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/* Copyright 2016 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects
* for all of the code used other than as permitted herein. If you modify
* file(s) with this exception, you may extend this exception to your
* version of the file(s), but you are not obligated to do so. If you do not
* wish to do so, delete this exception statement from your version. If you
* delete this exception statement from all source files in the program,
* then also delete it in the license file.
*/
#pragma once
#include "mongo/util/unordered_fast_key_table.h"
namespace mongo {
template <typename Key, typename Hasher>
struct UnorderedFastKeyTableTraitsFactoryForPtrKey {
struct Traits {
static uint32_t hash(const Key* a) {
return Hasher()(*a);
}
static bool equals(const Key* a, const Key* b) {
return *a == *b;
}
static Key toStorage(const Key* s) {
return *s;
}
static const Key* toLookup(const Key& s) {
return &s;
}
class HashedKey {
public:
HashedKey() = default;
explicit HashedKey(const Key* key) : _key(key), _hash(Traits::hash(_key)) {}
HashedKey(const Key* key, uint32_t hash) : _key(key), _hash(hash) {
// If you claim to know the hash, it better be correct.
dassert(_hash == Traits::hash(_key));
}
const Key* key() const {
return _key;
}
uint32_t hash() const {
return _hash;
}
private:
const Key* _key = nullptr;
uint32_t _hash = 0;
};
};
template <typename V>
using type = UnorderedFastKeyTable<Key*, Key, V, Traits>;
};
/**
* Provides a Hasher which forwards to an instance's .hash() method. This should only be used with
* high quality hashing functions because UnorderedFastKeyMap uses bit masks, rather than % by
* prime, which can provide poor behavior without good overall distribution.
*/
template <typename T>
struct UnorderedFastKeyTableInstanceMethodHasher {
auto operator()(const T& t) const -> decltype(t.hash()) {
return t.hash();
}
};
}
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