Rollup merge of #62074 - wizAmit:feature/mut_chunks_nth_back, r=scottmcm
squash of all commits for nth_back on ChunksMut wip nth_back for chunks_mut working chunksmut fixed nth_back for chunksmut Signed-off-by: wizAmit <amitforfriends_dns@yahoo.com> r? @timvermeulen r? @scottmcm
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cb8b491a65
2 changed files with 41 additions and 0 deletions
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@ -4339,6 +4339,25 @@ impl<'a, T> DoubleEndedIterator for ChunksMut<'a, T> {
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Some(tail)
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Some(tail)
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}
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}
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}
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}
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#[inline]
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fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
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let len = self.len();
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if n >= len {
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self.v = &mut [];
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None
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} else {
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let start = (len - 1 - n) * self.chunk_size;
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let end = match start.checked_add(self.chunk_size) {
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Some(res) => cmp::min(res, self.v.len()),
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None => self.v.len(),
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};
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let (temp, _tail) = mem::replace(&mut self.v, &mut []).split_at_mut(end);
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let (head, nth_back) = temp.split_at_mut(start);
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self.v = head;
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Some(nth_back)
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}
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}
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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#[stable(feature = "rust1", since = "1.0.0")]
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@ -222,6 +222,28 @@ fn test_chunks_mut_nth() {
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assert_eq!(c2.next(), None);
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assert_eq!(c2.next(), None);
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}
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}
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#[test]
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fn test_chunks_mut_nth_back() {
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let v: &mut [i32] = &mut [0, 1, 2, 3, 4, 5];
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let mut c = v.chunks_mut(2);
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assert_eq!(c.nth_back(1).unwrap(), &[2, 3]);
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assert_eq!(c.next().unwrap(), &[0, 1]);
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let v1: &mut [i32] = &mut [0, 1, 2, 3, 4];
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let mut c1 = v1.chunks_mut(3);
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assert_eq!(c1.nth_back(1).unwrap(), &[0, 1, 2]);
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assert_eq!(c1.next(), None);
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let v3: &mut [i32] = &mut [0, 1, 2, 3, 4];
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let mut c3 = v3.chunks_mut(10);
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assert_eq!(c3.nth_back(0).unwrap(), &[0, 1, 2, 3, 4]);
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assert_eq!(c3.next(), None);
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let v4: &mut [i32] = &mut [0, 1, 2];
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let mut c4 = v4.chunks_mut(10);
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assert_eq!(c4.nth_back(1_000_000_000usize), None);
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}
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#[test]
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#[test]
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fn test_chunks_mut_last() {
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fn test_chunks_mut_last() {
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let v: &mut [i32] = &mut [0, 1, 2, 3, 4, 5];
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let v: &mut [i32] = &mut [0, 1, 2, 3, 4, 5];
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