Initial import of rayon-1.5.0.

Bug: 155309706
Change-Id: I6ff7de1cb89d093d7938abf78d586ed76da85b0d

1 files changed, 245 insertions, 0 deletions

diff --git a/src/vec.rs b/src/vec.rs
new file mode 100644
index 0000000..686673b
--- /dev/null
+++ b/src/vec.rs
@@ -0,0 +1,245 @@
+//! Parallel iterator types for [vectors][std::vec] (`Vec<T>`)
+//!
+//! You will rarely need to interact with this module directly unless you need
+//! to name one of the iterator types.
+//!
+//! [std::vec]: https://doc.rust-lang.org/stable/std/vec/
+
+use crate::iter::plumbing::*;
+use crate::iter::*;
+use crate::math::simplify_range;
+use std::iter;
+use std::mem;
+use std::ops::{Range, RangeBounds};
+use std::ptr;
+use std::slice;
+
+/// Parallel iterator that moves out of a vector.
+#[derive(Debug, Clone)]
+pub struct IntoIter<T: Send> {
+    vec: Vec<T>,
+}
+
+impl<T: Send> IntoParallelIterator for Vec<T> {
+    type Item = T;
+    type Iter = IntoIter<T>;
+
+    fn into_par_iter(self) -> Self::Iter {
+        IntoIter { vec: self }
+    }
+}
+
+impl<T: Send> ParallelIterator for IntoIter<T> {
+    type Item = T;
+
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        bridge(self, consumer)
+    }
+
+    fn opt_len(&self) -> Option<usize> {
+        Some(self.len())
+    }
+}
+
+impl<T: Send> IndexedParallelIterator for IntoIter<T> {
+    fn drive<C>(self, consumer: C) -> C::Result
+    where
+        C: Consumer<Self::Item>,
+    {
+        bridge(self, consumer)
+    }
+
+    fn len(&self) -> usize {
+        self.vec.len()
+    }
+
+    fn with_producer<CB>(mut self, callback: CB) -> CB::Output
+    where
+        CB: ProducerCallback<Self::Item>,
+    {
+        // Drain every item, and then the vector only needs to free its buffer.
+        self.vec.par_drain(..).with_producer(callback)
+    }
+}
+
+impl<'data, T: Send> ParallelDrainRange<usize> for &'data mut Vec<T> {
+    type Iter = Drain<'data, T>;
+    type Item = T;
+
+    fn par_drain<R: RangeBounds<usize>>(self, range: R) -> Self::Iter {
+        Drain {
+            orig_len: self.len(),
+            range: simplify_range(range, self.len()),
+            vec: self,
+        }
+    }
+}
+
+/// Draining parallel iterator that moves a range out of a vector, but keeps the total capacity.
+#[derive(Debug)]
+pub struct Drain<'data, T: Send> {
+    vec: &'data mut Vec<T>,
+    range: Range<usize>,
+    orig_len: usize,
+}
+
+impl<'data, T: Send> ParallelIterator for Drain<'data, T> {
+    type Item = T;
+
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        bridge(self, consumer)
+    }
+
+    fn opt_len(&self) -> Option<usize> {
+        Some(self.len())
+    }
+}
+
+impl<'data, T: Send> IndexedParallelIterator for Drain<'data, T> {
+    fn drive<C>(self, consumer: C) -> C::Result
+    where
+        C: Consumer<Self::Item>,
+    {
+        bridge(self, consumer)
+    }
+
+    fn len(&self) -> usize {
+        self.range.len()
+    }
+
+    fn with_producer<CB>(self, callback: CB) -> CB::Output
+    where
+        CB: ProducerCallback<Self::Item>,
+    {
+        unsafe {
+            // Make the vector forget about the drained items, and temporarily the tail too.
+            let start = self.range.start;
+            self.vec.set_len(start);
+
+            // Get a correct borrow lifetime, then extend it to the original length.
+            let mut slice = &mut self.vec[start..];
+            slice = slice::from_raw_parts_mut(slice.as_mut_ptr(), self.range.len());
+
+            // The producer will move or drop each item from the drained range.
+            callback.callback(DrainProducer::new(slice))
+        }
+    }
+}
+
+impl<'data, T: Send> Drop for Drain<'data, T> {
+    fn drop(&mut self) {
+        if self.range.len() > 0 {
+            let Range { start, end } = self.range;
+            if self.vec.len() != start {
+                // We must not have produced, so just call a normal drain to remove the items.
+                assert_eq!(self.vec.len(), self.orig_len);
+                self.vec.drain(start..end);
+            } else if end < self.orig_len {
+                // The producer was responsible for consuming the drained items.
+                // Move the tail items to their new place, then set the length to include them.
+                unsafe {
+                    let ptr = self.vec.as_mut_ptr().add(start);
+                    let tail_ptr = self.vec.as_ptr().add(end);
+                    let tail_len = self.orig_len - end;
+                    ptr::copy(tail_ptr, ptr, tail_len);
+                    self.vec.set_len(start + tail_len);
+                }
+            }
+        }
+    }
+}
+
+/// ////////////////////////////////////////////////////////////////////////
+
+pub(crate) struct DrainProducer<'data, T: Send> {
+    slice: &'data mut [T],
+}
+
+impl<'data, T: 'data + Send> DrainProducer<'data, T> {
+    /// Creates a draining producer, which *moves* items from the slice.
+    ///
+    /// Unsafe bacause `!Copy` data must not be read after the borrow is released.
+    pub(crate) unsafe fn new(slice: &'data mut [T]) -> Self {
+        DrainProducer { slice }
+    }
+}
+
+impl<'data, T: 'data + Send> Producer for DrainProducer<'data, T> {
+    type Item = T;
+    type IntoIter = SliceDrain<'data, T>;
+
+    fn into_iter(mut self) -> Self::IntoIter {
+        // replace the slice so we don't drop it twice
+        let slice = mem::replace(&mut self.slice, &mut []);
+        SliceDrain {
+            iter: slice.iter_mut(),
+        }
+    }
+
+    fn split_at(mut self, index: usize) -> (Self, Self) {
+        // replace the slice so we don't drop it twice
+        let slice = mem::replace(&mut self.slice, &mut []);
+        let (left, right) = slice.split_at_mut(index);
+        unsafe { (DrainProducer::new(left), DrainProducer::new(right)) }
+    }
+}
+
+impl<'data, T: 'data + Send> Drop for DrainProducer<'data, T> {
+    fn drop(&mut self) {
+        // use `Drop for [T]`
+        unsafe { ptr::drop_in_place(self.slice) };
+    }
+}
+
+/// ////////////////////////////////////////////////////////////////////////
+
+// like std::vec::Drain, without updating a source Vec
+pub(crate) struct SliceDrain<'data, T> {
+    iter: slice::IterMut<'data, T>,
+}
+
+impl<'data, T: 'data> Iterator for SliceDrain<'data, T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<T> {
+        let ptr = self.iter.next()?;
+        Some(unsafe { ptr::read(ptr) })
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+
+    fn count(self) -> usize {
+        self.iter.len()
+    }
+}
+
+impl<'data, T: 'data> DoubleEndedIterator for SliceDrain<'data, T> {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        let ptr = self.iter.next_back()?;
+        Some(unsafe { ptr::read(ptr) })
+    }
+}
+
+impl<'data, T: 'data> ExactSizeIterator for SliceDrain<'data, T> {
+    fn len(&self) -> usize {
+        self.iter.len()
+    }
+}
+
+impl<'data, T: 'data> iter::FusedIterator for SliceDrain<'data, T> {}
+
+impl<'data, T: 'data> Drop for SliceDrain<'data, T> {
+    fn drop(&mut self) {
+        // extract the iterator so we can use `Drop for [T]`
+        let iter = mem::replace(&mut self.iter, [].iter_mut());
+        unsafe { ptr::drop_in_place(iter.into_slice()) };
+    }
+}