Files
scylladb/digester.hh
Duarte Nunes 42f407ad9e row: Use cached hash for hash calculation
This entails doing the cell hash calculation slightly differently,
where the cell is hashed individually, the resulting hash being added
to the running one.

Instead of propagating a flag all through the call chain, we detect
whether we are in the new mode by the employed hash algorithm.

Signed-off-by: Duarte Nunes <duarte@scylladb.com>
2018-02-01 01:02:49 +00:00

78 lines
2.1 KiB
C++

/*
* Copyright (C) 2018 ScyllaDB
*/
/*
* This file is part of Scylla.
*
* Scylla is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Scylla 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
*/
#pragma once
#include "digest_algorithm.hh"
#include "md5_hasher.hh"
#include "xx_hasher.hh"
#include <type_traits>
#include <variant>
namespace query {
struct noop_hasher {
void update(const char* ptr, size_t length) { }
std::array<uint8_t, 16> finalize_array() { return std::array<uint8_t, 16>(); };
};
class digester final {
std::variant<noop_hasher, md5_hasher, xx_hasher> _impl;
public:
explicit digester(digest_algorithm algo) {
switch (algo) {
case digest_algorithm::MD5:
_impl = md5_hasher();
break;
case digest_algorithm::xxHash:
_impl = xx_hasher();
break;
case digest_algorithm ::none:
_impl = noop_hasher();
break;
}
}
template<typename T, typename... Args>
void feed_hash(const T& value, Args&&... args) {
std::visit([&] (auto& hasher) {
::feed_hash(hasher, value, std::forward<Args>(args)...);
}, _impl);
};
std::array<uint8_t, 16> finalize_array() {
return std::visit([&] (auto& hasher) {
return hasher.finalize_array();
}, _impl);
}
};
using default_hasher = xx_hasher;
template<typename Hasher>
using using_hash_of_hash = std::negation<std::disjunction<std::is_same<Hasher, md5_hasher>, std::is_same<Hasher, noop_hasher>>>;
template<typename Hasher>
inline constexpr bool using_hash_of_hash_v = using_hash_of_hash<Hasher>::value;
}