refactor: moving Splice into splice.rs
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C
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434e5d1422
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2 changed files with 138 additions and 128 deletions
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@ -79,6 +79,11 @@ pub use self::drain_filter::DrainFilter;
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mod drain_filter;
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mod drain_filter;
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#[stable(feature = "vec_splice", since = "1.21.0")]
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pub use self::splice::Splice;
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mod splice;
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/// A contiguous growable array type, written `Vec<T>` but pronounced 'vector'.
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/// A contiguous growable array type, written `Vec<T>` but pronounced 'vector'.
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///
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///
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/// # Examples
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/// # Examples
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@ -3462,131 +3467,3 @@ unsafe impl<T, A: Allocator> TrustedLen for Drain<'_, T, A> {}
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#[stable(feature = "fused", since = "1.26.0")]
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#[stable(feature = "fused", since = "1.26.0")]
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impl<T, A: Allocator> FusedIterator for Drain<'_, T, A> {}
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impl<T, A: Allocator> FusedIterator for Drain<'_, T, A> {}
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/// A splicing iterator for `Vec`.
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///
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/// This struct is created by [`Vec::splice()`].
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/// See its documentation for more.
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///
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/// # Example
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///
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/// ```
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/// let mut v = vec![0, 1, 2];
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/// let new = [7, 8];
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/// let iter: std::vec::Splice<_> = v.splice(1.., new.iter().cloned());
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/// ```
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#[derive(Debug)]
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#[stable(feature = "vec_splice", since = "1.21.0")]
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pub struct Splice<
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'a,
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I: Iterator + 'a,
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#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator + 'a = Global,
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> {
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drain: Drain<'a, I::Item, A>,
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replace_with: I,
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}
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#[stable(feature = "vec_splice", since = "1.21.0")]
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impl<I: Iterator, A: Allocator> Iterator for Splice<'_, I, A> {
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type Item = I::Item;
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fn next(&mut self) -> Option<Self::Item> {
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self.drain.next()
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}
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fn size_hint(&self) -> (usize, Option<usize>) {
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self.drain.size_hint()
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}
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}
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#[stable(feature = "vec_splice", since = "1.21.0")]
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impl<I: Iterator, A: Allocator> DoubleEndedIterator for Splice<'_, I, A> {
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fn next_back(&mut self) -> Option<Self::Item> {
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self.drain.next_back()
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}
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}
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#[stable(feature = "vec_splice", since = "1.21.0")]
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impl<I: Iterator, A: Allocator> ExactSizeIterator for Splice<'_, I, A> {}
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#[stable(feature = "vec_splice", since = "1.21.0")]
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impl<I: Iterator, A: Allocator> Drop for Splice<'_, I, A> {
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fn drop(&mut self) {
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self.drain.by_ref().for_each(drop);
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unsafe {
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if self.drain.tail_len == 0 {
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self.drain.vec.as_mut().extend(self.replace_with.by_ref());
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return;
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}
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// First fill the range left by drain().
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if !self.drain.fill(&mut self.replace_with) {
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return;
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}
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// There may be more elements. Use the lower bound as an estimate.
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// FIXME: Is the upper bound a better guess? Or something else?
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let (lower_bound, _upper_bound) = self.replace_with.size_hint();
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if lower_bound > 0 {
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self.drain.move_tail(lower_bound);
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if !self.drain.fill(&mut self.replace_with) {
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return;
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}
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}
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// Collect any remaining elements.
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// This is a zero-length vector which does not allocate if `lower_bound` was exact.
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let mut collected = self.replace_with.by_ref().collect::<Vec<I::Item>>().into_iter();
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// Now we have an exact count.
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if collected.len() > 0 {
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self.drain.move_tail(collected.len());
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let filled = self.drain.fill(&mut collected);
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debug_assert!(filled);
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debug_assert_eq!(collected.len(), 0);
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}
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}
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// Let `Drain::drop` move the tail back if necessary and restore `vec.len`.
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}
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}
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/// Private helper methods for `Splice::drop`
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impl<T, A: Allocator> Drain<'_, T, A> {
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/// The range from `self.vec.len` to `self.tail_start` contains elements
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/// that have been moved out.
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/// Fill that range as much as possible with new elements from the `replace_with` iterator.
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/// Returns `true` if we filled the entire range. (`replace_with.next()` didn’t return `None`.)
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unsafe fn fill<I: Iterator<Item = T>>(&mut self, replace_with: &mut I) -> bool {
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let vec = unsafe { self.vec.as_mut() };
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let range_start = vec.len;
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let range_end = self.tail_start;
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let range_slice = unsafe {
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slice::from_raw_parts_mut(vec.as_mut_ptr().add(range_start), range_end - range_start)
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};
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for place in range_slice {
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if let Some(new_item) = replace_with.next() {
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unsafe { ptr::write(place, new_item) };
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vec.len += 1;
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} else {
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return false;
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}
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}
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true
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}
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/// Makes room for inserting more elements before the tail.
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unsafe fn move_tail(&mut self, additional: usize) {
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let vec = unsafe { self.vec.as_mut() };
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let len = self.tail_start + self.tail_len;
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vec.buf.reserve(len, additional);
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let new_tail_start = self.tail_start + additional;
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unsafe {
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let src = vec.as_ptr().add(self.tail_start);
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let dst = vec.as_mut_ptr().add(new_tail_start);
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ptr::copy(src, dst, self.tail_len);
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}
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self.tail_start = new_tail_start;
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}
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}
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133
library/alloc/src/vec/splice.rs
Normal file
133
library/alloc/src/vec/splice.rs
Normal file
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@ -0,0 +1,133 @@
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use crate::alloc::{Allocator, Global};
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use core::ptr::{self};
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use core::slice::{self};
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use super::{Vec, Drain};
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/// A splicing iterator for `Vec`.
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///
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/// This struct is created by [`Vec::splice()`].
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/// See its documentation for more.
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///
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/// # Example
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///
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/// ```
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/// let mut v = vec![0, 1, 2];
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/// let new = [7, 8];
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/// let iter: std::vec::Splice<_> = v.splice(1.., new.iter().cloned());
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/// ```
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#[derive(Debug)]
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#[stable(feature = "vec_splice", since = "1.21.0")]
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pub struct Splice<
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'a,
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I: Iterator + 'a,
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#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator + 'a = Global,
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> {
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pub(super) drain: Drain<'a, I::Item, A>,
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pub(super) replace_with: I,
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}
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#[stable(feature = "vec_splice", since = "1.21.0")]
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impl<I: Iterator, A: Allocator> Iterator for Splice<'_, I, A> {
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type Item = I::Item;
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fn next(&mut self) -> Option<Self::Item> {
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self.drain.next()
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}
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fn size_hint(&self) -> (usize, Option<usize>) {
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self.drain.size_hint()
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}
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}
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#[stable(feature = "vec_splice", since = "1.21.0")]
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impl<I: Iterator, A: Allocator> DoubleEndedIterator for Splice<'_, I, A> {
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fn next_back(&mut self) -> Option<Self::Item> {
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self.drain.next_back()
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}
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}
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#[stable(feature = "vec_splice", since = "1.21.0")]
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impl<I: Iterator, A: Allocator> ExactSizeIterator for Splice<'_, I, A> {}
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#[stable(feature = "vec_splice", since = "1.21.0")]
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impl<I: Iterator, A: Allocator> Drop for Splice<'_, I, A> {
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fn drop(&mut self) {
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self.drain.by_ref().for_each(drop);
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unsafe {
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if self.drain.tail_len == 0 {
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self.drain.vec.as_mut().extend(self.replace_with.by_ref());
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return;
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}
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// First fill the range left by drain().
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if !self.drain.fill(&mut self.replace_with) {
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return;
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}
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// There may be more elements. Use the lower bound as an estimate.
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// FIXME: Is the upper bound a better guess? Or something else?
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let (lower_bound, _upper_bound) = self.replace_with.size_hint();
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if lower_bound > 0 {
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self.drain.move_tail(lower_bound);
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if !self.drain.fill(&mut self.replace_with) {
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return;
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}
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}
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// Collect any remaining elements.
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// This is a zero-length vector which does not allocate if `lower_bound` was exact.
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let mut collected = self.replace_with.by_ref().collect::<Vec<I::Item>>().into_iter();
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// Now we have an exact count.
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if collected.len() > 0 {
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self.drain.move_tail(collected.len());
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let filled = self.drain.fill(&mut collected);
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debug_assert!(filled);
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debug_assert_eq!(collected.len(), 0);
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}
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}
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// Let `Drain::drop` move the tail back if necessary and restore `vec.len`.
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}
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}
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/// Private helper methods for `Splice::drop`
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impl<T, A: Allocator> Drain<'_, T, A> {
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/// The range from `self.vec.len` to `self.tail_start` contains elements
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/// that have been moved out.
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/// Fill that range as much as possible with new elements from the `replace_with` iterator.
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/// Returns `true` if we filled the entire range. (`replace_with.next()` didn’t return `None`.)
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unsafe fn fill<I: Iterator<Item = T>>(&mut self, replace_with: &mut I) -> bool {
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let vec = unsafe { self.vec.as_mut() };
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let range_start = vec.len;
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let range_end = self.tail_start;
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let range_slice = unsafe {
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slice::from_raw_parts_mut(vec.as_mut_ptr().add(range_start), range_end - range_start)
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};
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for place in range_slice {
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if let Some(new_item) = replace_with.next() {
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unsafe { ptr::write(place, new_item) };
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vec.len += 1;
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} else {
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return false;
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}
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}
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true
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}
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/// Makes room for inserting more elements before the tail.
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unsafe fn move_tail(&mut self, additional: usize) {
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let vec = unsafe { self.vec.as_mut() };
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let len = self.tail_start + self.tail_len;
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vec.buf.reserve(len, additional);
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let new_tail_start = self.tail_start + additional;
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unsafe {
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let src = vec.as_ptr().add(self.tail_start);
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let dst = vec.as_mut_ptr().add(new_tail_start);
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ptr::copy(src, dst, self.tail_len);
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}
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self.tail_start = new_tail_start;
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}
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}
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