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Don't hash the key when searching in an empty table. #305

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merged 1 commit into from
Jan 6, 2022
Merged

Don't hash the key when searching in an empty table. #305

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16 changes: 12 additions & 4 deletions src/map.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1096,8 +1096,12 @@ where
K: Borrow<Q>,
Q: Hash + Eq,
{
let hash = make_hash::<K, Q, S>(&self.hash_builder, k);
self.table.get(hash, equivalent_key(k))
if self.table.is_empty() {
None
} else {
let hash = make_hash::<K, Q, S>(&self.hash_builder, k);
self.table.get(hash, equivalent_key(k))
}
Comment on lines +1099 to +1104
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it may make sense, if the map contains a single element and the table is small, to skip hashing and compare directly the key with the key of the single entry in the table

}

/// Returns the key-value pair corresponding to the supplied key, with a mutable reference to value.
Expand Down Expand Up @@ -1204,8 +1208,12 @@ where
K: Borrow<Q>,
Q: Hash + Eq,
{
let hash = make_hash::<K, Q, S>(&self.hash_builder, k);
self.table.get_mut(hash, equivalent_key(k))
if self.table.is_empty() {
None
} else {
let hash = make_hash::<K, Q, S>(&self.hash_builder, k);
self.table.get_mut(hash, equivalent_key(k))
}
}

/// Attempts to get mutable references to `N` values in the map at once.
Expand Down