parent
5187be620c
commit
84ae9699c6
2 changed files with 162 additions and 10 deletions
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@ -2120,6 +2120,7 @@ impl<T> Vec<T> {
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del: 0,
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old_len,
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pred: filter,
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panic_flag: false,
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}
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}
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}
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@ -2751,6 +2752,7 @@ pub struct DrainFilter<'a, T, F>
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del: usize,
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old_len: usize,
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pred: F,
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panic_flag: bool,
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}
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#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
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@ -2760,21 +2762,34 @@ impl<T, F> Iterator for DrainFilter<'_, T, F>
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type Item = T;
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fn next(&mut self) -> Option<T> {
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struct SetIdxOnDrop<'a> {
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idx: &'a mut usize,
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new_idx: usize,
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}
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impl<'a> Drop for SetIdxOnDrop<'a> {
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fn drop(&mut self) {
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*self.idx = self.new_idx;
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}
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}
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unsafe {
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while self.idx != self.old_len {
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while self.idx < self.old_len {
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let i = self.idx;
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self.idx += 1;
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let v = slice::from_raw_parts_mut(self.vec.as_mut_ptr(), self.old_len);
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if (self.pred)(&mut v[i]) {
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let mut set_idx = SetIdxOnDrop { new_idx: self.idx, idx: &mut self.idx };
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self.panic_flag = true;
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let drained = (self.pred)(&mut v[i]);
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self.panic_flag = false;
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set_idx.new_idx += 1;
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if drained {
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self.del += 1;
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return Some(ptr::read(&v[i]));
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} else if self.del > 0 {
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}
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else if self.del > 0 {
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let del = self.del;
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let src: *const T = &v[i];
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let dst: *mut T = &mut v[i - del];
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// This is safe because self.vec has length 0
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// thus its elements will not have Drop::drop
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// called on them in the event of a panic.
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ptr::copy_nonoverlapping(src, dst, 1);
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}
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}
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@ -2792,9 +2807,47 @@ impl<T, F> Drop for DrainFilter<'_, T, F>
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where F: FnMut(&mut T) -> bool,
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{
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fn drop(&mut self) {
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self.for_each(drop);
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unsafe {
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self.vec.set_len(self.old_len - self.del);
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// If the predicate panics, we still need to backshift everything
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// down after the last successfully drained element, but no additional
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// elements are drained or checked.
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struct BackshiftOnDrop<'a, 'b, T, F>
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where
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F: FnMut(&mut T) -> bool,
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{
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drain: &'b mut DrainFilter<'a, T, F>,
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}
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impl<'a, 'b, T, F> Drop for BackshiftOnDrop<'a, 'b, T, F>
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where
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F: FnMut(&mut T) -> bool
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{
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fn drop(&mut self) {
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unsafe {
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while self.drain.idx < self.drain.old_len {
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let i = self.drain.idx;
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self.drain.idx += 1;
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let v = slice::from_raw_parts_mut(
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self.drain.vec.as_mut_ptr(),
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self.drain.old_len,
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);
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if self.drain.del > 0 {
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let del = self.drain.del;
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let src: *const T = &v[i];
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let dst: *mut T = &mut v[i - del];
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ptr::copy_nonoverlapping(src, dst, 1);
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}
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}
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self.drain.vec.set_len(self.drain.old_len - self.drain.del);
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}
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}
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}
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let backshift = BackshiftOnDrop {
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drain: self
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};
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if !backshift.drain.panic_flag {
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backshift.drain.for_each(drop);
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}
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}
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}
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