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// Copyright (c) 2019 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#ifndef BITCOIN_UTIL_HASHER_H
#define BITCOIN_UTIL_HASHER_H
#include <crypto/siphash.h>
#include <primitives/transaction.h>
#include <uint256.h>
class SaltedTxidHasher
{
private:
/** Salt */
const uint64_t k0, k1;
public:
SaltedTxidHasher();
size_t operator()(const uint256& txid) const {
return SipHashUint256(k0, k1, txid);
}
};
class SaltedOutpointHasher
{
private:
/** Salt */
const uint64_t k0, k1;
public:
SaltedOutpointHasher();
/**
* This *must* return size_t. With Boost 1.46 on 32-bit systems the
* unordered_map will behave unpredictably if the custom hasher returns a
* uint64_t, resulting in failures when syncing the chain (#4634).
*
* Having the hash noexcept allows libstdc++'s unordered_map to recalculate
* the hash during rehash, so it does not have to cache the value. This
* reduces node's memory by sizeof(size_t). The required recalculation has
* a slight performance penalty (around 1.6%), but this is compensated by
* memory savings of about 9% which allow for a larger dbcache setting.
*
* @see https://gcc.gnu.org/onlinedocs/gcc-9.2.0/libstdc++/manual/manual/unordered_associative.html
*/
size_t operator()(const COutPoint& id) const noexcept {
return SipHashUint256Extra(k0, k1, id.hash, id.n);
}
};
struct FilterHeaderHasher
{
size_t operator()(const uint256& hash) const { return ReadLE64(hash.begin()); }
};
/**
* We're hashing a nonce into the entries themselves, so we don't need extra
* blinding in the set hash computation.
*
* This may exhibit platform endian dependent behavior but because these are
* nonced hashes (random) and this state is only ever used locally it is safe.
* All that matters is local consistency.
*/
class SignatureCacheHasher
{
public:
template <uint8_t hash_select>
uint32_t operator()(const uint256& key) const
{
static_assert(hash_select <8, "SignatureCacheHasher only has 8 hashes available.");
uint32_t u;
std::memcpy(&u, key.begin()+4*hash_select, 4);
return u;
}
};
struct BlockHasher
{
// this used to call `GetCheapHash()` in uint256, which was later moved; the
// cheap hash function simply calls ReadLE64() however, so the end result is
// identical
size_t operator()(const uint256& hash) const { return ReadLE64(hash.begin()); }
};
class SaltedSipHasher
{
private:
/** Salt */
const uint64_t m_k0, m_k1;
public:
SaltedSipHasher();
size_t operator()(const Span<const unsigned char>& script) const;
};
#endif // BITCOIN_UTIL_HASHER_H
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