| use std::collections::HashSet; |
| use std::hash::{BuildHasher, Hash}; |
| use std::pin::Pin; |
| |
| use crate::prelude::*; |
| use crate::stream::{self, IntoStream}; |
| |
| impl<T, H> stream::Extend<T> for HashSet<T, H> |
| where |
| T: Eq + Hash, |
| H: BuildHasher + Default, |
| { |
| fn extend<'a, S: IntoStream<Item = T> + 'a>( |
| &'a mut self, |
| stream: S, |
| ) -> Pin<Box<dyn Future<Output = ()> + 'a>> { |
| // The Extend impl for HashSet in the standard library delegates to the internal HashMap. |
| // Thus, this impl is just a copy of the async Extend impl for HashMap in this crate. |
| |
| let stream = stream.into_stream(); |
| |
| // The following is adapted from the hashbrown source code: |
| // https://github.com/rust-lang/hashbrown/blob/d1ad4fc3aae2ade446738eea512e50b9e863dd0c/src/map.rs#L2470-L2491 |
| // |
| // Keys may be already present or show multiple times in the stream. Reserve the entire |
| // hint lower bound if the map is empty. Otherwise reserve half the hint (rounded up), so |
| // the map will only resize twice in the worst case. |
| |
| let additional = if self.is_empty() { |
| stream.size_hint().0 |
| } else { |
| (stream.size_hint().0 + 1) / 2 |
| }; |
| self.reserve(additional); |
| |
| Box::pin(stream.for_each(move |item| { |
| self.insert(item); |
| })) |
| } |
| } |