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ccf9172ab3
With respect to `std::unordered_map` documentation, the `Hash` type defined in the template is over the `Key` and not `T`, the value. This hasher is incorrectly named as the `FilterHeader` is the value within this map. I consider this a bug as opposed to a refactor as the key and value relationship is implied to be `filter header -> block hash` when it is the opposite. Further, the hasher for the key already exists via `BlockHasher`. ref: https://en.cppreference.com/w/cpp/container/unordered_map.html
121 lines
2.9 KiB
C++
121 lines
2.9 KiB
C++
// Copyright (c) 2019-present The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#ifndef BITCOIN_UTIL_HASHER_H
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#define BITCOIN_UTIL_HASHER_H
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#include <crypto/common.h>
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#include <crypto/siphash.h>
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#include <primitives/transaction.h>
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#include <span.h>
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#include <uint256.h>
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#include <concepts>
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#include <cstdint>
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#include <cstring>
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class SaltedUint256Hasher
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{
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const PresaltedSipHasher m_hasher;
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public:
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SaltedUint256Hasher();
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size_t operator()(const uint256& hash) const
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{
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return m_hasher(hash);
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}
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};
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class SaltedTxidHasher
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{
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const PresaltedSipHasher m_hasher;
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public:
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SaltedTxidHasher();
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size_t operator()(const Txid& txid) const
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{
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return m_hasher(txid.ToUint256());
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}
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};
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class SaltedWtxidHasher
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{
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const PresaltedSipHasher m_hasher;
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public:
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SaltedWtxidHasher();
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size_t operator()(const Wtxid& wtxid) const
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{
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return m_hasher(wtxid.ToUint256());
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}
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};
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class SaltedOutpointHasher
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{
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const PresaltedSipHasher m_hasher;
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public:
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SaltedOutpointHasher(bool deterministic = false);
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/**
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* Having the hash noexcept allows libstdc++'s unordered_map to recalculate
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* the hash during rehash, so it does not have to cache the value. This
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* reduces node's memory by sizeof(size_t). The required recalculation has
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* a slight performance penalty (around 1.6%), but this is compensated by
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* memory savings of about 9% which allow for a larger dbcache setting.
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*
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* @see https://gcc.gnu.org/onlinedocs/gcc-13.2.0/libstdc++/manual/manual/unordered_associative.html
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*/
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size_t operator()(const COutPoint& id) const noexcept
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{
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return m_hasher(id.hash.ToUint256(), id.n);
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}
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};
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/**
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* We're hashing a nonce into the entries themselves, so we don't need extra
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* blinding in the set hash computation.
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*
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* This may exhibit platform endian dependent behavior but because these are
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* nonced hashes (random) and this state is only ever used locally it is safe.
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* All that matters is local consistency.
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*/
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class SignatureCacheHasher
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{
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public:
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template <uint8_t hash_select>
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uint32_t operator()(const uint256& key) const
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{
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static_assert(hash_select <8, "SignatureCacheHasher only has 8 hashes available.");
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uint32_t u;
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std::memcpy(&u, key.begin()+4*hash_select, 4);
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return u;
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}
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};
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struct BlockHasher
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{
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// this used to call `GetCheapHash()` in uint256, which was later moved; the
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// cheap hash function simply calls ReadLE64() however, so the end result is
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// identical
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size_t operator()(const uint256& hash) const { return ReadLE64(hash.begin()); }
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};
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class SaltedSipHasher
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{
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private:
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/** Salt */
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const uint64_t m_k0, m_k1;
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public:
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SaltedSipHasher();
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size_t operator()(const std::span<const unsigned char>& script) const;
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};
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#endif // BITCOIN_UTIL_HASHER_H
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