From 45832383af02a377877c2701d90dbe29883532a2 Mon Sep 17 00:00:00 2001 From: "@amit.chandra" <@amit.chandra> Date: Sat, 22 Jun 2019 22:59:24 +0530 Subject: [PATCH] squash commit for nth_back on chunks exact wip nth_back for chunks_exact working nth_back for chunks exact Signed-off-by: wizAmit --- src/libcore/slice/mod.rs | 15 +++++++++++++++ src/libcore/tests/slice.rs | 19 +++++++++++++++++++ 2 files changed, 34 insertions(+) diff --git a/src/libcore/slice/mod.rs b/src/libcore/slice/mod.rs index c6d44324ef5..fe48e2458cd 100644 --- a/src/libcore/slice/mod.rs +++ b/src/libcore/slice/mod.rs @@ -4453,6 +4453,21 @@ fn next_back(&mut self) -> Option<&'a [T]> { Some(snd) } } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option { + let len = self.len(); + if n >= len { + self.v = &[]; + None + } else { + let start = (len - 1 - n) * self.chunk_size; + let end = start + self.chunk_size; + let nth_back = &self.v[start..end]; + self.v = &self.v[..start]; + Some(nth_back) + } + } } #[stable(feature = "chunks_exact", since = "1.31.0")] diff --git a/src/libcore/tests/slice.rs b/src/libcore/tests/slice.rs index 03e65d2fe0b..13b02c71842 100644 --- a/src/libcore/tests/slice.rs +++ b/src/libcore/tests/slice.rs @@ -275,6 +275,25 @@ fn test_chunks_exact_nth() { assert_eq!(c2.next(), None); } +#[test] +fn test_chunks_exact_nth_back() { + let v: &[i32] = &[0, 1, 2, 3, 4, 5]; + let mut c = v.chunks_exact(2); + assert_eq!(c.nth_back(1).unwrap(), &[2, 3]); + assert_eq!(c.next().unwrap(), &[0, 1]); + assert_eq!(c.next(), None); + + let v2: &[i32] = &[0, 1, 2, 3, 4]; + let mut c2 = v2.chunks_exact(3); + assert_eq!(c2.nth_back(0).unwrap(), &[0, 1, 2]); + assert_eq!(c2.next(), None); + assert_eq!(c2.next_back(), None); + + let v3: &[i32] = &[0, 1, 2, 3, 4]; + let mut c3 = v3.chunks_exact(10); + assert_eq!(c3.nth_back(0), None); +} + #[test] fn test_chunks_exact_last() { let v: &[i32] = &[0, 1, 2, 3, 4, 5]; -- 2.44.0