assert!(v.as_ptr() as usize & 0xff == 0);
}
}
+
+#[test]
+fn drain_filter_empty() {
+ let mut vec: Vec<i32> = vec![];
+
+ {
+ let mut iter = vec.drain_filter(|_| true);
+ assert_eq!(iter.size_hint(), (0, Some(0)));
+ assert_eq!(iter.next(), None);
+ assert_eq!(iter.size_hint(), (0, Some(0)));
+ assert_eq!(iter.next(), None);
+ assert_eq!(iter.size_hint(), (0, Some(0)));
+ }
+ assert_eq!(vec.len(), 0);
+ assert_eq!(vec, vec![]);
+}
+
+#[test]
+fn drain_filter_zst() {
+ let mut vec = vec![(), (), (), (), ()];
+ let initial_len = vec.len();
+ let mut count = 0;
+ {
+ let mut iter = vec.drain_filter(|_| true);
+ assert_eq!(iter.size_hint(), (0, Some(initial_len)));
+ while let Some(_) = iter.next() {
+ count += 1;
+ assert_eq!(iter.size_hint(), (0, Some(initial_len - count)));
+ }
+ assert_eq!(iter.size_hint(), (0, Some(0)));
+ assert_eq!(iter.next(), None);
+ assert_eq!(iter.size_hint(), (0, Some(0)));
+ }
+
+ assert_eq!(count, initial_len);
+ assert_eq!(vec.len(), 0);
+ assert_eq!(vec, vec![]);
+}
+
+#[test]
+fn drain_filter_false() {
+ let mut vec = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+
+ let initial_len = vec.len();
+ let mut count = 0;
+ {
+ let mut iter = vec.drain_filter(|_| false);
+ assert_eq!(iter.size_hint(), (0, Some(initial_len)));
+ for _ in iter.by_ref() {
+ count += 1;
+ }
+ assert_eq!(iter.size_hint(), (0, Some(0)));
+ assert_eq!(iter.next(), None);
+ assert_eq!(iter.size_hint(), (0, Some(0)));
+ }
+
+ assert_eq!(count, 0);
+ assert_eq!(vec.len(), initial_len);
+ assert_eq!(vec, vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
+}
+
+#[test]
+fn drain_filter_true() {
+ let mut vec = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+
+ let initial_len = vec.len();
+ let mut count = 0;
+ {
+ let mut iter = vec.drain_filter(|_| true);
+ assert_eq!(iter.size_hint(), (0, Some(initial_len)));
+ while let Some(_) = iter.next() {
+ count += 1;
+ assert_eq!(iter.size_hint(), (0, Some(initial_len - count)));
+ }
+ assert_eq!(iter.size_hint(), (0, Some(0)));
+ assert_eq!(iter.next(), None);
+ assert_eq!(iter.size_hint(), (0, Some(0)));
+ }
+
+ assert_eq!(count, initial_len);
+ assert_eq!(vec.len(), 0);
+ assert_eq!(vec, vec![]);
+}
+
+#[test]
+fn drain_filter_complex() {
+
+ { // [+xxx++++++xxxxx++++x+x++]
+ let mut vec = vec![1,
+ 2, 4, 6,
+ 7, 9, 11, 13, 15, 17,
+ 18, 20, 22, 24, 26,
+ 27, 29, 31, 33,
+ 34,
+ 35,
+ 36,
+ 37, 39];
+
+ let removed = vec.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+ assert_eq!(removed.len(), 10);
+ assert_eq!(removed, vec![2, 4, 6, 18, 20, 22, 24, 26, 34, 36]);
+
+ assert_eq!(vec.len(), 14);
+ assert_eq!(vec, vec![1, 7, 9, 11, 13, 15, 17, 27, 29, 31, 33, 35, 37, 39]);
+ }
+
+ { // [xxx++++++xxxxx++++x+x++]
+ let mut vec = vec![2, 4, 6,
+ 7, 9, 11, 13, 15, 17,
+ 18, 20, 22, 24, 26,
+ 27, 29, 31, 33,
+ 34,
+ 35,
+ 36,
+ 37, 39];
+
+ let removed = vec.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+ assert_eq!(removed.len(), 10);
+ assert_eq!(removed, vec![2, 4, 6, 18, 20, 22, 24, 26, 34, 36]);
+
+ assert_eq!(vec.len(), 13);
+ assert_eq!(vec, vec![7, 9, 11, 13, 15, 17, 27, 29, 31, 33, 35, 37, 39]);
+ }
+
+ { // [xxx++++++xxxxx++++x+x]
+ let mut vec = vec![2, 4, 6,
+ 7, 9, 11, 13, 15, 17,
+ 18, 20, 22, 24, 26,
+ 27, 29, 31, 33,
+ 34,
+ 35,
+ 36];
+
+ let removed = vec.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+ assert_eq!(removed.len(), 10);
+ assert_eq!(removed, vec![2, 4, 6, 18, 20, 22, 24, 26, 34, 36]);
+
+ assert_eq!(vec.len(), 11);
+ assert_eq!(vec, vec![7, 9, 11, 13, 15, 17, 27, 29, 31, 33, 35]);
+ }
+
+ { // [xxxxxxxxxx+++++++++++]
+ let mut vec = vec![2, 4, 6, 8, 10, 12, 14, 16, 18, 20,
+ 1, 3, 5, 7, 9, 11, 13, 15, 17, 19];
+
+ let removed = vec.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+ assert_eq!(removed.len(), 10);
+ assert_eq!(removed, vec![2, 4, 6, 8, 10, 12, 14, 16, 18, 20]);
+
+ assert_eq!(vec.len(), 10);
+ assert_eq!(vec, vec![1, 3, 5, 7, 9, 11, 13, 15, 17, 19]);
+ }
+
+ { // [+++++++++++xxxxxxxxxx]
+ let mut vec = vec![1, 3, 5, 7, 9, 11, 13, 15, 17, 19,
+ 2, 4, 6, 8, 10, 12, 14, 16, 18, 20];
+
+ let removed = vec.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+ assert_eq!(removed.len(), 10);
+ assert_eq!(removed, vec![2, 4, 6, 8, 10, 12, 14, 16, 18, 20]);
+
+ assert_eq!(vec.len(), 10);
+ assert_eq!(vec, vec![1, 3, 5, 7, 9, 11, 13, 15, 17, 19]);
+ }
+}
+
+
}
}
+ /// Creates an iterator which uses a closure to determine if an element should be removed.
+ ///
+ /// If the closure returns true, then the element is removed and yielded.
+ /// If the closure returns false, it will try again, and call the closure
+ /// on the next element, seeing if it passes the test.
+ ///
+ /// Using this method is equivalent to the following code:
+ ///
+ /// ```
+ /// # let some_predicate = |x: &mut i32| { *x == 2 };
+ /// # let mut vec = vec![1, 2, 3, 4, 5];
+ /// let mut i = 0;
+ /// while i != vec.len() {
+ /// if some_predicate(&mut vec[i]) {
+ /// let val = vec.remove(i);
+ /// // your code here
+ /// }
+ /// i += 1;
+ /// }
+ /// ```
+ ///
+ /// But `drain_filter` is easier to use. `drain_filter` is also more efficient,
+ /// because it can backshift the elements of the array in bulk.
+ ///
+ /// Note that `drain_filter` also lets you mutate every element in the filter closure,
+ /// regardless of whether you choose to keep or remove it.
+ ///
+ ///
+ /// # Examples
+ ///
+ /// Splitting an array into evens and odds, reusing the original allocation:
+ ///
+ /// ```
+ /// #![feature(drain_filter)]
+ /// let mut numbers = vec![1, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15];
+ ///
+ /// let evens = numbers.drain_filter(|x| *x % 2 == 0).collect::<Vec<_>>();
+ /// let odds = numbers;
+ ///
+ /// assert_eq!(evens, vec![2, 4, 6, 8, 14]);
+ /// assert_eq!(odds, vec![1, 3, 5, 9, 11, 13, 15]);
+ /// ```
+ #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+ pub fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<T, F>
+ where F: FnMut(&mut T) -> bool,
+ {
+ let old_len = self.len();
+
+ // Guard against us getting leaked (leak amplification)
+ unsafe { self.set_len(0); }
+
+ DrainFilter {
+ vec: self,
+ idx: 0,
+ del: 0,
+ old_len,
+ pred: filter,
+ }
+ }
}
#[stable(feature = "extend_ref", since = "1.2.0")]
self.tail_start = new_tail_start;
}
}
+
+/// An iterator produced by calling `drain_filter` on Vec.
+#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+#[derive(Debug)]
+pub struct DrainFilter<'a, T: 'a, F>
+ where F: FnMut(&mut T) -> bool,
+{
+ vec: &'a mut Vec<T>,
+ idx: usize,
+ del: usize,
+ old_len: usize,
+ pred: F,
+}
+
+#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+impl<'a, T, F> Iterator for DrainFilter<'a, T, F>
+ where F: FnMut(&mut T) -> bool,
+{
+ type Item = T;
+
+ fn next(&mut self) -> Option<T> {
+ unsafe {
+ while self.idx != self.old_len {
+ let i = self.idx;
+ self.idx += 1;
+ let v = slice::from_raw_parts_mut(self.vec.as_mut_ptr(), self.old_len);
+ if (self.pred)(&mut v[i]) {
+ self.del += 1;
+ return Some(ptr::read(&v[i]));
+ } else if self.del > 0 {
+ v.swap(i - self.del, i);
+ }
+ }
+ None
+ }
+ }
+
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ (0, Some(self.old_len - self.idx))
+ }
+}
+
+#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
+impl<'a, T, F> Drop for DrainFilter<'a, T, F>
+ where F: FnMut(&mut T) -> bool,
+{
+ fn drop(&mut self) {
+ for _ in self.by_ref() { }
+
+ unsafe {
+ self.vec.set_len(self.old_len - self.del);
+ }
+ }
+}