diff --git a/src/libcore/iter/mod.rs b/src/libcore/iter/mod.rs index 035418570a019..9eeb2608071c2 100644 --- a/src/libcore/iter/mod.rs +++ b/src/libcore/iter/mod.rs @@ -420,6 +420,18 @@ impl<'a, I, T: 'a> FusedIterator for Cloned where I: FusedIterator, T: Clone {} +#[doc(hidden)] +unsafe impl<'a, I, T: 'a> TrustedRandomAccess for Cloned + where I: TrustedRandomAccess, T: Clone +{ + unsafe fn get_unchecked(&mut self, i: usize) -> Self::Item { + self.it.get_unchecked(i).clone() + } + + #[inline] + fn may_have_side_effect() -> bool { true } +} + /// An iterator that repeats endlessly. /// /// This `struct` is created by the [`cycle()`] method on [`Iterator`]. See its @@ -773,6 +785,13 @@ impl ZipImpl for Zip unsafe { Some((self.a.get_unchecked(i), self.b.get_unchecked(i))) } + } else if A::may_have_side_effect() && self.index < self.a.len() { + // match the base implementation's potential side effects + unsafe { + self.a.get_unchecked(self.index); + } + self.index += 1; + None } else { None } @@ -789,6 +808,23 @@ impl ZipImpl for Zip where A: DoubleEndedIterator + ExactSizeIterator, B: DoubleEndedIterator + ExactSizeIterator { + // Adjust a, b to equal length + if A::may_have_side_effect() { + let sz = self.a.len(); + if sz > self.len { + for _ in 0..sz - cmp::max(self.len, self.index) { + self.a.next_back(); + } + } + } + if B::may_have_side_effect() { + let sz = self.b.len(); + if sz > self.len { + for _ in 0..sz - self.len { + self.b.next_back(); + } + } + } if self.index < self.len { self.len -= 1; let i = self.len; @@ -814,6 +850,9 @@ unsafe impl TrustedRandomAccess for Zip (self.a.get_unchecked(i), self.b.get_unchecked(i)) } + fn may_have_side_effect() -> bool { + A::may_have_side_effect() || B::may_have_side_effect() + } } #[unstable(feature = "fused", issue = "35602")] @@ -920,6 +959,18 @@ impl ExactSizeIterator for Map impl FusedIterator for Map where F: FnMut(I::Item) -> B {} +#[doc(hidden)] +unsafe impl TrustedRandomAccess for Map + where I: TrustedRandomAccess, + F: FnMut(I::Item) -> B, +{ + unsafe fn get_unchecked(&mut self, i: usize) -> Self::Item { + (self.f)(self.iter.get_unchecked(i)) + } + #[inline] + fn may_have_side_effect() -> bool { true } +} + /// An iterator that filters the elements of `iter` with `predicate`. /// /// This `struct` is created by the [`filter()`] method on [`Iterator`]. See its @@ -1135,6 +1186,10 @@ unsafe impl TrustedRandomAccess for Enumerate unsafe fn get_unchecked(&mut self, i: usize) -> (usize, I::Item) { (self.count + i, self.iter.get_unchecked(i)) } + + fn may_have_side_effect() -> bool { + I::may_have_side_effect() + } } #[unstable(feature = "fused", issue = "35602")] @@ -1764,6 +1819,10 @@ unsafe impl TrustedRandomAccess for Fuse unsafe fn get_unchecked(&mut self, i: usize) -> I::Item { self.iter.get_unchecked(i) } + + fn may_have_side_effect() -> bool { + I::may_have_side_effect() + } } #[unstable(feature = "fused", issue = "35602")] diff --git a/src/libcore/iter_private.rs b/src/libcore/iter_private.rs index 83eeef31ab054..bc1aaa09f3dbd 100644 --- a/src/libcore/iter_private.rs +++ b/src/libcore/iter_private.rs @@ -14,6 +14,7 @@ /// # Safety /// /// The iterator's .len() and size_hint() must be exact. +/// `.len()` must be cheap to call. /// /// .get_unchecked() must return distinct mutable references for distinct /// indices (if applicable), and must return a valid reference if index is in @@ -21,5 +22,7 @@ #[doc(hidden)] pub unsafe trait TrustedRandomAccess : ExactSizeIterator { unsafe fn get_unchecked(&mut self, i: usize) -> Self::Item; + /// Return `true` if getting an iterator element may have + /// side effects. Remember to take inner iterators into account. + fn may_have_side_effect() -> bool; } - diff --git a/src/libcore/slice.rs b/src/libcore/slice.rs index d1df56905df24..31be404ba905a 100644 --- a/src/libcore/slice.rs +++ b/src/libcore/slice.rs @@ -1968,6 +1968,7 @@ unsafe impl<'a, T> TrustedRandomAccess for Iter<'a, T> { unsafe fn get_unchecked(&mut self, i: usize) -> &'a T { &*self.ptr.offset(i as isize) } + fn may_have_side_effect() -> bool { false } } #[doc(hidden)] @@ -1975,4 +1976,5 @@ unsafe impl<'a, T> TrustedRandomAccess for IterMut<'a, T> { unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut T { &mut *self.ptr.offset(i as isize) } + fn may_have_side_effect() -> bool { false } } diff --git a/src/test/codegen/zip.rs b/src/test/codegen/zip.rs index 6c956364bf80f..d0051c5165fe1 100644 --- a/src/test/codegen/zip.rs +++ b/src/test/codegen/zip.rs @@ -20,3 +20,12 @@ pub fn zip_copy(xs: &[u8], ys: &mut [u8]) { *y = *x; } } + +// CHECK-LABEL: @zip_copy_mapped +#[no_mangle] +pub fn zip_copy_mapped(xs: &[u8], ys: &mut [u8]) { +// CHECK: memcpy + for (x, y) in xs.iter().map(|&x| x).zip(ys) { + *y = x; + } +} diff --git a/src/test/run-pass/iter-zip.rs b/src/test/run-pass/iter-zip.rs new file mode 100644 index 0000000000000..b0503bc2048e7 --- /dev/null +++ b/src/test/run-pass/iter-zip.rs @@ -0,0 +1,112 @@ +// Copyright 2016 The Rust Project Developers. See the COPYRIGHT +// file at the top-level directory of this distribution and at +// http://rust-lang.org/COPYRIGHT. +// +// Licensed under the Apache License, Version 2.0 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +// Test that .zip() specialization preserves side effects +// in sideeffectful iterator adaptors. + +use std::cell::Cell; + +#[derive(Debug)] +struct CountClone(Cell); + +fn count_clone() -> CountClone { CountClone(Cell::new(0)) } + +impl PartialEq for CountClone { + fn eq(&self, rhs: &i32) -> bool { + self.0.get() == *rhs + } +} + +impl Clone for CountClone { + fn clone(&self) -> Self { + let ret = CountClone(self.0.clone()); + let n = self.0.get(); + self.0.set(n + 1); + ret + } +} + +fn test_zip_cloned_sideffectful() { + let xs = [count_clone(), count_clone(), count_clone(), count_clone()]; + let ys = [count_clone(), count_clone()]; + + for _ in xs.iter().cloned().zip(ys.iter().cloned()) { } + + assert_eq!(&xs, &[1, 1, 1, 0][..]); + assert_eq!(&ys, &[1, 1][..]); + + let xs = [count_clone(), count_clone()]; + let ys = [count_clone(), count_clone(), count_clone(), count_clone()]; + + for _ in xs.iter().cloned().zip(ys.iter().cloned()) { } + + assert_eq!(&xs, &[1, 1][..]); + assert_eq!(&ys, &[1, 1, 0, 0][..]); +} + +fn test_zip_map_sideffectful() { + let mut xs = [0; 6]; + let mut ys = [0; 4]; + + for _ in xs.iter_mut().map(|x| *x += 1).zip(ys.iter_mut().map(|y| *y += 1)) { } + + assert_eq!(&xs, &[1, 1, 1, 1, 1, 0]); + assert_eq!(&ys, &[1, 1, 1, 1]); + + let mut xs = [0; 4]; + let mut ys = [0; 6]; + + for _ in xs.iter_mut().map(|x| *x += 1).zip(ys.iter_mut().map(|y| *y += 1)) { } + + assert_eq!(&xs, &[1, 1, 1, 1]); + assert_eq!(&ys, &[1, 1, 1, 1, 0, 0]); +} + +fn test_zip_map_rev_sideffectful() { + let mut xs = [0; 6]; + let mut ys = [0; 4]; + + { + let mut it = xs.iter_mut().map(|x| *x += 1).zip(ys.iter_mut().map(|y| *y += 1)); + it.next_back(); + } + assert_eq!(&xs, &[0, 0, 0, 1, 1, 1]); + assert_eq!(&ys, &[0, 0, 0, 1]); + + let mut xs = [0; 6]; + let mut ys = [0; 4]; + + { + let mut it = xs.iter_mut().map(|x| *x += 1).zip(ys.iter_mut().map(|y| *y += 1)); + (&mut it).take(5).count(); + it.next_back(); + } + assert_eq!(&xs, &[1, 1, 1, 1, 1, 1]); + assert_eq!(&ys, &[1, 1, 1, 1]); +} + +fn test_zip_nested_sideffectful() { + let mut xs = [0; 6]; + let ys = [0; 4]; + + { + // test that it has the side effect nested inside enumerate + let it = xs.iter_mut().map(|x| *x = 1).enumerate().zip(&ys); + it.count(); + } + assert_eq!(&xs, &[1, 1, 1, 1, 1, 0]); +} + +fn main() { + test_zip_cloned_sideffectful(); + test_zip_map_sideffectful(); + test_zip_map_rev_sideffectful(); + test_zip_nested_sideffectful(); +}