fallible_collections 0.1.3

//! Implement Fallible HashMap
use super::TryClone;
use crate::TryReserveError;
use core::default::Default;
use core::hash::Hash;

type HashMap<K, V> = hashbrown::hash_map::HashMap<K, V>;

#[derive(Default)]
pub struct TryHashMap<K, V> {
    inner: HashMap<K, V>,
}

impl<K, V> TryHashMap<K, V>
where
    K: Eq + Hash,
{
    pub fn with_capacity(capacity: usize) -> Result<Self, TryReserveError> {
        let mut map = Self {
            inner: HashMap::new(),
        };
        map.reserve(capacity)?;
        Ok(map)
    }

    pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V>
    where
        K: core::borrow::Borrow<Q>,
        Q: Hash + Eq,
    {
        self.inner.get(k)
    }

    pub fn insert(&mut self, k: K, v: V) -> Result<Option<V>, TryReserveError> {
        self.reserve(if self.inner.capacity() == 0 { 4 } else { 1 })?;
        Ok(self.inner.insert(k, v))
    }

    fn reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
        self.inner.try_reserve(additional)
    }
}

impl<K, V> TryClone for TryHashMap<K, V>
where
    K: Eq + Hash + TryClone,
    V: TryClone,
{
    fn try_clone(&self) -> Result<Self, TryReserveError> {
        let mut clone = Self::with_capacity(self.inner.len())?;

        for (key, value) in self.inner.iter() {
            clone.insert(key.try_clone()?, value.try_clone()?)?;
        }

        Ok(clone)
    }
}

#[test]
fn tryhashmap_oom() {
    match TryHashMap::<char, char>::default().reserve(core::usize::MAX) {
        Ok(_) => panic!("it should be OOM"),
        _ => (),
    }
}