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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:20:39 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:20:39 +0000 |
commit | 1376c5a617be5c25655d0d7cb63e3beaa5a6e026 (patch) | |
tree | 3bb8d61aee02bc7a15eab3f36e3b921afc2075d0 /library/core/src/iter/adapters/chain.rs | |
parent | Releasing progress-linux version 1.69.0+dfsg1-1~progress7.99u1. (diff) | |
download | rustc-1376c5a617be5c25655d0d7cb63e3beaa5a6e026.tar.xz rustc-1376c5a617be5c25655d0d7cb63e3beaa5a6e026.zip |
Merging upstream version 1.70.0+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'library/core/src/iter/adapters/chain.rs')
-rw-r--r-- | library/core/src/iter/adapters/chain.rs | 73 |
1 files changed, 43 insertions, 30 deletions
diff --git a/library/core/src/iter/adapters/chain.rs b/library/core/src/iter/adapters/chain.rs index 60eb3a6da..75727c3a2 100644 --- a/library/core/src/iter/adapters/chain.rs +++ b/library/core/src/iter/adapters/chain.rs @@ -1,4 +1,5 @@ use crate::iter::{DoubleEndedIterator, FusedIterator, Iterator, TrustedLen}; +use crate::num::NonZeroUsize; use crate::ops::Try; /// An iterator that links two iterators together, in a chain. @@ -95,38 +96,33 @@ where } #[inline] - fn advance_by(&mut self, n: usize) -> Result<(), usize> { - let mut rem = n; - + fn advance_by(&mut self, mut n: usize) -> Result<(), NonZeroUsize> { if let Some(ref mut a) = self.a { - match a.advance_by(rem) { + n = match a.advance_by(n) { Ok(()) => return Ok(()), - Err(k) => rem -= k, - } + Err(k) => k.get(), + }; self.a = None; } if let Some(ref mut b) = self.b { - match b.advance_by(rem) { - Ok(()) => return Ok(()), - Err(k) => rem -= k, - } + return b.advance_by(n); // we don't fuse the second iterator } - if rem == 0 { Ok(()) } else { Err(n - rem) } + NonZeroUsize::new(n).map_or(Ok(()), Err) } #[inline] fn nth(&mut self, mut n: usize) -> Option<Self::Item> { if let Some(ref mut a) = self.a { - match a.advance_by(n) { + n = match a.advance_by(n) { Ok(()) => match a.next() { - None => n = 0, + None => 0, x => return x, }, - Err(k) => n -= k, - } + Err(k) => k.get(), + }; self.a = None; } @@ -186,38 +182,33 @@ where } #[inline] - fn advance_back_by(&mut self, n: usize) -> Result<(), usize> { - let mut rem = n; - + fn advance_back_by(&mut self, mut n: usize) -> Result<(), NonZeroUsize> { if let Some(ref mut b) = self.b { - match b.advance_back_by(rem) { + n = match b.advance_back_by(n) { Ok(()) => return Ok(()), - Err(k) => rem -= k, - } + Err(k) => k.get(), + }; self.b = None; } if let Some(ref mut a) = self.a { - match a.advance_back_by(rem) { - Ok(()) => return Ok(()), - Err(k) => rem -= k, - } + return a.advance_back_by(n); // we don't fuse the second iterator } - if rem == 0 { Ok(()) } else { Err(n - rem) } + NonZeroUsize::new(n).map_or(Ok(()), Err) } #[inline] fn nth_back(&mut self, mut n: usize) -> Option<Self::Item> { if let Some(ref mut b) = self.b { - match b.advance_back_by(n) { + n = match b.advance_back_by(n) { Ok(()) => match b.next_back() { - None => n = 0, + None => 0, x => return x, }, - Err(k) => n -= k, - } + Err(k) => k.get(), + }; self.b = None; } @@ -282,6 +273,28 @@ where { } +#[stable(feature = "default_iters", since = "1.70.0")] +impl<A: Default, B: Default> Default for Chain<A, B> { + /// Creates a `Chain` from the default values for `A` and `B`. + /// + /// ``` + /// # use core::iter::Chain; + /// # use core::slice; + /// # use std::collections::{btree_set, BTreeSet}; + /// # use std::mem; + /// struct Foo<'a>(Chain<slice::Iter<'a, u8>, btree_set::Iter<'a, u8>>); + /// + /// let set = BTreeSet::<u8>::new(); + /// let slice: &[u8] = &[]; + /// let mut foo = Foo(slice.iter().chain(set.iter())); + /// + /// // take requires `Default` + /// let _: Chain<_, _> = mem::take(&mut foo.0); + fn default() -> Self { + Chain::new(Default::default(), Default::default()) + } +} + #[inline] fn and_then_or_clear<T, U>(opt: &mut Option<T>, f: impl FnOnce(&mut T) -> Option<U>) -> Option<U> { let x = f(opt.as_mut()?); |