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/*
* Copyright (C) 2023 Apple Inc. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public License
* along with this library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*
*/
#pragma once
#include <wtf/Assertions.h>
#include <wtf/text/StringHasher.h>
#include <wtf/text/SuperFastHash.h>
#include <wtf/text/WYHash.h>
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
namespace WTF {
template<typename T, typename Converter>
unsigned StringHasher::computeHashAndMaskTop8Bits(std::span<const T> data)
{
#if ENABLE(WYHASH_STRING_HASHER)
if (LIKELY(data.size() <= smallStringThreshold))
return SuperFastHash::computeHashAndMaskTop8Bits<T, Converter>(data);
return WYHash::computeHashAndMaskTop8Bits<T, Converter>(data);
#else
return SuperFastHash::computeHashAndMaskTop8Bits<T, Converter>(data);
#endif
}
template<typename T, unsigned characterCount>
constexpr unsigned StringHasher::computeLiteralHashAndMaskTop8Bits(const T (&characters)[characterCount])
{
constexpr unsigned characterCountWithoutNull = characterCount - 1;
#if ENABLE(WYHASH_STRING_HASHER)
if constexpr (LIKELY(characterCountWithoutNull <= smallStringThreshold))
return SuperFastHash::computeHashAndMaskTop8Bits<T>(std::span { characters, characterCountWithoutNull });
return WYHash::computeHashAndMaskTop8Bits<T>(std::span { characters, characterCountWithoutNull });
#else
return SuperFastHash::computeHashAndMaskTop8Bits<T>(std::span { characters, characterCountWithoutNull });
#endif
}
inline void StringHasher::addCharacter(UChar character)
{
#if ENABLE(WYHASH_STRING_HASHER)
if (m_bufferSize == smallStringThreshold) {
// This algorithm must stay in sync with WYHash::hash function.
if (!m_pendingHashValue) {
m_seed = WYHash::initSeed();
m_see1 = m_seed;
m_see2 = m_seed;
m_pendingHashValue = true;
}
UChar* p = m_buffer.data();
while (m_bufferSize >= 24) {
WYHash::consume24Characters(p, WYHash::Reader16Bit<UChar>::wyr8, m_seed, m_see1, m_see2);
p += 24;
m_bufferSize -= 24;
}
ASSERT(!m_bufferSize);
m_numberOfProcessedCharacters += smallStringThreshold;
}
ASSERT(m_bufferSize < smallStringThreshold);
m_buffer[m_bufferSize++] = character;
#else
SuperFastHash::addCharacterImpl(character, m_hasPendingCharacter, m_pendingCharacter, m_hash);
#endif
}
inline unsigned StringHasher::hashWithTop8BitsMasked()
{
#if ENABLE(WYHASH_STRING_HASHER)
unsigned hashValue;
if (!m_pendingHashValue) {
ASSERT(m_bufferSize <= smallStringThreshold);
hashValue = SuperFastHash::computeHashAndMaskTop8Bits<UChar>(std::span { m_buffer }.first(m_bufferSize));
} else {
// This algorithm must stay in sync with WYHash::hash function.
auto wyr8 = WYHash::Reader16Bit<UChar>::wyr8;
unsigned i = m_bufferSize;
if (i <= 24)
m_seed ^= m_see1 ^ m_see2;
UChar* p = m_buffer.data();
WYHash::handleGreaterThan8CharactersCase(p, i, wyr8, m_seed, m_see1, m_see2);
uint64_t a = 0;
uint64_t b = 0;
if (m_bufferSize >= 8) {
a = wyr8(p + i - 8);
b = wyr8(p + i - 4);
} else {
UChar tmp[8];
unsigned bufferIndex = smallStringThreshold - (8 - i);
for (unsigned tmpIndex = 0; tmpIndex < 8; tmpIndex++) {
tmp[tmpIndex] = m_buffer[bufferIndex];
bufferIndex = (bufferIndex + 1) % smallStringThreshold;
}
UChar* tmpPtr = tmp;
a = wyr8(tmpPtr);
b = wyr8(tmpPtr + 4);
}
const uint64_t totalByteCount = (static_cast<uint64_t>(m_numberOfProcessedCharacters) + static_cast<uint64_t>(m_bufferSize)) << 1;
hashValue = StringHasher::avoidZero(WYHash::handleEndCase(a, b, m_seed, totalByteCount) & StringHasher::maskHash);
m_pendingHashValue = false;
m_numberOfProcessedCharacters = m_seed = m_see1 = m_see2 = 0;
}
m_bufferSize = 0;
return hashValue;
#else
unsigned hashValue = SuperFastHash::hashWithTop8BitsMaskedImpl(m_hasPendingCharacter, m_pendingCharacter, m_hash);
m_hasPendingCharacter = false;
m_pendingCharacter = 0;
m_hash = stringHashingStartValue;
return hashValue;
#endif
}
} // namespace WTF
using WTF::StringHasher;
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
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