
|
|
|
|
|
|
|
fn next(&mut self) -> Option<T> { self.iter.next() }
|
|
|
|
|
|
|
|
fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() }
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
impl<T> DoubleEndedIterator for IntoIter<T> {
|
|
|
|
|
|
|
|
fn next_back(&mut self) -> Option<T> { self.iter.next_back() }
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
impl<T> Drop for IntoIter<T> {
|
|
|
|
|
|
|
|
fn drop(&mut self) {
|
|
|
|
|
|
|
|
for _ in &mut *self {}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
pub struct Drain<'a, T: 'a> {
|
|
|
|
|
|
|
|
vec: PhantomData<&'a mut Vec<T>>,
|
|
|
|
|
|
|
|
iter: RawValIter<T>,
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
impl<'a, T> Iterator for Drain<'a, T> {
|
|
|
|
|
|
|
|
type Item = T;
|
|
|
|
|
|
|
|
fn next(&mut self) -> Option<T> { self.iter.next_back() }
|
|
|
|
|
|
|
|
fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() }
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
impl<'a, T> DoubleEndedIterator for Drain<'a, T> {
|
|
|
|
|
|
|
|
fn next_back(&mut self) -> Option<T> { self.iter.next_back() }
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
impl<'a, T> Drop for Drain<'a, T> {
|
|
|
|
|
|
|
|
fn drop(&mut self) {
|
|
|
|
|
|
|
|
// pre-drain the iter
|
|
|
|
|
|
|
|
for _ in &mut self.iter {}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
/// Abort the process, we're out of memory!
|
|
|
|
|
|
|
|
///
|
|
|
|
|
|
|
|
/// In practice this is probably dead code on most OSes
|
|
|
|
|
|
|
|
fn oom() {
|
|
|
|
|
|
|
|
::std::process::exit(-1);
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
```
|
|
|
|