From 26a029d407be480d791972afb5975cf62c9360a6 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Fri, 19 Apr 2024 02:47:55 +0200
Subject: Adding upstream version 124.0.1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 third_party/rust/itertools/src/duplicates_impl.rs | 216 ++++++++++++++++++++++
 1 file changed, 216 insertions(+)
 create mode 100644 third_party/rust/itertools/src/duplicates_impl.rs

(limited to 'third_party/rust/itertools/src/duplicates_impl.rs')

diff --git a/third_party/rust/itertools/src/duplicates_impl.rs b/third_party/rust/itertools/src/duplicates_impl.rs
new file mode 100644
index 0000000000..28eda44a97
--- /dev/null
+++ b/third_party/rust/itertools/src/duplicates_impl.rs
@@ -0,0 +1,216 @@
+use std::hash::Hash;
+
+mod private {
+    use std::collections::HashMap;
+    use std::hash::Hash;
+    use std::fmt;
+
+    #[derive(Clone)]
+    #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
+    pub struct DuplicatesBy<I: Iterator, Key, F> {
+        pub(crate) iter: I,
+        pub(crate) meta: Meta<Key, F>,
+    }
+
+    impl<I, V, F> fmt::Debug for DuplicatesBy<I, V, F>
+    where
+        I: Iterator + fmt::Debug,
+        V: fmt::Debug + Hash + Eq,
+    {
+        debug_fmt_fields!(DuplicatesBy, iter, meta.used);
+    }
+
+    impl<I: Iterator, Key: Eq + Hash, F> DuplicatesBy<I, Key, F> {
+        pub(crate) fn new(iter: I, key_method: F) -> Self {
+            DuplicatesBy {
+                iter,
+                meta: Meta {
+                    used: HashMap::new(),
+                    pending: 0,
+                    key_method,
+                },
+            }
+        }
+    }
+
+    #[derive(Clone)]
+    pub struct Meta<Key, F> {
+        used: HashMap<Key, bool>,
+        pending: usize,
+        key_method: F,
+    }
+
+    impl<Key, F> Meta<Key, F>
+    where
+        Key: Eq + Hash,
+    {
+        /// Takes an item and returns it back to the caller if it's the second time we see it.
+        /// Otherwise the item is consumed and None is returned
+        #[inline(always)]
+        fn filter<I>(&mut self, item: I) -> Option<I>
+        where
+            F: KeyMethod<Key, I>,
+        {
+            let kv = self.key_method.make(item);
+            match self.used.get_mut(kv.key_ref()) {
+                None => {
+                    self.used.insert(kv.key(), false);
+                    self.pending += 1;
+                    None
+                }
+                Some(true) => None,
+                Some(produced) => {
+                    *produced = true;
+                    self.pending -= 1;
+                    Some(kv.value())
+                }
+            }
+        }
+    }
+
+    impl<I, Key, F> Iterator for DuplicatesBy<I, Key, F>
+    where
+        I: Iterator,
+        Key: Eq + Hash,
+        F: KeyMethod<Key, I::Item>,
+    {
+        type Item = I::Item;
+
+        fn next(&mut self) -> Option<Self::Item> {
+            let DuplicatesBy { iter, meta } = self;
+            iter.find_map(|v| meta.filter(v))
+        }
+
+        #[inline]
+        fn size_hint(&self) -> (usize, Option<usize>) {
+            let (_, hi) = self.iter.size_hint();
+            let hi = hi.map(|hi| {
+                if hi <= self.meta.pending {
+                    // fewer or equally many iter-remaining elements than pending elements
+                    // => at most, each iter-remaining element is matched
+                    hi
+                } else {
+                    // fewer pending elements than iter-remaining elements
+                    // => at most:
+                    //    * each pending element is matched
+                    //    * the other iter-remaining elements come in pairs
+                    self.meta.pending + (hi - self.meta.pending) / 2
+                }
+            });
+            // The lower bound is always 0 since we might only get unique items from now on
+            (0, hi)
+        }
+    }
+
+    impl<I, Key, F> DoubleEndedIterator for DuplicatesBy<I, Key, F>
+    where
+        I: DoubleEndedIterator,
+        Key: Eq + Hash,
+        F: KeyMethod<Key, I::Item>,
+    {
+        fn next_back(&mut self) -> Option<Self::Item> {
+            let DuplicatesBy { iter, meta } = self;
+            iter.rev().find_map(|v| meta.filter(v))
+        }
+    }
+
+    /// A keying method for use with `DuplicatesBy`
+    pub trait KeyMethod<K, V> {
+        type Container: KeyXorValue<K, V>;
+
+        fn make(&mut self, value: V) -> Self::Container;
+    }
+
+    /// Apply the identity function to elements before checking them for equality.
+    #[derive(Debug)]
+    pub struct ById;
+    impl<V> KeyMethod<V, V> for ById {
+        type Container = JustValue<V>;
+
+        fn make(&mut self, v: V) -> Self::Container {
+            JustValue(v)
+        }
+    }
+
+    /// Apply a user-supplied function to elements before checking them for equality.
+    pub struct ByFn<F>(pub(crate) F);
+    impl<F> fmt::Debug for ByFn<F> {
+        debug_fmt_fields!(ByFn,);
+    }
+    impl<K, V, F> KeyMethod<K, V> for ByFn<F>
+    where
+        F: FnMut(&V) -> K,
+    {
+        type Container = KeyValue<K, V>;
+
+        fn make(&mut self, v: V) -> Self::Container {
+            KeyValue((self.0)(&v), v)
+        }
+    }
+
+    // Implementors of this trait can hold onto a key and a value but only give access to one of them
+    // at a time. This allows the key and the value to be the same value internally
+    pub trait KeyXorValue<K, V> {
+        fn key_ref(&self) -> &K;
+        fn key(self) -> K;
+        fn value(self) -> V;
+    }
+
+    #[derive(Debug)]
+    pub struct KeyValue<K, V>(K, V);
+    impl<K, V> KeyXorValue<K, V> for KeyValue<K, V> {
+        fn key_ref(&self) -> &K {
+            &self.0
+        }
+        fn key(self) -> K {
+            self.0
+        }
+        fn value(self) -> V {
+            self.1
+        }
+    }
+
+    #[derive(Debug)]
+    pub struct JustValue<V>(V);
+    impl<V> KeyXorValue<V, V> for JustValue<V> {
+        fn key_ref(&self) -> &V {
+            &self.0
+        }
+        fn key(self) -> V {
+            self.0
+        }
+        fn value(self) -> V {
+            self.0
+        }
+    }
+}
+
+/// An iterator adapter to filter for duplicate elements.
+///
+/// See [`.duplicates_by()`](crate::Itertools::duplicates_by) for more information.
+pub type DuplicatesBy<I, V, F> = private::DuplicatesBy<I, V, private::ByFn<F>>;
+
+/// Create a new `DuplicatesBy` iterator.
+pub fn duplicates_by<I, Key, F>(iter: I, f: F) -> DuplicatesBy<I, Key, F>
+where
+    Key: Eq + Hash,
+    F: FnMut(&I::Item) -> Key,
+    I: Iterator,
+{
+    DuplicatesBy::new(iter, private::ByFn(f))
+}
+
+/// An iterator adapter to filter out duplicate elements.
+///
+/// See [`.duplicates()`](crate::Itertools::duplicates) for more information.
+pub type Duplicates<I> = private::DuplicatesBy<I, <I as Iterator>::Item, private::ById>;
+
+/// Create a new `Duplicates` iterator.
+pub fn duplicates<I>(iter: I) -> Duplicates<I>
+where
+    I: Iterator,
+    I::Item: Eq + Hash,
+{
+    Duplicates::new(iter, private::ById)
+}
+
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