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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* 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
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* 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 Server Side 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 <absl/container/flat_hash_map.h>
#include <absl/container/flat_hash_set.h>
#include "mongo/base/string_data.h"
#include "mongo/util/assert_util.h"
namespace mongo {
// Type that bundles a hashed key with the actual string so hashing can be performed outside of
// insert call by using heterogeneous lookup.
struct StringMapHashedKey {
public:
explicit StringMapHashedKey(StringData sd, std::size_t hash) : _sd(sd), _hash(hash) {}
explicit operator std::string() const {
return _sd.toString();
}
StringData key() const {
return _sd;
}
std::size_t hash() const {
return _hash;
}
private:
StringData _sd;
std::size_t _hash;
};
// Hasher to support heterogeneous lookup for StringData and string-like elements.
struct StringMapHasher {
// This using directive activates heterogeneous lookup in the hash table
using is_transparent = void;
std::size_t operator()(StringData sd) const {
// Use the default absl string hasher.
return absl::Hash<absl::string_view>{}(absl::string_view(sd.rawData(), sd.size()));
}
std::size_t operator()(const std::string& s) const {
return operator()(StringData(s));
}
std::size_t operator()(const char* s) const {
return operator()(StringData(s));
}
std::size_t operator()(StringMapHashedKey key) const {
return key.hash();
}
StringMapHashedKey hashed_key(StringData sd) {
return StringMapHashedKey(sd, operator()(sd));
}
};
struct StringMapEq {
// This using directive activates heterogeneous lookup in the hash table
using is_transparent = void;
bool operator()(StringData lhs, StringData rhs) const {
return lhs == rhs;
}
bool operator()(StringMapHashedKey lhs, StringData rhs) const {
return lhs.key() == rhs;
}
bool operator()(StringData lhs, StringMapHashedKey rhs) const {
return lhs == rhs.key();
}
bool operator()(StringMapHashedKey lhs, StringMapHashedKey rhs) const {
return lhs.key() == rhs.key();
}
};
template <typename V>
using StringMap = absl::flat_hash_map<std::string, V, StringMapHasher, StringMapEq>;
using StringSet = absl::flat_hash_set<std::string, StringMapHasher, StringMapEq>;
} // namespace mongo
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