Implement DoubleEndedIterator for PyListIterator by caching the length while still validating it before access.
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@ -1 +1 @@
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Add implementation `DoubleEndedIterator` for `PyTupleIterator`.
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Add implementations `DoubleEndedIterator` for `PyTupleIterator` and `PyListIterator`.
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@ -1,4 +1,5 @@
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use std::convert::TryInto;
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use std::iter::FusedIterator;
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use crate::err::{self, PyResult};
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use crate::ffi::{self, Py_ssize_t};
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@ -264,6 +265,7 @@ impl PyList {
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PyListIterator {
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list: self,
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index: 0,
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length: self.len(),
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}
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}
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@ -291,18 +293,28 @@ index_impls!(PyList, "list", PyList::len, PyList::get_slice);
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pub struct PyListIterator<'a> {
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list: &'a PyList,
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index: usize,
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length: usize,
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}
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impl<'a> PyListIterator<'a> {
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unsafe fn get_item(&self, index: usize) -> &'a PyAny {
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#[cfg(any(Py_LIMITED_API, PyPy))]
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let item = self.list.get_item(index).expect("list.get failed");
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#[cfg(not(any(Py_LIMITED_API, PyPy)))]
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let item = self.list.get_item_unchecked(index);
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item
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}
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}
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impl<'a> Iterator for PyListIterator<'a> {
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type Item = &'a PyAny;
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#[inline]
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fn next(&mut self) -> Option<&'a PyAny> {
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if self.index < self.list.len() {
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#[cfg(any(Py_LIMITED_API, PyPy))]
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let item = self.list.get_item(self.index).expect("list.get failed");
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#[cfg(not(any(Py_LIMITED_API, PyPy)))]
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let item = unsafe { self.list.get_item_unchecked(self.index) };
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fn next(&mut self) -> Option<Self::Item> {
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let length = self.length.min(self.list.len());
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if self.index < length {
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let item = unsafe { self.get_item(self.index) };
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self.index += 1;
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Some(item)
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} else {
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@ -317,13 +329,30 @@ impl<'a> Iterator for PyListIterator<'a> {
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}
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}
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impl<'a> ExactSizeIterator for PyListIterator<'a> {
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fn len(&self) -> usize {
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self.list.len().saturating_sub(self.index)
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impl<'a> DoubleEndedIterator for PyListIterator<'a> {
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#[inline]
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fn next_back(&mut self) -> Option<Self::Item> {
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let length = self.length.min(self.list.len());
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if self.index < length {
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let item = unsafe { self.get_item(length - 1) };
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self.length = length - 1;
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Some(item)
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} else {
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None
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}
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}
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}
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impl<'a> std::iter::IntoIterator for &'a PyList {
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impl<'a> ExactSizeIterator for PyListIterator<'a> {
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fn len(&self) -> usize {
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self.length.saturating_sub(self.index)
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}
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}
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impl FusedIterator for PyListIterator<'_> {}
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impl<'a> IntoIterator for &'a PyList {
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type Item = &'a PyAny;
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type IntoIter = PyListIterator<'a>;
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@ -494,13 +523,41 @@ mod tests {
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iter.next();
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assert_eq!(iter.size_hint(), (v.len() - 1, Some(v.len() - 1)));
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// Exhust iterator.
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// Exhaust iterator.
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for _ in &mut iter {}
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assert_eq!(iter.size_hint(), (0, Some(0)));
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});
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}
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#[test]
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fn test_iter_rev() {
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Python::with_gil(|py| {
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let v = vec![2, 3, 5, 7];
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let ob = v.to_object(py);
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let list: &PyList = ob.downcast(py).unwrap();
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let mut iter = list.iter().rev();
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assert_eq!(iter.size_hint(), (4, Some(4)));
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assert_eq!(iter.next().unwrap().extract::<i32>().unwrap(), 7);
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assert_eq!(iter.size_hint(), (3, Some(3)));
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assert_eq!(iter.next().unwrap().extract::<i32>().unwrap(), 5);
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assert_eq!(iter.size_hint(), (2, Some(2)));
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assert_eq!(iter.next().unwrap().extract::<i32>().unwrap(), 3);
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assert_eq!(iter.size_hint(), (1, Some(1)));
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assert_eq!(iter.next().unwrap().extract::<i32>().unwrap(), 2);
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assert_eq!(iter.size_hint(), (0, Some(0)));
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assert!(iter.next().is_none());
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assert!(iter.next().is_none());
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});
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}
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#[test]
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fn test_into_iter() {
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Python::with_gil(|py| {
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